Control of Air Pollution from New Motor Vehicles: Heavy-Duty Engine and Vehicle Standards and Highway Diesel Fuel Sulfur Control Requirements

Related Material

Other Related Documents

[Federal Register: January 18, 2001 (Volume 66, Number 12)]
[Rules and Regulations]
[Page 5001-5050]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr18ja01-16]

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Part V

Environmental Protection Agency

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40 CFR Parts 69, 80, and 86

Control of Air Pollution From New Motor Vehicles: Heavy-Duty Engine and
Vehicle Standards and Highway Diesel Fuel Sulfur Control Requirements;
Final Rule

[[Page 5002]]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 69, 80, and 86

[AMS-FRL-6923-7]
RIN 2060-AI69

Control of Air Pollution from New Motor Vehicles: Heavy-Duty
Engine and Vehicle Standards and Highway Diesel Fuel Sulfur Control
Requirements

AGENCY: Environmental Protection Agency.

ACTION: Final rule.

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SUMMARY: The pollution emitted by diesel engines contributes greatly to
our nation's continuing air quality problems. Even with more stringent
heavy-duty highway engine standards set to take effect in 2004, these
engines will continue to emit large amounts of nitrogen oxides and
particulate matter, both of which contribute to serious public health
problems in the United States. These problems include premature
mortality, aggravation of respiratory and cardiovascular disease,
aggravation of existing asthma, acute respiratory symptoms, chronic
bronchitis, and decreased lung function. Numerous studies also link
diesel exhaust to increased incidence of lung cancer. We believe that
diesel exhaust is likely to be carcinogenic to humans by inhalation and
that this cancer hazard exists for occupational and environmental
levels of exposure.
We are establishing a comprehensive national control program that
will regulate the heavy-duty vehicle and its fuel as a single system.
As part of this program, new emission standards will begin to take
effect in model year 2007, and will apply to heavy-duty highway engines
and vehicles. These standards are based on the use of high-efficiency
catalytic exhaust emission control devices or comparably effective
advanced technologies. Because these devices are damaged by sulfur, we
are also reducing the level of sulfur in highway diesel fuel
significantly by mid-2006. The program provides substantial flexibility
for refiners, especially small refiners, and for manufacturers of
engines and vehicles. These options will ensure that there is
widespread availability and supply of the low sulfur diesel fuel from
the very beginning of the program, and will provide engine
manufacturers with the lead time needed to efficiently phase-in the
exhaust emission control technology that will be used to achieve the
emissions benefits of the new standards.
We estimate that heavy-duty trucks and buses today account for
about one-third of nitrogen oxides emissions and one-quarter of
particulate matter emissions from mobile sources. In some urban areas,
the contribution is even greater. This program will reduce particulate
matter and oxides of nitrogen emissions from heavy duty engines by 90
percent and 95 percent below current standard levels, respectively. In
order to meet these more stringent standards for diesel engines, the
program calls for a 97 percent reduction in the sulfur content of
diesel fuel. As a result, diesel vehicles will achieve gasoline-like
exhaust emission levels. We are also finalizing more stringent
standards for heavy-duty gasoline vehicles, based in part on the use of
the low sulfur gasoline that will be available when the standards go
into effect.
The clean air impact of this program will be dramatic when fully
implemented. By 2030, this program will reduce annual emissions of
nitrogen oxides, nonmethane hydrocarbons, and particulate matter by a
projected 2.6 million, 115,000 and 109,000 tons, respectively. We
project that these reductions and the resulting significant
environmental benefits of this program will come at an average cost
increase of about $2,000 to $3,200 per new vehicle in the near term and
about $1,200 to $1,900 per new vehicle in the long term, depending on
the vehicle size. In comparison, new vehicle prices today can range
well over $100,000 for larger heavy-duty vehicles. We estimate that
when fully implemented the sulfur reduction requirement will increase
the cost of producing and distributing diesel fuel by about five cents
per gallon.

DATES: This rule will become effective March 19, 2001. The
incorporation by reference of certain publications listed in this rule
is approved by the Director of the Office of Federal Register as of
March 19, 2001.

ADDRESSES: Comments: All comments and materials relevant to today's
action have been placed in Public Docket No. A-99-06 at the following
address: U.S. Environmental Protection Agency (EPA), Air Docket (6102),
Room M-1500, 401 M Street, SW, Washington, DC 20460 (on the ground
floor in Waterside Mall) from 8:00 a.m. to 5:30 p.m., Monday through
Friday, except on government holidays. You can reach the Air Docket by
telephone at (202) 260-7548 and by facsimile at (202) 260-4400. We may
charge a reasonable fee for copying docket materials, as provided in 40
CFR part 2.

FOR FURTHER INFORMATION CONTACT: Margaret Borushko, U.S. EPA, National
Vehicle and Fuel Emissions Laboratory, 2000 Traverwood, Ann Arbor MI
48105; Telephone (734) 214-4334, FAX (734) 214-4816, E-mail
borushko.margaret@epa.gov

SUPPLEMENTARY INFORMATION:

Regulated Entities

This action will affect you if you produce or import new heavy-duty
engines which are intended for use in highway vehicles such as trucks
and buses, or produce or import such highway vehicles, or convert
heavy-duty vehicles or heavy-duty engines used in highway vehicles to
use alternative fuels, or produce or import light-duty highway diesel
vehicles. It will also affect you if you produce, import, distribute,
or sell highway diesel fuel, or sell nonroad diesel fuel.
The following table gives some examples of entities that may have
to follow the regulations. But because these are only examples, you
should carefully examine the regulations in 40 CFR parts 69, 80, and
86. If you have questions, call the person listed in the FOR FURTHER
INFORMATION CONTACT section of this preamble:

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NAICS
Category Codes a SIC Codes Examples of potentially regulated entities
----------------------------------------------------b-----------------------------------------------------------
Industry........................ 336112 3711 Engine and Truck Manufacturers
336120
Industry........................ 811112 7533 Commercial Importers of Vehicles and
811198 7549 Vehicle Components
Industry........................ 324110 2911 Petroleum Refiners
Industry........................ 422710 5171 Diesel Fuel Marketers and Distributors
422720 5172
industry........................ 484220 4212 Diesel Fuel Carriers

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484230 4213
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a North American Industry Classifications System (NAICS).
b Standard Industrial Classification (SIC) system code.

Access to Rulemaking Documents Through the Internet

Today's final rule is available electronically on the day of
publication from the Environmental Protection Agency Internet Web site
listed below. Electronic copies of the preamble, regulatory language,
Regulatory Impact Analysis, and other documents associated with today's
final rule are available from the EPA Office of Transportation and Air
Quality (formerly the Office of Mobile Sources) Web site listed below
shortly after the rule is signed by the Administrator. This service is
free of charge, except any cost that you incur for connecting to the
Internet.
Environmental Protection Agency Web Site: http://www.epa.gov/
fedrgstr/ (Either select a desired date or use the Search feature.)
Office of Transportation and Air Quality (OTAQ) Web Site: http://
www.epa.gov/otaq/ (Look in ``What's New'' or under the ``Heavy Trucks/
Busses'' topic.)
Please note that due to differences between the software used to
develop the document and the software into which document may be
downloaded, changes in format, page length, etc. may occur.

Table of Contents

I. Overview
A. What Requirements Are Being Set?
1. Heavy-Duty Emission Standards
2. Fuel Quality Standards
B. Why is EPA Taking This Action?
1. Heavy-Duty Vehicles Contribute to Serious Air Pollution
Problems
2. Technology-Based Solutions
3. Basis for Action Under the Clean Air Act
C. Putting This Rule in Perspective
1. Diesel Popularity
2. Past Progress and New Developments
3. Tier 2 Emissions Standards
4. Mobile Source Air Toxics Rulemaking
5. Nonroad Engine Standards and Fuel
6. State Initiatives
7. Retrofit Programs
8. Actions in Other Countries
II. The Air Quality Need and Projected Benefits
A. Overview
B. Public Health and Welfare Concerns
1. Health and Welfare Concerns Raised During Public Hearings
2. Ozone and its Precursors
a. Health and Welfare Effects From Short-Term Exposures to Ozone
b. Current and Future Nonattainment Status With the 1-Hour Ozone
NAAQS
c. Public Health and Welfare Concerns from Prolonged and
Repeated Exposures to Ozone
3. Particulate Matter
a. Health and Welfare Effects
b. Attainment and Maintenance of the PM10 NAAQS
c. Public Health and Welfare Concerns from Exposure to Fine PM
d. Other Welfare Effects Associated with PM
e. Conclusions Regarding PM
4. Diesel Exhaust
a. Potential Cancer Effects of Diesel Exhaust
b. Noncancer Effects of Diesel Exhaust
5. Other Criteria Pollutants
6. Other Air Toxics
a. Benzene
b. 1,3-Butadiene
c. Formaldehyde
d. Acetaldehyde
e. Acrolein
f. Dioxins
7. Other Welfare and Environmental Effects
a. Acid Deposition
b. Eutrophication and Nitrification
c. Polycyclic Organic Matter Deposition
d. Visibility and Regional Haze
C. Contribution From Heavy-Duty Vehicles
1. NOX Emissions
2. PM Emissions
3. Environmental Justice
D. Anticipated Emissions Benefits
1. NOX Reductions
2. PM Reductions
3. NMHC Reductions
4. Additional Emissions Benefits
a. CO Reductions
b. SOX Reductions
c. Air Toxics Reductions
E. Clean Heavy-Duty Vehicles and Low-Sulfur Diesel Fuel are
Critically Important for Improving Human Health and Welfare
III. Heavy-Duty Engine and Vehicle Standards
A. Why Are We Setting New Heavy-Duty Standards?
B. Emission Control Technologies for Heavy-Duty Vehicles and
Engines
C. What Engine and Vehicle Standards are We Finalizing?
1. Heavy-Duty Engine Exhaust Emissions Standards
a. FTP Standards
b. Supplemental Provisions for HD Diesel Engines (SET & NTE)
c. Crankcase Emissions Control
d. On-Board Diagnostics (OBD)
2. Heavy-Duty Vehicle Exhaust Emissions Standards
a. FTP Standards
b. Supplemental Federal Test Procedure
c. On-Board Diagnostics (OBD)
3. Heavy-Duty Evaporative Emission Standards
D. Incentives for Early Introduction of Clean Engines and
Vehicles
E. Feasibility of the New Engine and Vehicle Standards
1. Feasibility of Stringent Standards for Heavy-Duty Diesel
a. Meeting the PM Standard
b. Meeting the NOX Standard
c. Meeting the NMHC Standard
d. Meeting the Crankcase Emissions Requirements
e. The Complete System
2. Feasibility of Stringent Standards for Heavy-Duty Gasoline
3. Feasibility of the New Evaporative Emission Standards
F. Need for Low Sulfur Diesel Fuel
1. Catalyzed Diesel Particulate Filters and the Need for Low
Sulfur Fuel
a. Inhibition of Trap Regeneration Due to Sulfur
b. Loss of PM Control Effectiveness
c. Increased Maintenance Cost for Diesel Particulate Filters Due
to Sulfur
2. Diesel NOX Catalysts and the Need for Low Sulfur
Fuel
a. Sulfur Poisoning (Sulfate Storage) on NOX
Adsorbers
b. Sulfate Particulate Production and Sulfur Impacts on
Effectiveness of NOX Control Technologies
3. What About Sulfur in Engine Lubricating Oils?
G. Fuel Economy Impact of High Efficiency Control Technologies
1. Diesel Particulate Filters and Fuel Economy
2. NOX Control Technologies and Fuel Economy
3. Emission Control Systems for 2007 and Net Fuel Economy
Impacts
H. Review of the Status of Heavy-Duty Diesel NOX
Emission Control Technology
IV. Our Program for Controlling Highway Diesel Sulfur
A. Highway Diesel Sulfur Standards for Refiners and Importers
1. Standards and Deadlines that Refiners and Importers Must Meet
2. Temporary Compliance Option for Refiners and Importers
a. Generating Credits
b. Using Credits
c. How Long Will Credits Last?
d. Additional Limitations on Credit Trading for Some States
3. What Information Must Refiners/Importers Submit to Us?
4. Impacts of the Highway Diesel Fuel Program
a. Ensures Adequate Supplies of Highway Diesel Fuel
b. Ensures Widespread Availability of Low Sulfur Diesel Fuel
c. Provides Lower Costs to Refineries
d. Misfueling Concerns Should Be Minimized

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e. Summary
B. What Provisions Apply in the Geographic Phase-in Area?
1. What Is the Geographic Phase-in Area and How Was it
Established?
2. Highway Diesel Provisions for GPA Refiners
3. How Do Refiners Apply for an Extension of the GPA Gasoline
Program?
4. Required Reporting for GPA Refiners
C. Hardship Provisions for Qualifying Refiners
1. Hardship Provisions for Qualifying Small Refiners
a. Qualifying Small Refiners
b. How Do We Define Small Refiners?
c. What Options Are Available for Small Refiners?
d. How Do Small Refiners Apply for Small Refiner Status?
2. Farmer Cooperative Refiners Will Benefit From the Flexible
Provisions Available to Other Refiners
3. General Hardship Provisions
a. Temporary Waivers from Low Sulfur Diesel Requirements in
Extreme Unforseen Circumstances
b. Temporary Waivers Based on Extreme Hardship Circumstances
D. Technological Feasibility of the Low Sulfur Diesel Fuel
Program
1. What Technology Will Refiners Use?
2. Have These Technologies Been Commercially Demonstrated?
3. Feasibility of Distributing Low Sulfur Highway Diesel Fuel
E. What Are the Potential Impacts of the Low Sulfur Diesel
Program on Lubricity and Other Fuel Properties?
1. What Is Lubricity and Why Might It Be a Concern?
2. Today's Action on Lubricity: a Voluntary Approach
3. What Are Today's Actions on Fuel Properties Other than
Sulfur?
F. How Are State Programs Affected by the Low Sulfur Diesel
Program?
1. State Preemption
2. What Provisions Apply in Alaska?
a. Today's Action Regarding the 500 ppm Standard in Alaska
b. Why Are We Treating Alaska Uniquely?
3. What Provisions Apply in American Samoa, Guam, and the
Commonwealth of Northern Mariana Islands?
a. Today's Action Regarding the Highway Diesel Fuel Standard in
the Territories
b. Why Are We Treating These Territories Uniquely?
G. Refinery Air Permitting
V. Economic Impact
A. Cost for Diesel Vehicles to Meet Emissions Standards
1. Summary of New System and Operating Costs
2. New System Costs for NOX and PM Emission Control
3. Operating Costs Associated With NOX and PM Control
B. Cost for Gasoline Vehicles to Meet the New Emissions
Standards
1. Summary of New System Costs
2. Operating Costs Associated With Meeting the Heavy-Duty
Gasoline Standard
C. Cost of Fuel Change
1. Refinery Costs
2. Highway Diesel Fuel Supply
3. Cost of Lubricity Additives
4. Distribution Costs
a. Distribution Costs Under the Fully Implemented Program
b. Distribution Costs During the Initial Years
5. Benefits of Low-sulfur Diesel Fuel for the Existing Diesel
Fleet
D. Aggregate Costs
E. Cost Effectiveness
1. What Is the Cost Effectiveness of This Program?
2. Comparison With Other Means of Reducing Emissions
F. Does the Value of the Benefits Outweigh the Cost of the
Standards?
1. What Was Our Overall Approach to the Benefit-Cost Analysis?
2. What Are the Significant Limitations of the Benefit-Cost
Analysis?
3. How Has the Benefit-Cost Analysis Changed from Proposal?
4. What Are the Benefits in the Years Leading up to 2030?
5. What Were the Results of the Benefit-Cost Analysis?
VI. Requirements for Engine and Vehicle Manufacturers
A. Compliance with Standards and Enforcement
1. Allowable Maintenance
2. Emission Data Waivers
3. Crankcase Emissions
4. Non-Conformance Penalties
5. Idle CO Standards
B. Compliance With Phase-in Schedules
C. Averaging, Banking, and Trading
D. FTP Changes to Accommodate Regeneration of Exhaust Emission
Controls
E. Improvements to the Test Procedures
F. Certification Fuel
G. Misfueling Concerns for Light-and Heavy-duty Diesel Vehicles
H. In-Use Compliance Levels During the Transition Years to New
Technologies
VII. Highway Diesel Fuel Program: Compliance, Enforcement and
Downstream Provisions
A. General Provisions
1. Definition of Diesel Fuel Covered by This Program
2. Relationship to Highway Diesel Standards
B. What Are the Requirements for Refiners and Importers?
1. General Requirements
2. Refiner and Importer Temporary Compliance Option Provisions
and the Credit Trading Program
a. Early Credits Program
b. Credit Use in a Credit Deficit Situation
c. Resolving Issues of Invalid Credits
d. Compliance Provisions
e. Additional Provisions for Importers of Diesel Fuel and for
Foreign Refiners Subject to the Temporary Compliance Option and
Hardship Provisions
3. Refiner Hardship Provisions
a. General Refiner Hardship Provisions
b. Small Refiner Hardship Provisions
c. Relief for Refiners Supplying Gasoline to the Tier 2
Geographic Phase-In Area (GPA)
C. What Requirements Apply Downstream of the Refinery or Import
Facility?
1. Downstream Enforcement of the Standards
2. Other Provisions
a. Implementation Dates
b. Product Segregation and Contamination
c. Diesel Fuel Pump Labeling
3. Use of Used Motor Oil in New Diesel Vehicles
4. Use of Kerosene in Diesel Fuel
5. Use of Diesel Fuel Additives
D. What Are the Testing and Sampling Methods and Requirements?
1. Diesel Fuel Testing Requirements and Test Methods
2. Diesel Fuel Sampling Methods
E. What Are the Recordkeeping, Reporting and Product Transfer
Document Requirements?
1. Registration of Refiners and Importers
a. All Refiners and Importers
b. Prospective Small Refiners
c. Refiners Seeking an Extension of the GPA Gasoline Sulfur
Standards
2. Pre-Compliance Reports
a. All Refiners
b. Small Refiners
c. GPA Refiners
3. Annual Compliance Reports
a. All Refiners
b. Small Refiners
4. Initial Confirmation of 15 ppm Fuel Production
5. Product Transfer Documents (PTDs)
a. Diesel Fuel
b. Additives
6. Recordkeeping Requirements
7. Record Retention
F. Are There Any Exemptions From the Highway Diesel Fuel
Requirements?
1. Research and Development
2. Racing Vehicles
3. Military Fuel
G. Liability and Penalty Provisions for Noncompliance
1. General
2. What Is the Liability That Additive Manufacturers and
Distributors, and Parties That Blend Additives into Diesel Fuel, Are
Subject To?
a. General
b. Liability When the Additive Is Designated as Complying with
the 15 ppm Sulfur Standard
c. Liability When the Additive Is Designated as Having a
Possible Sulfur Content Greater than 15 ppm
H. How Will Compliance With the Sulfur Standards Be Determined?
VIII.Standards and Fuel for Nonroad Diesel Engines
IX. Public Participation
X. Administrative Requirements
A. Administrative Designation and Regulatory Analysis
B. Regulatory Flexibility Analysis
1. Need for and Objectives of the Rule
2. Summary of Significant Public Comments on the IRFA
3. Types and Number of Small Entities
4. Reporting, Recordkeeping and Other Compliance Requirements
5. Regulatory Alternatives To Minimize Impact on Small Entities
C. Paperwork Reduction Act

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D. Intergovernmental Relations
1. Unfunded Mandates Reform Act
2. Executive Order 13084: Consultation and Coordination with
Indian Tribal Governments
E. National Technology Transfer and Advancement Act
F. Executive Order 13045: Children's Health Protection
G. Executive Order 13132: Federalism
H. Congressional Review Act
XI. Statutory Provisions and Legal Authority

I. Overview

This rule covers the second of two phases in a comprehensive
nationwide program for controlling emissions from heavy-duty engines
(HDEs) and vehicles. It builds upon the phase 1 program we recently
finalized (65 FR 59896, October 6, 2000). That action affirmed the 50
percent reduction in emissions of oxides of nitrogen ( NOX)
from 2004 model year highway diesel engines, set in 1997 (62 FR 54693,
October 21, 1997), and set new emission standards for heavy-duty
gasoline-fueled engines and vehicles for 2005.
This second phase of the program looks beyond 2004, based on the
use of high-efficiency exhaust emission control devices and the
consideration of the vehicle and its fuel as a single system. In
developing this rule, we took into consideration comments received in
response to the advance notice of proposed rulemaking (64 FR 26142, May
13, 1999) and the notice of proposed rulemaking (NPRM) (65 FR 35430,
June 2, 2000), including comments provided at five public hearings last
June.
This program will result in particulate matter (PM) and
NOX emission levels that are 90 percent and 95 percent below
the standard levels in effect today, respectively. In order to meet
these more stringent standards for diesel engines, the rule mandates a
97 percent reduction in the sulfur content of diesel fuel. The heavy-
duty engine standards will be effective starting in the 2007 model year
and the low sulfur diesel fuel needed to facilitate the standards will
be widely available in September 2006. As a result, diesel vehicles
will achieve gasoline-like exhaust emission levels, in addition to
their inherent advantages over gasoline vehicles with respect to fuel
economy, lower greenhouse gas emissions, and lower evaporative
hydrocarbon emissions. The rule also includes more stringent standards
for heavy-duty gasoline vehicles. In addition to its impact on heavy-
duty vehicle emissions, this rule will make clean diesel fuel available
in time for implementation of the light-duty Tier 2 standards.
The standards will result in substantial benefits to public health
and welfare and the environment through significant reductions in
emissions of NOX, PM, nonmethane hydrocarbons (NMHC), carbon
monoxide (CO), sulfur oxides (SOX), and air toxics. We
project that by 2030, this phase 2 program will reduce annual emissions
of NOX, NMHC, and PM by 2.6 million, 115,000 and 109,000
tons, respectively. These emission reductions will prevent 8,300
premature deaths, over 9,500 hospitalizations, and 1.5 million work
days lost. All told the benefits of this rule equal $70.3 billion. A
sizeable part of the benefits in the early years of this program come
from large reductions in the amount of direct and secondary PM caused
by the existing fleet of heavy-duty vehicles. These reductions are due
to the use of the higher quality diesel fuel in these vehicles.

A. What Requirements Are Being Set?

There are two basic parts to this program: (1) New exhaust emission
standards for heavy-duty highway engines and vehicles, and (2) new
quality standards for highway diesel fuel. The systems approach of
combining the engine and fuel standards into a single program is
critical to the success of our overall efforts to reduce emissions,
because the emission standards will not be feasible without the fuel
change. The feasibility of the emission standards is based on the use
of high-efficiency exhaust emission control devices that would be
damaged by sulfur in the fuel. This rule, by providing extremely low
sulfur diesel fuel, will also enable cleaner diesel passenger vehicles
and light-duty trucks. This is because the same pool of highway diesel
fuel also services these light-duty diesel vehicles, and these vehicles
can employ technologies similar to the high-efficiency heavy-duty
exhaust emission control technologies that will be enabled by the fuel
change. We believe these technologies are needed for diesel vehicles to
comply with our Tier 2 emissions standards for light-duty highway
vehicles (65 FR 6698, February 10, 2000).
We believe that this systems approach is a comprehensive way to
enable effective new technologies for clean diesel, affecting all sizes
of highway diesel engines, and may translate to future reductions from
diesel engines used in nonroad applications too. The fuel change, in
addition to enabling new technologies, will also produce emissions and
maintenance benefits in the existing fleet of highway diesel vehicles.
These benefits will include reduced sulfate PM and sulfur oxides
emissions, reduced engine wear and less frequent oil changes, and
longer-lasting exhaust gas recirculation (EGR) components on engines
equipped with EGR. Heavy-duty gasoline vehicles will also be expected
to have much lower emissions due to the transfer of recent technology
developments for light-duty applications, and the recent action taken
to reduce sulfur in gasoline as part of the Tier 2 rule.
The basic elements of the rule are outlined below. Detailed
provisions and justifications for our rule are discussed in subsequent
sections.
1. Heavy-Duty Emission Standards
We are finalizing a PM emissions standard for new heavy-duty
engines of 0.01 grams per brake-horsepower-hour (g/bhp-hr), to take
full effect for diesels in the 2007 model year.1 We are also
finalizing standards for NOX and NMHC of 0.20 g/bhp-hr and
0.14 g/bhp-hr, respectively. These NOX and NMHC standards
will be phased in together between 2007 and 2010, for diesel engines.
The phase-in will be on a percent-of-sales basis: 50 percent from 2007
to 2009 and 100 percent in 2010. This phase-in schedule differs
somewhat from the proposed schedule for reasons explained in Section
III. Gasoline engines will be subject to these standards based on a
phase-in requiring 50 percent compliance in the 2008 model year and 100
percent compliance in the 2009 model year. This phase-in schedule also
differs from that proposed for reasons explained in Section III. In
addition, we are finalizing our proposal to include turbocharged
diesels in the existing crankcase emissions prohibition, effective in
2007.
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\1\ Note that throughout this preamble we refer to diesel and
gasoline vehicles and engines. We tend to use those terms given the
preponderance of vehicles using diesel fuel or gasoline fuel in the
U.S. heavy-duty highway market. However, when we refer to a diesel
engine, we generally mean any engine using the diesel cycle. When we
refer to a gasoline engine or vehicle, we generally mean any Otto-
cycle vehicle or engine. Therefore, the emission standards discussed
throughout this preamble apply equally to engines and vehicles
fueled by alternative fuels, unless otherwise specified in the
regulatory text accompanying today's rule.
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Standards for complete HDVs will be implemented on the same
schedule as for gasoline engine standards. For certification of
complete vehicles between 8500 and 10,000 pounds gross vehicle weight
rating (GVWR), the standards are 0.2 grams per mile (g/mi) for
NOX, 0.02 g/mi for PM, 0.195 g/mi for NMHC, and 0.032 g/mi
for formaldehyde.2 For vehicles between

[[Page 5006]]

10,000 and 14,000 pounds, the standards are 0.4 g/mi for
NOX, 0.02 g/mi for PM, 0.230 g/mi for NMHC, and 0.040 g/mi
for formaldehyde. These standards levels are roughly comparable to the
engine-based standards in these size ranges. Note that these standards
will not apply to vehicles above 8500 pounds that we classify as
medium-duty passenger vehicles as part of our Tier 2 program.
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\2\ Vehicle weight ratings in this rule refer to GVWR (the curb
weight of the vehicle plus its maximum recommended load of
passengers and cargo) unless noted otherwise.
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Finally, we are adopting new evaporative emissions standards for
heavy-duty engines and vehicles, effective on the same schedule as the
gasoline engine and vehicle exhaust emission standards. The new
standards for 8500 to 14,000 pound vehicles are 1.4 and 1.75 grams per
test for the 3-day diurnal and supplemental 2-day diurnal tests,
respectively. Standards levels of 1.9 and 2.3 grams per test will apply
for vehicles over 14,000 pounds. These standards represent more than a
50 percent reduction in the numerical standards as they exist today.
The program includes flexibility provisions to facilitate the
transition to the new standards and to encourage the early introduction
of clean technologies, and adjustments to various testing and
compliance requirements to address differences between the new
technologies and existing engine-based technologies. These provisions
are described in Sections III and VI.
2. Fuel Quality Standards
This rule specifies that, beginning June 1, 2006, refiners must
begin producing highway diesel fuel that meets a maximum sulfur
standard of 15 parts per million (ppm). All 2007 and later model year
diesel-fueled vehicles must be refueled with this new low sulfur diesel
fuel. This sulfur standard is based on our assessment of the impact of
sulfur on advanced exhaust emission control technologies, and a
corresponding assessment of the feasibility of low sulfur fuel
production and distribution.
Today's program includes a combination of flexibilities available
to refiners to ensure a smooth transition to low sulfur highway diesel
fuel. First, refiners can take advantage of a temporary compliance
option, including an averaging, banking and trading component,
beginning in June 2006 and lasting through 2009, with credit given for
early compliance before June 2006. Under this temporary compliance
option, up to 20 percent of highway diesel fuel may continue to be
produced at the existing 500 ppm sulfur maximum standard. Highway
diesel fuel marketed as complying with the 500 ppm sulfur standard must
be segregated from 15 ppm fuel in the distribution system, and may only
be used in pre-2007 model year heavy-duty vehicles. Second, we are
providing additional hardship provisions for small refiners to minimize
their economic burden in complying with the 15 ppm sulfur standard.
Third, we are providing additional flexibility to refiners subject to
the Geographic Phase-in Area (GPA) provisions of the Tier 2 gasoline
sulfur program, which will allow them the option of staggering their
gasoline and diesel investments. Finally, we are adopting a general
hardship provision for which any refiner may apply on a case-by-case
basis under certain conditions. These hardship provisions, coupled with
the temporary compliance option, will provide a ``safety valve''
allowing up to 25 percent of highway diesel fuel produced to remain at
500 ppm for these transitional years to minimize any potential for
highway diesel fuel supply problems.
In addition, today's program includes unique provisions for
implementing the low sulfur diesel fuel program in the State of Alaska,
given that it is exempt from the current 500 ppm standard. Certain U.S.
territories are excluded from both the new engine standards and highway
diesel fuel standards.
The compliance provisions for ensuring diesel fuel quality are
essentially consistent with those that have been in effect since 1993
under the existing 500 ppm sulfur standard (55 FR 34120, August 21,
1990). Additional compliance provisions have been established primarily
during the transition years of the program to verify refiners'
compliance with the temporary compliance option to ensure the two
grades of highway diesel fuel remain segregated, and to discourage
misfueling of model year 2007 and later diesel vehicles.

B. Why is EPA Taking This Action?

1. Heavy-Duty Vehicles Contribute to Serious Air Pollution Problems
As discussed in detail in Section II, emissions from heavy-duty
vehicles contribute greatly to a number of serious air pollution
problems, and would have continued to do so into the future absent
further controls to reduce these emissions. First, heavy-duty vehicles
contribute to the health and welfare effects of ozone, PM,
NOX, SOX, and volatile organic compounds (VOCs),
including toxic compounds such as formaldehyde. These adverse effects
include premature mortality, aggravation of respiratory and
cardiovascular disease (as indicated by increased hospital admissions
and emergency room visits, school absences, work loss days, and
restricted activity days), changes in lung function and increased
respiratory symptoms, changes to lung tissues and structures, altered
respiratory defense mechanisms, chronic bronchitis, and decreased lung
function. Ozone also causes crop and forestry losses, and PM causes
damage to materials and soiling of commonly used building materials and
culturally important items such as statues and works of art. Second,
NOX, SOX and PM contribute to substantial
visibility impairment in many parts of the U.S. Third, NOX
emissions from heavy-duty trucks contribute to the acidification,
nitrification and eutrophication of water bodies. Fourth, the Agency
has concluded, and the Clean Air Scientific Advisory Committee has
approved in public session, that diesel exhaust is likely to be
carcinogenic to humans.
Millions of Americans live in areas with unhealthful air quality
that currently endangers public health and welfare. Without emission
reductions from the standards for heavy-duty vehicles, there is a
significant risk that an appreciable number of 45 areas with 128
million people across the country will violate the 1-hour ozone
national ambient air quality standard (NAAQS) during the period when
these standards will take effect. Furthermore, our analysis shows that
PM10 concentrations in 10 areas with a population of 28
million people face a significant risk of exceeding the PM10
NAAQS without significant additional controls between 2007 and 2030.
Under the mandates and authorities in the Clean Air Act, Federal,
state, and local governments are working to bring ozone and particulate
levels into compliance with the 1-hour ozone and PM10 NAAQS
through State Implementation Plan (SIP) attainment and maintenance
plans, and to ensure that future air quality reaches and continues to
achieve these health-based standards. The reductions in this rulemaking
will play a critical part in these important efforts to attain and
maintain the NAAQS. In addition, reductions from this action will also
reduce public health and welfare effects associated with ozone and fine
PM at concentrations that do not constitute a violation of the 1-hour
ozone and PM10 NAAQS.
Emissions from heavy-duty vehicles account for substantial portions
of the country's ambient PM and NOX levels. ( NOX
is a key precursor to ozone formation). By 2007, we estimate that
heavy-duty vehicles will account for 28 percent of mobile source
NOX emissions and 20 percent of mobile source PM emissions.
These proportions are even

[[Page 5007]]

higher in some urban areas, such as in Sacramento, Atlanta, and
Washington, DC, where HDVs contribute over 34 percent of the mobile
source NOX emissions, and in Santa Fe, Los Angeles, and
Hartford, where heavy-duty vehicle PM emissions account for 38, 25 and
30 percent of the mobile source PM emissions inventory, respectively.
Over time, the relative contribution of diesel engines to air quality
problems will go even higher if diesel-equipped light-duty vehicles
become more popular, as is expected by some automobile manufacturers.
The PM and NOX standards for heavy-duty vehicles in this
rule will have a substantial impact on emissions. By 2030,
NOX emissions from heavy-duty vehicles under today's
standards will be reduced by 2.6 million tons, and PM emissions will
decline by about 109,000 tons, dramatically reducing this source of
NOX and PM emissions. Urban areas, which include many poorer
neighborhoods, can be disproportionately impacted by HDV emissions, and
these neighborhoods will thus receive a relatively larger portion of
the benefits expected from new HDV emissions controls.
In addition to its contribution to PM inventories, diesel exhaust
PM is of special concern because it has been implicated in an increased
risk of lung cancer and respiratory disease. The EPA draft Health
Assessment Document for Diesel Exhaust (Draft Assessment) was reviewed
in public session by the Clean Air Scientific Advisory Committee
(CASAC) on October 12-13, 2000.3 The Agency has concluded,
and the CASAC approved at this session, that diesel exhaust is likely
to be carcinogenic to humans. State and local governments, in their
efforts to protect the health of their citizens and comply with
requirements of the Clean Air Act (CAA or ``the Act''), have recognized
the need to achieve major reductions in diesel PM emissions, and have
been seeking Agency action in setting stringent new standards to bring
this about.4
---------------------------------------------------------------------------

\3\ EPA (2000) Review of EPA's Health Assessment Document for
Diesel Exhaust (EPA 600/8-90/057E). Review by the Clean Air
Scientific Advisory Committee (CASAC) December 2000. EPA-SAB-CASAC-
01-003.
\4\ For example, see letter dated July 13, 1999 from John Elston
and Richard Baldwin on behalf of the State and Territorial Air
Pollution Program Administrators and the Association of Local Air
Pollution Control Officials (docket A-99-06, item II-D-78).
---------------------------------------------------------------------------

2. Technology-Based Solutions
Although the air quality problems caused by diesel exhaust are
challenging, we believe they can be resolved through the application of
high-efficiency emissions control technologies. As discussed in detail
in Section III, the development of diesel emissions control technology
has advanced in recent years so that very large emission reductions (in
excess of 90 percent) are possible, especially through the use of
catalytic emission control devices installed in the vehicle's exhaust
system and integrated with the engine controls. These devices are often
referred to as ``exhaust emission control'' or ``aftertreatment''
devices. Exhaust emission control devices, in the form of the well-
known catalytic converter, have been used in gasoline-fueled
automobiles for 25 years, but have had only limited application in
diesel vehicles.
Based on the Clean Air Act requirements discussed in Section I.B.3,
we are setting stringent new emission standards that will result in the
use of these diesel exhaust emission control devices (see Section III).
We are also finalizing changes to diesel fuel quality standards in
order to enable these high-efficiency technologies (Section IV). Heavy-
duty gasoline engines will also be able to reach the significantly
lower emission levels envisioned in this rule by relying on the
transfer of recent technology developments for light-duty applications,
given the recent action taken to reduce sulfur in gasoline (65 FR 6698,
February 10, 2000).
To meet the new standards, application of high-efficiency exhaust
emission controls for both PM and NOX will be needed. High-
efficiency PM exhaust emission control technology has been available
for several years, although engine manufacturers have generally not
needed this technology in order to meet our PM emission standards. This
technology has continued to improve over the years, especially with
respect to durability and robust operation in use. It has also proven
extremely effective in reducing exhaust hydrocarbon emissions.
Thousands of such systems are now in use in fleet programs, especially
in Europe. However, as discussed in detail in Section III, these
systems are very sensitive to sulfur in the fuel. For the technology to
be viable and capable of meeting the standards, we believe that it will
require diesel fuel with sulfur content capped at the 15 ppm level.
Similarly, high-efficiency NOX exhaust emission control
technology will be needed if heavy-duty vehicles are to attain the new
standards. We believe this technology, like the PM technology, is
dependent on the 15 ppm maximum diesel fuel sulfur levels being adopted
in this rule to be feasible and capable of achieving the standards.
Similar high-efficiency NOX exhaust emission control
technology has been quite successful in gasoline direct injection
engines that operate with an exhaust composition fairly similar to
diesel exhaust. However, as discussed in Section III, application of
this technology to diesels has some additional engineering challenges.
In that section we discuss the current status of this technology. We
also discuss the major development issues still to be addressed and the
development steps that can be taken to address these issues. With the
lead time available and the certainty of low-sulfur diesel fuel
established by today's action, the evidence leaves us confident that
the application of this technology to diesels will proceed at a
reasonable rate of progress and will result in systems capable of
achieving the standards.
The need to reduce the sulfur in diesel fuel is driven by the
requirements of the exhaust emission control technology that we project
will be needed to meet the standards. The challenge in accomplishing
the sulfur reduction is driven by the feasibility of needed refinery
modifications, and by the costs of making the modifications and running
the equipment. Today, a number of refiners are acting to provide low
sulfur diesel to some markets. In consideration of the impacts that
sulfur has on the efficiency, reliability, and fuel economy impact of
diesel engine exhaust emission control devices, we believe that
controlling the sulfur content of highway diesel fuel to the 15 ppm
level is necessary and feasible, and, in the context of this rule's
overall program, cost effective.
3. Basis For Action Under the Clean Air Act
Section 202(a)(1) of the Act directs us to establish standards
regulating the emission of any air pollutant from any class or classes
of new motor vehicles or engines that, in the Administrator's judgment,
cause or contribute to air pollution which may reasonably be
anticipated to endanger public health or welfare. Section 202(a)(3)
requires that EPA set standards for heavy-duty trucks that reflect the
greatest degree of emission reduction achievable through the
application of technology which we determine will be available for the
model year to which the standards apply. We are to give appropriate
consideration to cost, energy, and safety factors associated with the
application of such technology. We may revise such technology-based
standards, taking costs into account, on the basis of information
concerning the effects of air pollution from heavy-duty vehicles or
engines and other sources of mobile source related

[[Page 5008]]

pollutants on the public health and welfare. Section 202(a)(3)(C)
requires that promulgated standards apply for no less than three years
and go into effect no less than 4 years after promulgation. This rule
conforms with these statutory requirements.
We believe the evidence provided in Section III and the Regulatory
Impact Analysis (RIA) indicates that the stringent emission standards
finalized today are feasible and reflect the greatest degree of
emission reduction achievable in the model years to which they apply.
We have given appropriate consideration to costs in choosing these
standards. Our review of the costs and cost-effectiveness of these
standards indicate that they will be reasonable and comparable to the
cost-effectiveness of other emission reduction strategies that have
been required or could be required in the future. We have also reviewed
and given appropriate consideration to the energy factors of this rule
in terms of fuel efficiency and effects on diesel fuel supply,
production, and distribution, as discussed below, as well as any safety
factors associated with these standards.
The information regarding air quality and the contribution of
heavy-duty engines to air pollution in Section II and the RIA provides
strong evidence that emissions from such engines significantly and
adversely impact public health or welfare. First, there is a
significant risk that several areas will fail to attain or maintain
compliance with the NAAQS for 1-hour ozone concentrations or
PM10 concentrations during the period that these new vehicle
and engine standards will be phased into the vehicle population, and
that heavy-duty engines contribute to such concentrations, as well as
to concentrations of other NAAQS-related pollutants. This risk will be
significantly reduced by the standards adopted today; however, the
evidence indicates that some risk remains even after the reductions
achieved by these new controls on heavy-duty vehicles and diesel fuel.
Second, EPA believes that diesel exhaust is likely to be carcinogenic
to humans. The risk associated with exposure to diesel exhaust includes
the particulate and gaseous components. Some of the toxic air
pollutants associated with emissions from heavy-duty vehicles and
engines include benzene, formaldehyde, acetaldehyde, dioxin, acrolein,
and 1,3-butadiene. Third, emissions from heavy-duty engines contribute
to regional haze and impaired visibility across the nation, as well as
acid deposition, POM deposition, eutrophication and nitrification, all
of which are serious environmental welfare problems.
Based on this evidence, EPA believes that, for purposes of section
202(a)(1), emissions of NOX, VOCs, SOx and PM
from heavy-duty trucks can reasonably be anticipated to endanger the
public health or welfare. In addition, this evidence indicates that it
will not be appropriate to modify the technology-based standards
pursuant to section 202(a)(3)(B). EPA believes that it is required
under section 202(a)(3)(A) to set technology-based standards that meet
the criteria of that provision, and is not required to make an
affirmative determination under section 202(a)(1). Instead EPA is
authorized to take air quality into consideration under section
202(a)(3)(B) in deciding whether to modify or not set standard under
section 202(a)(3)(A). In this case, however, EPA believes the evidence
fully supports a determination under section 202(a)(1) to set
standards, and a determination not to modify such standards under
section 202(a)(3)(B).
In addition, there is significant evidence that emissions from
heavy-duty trucks contribute to levels of ozone such that large
segments of the national population are expected to experience
prolonged exposure over several hours at levels that present serious
concern for the public health and welfare. The same is true for
exposure to fine PM. These public health and welfare problems are
expected to occur in many parts of the country, including areas that
are in compliance with the 1-hour ozone and PM10 NAAQS
(PM10 is particulate matter that is 10 microns or smaller).
This evidence is an additional reason why the controls finalized today
are justified and appropriate under the Act. While EPA sees this as
additional support for this action, EPA also believes that the evidence
of air pollution problems summarized above and described in greater
detail elsewhere is an adequate justification for this rule independent
of concern over prolonged exposure to ozone and fine PM levels.
Section 211(c) of the CAA allows us to regulate fuels where
emission products of the fuel either: (1) Cause or contribute to air
pollution that reasonably may be anticipated to endanger public health
or welfare, or (2) will impair to a significant degree the performance
of any emission control device or system which is in general use, or
which the Administrator finds has been developed to a point where in a
reasonable time it will be in general use were such a regulation to be
promulgated. This rule meets each of these criteria. The discussion of
the first test is substantially the same as the above discussion for
the heavy-duty engine standards, because SOx and sulfate PM
emissions from heavy-duty diesel vehicles are due to sulfur in diesel
fuel. The substantial adverse effect of high diesel sulfur levels on
diesel control devices or systems expected to be used to meet the
heavy-duty standards is discussed in depth in Section III.F and in the
RIA. In addition, our authority under section 211(c) is discussed in
more detail in Appendix A to the RIA.

C. Putting This Rule In Perspective

There are several helpful perspectives to establish in
understanding the context for this rule: the growing popularity of
diesel engines, past progress and new developments in diesel emissions
control, Tier 2 light-duty emission standards and other related EPA
initiatives (besides the above-discussed rulemaking for highway heavy-
duty engine emission standards in 2004), and recent actions and plans
to control diesel emissions by the States and in other countries.
1. Diesel Popularity
The diesel engine is increasingly becoming a vital workhorse in the
United States, moving much of the nation's freight, and carrying out
much of its farm, construction, and other labor. Diesel engine sales
have grown significantly over the last decade, so that now about a
million new diesel engines are put to work in the U.S. every year.
Unfortunately, these diesel engines emit large quantities of harmful
pollutants annually.
Furthermore, although diesel emissions in this country come mostly
from heavy-duty trucks and nonroad equipment, an additional source may
grow out of auto manufacturers' plans to greatly increase the sales of
diesel-powered light-duty vehicles (LDVs) and especially of light-duty
trucks (LDTs), a category that includes the fast-selling sport-utility
vehicles, minivans, and pickup trucks. These plans reflect the
continuation of an ongoing dieselization trend, a trend recently most
evident in the growing popularity of diesel-powered light heavy-duty
trucks (8500 to 19,500 pounds). Diesel market penetration is working
its way from larger to smaller highway applications and to a broader
array of nonroad equipment applications. Finally, especially in Europe
where diesels have already gained a broad consumer acceptance, the
diesel engine is increasingly viewed as an attractive technology option
for reducing emissions of gases that contribute to

[[Page 5009]]

global warming, because it has greater operating efficiency than a
gasoline engine.
2. Past Progress and New Developments
Since the 1970's, highway diesel engine designers have employed
numerous strategies to meet our emissions standards, beginning with
smoke controls, and focusing in the 1990's on increasingly stringent
NOX, hydrocarbon, and PM standards. These strategies have
generally focused on reducing engine-out emissions and not on exhaust
emission controls, although relatively low-efficiency oxidation
catalysts have been applied in some designs to reduce PM, with the
recognition that their effectiveness is limited by sulfur in the fuel.
On the fuel side, we set quality standards that provided emissions
benefits by limiting the amount of sulfur and aromatics in highway
diesel fuel beginning in 1993 (55 FR 34120, August 21, 1990). Our most
recent round of standard setting for heavy-duty highway diesels
occurred in 1997 (62 FR 54693, October 21, 1997), effective with the
2004 model year. These standards were recently reviewed in a final
rulemaking (65 FR 59896, October 6, 2000). These actions will result in
engines that emit only a fraction of the NOX, hydrocarbons,
and PM produced by engines manufactured just a decade ago. We consider
this an important first phase of our current initiative to reconcile
the diesel engine with the environment.
Nevertheless, certain characteristics inherent in the way diesel
fuel combustion occurs have prevented achievement of emission levels
comparable to those of today's gasoline-fueled vehicles. Although
diesel engines provide advantages in terms of fuel economy, durability,
and evaporative emissions, and have inherently low exhaust emissions of
hydrocarbons and carbon monoxide, controlling NOX emissions
is a greater challenge for diesel engines than for gasoline engines,
primarily because of the ineffectiveness of three-way catalysis in the
oxygen-rich and relatively cool diesel exhaust environment. Similarly,
PM emissions, which are inherently low for properly operating gasoline
engines, are more difficult to control in diesel engines, because the
diesel combustion process tends to form soot particles. The challenge
is somewhat complicated by the fact that historical diesel
NOX control approaches tend to increase PM, and vice versa,
but both are harmful pollutants that need to be controlled.
Considering the air quality impacts of diesel engines and the
potential for growth of diesels in the lighter-duty portion of the
market, it is imperative that progress in diesel emissions control
continue. Significant progress has already been made in the design of
exhaust emission control devices for diesel applications, driven in
part by the challenge presented by the stringent Tier 2 standards for
light-duty vehicles. As discussed in detail in Section III, new exhaust
emission control technologies for NOX, PM, and hydrocarbon
reduction will allow a major advancement in diesel emissions control of
a magnitude comparable to that ushered in by the automotive catalytic
converter in the 1970's. However, changes in diesel fuel quality will
be needed to enable these high-efficiency exhaust emission control
devices.
3. Tier 2 Emissions Standards
Auto manufacturers' design plans for new light-duty diesel vehicle
models will be greatly affected by our recent adoption of stringent new
emission standards for light-duty highway vehicles (referred to as
``Tier 2'' standards) that will phase in between 2004 and 2009. These
Tier 2 standards will require significant improvements in electronic
engine controls and catalysts on gasoline vehicles. We anticipate that
these advances will be transferred over to heavy-duty gasoline vehicles
in meeting the standards finalized in this rule. The Tier 2
NOX and PM standards, that apply equally to gasoline and
diesel vehicles, will also require the use of high-efficiency emission
control technologies on light-duty diesel vehicles. The low sulfur
highway diesel fuel brought about by this rule will make it possible
for designers to employ these high-efficiency exhaust emission control
technologies in these light-duty applications. The timing of the fuel
change provides for the use of these devices in time to satisfy Tier 2
phase-in requirements.
The Tier 2 program phases in interim and final standards over a
number of years, providing manufacturers the option of delaying some of
their production of final Tier 2 designs until later in the phase-in.
For vehicles up to 6000 lbs GVWR (LDVs) and light light-duty trucks
(LLDTs)), the interim standards begin in 2004 and phase out by 2007, as
they are replaced by the final Tier 2 standards. For vehicles between
6000 and 8500 lbs ( heavy light-duty trucks (HLDTs)), the interim
standards begin in 2004 and phase out by 2009 as they are replaced by
the final Tier 2 standards. A new category of vehicles between 8,500
and 10,000 lbs, medium-duty passenger vehicles (MDPVs), will follow the
same phase-in schedule as HLDTs.
Our assessment in the Tier 2 final rule is that the interim
standards are feasible for diesel vehicles without a need for fuel
quality changes. Manufacturers can take advantage of the flexibilities
provided in the Tier 2 program to delay the need for light-duty diesels
to meet the final Tier 2 levels until late in the phase-in period (as
late as 2007 for LDVs and LLDTs, and 2009 for HLDTs and MDPVs).
However, low sulfur fuel is expected to be needed for diesel vehicles
designed to meet the final NOX and PM standards, because
these vehicles are likely to employ light-duty versions of the sulfur-
sensitive exhaust emission control technologies discussed in Section
III. The gasoline quality changes and light-duty gasoline engine
developments that will result from the Tier 2 rule will also help make
it feasible for heavy-duty gasoline engines to meet the standards in
this rule.
4. Mobile Source Air Toxics Rulemaking
Passenger cars, on-highway trucks, and nonroad equipment emit
hundreds of different compounds and elements. Several of these are
considered to be known, likely, or possible human carcinogens. These
include diesel exhaust, plus several VOCs such as acetaldehyde,
benzene, 1,3-butadiene, formaldehyde, and acrolein. Trace metals may
also be present in heavy-duty diesel engine emissions, resulting from
metals in fuels and lubricating oil, and from engine wear. Several of
these metals have carcinogenic and mutagenic effects.
Important reductions in these and other mobile source air toxics
have occurred under existing programs established under Clean Air Act
Sections 202(a) (on-highway engine requirements), 211 (the fuel
requirements), and 213 (nonroad engine requirements). Although these
programs are primarily designed for control of criteria pollutants,
especially ozone and PM10, they also achieve important
reductions in diesel PM and gaseous air toxics through VOC and
hydrocarbon controls.
In addition to these programs, Section 202(l)(2) of the Act directs
us to consider additional controls to reduce emissions of hazardous air
pollutants from motor vehicles, their fuels, or both. Those standards
are to reflect the greatest degree of emission reduction achievable
through the application of technology which will be available, taking
into account existing standards, costs, noise, energy, and safety
factors. We published a proposed rule on mobile source air toxics on
August 4,

[[Page 5010]]

2000 (65 FR 48058). This MSAT final rule was signed on December 20,
2000. Interested parties should refer to the final rule if interested
in the ultimate form of the regulation.
The mobile source air toxics (MSATs) rule consists of four parts.
First, we identify a list of 21 MSATs that are known to be emitted from
motor vehicles or their fuels and are considered by the Agency to pose
potential adverse human health risks. Diesel exhaust is included on
this MSAT list because, as discussed in Section II, human
epidemiological studies have suggested that diesel exhaust is
associated with increased risk of adverse respiratory effects and lung
cancer. Second, the MSAT rule considers the contribution of mobile
sources to the nation's air toxics inventory and evaluates the toxics
benefits of existing mobile source emission control programs. The
benefits of the program as proposed are included in this analysis.
Third, the MSAT final rule considers whether additional controls are
appropriate at this time, given technological feasibility, cost, and
the other criteria specified in the Act. The final rule includes a
toxics performance standard applicable to reformulated gasoline and
anti-dumping standards that apply to conventional gasoline. With regard
to additional vehicle-based controls, we proposed that it is not
appropriate at this time to set more stringent standards than the
technology forcing standards found in this rule and our recently
adopted Tier 2 rulemaking. Finally, because of our concern about the
potential future health impacts of exposure to the public of air toxics
from the remaining emissions from mobile sources in the future, we
continue our toxics-related research activities and to conduct a future
rulemaking to evaluate whether, based on the additional data,
additional mobile source air toxics controls should be adopted. This
rulemaking would be completed no later than 2004.
EPA also intends to rely on today's rule to satisfy in part its
obligations under section 202(l) of the Clean Air Act. In the mobile
source air toxics NPRM, the Agency proposed a list of mobile source air
toxics, including diesel exhaust, as well as a number of specific
constituents of heavy-duty vehicle exhaust (gasoline and
diesel).5 The emissions standards established in today's
action result in the greatest achievable reductions of diesel PM and
heavy-duty vehicle NMHC. The Agency is scheduled to finalize the mobile
source air toxics rulemaking on or before December 20, 2000.
---------------------------------------------------------------------------

\5\ 65 FR 48058, August 4, 2000.
---------------------------------------------------------------------------

5. Nonroad Engine Standards and Fuel
Although this rule covers only highway diesel engines and fuel, it
is clear that potential requirements for nonroad diesel engines and
fuel are related. It is expected that nonroad diesel fuel quality,
currently unregulated, may need to be controlled in the future in order
to reduce the large contribution of nonroad engines to NOX
and PM inventories. Refiners, fuel distributors, states, environmental
organizations, and others have asked that we provide as much
information as possible about the future specifications for both types
of fuel as early as possible.
We do plan to give further consideration to additional control of
nonroad engine emissions. As discussed below in Section VIII, an
effective control program for these engines requires the resolution of
several major issues relating to engine emission control technologies
and how they are affected by fuel sulfur content. The many issues
connected with any rulemaking for nonroad engines and fuel warrant
serious attention, and we believe it is premature for us to take any
action on this initiative in this rule. We plan to initiate action in
the future to formulate proposals that would address both nonroad
diesel fuel and engines.
6. State Initiatives
The California Air Resources Board (ARB) and local air quality
management districts within California are also pursuing measures to
better control diesel emissions. Key among these efforts is work
resulting from the Board's designation of particulate emissions from
diesel-fueled engines as a toxic air contaminant (TAC) on August 27,
1998. TACs are air pollutants that may cause or contribute to an
increase in death or serious illness or may pose a present or future
hazard to human health. The TAC designation was based on research
studies showing that emissions from diesel-fueled engines may cause
cancer in animals and humans, and that workers exposed to higher levels
of emissions from diesel-fueled engines are more likely to develop lung
cancer.
In September 2000 the ARB approved a Diesel Risk Reduction Plan
developed by its staff following an extensive public
process.6 This plan includes several California measures
related to highway diesel vehicles, including the major elements of the
program we are establishing on a nationwide basis in this final rule.
Because truck travel from other states has a large effect on
California's air quality, the plan and the Board's resolution further
encourages the EPA adopt this nationwide program, as well as other
diesel-related emissions reduction programs.
---------------------------------------------------------------------------

\6\ State of California Air Resources Board Resolution 00-30,
September 28, 2000.
---------------------------------------------------------------------------

The ARB has also adopted stringent new emission requirements for
urban transit buses and is considering similar requirements for school
buses.7 This program is aimed at encouraging the use of
clean alternative fuels and high-efficiency diesel emission control
technologies. Their program includes requirements for zero-emissions
buses, fleet average NOX levels, and retrofits for PM
control, as well as model year 2007 NOX and PM standards
levels of 0.2 and 0.01 g/bhp-hr, respectively (equal to the levels
finalized in this rule). It also requires that all diesel fuel used by
transit agencies after July 1, 2002 must meet a cap of 15 ppm sulfur.
This is a much earlier schedule than that finalized in this rule, to
support the ARB's proposed transit bus fleet program.
---------------------------------------------------------------------------

\7\ ``Notice of Public Hearing To Consider the Adoption of a
Public Transit Bus Fleet Rule and Emission Standards For New Urban
Buses'', California ARB, November 30, 1999, and ARB Resolution 00-2,
dated February 24, 2000.
---------------------------------------------------------------------------

Other states, most notably Texas, have taken steps toward adopting
programs for cleaner diesel fuel and cleaner diesel engines. On
December 6, 2000, the Texas Natural Resource Conservation Commission
adopted a program that, among other things, would require the capping
of diesel fuel sulfur levels in many counties to 15 ppm by June
2006.8 This proposal exemplifies the importance that states
with air quality problems have attached to clean diesel fuel, and
specifically to the 15 ppm maximum sulfur requirement in 2006 being set
in this rule
---------------------------------------------------------------------------

\8\ Title 30, Texas Administrative Code, Chapter 114, Subchapter
H, Division 2. Also see Texas Natural Resource Conservation
Commission website www.tnrcc.state.tx.us..
---------------------------------------------------------------------------

7. Retrofit Programs
Many States facing air quality improvement challenges have
expressed strong interest in programs that will reduce emissions from
existing highway and nonroad diesel engines through the retrofitting of
these engines with improved emission control devices. The urban transit
bus program adopted by the California ARB includes such a retrofit
requirement as one of its major components (see Section I.C.6). In
March 2000 we announced our own Diesel Retrofit Initiative to support
and

[[Page 5011]]

encourage fleet operators, air quality planners, and retrofit
manufacturers in creating effective retrofit programs. These programs
are appealing because the slow turnover of the diesel fleet to the new
low-emitting engines makes it difficult to achieve near-term air
quality goals through new engine programs alone. Some of the exhaust
emission control technologies discussed in this rule are especially
appealing for use in retrofits because they can be fitted to an
existing vehicle as add-on devices without major engine modifications,
although some of the more sophisticated systems that require careful
control of engine parameters may be more challenging.
Because of the uncertainty at this time in how and when such
programs may be implemented, our analysis for today's rule does not
calculate any benefits from them. Nevertheless, we believe that this
program can enable the viability of these retrofit technologies. We
expect that large emission benefits from the existing fleet could be
realized as a result of the fuel changes we are finalizing here,
combined with retrofit versions of the technologies that will be
developed in response to the finalized engine standards. These benefits
will be especially important in the early years of the program when new
vehicles standards are just beginning to have an impact, and when
States and local areas need to gain large reductions to attain air
quality goals.
8. Actions In Other Countries
There is substantial activity taking place in many countries
related to the regulation of diesel fuel and engines. The large light-
duty vehicle market share enjoyed by diesels in many European countries
has helped to stir innovation in dealing with diesel emissions
problems. Advanced emissions control technologies are being evaluated
there in the in-use fleet and experience gained from these trials is
helping to inform the diesel emissions control discussion in the U.S.
In addition, several European countries have low sulfur diesel fuel,
with maximum sulfur levels varying from 10 to 50 ppm, and so experience
gained from the use of these fuels, though not completely transferable
to the U.S. situation, also provides valuable experience. European
Union countries will limit sulfur in diesel fuel to 50 ppm by 2005, and
even more aggressive plans are being discussed or implemented. The
United Kingdom made a rapid conversion to 50 ppm maximum sulfur diesel
fuel in 1999 by offering tax incentives. This change occurred with much
smaller refinery investments than had been predicted, and some refinery
production there is actually at levels well below the 50 ppm cap.
Germany is moving forward with plans to introduce a 10 ppm sulfur cap
for diesel fuel by 2003, also via tax incentives, and is attempting to
get the 50 ppm specification that was adopted by the European
Commission revised downward to the 10 ppm cap level. The Commission is
reviewing the implications of moving to this level.
One European country has had extensive experience with the
transition to low sulfur diesel fuel. In the early 1990's, Sweden
decided to take advantage of the environmental benefits of 10 ppm
sulfur/low aromatics fuel by introducing it with a reduction in the
diesel fuel tax. The program has been quite successful, and in excess
of 90 percent of the highway diesel fuel used there is of this 10 ppm
maximum sulfur class.9
---------------------------------------------------------------------------

\9\ Memo from Thomas M. Baines to Docket A-99-06, October 29,
1999, Docket #A-99-06, Item II-G-12.
---------------------------------------------------------------------------

The government of Canada has expressed its intent to harmonize its
fuel regulations with the U.S. fuels standards being adopted
today.10 This would simplify the operation of new-technology
vehicles that cross the U.S-Canada border. However, the success of the
U.S. program does not depend on harmonized diesel fuel standards, and
Section VI.H discusses how differences between the future fuel
specifications in the U.S. and those in Canada and Mexico may be
accommodated.
---------------------------------------------------------------------------

\10\ ``Process Begins to Develop Long term Agenda to Reduce Air
Pollution from Vehicles and Fuels'', Environment Canada press
release, May 26, 2000.
---------------------------------------------------------------------------

II. The Air Quality Need and Projected Benefits

A. Overview

Heavy-duty vehicle emissions contribute to air pollution with a
wide range of adverse health and welfare impacts. Emissions of VOC, CO,
NOX, SOx, and PM from HD vehicles contribute a
substantial percentage of the precursors or direct components of
ambient concentrations of ozone, PM, sulfur and nitrogen compounds,
aldehydes, and substances known or considered likely to be carcinogens.
Emissions of VOCs include some specific substances known or suspected
to cause cancer. Of particular concern is human epidemiological
evidence linking diesel exhaust to an increased risk of lung cancer,
and the Agency is also concerned about the noncancer health effects of
diesel exhaust We have finalized on December 20, 2000 a rule which
lists diesel particulate matter and diesel exhaust organic gases as a
mobile source air toxic under section 202(l) of the Clean Air Act, and
the particulate matter standard finalized today reflects the greatest
degree of emissions reductions achievable under section 202(l) for on-
highway heavy-duty vehicle PM emissions. Heavy-duty vehicle emissions
also cause adverse environmental effects including visibility
reductions, acid rain, nitrification and eutrophication of water
bodies.
Emissions from heavy-duty vehicles, which are predominantly diesel-
powered, account for substantial portions of the country's ambient PM
and ground-level ozone levels. By 2007, we estimate that heavy-duty
vehicles will account for 28 percent of mobile source NOX
emissions (including highway and non-road), and 20 percent of mobile
source PM emissions. These proportions are even higher in some urban
areas, such as Atlanta and Los Angeles. Urban areas, which include many
poorer neighborhoods, can be disproportionately impacted by HDV
emissions because of heavy traffic in and out of densely populated
urban areas.
The Agency developed new emissions inventories and conducted new
air quality modeling for this rule to determine the risk of exposure to
unhealthy ambient concentrations of ozone and particulate matter in
2007, 2020 and 2030. This analysis, supplemented with local air quality
modeling and other information on emissions and air quality trends,
indicates that an appreciable number of the 45 areas with a total
population of 128 million people face a significant risk of violating
the 1-hour ozone standard between 2007 and 2030. Ten PM10
nonattainment areas with 28 million people face a significant risk of
experiencing particulate matter levels that violate the PM10
standard during the same period.
Under the mandates and authorities in the Clean Air Act, federal,
state, and local governments are working to bring ozone and particulate
levels into compliance with the 1-hour ozone and PM10 NAAQS
through SIP attainment plans. Areas that reach attainment without
reductions from this rule are likely to need additional reductions to
ensure that future air quality continues to achieve ozone and PM
standards, and areas that seek redesignation to attainment may use the
reductions from this rule in future maintenance plans.
The heavy-duty vehicle and engine emission standards, along with
the diesel fuel sulfur standard finalized today, will have a dramatic
impact in

[[Page 5012]]

reducing the large contribution of HDVs to air pollution. These
standards will result in substantial benefits to public health and
welfare through significant annual reductions in emissions of
NOX, PM, NMHC, carbon monoxide, sulfur dioxide, and air
toxics. For example, we project a 1.8 million ton reduction in
NOX emissions from HD vehicles in 2020, which will increase
to 2.6 million tons in 2030 when the current HD vehicle fleet is
completely replaced with newer HD vehicles that comply with these
emission standards. When coupled with the emission reductions projected
to result from the Phase 1 (model year 2004) HDV standards, the
emission reductions from heavy-duty vehicles are projected to be as
large as the substantial reductions the Agency expects from light-duty
vehicles as a result of its recently promulgated Tier 2 rulemaking.
In sum, the Agency's air quality modeling and other evidence
demonstrates that ambient concentrations of ozone, particulate matter,
sulfur and nitrogen compounds, VOCs, air toxics, CO and diesel exhaust
are anticipated to endanger public health, welfare and the environment
in the time period between 2007 and 2030. Emission reductions expected
from today's action are predicted to lessen future ambient
concentrations of ozone and particulate matter and associated adverse
public health and welfare effects.

B. Public Health and Welfare Concerns

1. Health and Welfare Concerns Raised During Public Hearings
The Agency received a significant number of comments on this
section during the public hearings and in written comments from
interested parties. Comments are addressed in this section as well as
in the Response to Comment document that accompanies this action.
Throughout the five public hearings held around the country on the
proposed heavy-duty engine and diesel fuel rule, the Agency received
strong public support at each venue for increasing the stringency of
heavy-duty truck and bus emission standards, and for further controls
on sulfur in diesel fuel, in order to enable the necessary exhaust
emission control. In addition to the 55,000 comments received from
citizens in support of the Agency proposal to clean diesel fuel by mid-
2006 and reduce emissions from diesel engines in 2007, we received
8,500 comments from citizens urging the Agency to act prior to 2007.
Public officials and representatives of environmental, public
health, or community-based organizations testified regularly about the
link between public health ailments, such as asthma and lung cancer,
and air pollution caused by diesel exhaust and particulate matter. In
different ways, many noted that the impact of diesel soot is compounded
by the fact that it is discharged at street level where people live and
breathe. A regular complaint was the close proximity of bus depots,
transfer terminals, and heavily-trafficked roadways to homes and
apartment buildings, and in particular, to hospitals, playgrounds and
schools. A common theme revolved around the notion that since asthma is
an incurable disease, it was of utmost importance to help reduce the
severity and frequency of attacks by reducing environmental triggers
such as ozone, particulate matter and diesel exhaust.
Major industries represented during these public hearings were the
heavy-duty vehicle engine manufacturers, the oil industry, and the
commercial truckers. While each had a different perspective, most
supported the underlying intent of the proposal to improve public
health and welfare, and some also supported the specific requirements
as proposed. For those who objected to the proposal, the main thrust of
their concerns related to the stringency and public health necessity of
the new standards and the diesel fuel sulfur requirement. Largely in
their written comments, these industries raised questions about the
need for additional reductions in order to meet existing ozone and PM
national ambient air quality standards and took exception with the
Agency's characterization of diesel exhaust as a human carcinogen at
environmental levels of exposure. Some industry commenters also
challenged the Agency's reliance on public welfare and environmental
effects such as visibility impairment and eutrophication of water
bodies because the Agency had insufficiently quantified the benefits
that would result from new standards on heavy-duty vehicles and diesel
fuel.
The following subsections present the available information on the
air pollution situation that is likely to exist without this rule for
each ambient pollutant. We also present information on the improvement
that is expected to result from this rule.
2. Ozone and Its Precursors
a. Health and Welfare Effects From Short-Term Exposures to Ozone
NOX and VOC are precursors in the photochemical reaction
which forms tropospheric ozone. A large body of evidence shows that
ozone can cause harmful respiratory effects including chest pain,
coughing, and shortness of breath, which affect people with compromised
respiratory systems most severely. When inhaled, ozone can cause acute
respiratory problems; aggravate asthma; cause significant temporary
decreases in lung function of 15 to over 20 percent in some healthy
adults; cause inflammation of lung tissue; produce changes in lung
tissue and structure; may increase hospital admissions and emergency
room visits; and impair the body's immune system defenses, making
people more susceptible to respiratory illnesses. Children and outdoor
workers are likely to be exposed to elevated ambient levels of ozone
during exercise and, therefore, are at greater risk of experiencing
adverse health effects. Beyond its human health effects, ozone has been
shown to injure plants, which has the effect of reducing crop yields
and reducing productivity in forest ecosystems.
There is strong and convincing evidence that exposure to ozone is
associated with exacerbation of asthma-related symptoms. Increases in
ozone concentrations in the air have been associated with increases in
hospitalization for respiratory causes for individuals with asthma,
worsening of symptoms, decrements in lung function and increased
medication use. Studies have also indicated that exposure to
particulate matter can be associated with altered lung function and
increased respiratory symptoms, and asthmatic children are considered
to be particularly sensitive to these effects. In addition, exposures
to particulate matter or ozone have been shown to have a priming effect
for responsiveness to allergens, with the pollutant exposure leading to
heightened responses to allergens among allergic asthmatics. It is not
believed, based on the current evidence, that exposure to outdoor
pollutants such as ozone or particulate matter is a cause of asthma.
Asthma is one of the most common and costly diseases in the United
States. According to the President's Task Force on Environmental Health
Risks and Safety Risks to Children, America is in the midst of an
asthma epidemic.11

[[Page 5013]]

Since 1980, the number of asthma sufferers in the United States has
more than doubled from 6.7 million to 17.3 million in
1998.12 Today, more than 5 percent of the US population has
asthma. On average, 15 people died every day from asthma in 1995, and
the death rate has nearly tripled since 1975. In 1998, the cost of
asthma to the U.S. economy was estimated to be $11.3 billion, with
hospitalizations accounting for the single largest portion of the
cost.13 A recent report by the Pew Environmental Health
Commission at Johns Hopkins School of Public Health estimates that by
2010, 22 million Americans will suffer from asthma, or one in 14
Americans and one in every five families.14 At present,
asthma cannot be cured, only controlled.
---------------------------------------------------------------------------

\11\ Asthma and the Environment: A Strategy to Protect Children,
President's Task Force on Environmental Health Risks and Safety
Risks to Children, January 28, 1999, Revised May, 2000.
\12\ Asthma Prevention Program of the National Center for
Environmental Health, Centers for Disease Control and Prevention,
``At-A-Glance, 1999; Centers for Disease Control and Prevention,
CDC, Surveillance for Asthma--United States, 1960-1995,'' MMWR 47
(No. SS-1) (April 1998).
\13\ Asthma Statistics, National Institutes of Health, National,
Heart, Lung, and Blood Institute, January, 1999.
\14\ Attack Asthma: Why America Needs A Public Health Defense
System to Battle Environmental Threats, Pew Environmental Health
Commissions at the Johns Hopkins School of Public Health, June,
2000.
---------------------------------------------------------------------------

To address this growing public health problem, the President's Task
Force on Environmental Health Risks and Safety Risks to Children ranked
asthma as its highest priority. The President's Task Force created and
charged the Asthma Priority Area Workgroup, co-chaired by EPA and the
Department of Health and Human Services, with reviewing current Federal
efforts to address the issue, and to make recommendations. In May,
2000, the Task Force issued a strategy that focused on developing a
greater understanding of the role environmental factors associated with
the onset of asthma; and triggers of asthma. The report found that
``children with asthma have long been recognized as particularly
sensitive to outdoor air pollution,'' The report noted that ``25
percent of children in America live in areas that regularly exceed EPA
limits for ozone.'' The first guiding principle was to focus efforts to
``eliminate the disproportionate impact of asthma in minority
populations and those living in poverty.'' Testimony received during
the Agency's five public hearings on this rule contained numerous
references and detailed personal accounts as to the severe and
sometimes fatal impact of asthma on the lives of American citizens.
b. Current and Future Nonattainment Status With the 1-Hour Ozone NAAQS
Today, ground level ozone remains a pervasive pollution problem in
the United States. As of July, 2000, 102 million people (1999 census)
lived in 31 metropolitan areas designated nonattainment under the 1-
hour ozone NAAQS.15 This is a sharp decline from the 101
nonattainment areas originally identified under the Clean Air Act
Amendments of 1990, but elevated ozone concentrations remain a serious
public health concern throughout the nation.
---------------------------------------------------------------------------

\15\ Memorandum to Air Docket, September 18, 2000. Information
on ozone nonattainment areas and populations as of July 31, 2000
from US EPA website www.epa.gov/airs/nonattn.html, USA Air Quality
Nonattainment Areas, Office of Air Quality Planning and Standards.
---------------------------------------------------------------------------

Over the last decade, declines in ozone levels were found mostly in
urban areas, where emissions are heavily influenced by controls on
mobile sources and their fuels.16 Twenty-three metropolitan
areas have realized a decline in ozone levels since 1989, but at the
same time, ozone levels in 11 metropolitan areas with 7 million people
have increased.17 Regionally, California and the Northeast
have recorded significant reductions in peak ozone levels, while four
other regions (the Mid-Atlantic, the Southeast, the Central and Pacific
Northwest) have seen ozone levels increase.
---------------------------------------------------------------------------

\16\ National Emissions Trends database.
\17\ National Air Quality and Emissions Trends Report, 1998,
March, 2000, at 28.
---------------------------------------------------------------------------

The highest ambient concentrations are currently found in suburban
areas, consistent with downwind transport of emissions from urban
centers. Concentrations in rural areas have risen to the levels
previously found only in cities. Over the last decade, ozone levels at
17 of our National Parks have increased, and in 1998, ozone levels in
two parks were 30 to 40 percent higher than the ozone NAAQS.
i. Results of Photochemical Ozone Modeling and Analysis of Emissions
Inventories
In conjunction with this rulemaking, the Agency performed ozone air
quality modeling for nearly the entire Eastern U.S covering
metropolitan areas from Texas to the Northeast.18 This ozone
air quality modeling was based upon the same modeling system as was
used in the Tier 2 air quality analysis, with the addition of updated
inventory estimates for 2007 and 2030.19 This modeling
supports the conclusion that there is a broad set of areas with
predicted ozone concentrations in 2007 and 2030 at or above 0.125 ppm,
in the baseline scenarios without additional emission reductions. EPA
established the 1-hour standard at 0.12 parts per million (ppm) daily
maximum 1-hour average concentration not to be exceeded more than once
per year on average. Compliance with the 1-hour standard is judged on
the basis of the most recent three years of ambient air quality
monitoring data.
---------------------------------------------------------------------------

\18\ EPA also performed ozone air quality modeling for the
western United States but, as described further in the air quality
technical support document, model predictions were well below
corresponding ambient concentrations. Because of poor model
performance for this region of the country, the results of western
ozone modeling were not relied on for this rule.
\19\ Consistent with a commitment expressed in the proposal, the
Agency released the emissions inventory inputs for, and a
description of, ozone modeling into the public record (docket number
A-99-06), and also onto a website developed expressly for this
purpose, on a continuous basis as they were developed. Further
discussion of this modeling, including evaluations of model
performance relative to predicted future air quality, is provided in
the air quality modeling Technical Support Document (TSD).
---------------------------------------------------------------------------

We have compared and supplemented our own ozone modeling with other
modeling studies, submitted to us as state implementation plan (SIP)
revisions, or brought to our attention through our consultations with
states on SIP revisions that are in development. The ozone modeling in
the SIP revisions has the advantage of using emission inventories that
are more specific to the area being modeled, and of using
meteorological conditions selected specifically for each area. Also,
the SIP revisions included other evidence and analysis, such as
analysis of air quality and emissions trends, observation-based models
that make use of data on concentrations of ozone precursors,
alternative rollback analyses, and information on the responsiveness of
the air quality model. For some areas, we decided that the predictions
of 1-hour ozone exceedances from our modeling were less reliable than
conclusions that could be drawn from this additional evidence and
analysis. For example, in some areas our episodes did not capture the
meteorological conditions that have caused high ozone, while local
modeling did so. Thus, these local analyses are considered to be more
extensive than our own modeling for estimating whether there would be
NAAQS nonattainment without further emission reductions, when
interpreted by a weight of evidence method which meets our guidance for
such modeling.
Photochemical ozone modeling conducted for this rulemaking was
based in part on updated national emissions inventories for all
sources. National emission trends for NOX

[[Page 5014]]

predict a significant decline from 1996 to 2007, a leveling off of the
downward trend between 2007 to 2020, and an increase in NOX
inventories from 2020 to 2030. By 2030, national NOX levels
are estimated to reach levels that are within ten percent of 2007
levels. Predictions of national VOC emissions indicate a reduction from
1996 to 2007, followed by an increase between 2007 and 2030 resulting
in 2030 levels that are estimated to be 10 percent greater than VOC
emissions levels in 2007. In metropolitan ozone nonattainment areas,
such as Charleston, Chicago and Houston, NOX or VOC
emissions in 2030 are predicted to reach or exceed 2007 levels. These
estimated national and metropolitan area emissions inventories of ozone
precursors are consistent with the conclusions reached by analysis of
ozone modeling conducted for this rule that additional reductions are
needed in order to enable areas to reach and maintain attainment of the
ozone standard between 2007 and 2030.
The Agency conducted ozone modeling based on inventories developed
with and without reductions from this rulemaking for three future
years: 2007, 2020 and 2030. The year 2007 was chosen because it is also
the first year of implementation for the new standards adopted in
today's action. It is also the year that nine major urban areas with a
history of persistent and elevated ozone concentrations must
demonstrate attainment, and is also relevant to the South Coast Air
Basin of California (South Coast) with an attainment date of 2010. In
addition, modeling was performed for 2030 when the full benefits of the
rule are expected to be realized and for 2020 which represents an
intermediate year between the start of the program and full turnover of
the affected vehicle fleet. The year 2020 is also representative of the
period when areas that have come into attainment may need additional
reductions in order to maintain the standard.
Today's rule will provide a substantial reduction in emissions of
ozone precursors, particularly NOX. These emissions
reductions will greatly lower ozone concentrations which will help
federal and State efforts to bring about attainment of the current 1-
hour ozone standard. As described in the Air Quality Modeling Technical
Support Document for this rule, EPA performed regional scale ozone
modeling for the Eastern U.S. to assess the impacts of the controls in
this rule on predicted 1-hour ozone exceedances. The results of this
modeling were examined for those 37 areas in the East for which EPA's
modeling predicted exceedances in 2007, 2020 and/or 2030 and current 1-
hour design values are above the standard or within 10 percent of the
standard. The results for these areas combined indicate that there will
be substantial reductions in the number of exceedances and the
magnitude of high ozone concentrations in both 2020 and 2030 due to
this rule. The modeling also indicates that without the rule,
exceedances would otherwise increase by 37 percent between 2020 and
2030 as growth in emissions offsets the reductions from Tier 2 and
other current control programs.
For all areas combined, the rule is forecast to provide a 33
percent reduction in exceedances in 2020 and a 38 percent reduction in
2030. The total amount of ozone above the standard is expected to
decline by nearly 37 percent in 2020 and 44 percent in 2030. Also,
daily maximum ozone exceedances are lowered by 5 ppb on average in 2020
and nearly 7 ppb in 2030. The modeling forecasts an overall net
reduction of 39 percent in exceedances from 2007, which is close to the
start of this program, to 2030 when controls will be fully in place. In
addition, the results for each individual area indicates that all areas
are expected to have fewer exceedances in 2030 with the HDV controls
than without this rule.
During the public comment period on the proposed rule, EPA received
several comments that expressed concern about potential increases in
ozone that might result from this rule. As indicated above, the air
quality modeling results indicate an overall reduction in ozone levels
in 2007 and 2030 during the various episodes modeled. Examining
individual areas, nearly the entire country is projected to benefit
substantially from the reductions in this rule.20 There is a
metropolitan area that EPA modeled as having exceedances with the one-
hour ozone standard under baseline conditions in 2007 through 2030,
which the Agency's modeling for the HDV rule estimated could have less
than a 3 percent increase in its peak ozone levels in 2020 and 2030 and
small net increase (i.e., less than 1 ppb) in levels above the 1-hour
standard in 2030. However, EPA's air quality modeling did not predict
an increase in the number of exceedances in this CMSA/MSA in 2020 and a
decrease in exceedances occurred in 2030. In another CMSA/MSA in
another State, in 2030 there was less than a one percent increase in
the summer peak level. Yet, this area had fewer exceedances and lower
ozone above the 1-hour standard in both 2020 and 2030 under the rule.
EPA expects that the States will have State Implementation Plans that
will consider federal controls and complement them with State actions
to provide attainment and will work with the States to ensure this
occurs.
---------------------------------------------------------------------------

\20\ The air quality modeling was performed for the Eastern
region of the United States, but EPA also expects the rule to
benefit nonattainment areas throughout the entire nation, including
California.
---------------------------------------------------------------------------

Considering all of EPA's air quality modeling results, it is clear
that the significant ozone reductions from this rule outweigh the
limited ozone increases that may occur in the future assuming no
additional reductions from federal or local controls. Additional
details on this are provided in the Response to Comments document and
in EPA's Heavy Duty Rule Air Quality Modeling Technical Support
Document. Furthermore, EPA's Regulatory Impact Analysis for this rule
shows significant health and welfare benefits occurring from the ozone
reductions that the rule provides (see details on the benefits in
Section V.F.5 of the preamble and Chapter VII of the RIA).
ii. Areas At Risk of Exceeding the 1-Hour Ozone Standard in the Future
This section presents the Agency's conclusions about the risk of
future nonattainment for 45 areas listed in Table II.B-1 based on
photochemical ozone modeling conducted for this rule and other evidence
such as local air quality modeling.21 The areas listed in
Table II.B-1 are separated into two broad groups: (1) Those areas with
attainment dates in 2007 or 2010 that will benefit from reductions from
this rule to attain and maintain the standard; and (2) those areas with
attainment dates prior to 2007 that will benefit from reductions from
this rule to maintain the standard after their attainment dates.
Because ozone concentrations causing violations of the 1-hour ozone
standard are well established to endanger public health and welfare,
this indicates that it is appropriate for the Agency to set new
standards for heavy-duty vehicles. The following discussion follows
these groupings from top to bottom. A more detailed discussion is found
in the Regulatory Impact Analysis (RIA).
---------------------------------------------------------------------------

\21\ In the proposal, we relied on photochemical ozone modeling
performed for recently promulgated standards on light duty vehicles,
or Tier 2. The results presented in this final rulemaking for heavy-
duty vehicles and diesel fuel are largely consistent with the
findings presented in the proposal, with small differences due to
updated emissions inventories. As stated in the proposal, the ozone
modeling methodologies used in the proposal and presented here in
the final rule are identical.
---------------------------------------------------------------------------

Ten metropolitan areas contained within designated ozone
nonattainment areas have statutorily-defined attainment dates of 2007
or 2010, or

[[Page 5015]]

have requested attainment date extensions to 2007. These 10 areas are
listed at the top of Table II.B-1, and are New York City, Houston,
Hartford, New London, Chicago, Milwaukee, Dallas, Beaumont-Port Arthur,
Los Angeles, and Southeast Desert.
Each of these areas needs additional emission reductions in order
to reach attainment by 2007, and to maintain the standards in the
future. Some of these areas have emission reduction shortfalls that are
identified in their attainment demonstrations (i.e., South Coast Air
Basin, New York and Houston), and reductions from this rule will assist
State efforts to reach attainment.22 Three other areas--
Southeast Desert, Hartford, New London--are subject to ozone transport
from upwind areas with identified shortfalls (South Coast and New
York), and depend upon attainment from these upwind areas to reach
attainment themselves. We have received attainment plans for two areas
in Texas (Dallas and Beaumont-Port Arthur), and the Agency is likely to
consider the reductions from this rule in its proposed approval of
these attainment plans in Federal Register notices. Finally, there are
two areas in the Midwest--Chicago and Milwaukee--that have incorporated
reductions from this rule into their regional ozone modeling, and plan
to rely on reductions from this rule to support their 2007 attainment
demonstration.23
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\22\ The South Coast's ``additional measures'' which rely on new
technologies, are located in its 1994 SIP.
\23\ Technical Support Document, Midwest Subregional Modeling:
1-Hour Attainment Demonstration for Lake Michigan Area and Emissions
Inventory, Illinois Environmental Protection Agency, Indiana
Department of Environmental Management, Michigan Department of
Environmental Quality, Wisconsin Department of Natural Resources,
September 27, 2000, at 14 and at 8.
---------------------------------------------------------------------------

For all ten areas, even if all shortfalls were filled by the
States, there is some risk that at least some of the areas will not
attain the standards by their attainment dates of 2007, or 2010 for Los
Angeles. In that event, the reductions associated with this program,
which increase substantially after 2007, will help assure that any
residual failures to attain are remedied. Finally, there is also some
risk that the areas will be unable to maintain attainment after 2007.
Considered collectively, there is a significant risk that some areas
will not be in attainment throughout the period when the new standards
will reduce heavy-duty vehicle emissions.
The rest of the areas have required attainment dates prior to 2007,
or have no attainment date but are subject to a general obligation to
have a SIP that provides for attainment and maintenance. These 34
areas, according to our modeling, are at risk of exceeding the ozone
NAAQS between 2007 and 2030. These areas will be able to rely on
reductions from this rule to continue to maintain the standard after
attainment is reached, and will be able to take credit for this program
in their maintenance plans when they seek redesignation to attainment
of the ozone standard. If any of these areas reach attainment, and then
fall back into nonattainment, or fail to reach attainment by 2007,
reductions from this rule will assist these areas in achieving the
ozone standard. If an area does not choose to seek redesignation, the
continuing reductions from this rulemaking will help ensure maintenance
(i.e., prevent future exceedances) with the 1-hour standard after
initial attainment is reached.
Areas with attainment dates prior to 2007 are presented in two
groupings in the table at the end of this section: a group of 20 areas
in the middle of Table II.B-1, and a group of 15 areas at the bottom of
Table II.B-1. For the middle group of 20 areas, EPA and the States are
pursuing the established statutory processes for attaining and
maintaining the ozone standard, or have already redesignated these
areas to attainment with a maintenance plan (e.g., Cincinnati). EPA has
re-instated the 1-hour ozone standard to some of these areas, restoring
the applicability of these processes to them. The Agency believes that
there is a significant risk that future air quality in a number of
these areas will exceed the ozone standard at some time in the 2007 and
later period. This belief is based on three factors: (1) Recent
exceedances in 1997-1999, (2) predicted exceedances in 2007, 2020 or
2030 after accounting for existing mobile source requirements and other
local or regional controls currently in place or required, and (3) our
assessment of the magnitude of recent violations, the year-to-year
variability of meteorological conditions conducive to ozone formation,
transport from areas with later attainment dates, and other variables
inherent in predicting future attainment such as the potential for some
areas to experience unexpectedly high economic growth rates, growth in
vehicle miles traveled, varying population growth from area to area,
and differences in vehicle choice.
Only a subset of these 20 areas have yet adopted specific control
measures that have allowed the Agency to fully approve an attainment
plan. For some of these areas, we have proposed a finding, based on all
the available evidence, that the area will attain by its applicable
attainment date. We have approved a 10-year maintenance plan for
Cincinnati, OH from 1999 to 2009. However, in many cases, these
proposals depend on the State adopting additional emission reduction
measures. The RIA provides more information on our recent proposals on
attainment demonstrations and maintenance plans.24 Until the
SIPs for these areas are actually submitted, reviewed and approved by
EPA, there is some risk that these areas will not adopt fully
approvable SIPs.
---------------------------------------------------------------------------

\24\ We have recently proposed favorable action, in some cases
with a condition that more emission reductions be obtained, on
attainment demonstrations in these areas with attainment dates prior
to 2007: Philadelphia, Washington-Baltimore, Atlanta, and St. Louis.
---------------------------------------------------------------------------

Finally, there are 15 additional metropolitan areas for which the
available ozone modeling and other evidence is less clear regarding the
need for additional reductions (see Table II.B-1). Our ozone modeling
predicted these areas to need further reductions to avoid exceedances
in 2007, 2020 or 2030. The recent air quality monitoring data for these
areas shows ozone levels with less than a 10 percent margin below the
NAAQS. We believe there is a risk that future ozone levels will be
above the NAAQS because of the year-to-year variability of
meteorological conditions conducive to ozone formation, or because
local emissions inventories may increase faster than national
inventories.
iii. Conclusion
In sum, without these reductions, there is a significant risk that
an appreciable number of the 45 areas, with a population of 128 million
people in 1999, will violate the 1-hour ozone standard during the time
period when these standards will apply to heavy-duty vehicles. The
evidence summarized in this section, and presented in more detail in
the air quality modeling TSD and the RIA, supports the Agency's belief
that emissions of NOX and VOC from heavy-duty vehicles in
2007 and later will contribute to a national ozone air pollution
problem that warrants regulatory action under section 202(a)(3) of the
Act.

[[Page 5016]]

Table II.B-1 a
[Areas and 1999 Populations at Risk of Exceeding the Ozone Standard
between 2007 and 2030]
------------------------------------------------------------------------
1999
Population
MSA/CMSA/State (in
millions)
------------------------------------------------------------------------
Areas with 2007/2010 Attainment Dates (Established or Requested)
------------------------------------------------------------------------
Beaumont-Port Arthur, TX................................... 0.4
Chicago-Gary-Kenosha, IL-IN-WI............................. 8.9
Dallas-Fort Worth, TX...................................... 4.9
Hartford, CT............................................... 1.1
Houston-Galveston-Brazoria, TX............................. 4.5
Los Angeles-Riverside-Orange County, CA.................... 16.0
Milwaukee-Racine, WI....................................... 1.6
New London-Norwich, CT-RI.................................. 0.3
New York-Northern New Jersey-Long Island, NY-NJ-CT-PA...... 20.2
Southeast Desert, CA....................................... 0.5
10 areas................................................... 58.4
------------------------------------------------------------------------
Areas with Pre-2007 Attainment Dates or No Specific Attainment Date,
with a Recent History of Nonattainment.
------------------------------------------------------------------------
Atlanta, GA................................................ 3.9
Baton Rouge, LA............................................ 0.6
Birmingham, AL............................................. 0.9
Boston-Worcester-Lawrence, MA-HN-ME-CT..................... 5.7
Charlotte-Gastonia-Rock Hill, NC-SC........................ 1.4
Detroit-Ann Arbor-Flint, MI MSA............................ 5.5
Huntington-Ashland, WV-KY-OH............................... 0.3
Louisville, KY-IN.......................................... 1.0
Macon, GA MSA.............................................. 0.3
Memphis, TN-AR-MS.......................................... 1.1
Nashville, TN.............................................. 1.2
Philadelphia-Wilmington-Atlantic City, PA-NJ-DE-MD......... 6
Richmond-Petersburg, VA.................................... 1
Sacramento-Yolo, CA........................................ 1.7
San Diego, CA.............................................. 2.8
San Francisco-Oakland-San Jose, CA......................... 6.9
San Joaquin Valley, CA..................................... 3.2
St. Louis, MO-IL........................................... 2.6
Ventura County, CA......................................... 0.7
Washington, DC--Baltimore, DC, MD, VA MSA.................. 7.4
20 Areas................................................... 54.2
------------------------------------------------------------------------
Areas with Pre-2007 Attainment Dates and Recent Concentrations within 10
percent of an Exceedance.
------------------------------------------------------------------------
Barnstable-Yarmouth, MA.................................... 0.2
Benton Harbor, MI.......................................... 0.2
Biloxi-Gulfport-Pascagoula, MS MSA......................... 0.4
Charleston, WV MSA......................................... 0.3
Cincinnati-Hamilton, OH-KY-IN.............................. 2.0
Cleveland-Akron, OH CMSA................................... 2.9
Grand Rapids-Muskegon-Holland, MI MSA...................... 1.1
Houma, LA.................................................. 0.2
Lake Charles, LA........................................... 0.2
New Orleans, LA MSA........................................ 1.3
Norfolk-Virginia Beach-Newport News, VA-NC MSA............. 1.6
Orlando, FL MSA............................................ 1.5
Pensacola, FL MSA.......................................... 0.4
Providence-Fall River-Warwick, RI-MA....................... 1.1
Tampa-St. Petersburg-Clearwater, FL MSA.................... 2.3
15 areas................................................... 15.7
------------------------------------------------------------------------
Total Areas: 45........................................ Population:
128
------------------------------------------------------------------------
a In order to determine the reliability of model predictions the Agency
ran the ozone model for current ozone concentrations and compared
those predictions with actual ozone levels recorded by ozone monitors.
The results of the model's performance are presented in the RIA for
this rule.

[[Page 5017]]

c. Public Health and Welfare Concerns from Prolonged and Repeated
Exposures to Ozone
A large body of scientific literature regarding health and welfare
effects of ozone has associated health effects with certain patterns of
ozone exposures that do not necessarily include any hourly ozone
concentration above the 0.12 parts per million (ppm) level of the 1-
hour NAAQS. The science indicates that there are health effects
attributable to prolonged and repeated exposures to lower ozone
concentrations. Studies of 6 to 8 hour exposures showed health effects
from prolonged and repeated exposures at moderate levels of exertion to
ozone concentrations as low as 0.08 ppm. Prolonged and repeated ozone
concentrations at these levels are common in areas throughout the
country, and are found in areas that are exceeding, and areas that are
not exceeding, the 1-hour ozone standard. For example, 153 million
people, or 87 percent of the total population in counties evaluated
(176 million), lived in areas with 2 or more days with concentrations
of 0.09 ppm or higher in 1998, including areas currently violating the
1-hour NAAQS. In the 2007, before the application of emission
reductions resulting from this rule, we estimated that 116 million, or
93 percent of the total population considered in the analysis, are
predicted to live in areas with at least 2 days with model-adjusted 8-
hour average concentrations of 0.08 ppm or higher. By 2030, the number
of people (139 million) and the relative percentage (91 percent) of the
total population considered in the analysis is projected to grow
significantly without reductions from this rule. Since prolonged
exposures at moderate levels of ozone are more widespread than
exceedances of the 1-hour ozone standard, and given the continuing
nature of the 1-hour ozone problem described above, adverse health
effects from this type of ozone exposure can reasonably be anticipated
to occur in the future in the absence of this rule. Adverse welfare
effects can also be anticipated, primarily from damage to vegetation.
See the RIA for further details.
Studies of acute health effects have shown transient pulmonary
function responses, transient respiratory symptoms, effects on exercise
performance, increased airway responsiveness, increased susceptibility
to respiratory infection, increased hospital and emergency room visits,
and transient pulmonary respiratory inflammation. Such acute health
effects have been observed following prolonged exposures at moderate
levels of exertion at concentrations of ozone well below the current
standard of 0.12 ppm. The effects are more pronounced at concentrations
above 0.09 ppm, affecting more subjects or having a greater effect on a
given subject in terms of functional changes or symptoms. A more
detailed discussion may be found in the RIA.
With regard to chronic health effects, the collective data have
many ambiguities, but provide suggestive evidence of chronic effects in
humans. There is a biologically plausible basis for considering the
possibility that repeated inflammation associated with exposure to
ozone over a lifetime, as can occur with prolonged exposure to moderate
ozone levels below peak levels, may result in sufficient damage to
respiratory tissue that individuals later in life may experience a
reduced quality of life, although such relationships remain highly
uncertain.
Ozone has many welfare effects, with damage to plants being of most
concern. Plant damage affects crop yields, forestry production, and
ornamentals. The adverse effect of ozone on forests and other natural
vegetation can in turn cause damage to associated ecosystems, with
additional resulting economic losses, as well as aesthetic impacts
which may not be fully quantifiable in economic terms. Ozone
concentrations of 0.10 ppm can be phytotoxic to a large number of plant
species, and can produce acute injury and reduced crop yield and
biomass production. Ozone concentrations at or below 0.10 ppm have the
potential over a longer duration of creating chronic stress on
vegetation that can result in reduced plant growth and yield, shifts in
competitive advantages in mixed populations, decreased vigor, and
injury from other environmental stresses.
Section 202(a) provides EPA with authority to promulgate standards
applicable to motor vehicle emissions that ``in the Administrator's
judgment, cause or contribute to air pollution reasonably anticipated
to endanger public health and welfare.'' The evidence in the RIA
regarding the occurrence of adverse health effects due to prolonged and
repeated exposure to ozone concentrations in the range discussed above,
and regarding the populations that are expected to receive exposures at
these levels, along with the welfare effects described above, supports
a conclusion that emissions of NOX and VOC from heavy-duty
vehicles in 2007 and later will be contributing to a national air
pollution problem that warrants regulatory action under section 202(a)
of the Act.
3. Particulate Matter
a. Health and Welfare Effects
Particulate matter (PM) represents a broad class of chemically and
physically diverse substances. It can be principally characterized as
discrete particles that exist in the condensed (liquid or solid) phase
spanning several orders of magnitude in size. All particles equal to
and less than 10 microns are called PM10. Fine particles can
be generally defined as those particles with an aerodynamic diameter of
2.5 microns or less (also known as PM2.5), and coarse
fraction particles are those particles with an aerodynamic diameter
greater than 2.5 microns, but equal to or less than a nominal 10
microns. The health and environmental effects of PM are strongly
related to the size of the particles.
The emission sources, formation processes, chemical composition,
atmospheric residence times, transport distances and other parameters
of fine and coarse particles are distinct. Fine particles are directly
emitted from combustion sources and are formed secondarily from gaseous
precursors such as sulfur dioxide, nitrogen oxides, or organic
compounds. Fine particles are generally composed of sulfate, nitrate,
chloride and ammonium compounds; organic and elemental carbon; and
metals. Combustion of coal, oil, diesel, gasoline, and wood, as well as
high temperature process sources such as smelters and steel mills,
produce emissions that contribute to fine particle formation. In
contrast, coarse particles are typically mechanically generated by
crushing or grinding and are often dominated by resuspended dusts and
crustal material from paved or unpaved roads or from construction,
farming, and mining activities. Fine particles can remain in the
atmosphere for days to weeks and travel through the atmosphere hundreds
to thousands of kilometers, while coarse particles deposit to the earth
within minutes to hours and within tens of kilometers from the emission
source.
Diesel particles are a component of both coarse and fine PM, but
fall mostly in the fine and ultrafine size range.25 Diesel
PM contains small quantities of numerous mutagenic and carcinogenic
compounds. While representing a very small portion (less than one
percent) of the national emissions of metals, and a small portion of
diesel particulate matter (one to five percent), we note that several
toxic trace metals of potential

[[Page 5018]]

toxicological significance are also emitted by diesel engines including
chromium, manganese, mercury and nickel. In addition, small amounts of
dioxins have been measured in diesel exhaust, some of which may
partition into the particle phase, though the impact of these emissions
on human health is not clear.
---------------------------------------------------------------------------

\25\ Fine particulate matter includes particles with a diameter
less than 2.5 micrometers. Ultrafine particulate matter include
particles with a diameter less than 100 nanometers.
---------------------------------------------------------------------------

Particulate matter, like ozone, has been linked to a range of
serious respiratory health problems. Scientific studies suggest a
likely causal role of ambient particulate matter (which is attributable
to a number of sources including diesel) in contributing to a series of
health effects. The key health effects categories associated with
ambient particulate matter include premature mortality, aggravation of
respiratory and cardiovascular disease (as indicated by increased
hospital admissions and emergency room visits, school absences, work
loss days, and restricted activity days), aggravated asthma, acute
respiratory symptoms, including aggravated coughing and difficult or
painful breathing, chronic bronchitis, and decreased lung function that
can be experienced as shortness of breath. Observable human noncancer
health effects associated with exposure to diesel PM include some of
the same health effects reported for ambient PM such as respiratory
symptoms (cough, labored breathing, chest tightness, wheezing), and
chronic respiratory disease (cough, phlegm, chronic bronchitis and
suggestive evidence for decreases in pulmonary function). Symptoms of
immunological effects such as wheezing and increased allergenicity are
also seen. Studies in rodents, especially rats, show the potential for
human inflammatory effects in the lung and consequential lung tissue
damage from chronic diesel exhaust inhalation exposure. Both fine and
coarse particles can accumulate in the respiratory system. Exposure to
fine particles is most closely associated with such health effects as
premature mortality or hospital admissions for cardiopulmonary disease.
For additional information on health effects, see the RIA. PM also
causes damage to materials and soiling of commonly used building
materials and culturally important items such as statutes and works of
art. It is a major cause of substantial visibility impairment in many
parts of the U.S.
Heavy-duty vehicles contribute to particle formation through a
number of pollutants. The contribution to PM fine varies by region of
the country. Sulfate plays a major role in the composition of fine
particulate across the country, but typically makes up over half the
fine particles found in the Eastern United States. Organic carbon
accounts for a large portion of fine particle mass, with a slightly
higher fraction in the west. Diesel engines are the principal source of
elemental carbon, which makes up about 5-6 percent of particle mass.
Nationally, nitrate plays a relatively small role in the make up of
fine particles, but ammonium nitrate plays a far larger role in
southern California. Ammonium nitrate-formed secondarily from
NOX and ammonia emissions--is one of the most significant
components of particulate matter pollution in California. During some
of the worst episodes of elevated particle levels in the South Coast,
ammonium nitrate can account for about 65-75 percent of the
PM2.5 mass. Reducing ammonium nitrate through controls on
NOX sources is a critical part of California's particulate
matter strategy. Nationally, the standards finalized in this rule will
significantly reduce HDV emissions of SOX, NOX,
VOCs and elemental carbon, and thus contribute to reductions in ambient
concentrations of PM10 and PM2.5.
b. Attainment and Maintenance of the PM10 NAAQS
Under the CAA, we are to regulate HDV emissions if they contribute
to air pollution that can reasonably be anticipated to endanger public
health and welfare. We have already addressed the question of what
concentration patterns of PM endanger public health, in setting the
NAAQS for PM10 in 1987. The PM NAAQS were revised in 1997,
largely by adding new standards for fine particles (PM2.5)
and modifying the form of the daily PM10 standard. On
judicial review, the revised standards were remanded for further
proceedings, and the revised PM10 standards were vacated.
The Supreme Court is currently reviewing that decision. Oral arguments
were held on November 7, 2000 and a decision by the Court is expected
in 2001. Pending final resolution of the litigation, the 1987
PM10 standard is the applicable NAAQS for PM10.
Commenters questioned the need for additional PM10
reductions in order to achieve attainment with the PM10
NAAQS, and questioned the Agency's statement that, unlike ozone,
PM10 emissions are projected to increase in the future.
Commenters are correct that significant progress has occurred over the
last decade,26 but the Agency's statement was based on
projected PM10 inventory increases in the future between
1996 and 2030. During this period, inventory trends for current
PM10 nonattainment areas, or those with concentrations
within 10 percent of the standard, are predicted to increase
significantly. For example, from 1996 to 2030, increases are predicted
in Clark County (Las Vegas) of 41 percent, Harris County (Houston) of
37 percent, and Phoenix of 24 percent. A more detailed discussion is
provided in the RIA.
---------------------------------------------------------------------------

\26\ Ambient concentrations of PM10 and
PM10 emissions have declined over the last ten years by
25 percent and 19 percent, respectively. National Air Quality and
Emissions Trends Report, 1998, US EPA, March, 2000.
---------------------------------------------------------------------------

i. Current PM10 Nonattainment
The most recent PM10 monitoring data indicates that 14
designated PM10 nonattainment areas with a projected
population of 23 million violated the PM10 NAAQS in the
period 1997-1999. Table II.B-3 lists the 14 areas, and also indicates
the PM10 nonattainment classification and 1999 projected
population for each PM10 nonattainment area. The projected
population in 1999 was based on 1990 population figures which were then
increased by the amount of population growth in the relevant county
from 1990 to 1999.

Table II.B-3.--PM10 Nonattainment Areas Violating the PM10 NAAQS in 1997-
99
------------------------------------------------------------------------
1999
Population
Area Classification (projected, in
millions)
------------------------------------------------------------------------
Hayden/Miami, AZ.................. Moderate............ 0.004
Phoenix, AZ....................... Serious............. 2.977
Nogales, AZ....................... Moderate............ 0.025
San Joaquin Valley, CA............ Serious............. 3.214
Imperial Valley, CA............... Moderate............ 0.122

[[Page 5019]]

Owens Valley, CA.................. Serious............. 0.018
Searles Valley, CA................ Moderate............ 0.029
Coachella Valley, CA.............. Serious............. 0.239
South Coast Air Basin............. Serious............. 14.352
Las Vegas, NV..................... Serious............. 1.200
Reno, NV.......................... Moderate............ 0.320
Anthony, NM b..................... Moderate............ 0.003
El Paso, TX a..................... Moderate............ 0.611
Wallula, WA b..................... Moderate............ 0.052
Total Areas: 14............. .................... 23.167
------------------------------------------------------------------------
a EPA has determined that continuing PM10 nonattainment in El Paso, TX
is attributable to international transport under section 179(B).
b The violation in this area has been determined to be attributable to
natural events under section 188(f) of the Act.

In addition to the 14 PM10 nonattainment areas that are
currently violating the PM10 NAAQS, there are 25
unclassifiable areas that have recently recorded ambient concentrations
of PM10 above the PM10 NAAQS. EPA adopted a
policy in 1996 that allows areas with PM10 exceedances that
are attributable to natural events to retain their designation as
unclassifiable if the State is taking all reasonable measures to
safeguard public health regardless of the sources of PM10
emissions. Areas that remain unclassifiable areas are not required
under the Clean Air Act to submit attainment plans, but we work with
each of these areas to understand the nature of the PM10
problem and to determine what best can be done to reduce it. With
respect to the monitored violations reported in 1997-99 in the 25 areas
designated as unclassifiable, we have not yet excluded the possibility
that factors such as a one-time monitoring upset or natural events,
which ordinarily would not result in an area being designated as
nonattainment for PM10, may be responsible for the problem.
Emission reductions from today's action will assist these currently
unclassifiable areas to achieve ambient PM10 concentrations
below the current PM10 NAAQS.
ii. Risk of Future Exceedances of the PM10 Standard
The new standards for heavy-duty vehicles will benefit public
health and welfare through reductions in direct diesel particles and
NOX, VOCs, and SOX which contribute to secondary
formation of particulate matter. Because ambient particle
concentrations causing violations of the PM10 standard are
well established to endanger public health and welfare, this
information supports the new standards for heavy-duty vehicles. The
reductions from today's rule will assist States as they work with the
Agency through implementation of local controls including development
and adoption of additional controls as needed to move their areas into
attainment by the applicable deadline, and maintain the standards
thereafter.
The Agency's PM inventory analysis performed for this rulemaking
predicts that without additional reductions 10 areas face a significant
risk of failing to meet or to maintain the PM10 NAAQS even
with federal, State and local controls currently in place.27
Table II.B-4 presents information about these 10 areas and subdivides
them into two groups. The first group of 6 areas are designated
PM10 nonattainment areas which had recent monitored
violations of the PM10 NAAQS in 1997-1999 and increasing
inventories of PM10 from 2007 to 2030 (see Table II.B-3 for
predicted increases in emissions). These areas have a population of 19
million. Included in the group are the nonattainment areas that are
part of the Los Angeles, Phoenix and Las Vegas (Clark County)
metropolitan areas, where traffic from heavy-duty vehicles is
substantial. These six areas will benefit from the reductions in
emissions that will occur from the new standards for heavy-duty
vehicles, as will other areas impacted by heavy-duty vehicle emissions.
---------------------------------------------------------------------------

\27\ EPA has evaluated projected emissions for this analysis
rather than future air quality because REMSAD, the model EPA has
used for analyses related to this rule, was designed principally to
estimate long-term average concentrations of fine particulate matter
and its ability to predict short-term PM10 concentrations
has not been satisfactorily demonstrated. In contrast with ozone,
which is the product of complex photochemical reactions and
therefore difficult to directly relate to precursor emissions,
ambient PM10 concentrations are more heavily influenced
by direct emissions of particulate matter and can therefore be
correlated more meaningfully with emissions inventories.
---------------------------------------------------------------------------

The second group of four counties listed in Table II.B-4 with a
total of nine million people in 1999 also had predicted exceedances of
the PM10 standard. While these four areas registered, in
either 1997 or 1998, single-year annual average monitored
PM10 levels of at least 90 percent of the PM10
NAAQS, these areas did not exceed the formal definition of the
PM10 NAAQS over the three-year period ending in 1999. For
each of these four areas (i.e., Cuyahoga, Harris, New York, and San
Diego), inventories of total PM10 are predicted to increase
between 1996, when these areas recorded values within 10 percent of the
PM10 standard, and 2030 when this rule will take full
effect. Additionally, EPA is in the process of taking final action on a
request by the State of Ohio to redesignate Cuyahoga County as
attainment. This action is based on locally developed information and
is consistent with the requirements of the CAA which include, among
other requirements a 10-year plan for maintenance of the
PM10 standard.
For some of these areas, total PM10 inventories are
predicted to decline or stay relatively constant from 1996 to 2007, and
then increase after 2007. Based on inventory projections, the small
margin of attainment which the four areas currently enjoy will likely
erode between 1996 and 2030, and for some areas before 2007, if
additional actions to reduce the growth of future emissions are not
taken. We therefore consider these four areas to each individually have
a significant risk of exceeding the PM10 standard between
2007 and 2030 without further emission reductions. The emission
reductions from the new standards for heavy-duty vehicles will help
these areas attain and maintain the PM10 NAAQS in
conjunction with other processes that

[[Page 5020]]

are currently moving these areas towards attainment.

Table II.B-4--Areas With Significant Risk of Exceeding the PM10 NAAQS
Without Further Emission Reductions Between 2007 and 2030
------------------------------------------------------------------------
Percent 1999
increases in Population
Area PM10 emissions (projected)
(1996-2030) (millions)
------------------------------------------------------------------------
Areas currently exceeding the PM10
standard:
Clark Co., NV (Las Vegas)........... 41 1.217
El Paso, TX a....................... 14 0.611
Hayden/Miami, AZ.................... 4 0.004
Los Angeles South Coast Air Basin, 14 14.352
CA.................................
Nogales, AZ......................... 3 0.025
Phoenix, AZ......................... 24 3.012
-------------------------------
Subtotal for 6 Areas............ .............. 19.22
===============================
Areas within 10% of exceeding the PM10
standard:
Cuyahoga Co., OH (Cleveland)........ 28 1.37
Harris, Co., TX (Houston)........... 37 3.26
New York Co., NY.................... 14 1.55
San Diego Co., CA................... 13 2.83
-------------------------------
Subtotal for 4 Areas............ .............. 9.01
===============================
10 Areas........................ .............. 28.23
------------------------------------------------------------------------
a EPA has determined that PM10 nonattainment in this area is
attributable to international transport. While reductions in heavy-
duty vehicle emissions cannot be expected to result in attainment,
they will help reduce the degree of PM10 nonattainment.

EPA recognizes that the SIP process is ongoing and that
nonattainment areas are in the process of implementing, or will be
adopting and implementing, additional control measures to achieve the
PM10 NAAQS in accordance with their attainment dates under
the Clean Air Act. EPA believes, however, that as in the case of ozone,
there are uncertainties inherent in any demonstration of attainment
that is premised on forecasts of emission levels in future years. Even
if these areas adopt and submit SIPs that EPA is able to approve as
demonstrating attainment of the PM10 standard, and attain
the standard by the appropriate attainment dates, the inventory
analysis conducted for this rule and the history of PM10
levels in these areas indicates that there is still a significant risk
that these areas will need the reductions from the heavy-duty vehicle
standards adopted today to maintain the PM10 standards in
the long term (ie, between 2007 and 2030). In addition, this list does
not fully consider the possibility that there are other areas which are
now meeting the PM10 NAAQS that have at least a significant
probability of requiring further reductions to continue to maintain it.
c. Public Health and Welfare Concerns From Exposure to Fine PM
Many epidemiologic studies have shown statistically significant
associations of ambient PM levels with a variety of human health
endpoints in sensitive populations, including mortality, hospital
admissions and emergency room visits, respiratory illness and symptoms
measured in community surveys, and physiologic changes in mechanical
pulmonary function. These effects have been observed in many areas with
ambient PM levels at or below the current PM10 NAAQS. The
epidemiologic science points to fine PM as being more strongly
associated with some health effects, such as premature mortality, than
coarse PM.
Associations of both short-term and long-term PM exposure with most
of the above health endpoints have been consistently observed. The
general internal consistency of the epidemiologic data base and
available findings have led to increasing public health concern, due to
the severity of several studied endpoints and the frequent
demonstration of associations of health and physiologic effects with
ambient PM levels at or below the current PM10 NAAQS. The
weight of epidemiologic evidence suggests that ambient PM exposure has
affected the public health of U.S. populations. Specifically, increased
mortality associated with fine PM was observed in cities with longer-
term average fine PM concentrations in the range of 16 to 21
g/m 3.
Current 1999 PM2.5 monitored values, which cover about a
third of the nation's counties, indicate that at least 40 million
people live in areas where long term ambient fine particulate matter
levels are at or above 16 g/m 3 (37 percent of the
population in the areas with monitors), which is the low end of the
range of long term average PM2.5 concentrations in cities
where statistically significant associations were found with serious
health effects, including premature mortality (EPA, 1996).28
---------------------------------------------------------------------------

\28\ EPA (1996) Review of the National Ambient Air Quality
Standards for Particulate Matter: Policy Assessment of Scientific
and Technical Information OAQPS Staff Paper. EPA-452/R-96-013.
---------------------------------------------------------------------------

The Agency used the Regulatory Model System for Aerosols and
Desposition (REMSAD) to model baseline and post-control ambient PM
concentrations. For a description of the REMSAD model, the reader is
referred to Chapter VII of the RIA.
Our REMSAD modeled predictions allow us to also estimate the
affected population for the counties which do not currently have
PM2.5 monitors. According to our national modeled
predictions, there were a total of 76

[[Page 5021]]

million people (1996 populations) living in areas with modeled annual
average PM2.5 concentrations at or above 16 g/m
3 (29 percent of the population).29
---------------------------------------------------------------------------

\29\ REMSAD modeling for PM2.5 annual average
concentrations. Total 1996 population in all REMSAD grid cells is
263 million.
---------------------------------------------------------------------------

The REMSAD model also allows us to estimate future PM2.5
levels. However, the most appropriate method of making these
projections relies on the model to predict changes between current and
future states. Thus, we have estimated future conditions only for the
areas with current PM2.5 monitored data (which, as just
noted, covers about a third of the nation's counties). For these
counties, REMSAD predicts the current level of 37 percent of the
population living in areas where fine PM levels are at or above 16
g/m 3 to increase to 59 percent in 2030.
It is reasonable to anticipate that sensitive populations exposed
to similar or higher levels, now and in the 2007 and later time frame,
will also be at increased risk relative to the general population of
premature mortality associated with exposures to fine PM. In addition,
statistically significant relationships have also been observed in U.S.
cities between PM levels and increased respiratory symptoms and
decreased lung functions in children.
Since EPA's examination in the mid-1990s of the epidemiological and
toxicological evidence of the health effects of PM, many new studies
have been published that reevaluate or extend the initial research. The
Agency is currently reviewing these new studies to stay abreast of the
literature and adjust as necessary its assessment of PM's health
effects. It is worth noting that within this new body of scientific
literature, there are two new studies funded by the Health Effects
Institute, a EPA-industry jointly funded group, that have generally
confirmed the mid-1990s findings of the Agency about the association of
fine particles and premature mortality and various other respiratory
and cardiovascular effects. HEI's National Morbidity, Mortality and Air
Pollution Study (NMMAPS), evaluated associations between air pollutants
and mortality in 90 U.S. cities, and also evaluated associations
between air pollutants and hospital admissions among the elderly in 14
U.S. cities.30 In HEI's Reanalysis of the Harvard Six Cities
Study and the American Cancer Society Study of Particulate Air
Pollution and Mortality, data were obtained from the original
investigators for two previous studies.31 32, The extensive
analyses included replication and validation of the previous findings,
as well as sensitivity analyses using alternative analytic techniques,
including different methods of covariate adjustment, exposure
characterization, and exposure-response modeling.33
---------------------------------------------------------------------------

\30\ Samet JM, Zeger SL, Dominici F, Curriero F, Coursac I,
Dockery DW, Schwartz J, Zanobetti A. 2000. The National Morbidity,
Mortality and Air Pollution Study: Part II: Morbidity, Mortality and
Air Pollution in the United States. Research Report No. 94, Part II.
Health Effects Institute, Cambridge MA, June 2000.
\31\ Dockery, D.W., Pope, C.A., III, Xu, X., Spengler, J.D.,
Ware, J.H., Fay, M.E., Ferris, B.G., Speizer, F.E. (1993) An
association between air pollution and mortality in six U.S. cities.
N. Engl. J. Med. 329:1753-1759.
32 Pope, C. A., III, Thun, M. J., Namboodiri, M. M.,
Dockery, D. W., Evans, J. S., Speizer, F. E., Heath, C. W., Jr.
(1995) Particulate air pollution as a predictor of mortality in a
prospective study of U.S. adults. Am. J. Respir. Crit. Care Med.
151: 669-674.
\33\ Krewski D, Burnett RT, Goldbert MS, Hoover K, Siemiatycki
J, Jarrett M, Abrahamowicz M, White WH. (2000) Reanalysis of the
Harvard Six Cities Study and the American Cancer Society Study of
Particulate Air Pollution and Mortality. Special Report to the
Health Effects Institute, Cambridge MA, July 2000.
---------------------------------------------------------------------------

Section 202(a) provides EPA with independent authority to
promulgate standards applicable to motor vehicle emissions that ``in
the Administrator's judgment, cause or contribute to air pollution
reasonably anticipated to endanger public health and welfare.'' The
body of health evidence is supportive of our view that PM exposures are
a serious public health concern. This concern exists for current
exposures as well as exposures that can reasonably be anticipated to
occur in the future. The risk is significant from an overall public
health perspective because of the large number of individuals in
sensitive populations that we expect to be exposed to ambient fine PM
in the 2007 and later time frame, as well as the importance of the
negative health effects. This information warrants a requirement to
reduce emissions from heavy-duty vehicles, to address elevated levels
of fine PM. This evidence supports EPA's conclusion that emissions from
heavy-duty vehicles that lead to the formation of fine PM in 2007 and
later will be contributing to a national air pollution problem that
warrants action under section 202(a)(3).
d. Other Welfare Effects Associated with PM
The deposition of airborne particles reduces the aesthetic appeal
of buildings, and promotes and accelerates the corrosion of metals,
degrades paints, and deteriorates building materials such as concrete
and limestone. This materials damage and soiling are related to the
ambient levels of airborne particulates, which are emitted by heavy-
duty vehicles. Although there was insufficient data to relate materials
damage and soiling to specific concentrations, and thereby to allow the
Agency to establish a secondary PM standard for these impacts, we
believe that the welfare effects are real and that heavy-duty vehicle
PM, NOX, SOX, and VOC contribute to materials
damage and soiling.
e. Conclusions Regarding PM
There is a significant risk that, despite statutory requirements
and EPA and State efforts towards attainment and maintenance, some
areas of the U.S. will violate the PM10 NAAQS in 2007 and
thereafter. Heavy-duty vehicles contribute substantially to
PM10 levels, as shown in Section II.C below.
It is also reasonable to anticipate that concentrations of fine PM,
as represented for example by PM2.5 concentrations, will
also endanger public health and welfare even if all areas attain and
maintain the PM10 NAAQS. Heavy-duty vehicles contribute to
this air pollution problem.
There are also important environmental impacts of PM10,
such as regional haze which impairs visibility. Furthermore, while the
evidence on soiling and materials damage is limited and the magnitude
of the impact of heavy-duty vehicles on these welfare effects is
difficult to quantify, these welfare effects support our belief that
this action is necessary and appropriate.
Finally, in addition to its contribution to PM inventories, diesel
exhaust PM is of special concern because it has been implicated in an
increased risk of lung cancer and respiratory disease in human studies,
and an increased risk of noncancer health effects as well. The
information provided in this section shows that there will be air
pollution that warrants regulatory action under section 202(a)(3) of
the Act.
4. Diesel Exhaust
Diesel emissions are of concern to the agency beyond their
contribution to ambient PM. As discussed in detail in the draft RIA,
there have been health studies specific to diesel exhaust emissions
which indicate potential hazards to human health that appear to be
specific to this emissions source. For chronic exposure, these hazards
included respiratory system toxicity and carcinogenicity. Acute
exposure also causes transient effects (a wide range of physiological
symptoms stemming from irritation and inflammation mostly in the
respiratory system) in humans though they are highly variable depending
on individual human susceptibility. The chemical

[[Page 5022]]

composition of diesel exhaust includes several hazardous air
pollutants, or air toxics. In our Mobile Source Air Toxic Rulemaking
under section 202(l) of the Act discussed above, EPA determined that
diesel particulate matter and diesel exhaust organic gases be
identified as a Mobile Source Air Toxic (MSAT). The purpose of the MSAT
list is to provide a screening tool that identifies compounds emitted
from motor vehicles or their fuels for which further evaluation of
emissions controls is appropriate. As discussed in chapter 3 on engine
technology, the particulate matter standard finalized today reflects
the greatest degree of emissions reductions achievable under section
202(l) for on-highway heavy-duty vehicle PM emissions.
a. Potential Cancer Effects of Diesel Exhaust
The EPA has concluded that diesel exhaust is likely to be
carcinogenic to humans by inhalation at occupational and environmental
levels of exposure.34 The draft Health Assessment Document
for Diesel Exhaust (draft Assessment), was reviewed in public session
by the Clean Air Scientific Advisory Committee (CASAC) on October 12-
13, 2000.35 The CASAC found that the Agency's conclusion
that diesel exhaust is likely to be carcinogenic to humans is
scientifically sound. CASAC concurred with the draft Assessment's
findings with the proviso that EPA provide modifications and
clarifications on certain topics. The Agency expects to produce the
finalized Assessment in early 2001. Information presented here is
consistent with that to be provided in the final Assessment.
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\34\ U.S. EPA (2000) Health Assessment Document for Diesel
Exhaust: SAB Review Draft. EPA/600/8-90/057E Office of Research and
Development, Washington, D.C. The document is available
electronically at www.epa.gov/ncea/dieslexh.htm.
\35\ EPA (2000) Review of EPA's Health Assessment Document for
Diesel Exhaust (EPA 600/8-90/057E). Review by the Clean Air
Scientific Advisory Committee (CASAC) December 2000. EPA-SAB-CASAC-
01-003.
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In its review of the published literature, EPA found that about 30
individual epidemiologic studies show increased lung cancer risk
associated with diesel emissions. In the draft Assessment EPA evaluated
22 studies that were most relevant for risk assessment, 16 of which
reported significant increased lung cancer risks, ranging from 20 to
167 percent, associated with diesel exhaust exposure. Published
analytical results of pooling many of the 30 studies showed that on
average, the risks were increased by 33 to 47 percent. Questions remain
about the influence of other factors (e.g., effect of smoking, other
particulate sources), the quality of the individual epidemiologic
studies, exposure levels, and consequently the precise magnitude of the
increased risk of lung cancer. From a weight of evidence perspective,
EPA concludes that the epidemiologic evidence, as well as supporting
data from certain animal and mode of action studies, support the
Agency's conclusion that exposure to diesel exhaust is likely to pose a
human lung cancer hazard to occupationally exposed individuals as well
as to the general public exposed to typically lower environmental
levels of diesel exhaust.
Risk assessments in the peer-reviewed literature have attempted to
assess the lifetime risk of lung cancer in workers occupationally
exposed to diesel exhaust. These estimates suggest that lung cancer
risk may range from 10-4 to 10-2. 36
37 38 The Agency recognizes the significant
uncertainties in these studies, and has not used these estimates to
assess the possible cancer unit risk associated with ambient exposure
to diesel exhaust.
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\36\ California Environmental Protection Agency, Office of
Health Hazard Assessment (CAL-EPA, OEHHA) (1998) Proposed
Identification of Diesel Exhaust as a Toxic Air Contaminant.
Appendix III Part B Health Risk Assessment for Diesel Exhaust. April
22, 1998.
\37\ Harris, J.E. (1983) Diesel emissions and Lung Cancer. Risk
Anal. 3:83-100.
\38\ Stayner, L.S., Dankovic, D., Smith, R., Steenland, K.
(1998) Predicted Lung Cancer Risk Among Miners Exposed to Diesel
Exhaust Particles. Am. J. of Indus. Medicine 34:207-219.
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While available evidence supports EPA's conclusion that diesel
exhaust is likely to be a human lung carcinogen, and thus is likely to
pose a cancer hazard to humans, EPA has concluded that the available
data are not sufficient to develop a confident estimate of cancer unit
risk. The absence of a cancer unit risk for diesel exhaust limits our
ability to quantify, with confidence, the potential impact of the
hazard (magnitude of risk) on exposed populations. In the draft
Assessment, EPA acknowledged this limitation and provided a discussion
of the possible environmental cancer risk consistent with the majority
of the occupational epidemiological findings of increased lung cancer
risk and the exposure differences between the occupational and
environmental settings.39 The Agency concluded in developing
its perspective on risk that there is a reasonable potential that
environmental lifetime cancer risks (``environmental risk range'') from
diesel exhaust may exceed 10-5 and could be as high as
10-3.40
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\39\ See Chapter 8.4 and 9.5.2 of the U.S. EPA (2000) Health
Assessment Document for Diesel Emissions: SAB Review Draft. EPA/600/
8-90/057E Office of Research and Development, Washington, D.C. The
document is available electronically at www.epa.gov/ncea/
dieselexh.htm.
\40\ As used in this rule, environmental risk is defined as the
risk (i.e. a mathematical probability) that lung cancer would be
observed in the population after a lifetime exposure to diesel
exhaust. Exposure levels may be occupational lifetime or
environmental lifetime exposures. An environmental risk in the
magnitude of 10-5 translates as the probability of lung
cancer being evidenced in one person in a population of one hundred
thousand having a lifetime exposure.
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The environmental risk estimates included in the Agency's risk
perspective are meant only to gauge the possible magnitude of risk to
provide a means to understand the potential significance of the lung
cancer hazard. The estimates are not to be construed as cancer unit
risk estimates and are not suitable for use in analyses which would
estimate possible lung cancer cases in exposed populations.
EPA recognizes that, as in all such risk assessments, there are
uncertainties in this assessment of the environmental risk range
including limitations in exposure data, uncertainty with respect to the
most accurate characterization of the risk increases observed in the
epidemiological studies, chemical changes in diesel exhaust over time,
and extrapolation of the risk from occupational to ambient
environmental exposures. As with any such risk assessment for a
carcinogen, despite EPA's thorough examination of the available
epidemiologic evidence and exposure information, at this time EPA can
not rule out the possibility that the lower end of the risk range
includes zero.41 However, it is the Agency's best scientific
judgement that the assumptions and other elements of this analysis are
reasonable and appropriate for identifying the risk potential based on
the scientific information currently available.
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\41\ EPA's scientific judgment (which CASAC has supported) is
that diesel exhaust is likely to be carcinogenic to humans. Notably,
similar scientific judgements about the carcinogenicity of diesel
exhaust have been recently made by the National Toxicology Program
of the Department of Health and Human Services, NIOSH, WHO, and OEHA
of the State of California. In the risk perspective discussed above,
EPA recognizes the possibility that the lower end of the
environmental risk range includes zero. The risks could be zero
because (1) some individuals within the population may have a high
tolerance level to exposure from diesel exhaust and therefore are
not susceptible to the cancer risks from environmental exposure and
(2) although EPA has not seen evidence of this, there could be a
threshold of exposure below which there is no cancer risk.
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The Agency believes that the risk estimation techniques that were
used in the draft Assessment to gauge the potential for and possible
magnitude of risk are reasonable and the CASAC

[[Page 5023]]

panel has concurred with the Assessment's discussion of the possible
environmental risk range with an understanding that some clarifications
and caveats would be added to the final version of the Assessment.
Details of the technical approach used in estimating the possible range
of environmental risks and uncertainties are provided in the RIA.
In the draft Assessment, the Agency also provided a discussion of
the potential overlap and/or relatively small difference between some
occupational settings where increased lung cancer risk is reported and
ambient environmental exposures. The potential for small exposure
differences underscores the concern that some degree of occupational
risk may also be present in the environmental setting and that
extrapolation of occupational risk to ambient environmental exposure
levels should be more confidently judged to be appropriate. The
relevant exposure information is presented in the RIA.
In the absence of having a unit cancer risk to assess environmental
risk, EPA has considered the relevant epidemiological studies and
principles for their assessment, the relative risk from occupational
exposure as assessed by others, and relative exposure differences
between occupational and ambient environmental levels of diesel exhaust
exposure.
While uncertainty exists in estimating the possible magnitude of
the environmental risk range, the likely hazard to humans together with
the potential for significant environmental risks leads the Agency to
believe that diesel exhaust emissions should be reduced in order to
protect the public's health. We believe that this is a prudent measure
in light of:
The designation that diesel exhaust is likely to be
carcinogenic to humans,
The exposure of the entire population to various levels of
diesel exhaust,
The consistent observation of significantly increased lung
cancer risk in workers exposed to diesel exhaust, and
The potential overlap and/or relatively small difference
between some occupational settings where increased lung cancer risk is
reported and ambient exposures.
In the late 1980s, the International Agency for Research on Cancer
(IARC) determined that diesel exhaust is ``probably carcinogenic to
humans'' and the National Institute for Occupational Safety and Health
classified diesel exhaust a ``potential occupational
carcinogen.''42 43 Based on IARC findings, the
State of California identified diesel exhaust in 1990 as a chemical
known to the State to cause cancer. In 1996, the International
Programme on Chemical Safety of the World Health Organization listed
diesel exhaust as a ``probable'' human carcinogen.44 In
1998, the California Office of Environmental Health Hazard Assessment
(OEHHA, California EPA) identified diesel PM as a toxic air contaminant
due to the noncancer and cancer hazard and because of the potential
magnitude of the cancer risk.45 Most recently, the U.S.
Department of Health and Human Services National Toxicology Program
designated diesel exhaust particles as ``reasonably anticipated to be a
human carcinogen'' in its Ninth Report on Carcinogens.46 The
concern for a carcinogenicity hazard resulting from diesel exhaust
exposures is longstanding and widespread.
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\42\ National Institute for Occupational Safety and Health
(NIOSH) (1988) Carcinogenic effects of exposure to diesel exhaust.
NIOSH Current Intelligence Bulletin 50. DHHS, Publication No. 88-
116. Centers for Disease Control, Atlanta, GA.
43 International Agency for Research on Cancer (1989)
Diesel and gasoline engine exhausts and some nitroarenes, Vol. 46.
Monographs on the evaluation of carcinogenic risks to humans. World
Heath Organization, International Agency for Research on Cancer,
Lyon, France.
\44\ World Health Organization (1996) Diesel fuel and exhaust
emissions: International program on chemical safety. World Health
Organization, Geneva, Switzerland.
\45\ Office of Environmental Health Hazard Assessment (1998)
Health risk assessment for diesel exhaust, April 1998. California
Environmental Protection Agency, Sacramento, CA.
\46\ U.S. Department of Health and Human Services (2000) Ninth
report on carcinogens. National Toxicology Program, Research
Triangle Park, NC. ehis.niehs.nih.gov/roc/toc9.html.
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b. Noncancer Effects of Diesel Exhaust
The acute and chronic exposure-related noncancer effects of diesel
exhaust emissions are also of concern to the Agency. Acute exposure to
diesel exhaust can result in physiologic symptoms consistent with
irritation and inflammation, and evidence of immunological effects
including increased reaction to allergens and some symptoms associated
with asthma. The acute effects data, however, lack sufficient detail to
permit the calculation of protective levels for human exposure.
For chronic diesel exhaust exposure, EPA is completing the
development of an inhalation reference concentration (RfC). The RfC is
an estimate of the continuous human inhalation exposure (including
sensitive subgroups) that is likely to be without an appreciable risk
of deleterious noncancer effects during a lifetime. While the limited
amount of human data are suggestive of respiratory distress, animal
test data are quite definitive in providing a basis to anticipate a
hazard to the human lung based on the irritant and inflammatory
reactions in test animals. Thus, EPA believes that chronic diesel
exhaust exposure, at sufficient exposure levels, increases the hazard
and risk of an adverse health effect. Based on CASAC advice regarding
the use of the animal data to derive the RfC, the Agency will provide
in the final Assessment in 2001 an RfC based on diesel exhaust effects
in test animals of approximately 5 g/m 3.
In addition, it is also instructive to recognize that diesel
exhaust particulate matter is part of ambient fine PM. A qualitative
comparison of adverse effects of exposure to ambient fine PM and diesel
exhaust particulate matter shows that the respiratory system is
adversely affected in both cases, though a wider spectrum of adverse
effects has been identified for ambient fine PM. Relative to the diesel
PM database, there is a wealth of human data for fine PM noncancer
effects. Since diesel exhaust PM is a component of ambient fine PM, the
fine PM health effects data base can be informative. The final
Assessment will discuss the fine PM health effects data and its
relation to evaluating health effects associated with diesel exhaust.
5. Other Criteria Pollutants
The standards being finalized today will help reduce levels of
three other pollutants for which NAAQS have been established: carbon
monoxide (CO), nitrogen dioxide (NO2), and sulfur dioxide
(SO2). As of July, 2000, every area in the United States has
been designated to be in attainment with the NO2 NAAQS.
There were 28 areas designated as nonattainment with the SO2
standard, and 17 areas designated CO nonattainment areas.
A health threat of carbon monoxide at outdoor levels occurs for
those who suffer from cardiovascular disease, such as angina petoris,
where it can exacerbate the effects. Studies also show that outdoor
levels can lower peak performance from individuals that are exercising
and lower exercise tolerance of sensitive individuals. EPA believes
that epidemiological evidence suggests that there is a risk of
premature mortality and lowered birth weight from CO
exposure.47 The Carbon Monoxide Criteria Document was
finalized in

[[Page 5024]]

August 2000 and made available to the public at that time.
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\47\ U.S. Environmental Protection Agency, Air Quality Criteria
for Carbon Monoxide, June 2000.
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6. Other Air Toxics
In addition to NOX and particulates, heavy-duty vehicle
emissions contain several other substances that are known or suspected
human or animal carcinogens, or have serious noncancer health effects.
These include benzene,1,3-butadiene, formaldehyde, acetaldehyde,
acrolein, and dioxin. For some of these pollutants, heavy-duty engine
emissions are believed to account for a significant proportion of total
nation-wide emissions. Although these emissions will decrease in the
short term, they are expected to increase between 2010 and 2020 without
the emission limits, as the number of miles traveled by heavy-duty
trucks increases. In the RIA, we present current and projected
exposures to benzene, 1,3-butadiene, formaldehyde, and acetaldehyde
from all on-highway motor vehicles.
By reducing hydrocarbon and other organic emissions, both in gas
phase and bound to particles, the emission control program in today's
action will also reduce the direct emissions of air toxics from HDVs.
Today's action will reduce exposure to hydrocarbon and other organic
emissions and therefore help reduce the impact of HDV emissions on
cancer and noncancer health effects.
a. Benzene
Highway mobile sources account for 42 percent of nationwide
emissions of benzene and HDVs account for 7 percent of all highway
vehicle benzene emissions.48 The EPA has recently
reconfirmed that benzene is a known human carcinogen by all routes of
exposure (including leukemia at high, prolonged air exposures), and is
associated with additional health effects including genetic changes in
humans and animals and increased proliferation of bone marrow cells in
mice.49 50 51 EPA believes that the
data indicate a causal relationship between benzene exposure and acute
lymphocytic leukemia and suggest a relationship between benzene
exposure and chronic non-lymphocytic leukemia and chronic lymphocytic
leukemia. Respiration is the major source of human exposure and at
least half of this exposure is attributable to gasoline vapors and
automotive emissions. A number of adverse noncancer health effects
including blood, disorders, such as preleukemia and aplastic anemia,
have also been associated with low-dose, long-term exposure to benzene.
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\48\ U.S. EPA (2000) 1996 National Toxics Inventory. http://
www.epa.gov/ttnatw01/nata. Inventory values for 1,3 butadiene,
formaldehyde, acetaldehyde, and acrolein discussed below also come
from this source.
\49\ International Agency for Research on Cancer, IARC
monographs on the evaluation of carcinogenic risk of chemicals to
humans, Volume 29, Some industrial chemicals and dyestuffs,
International Agency for Research on Cancer, World Health
Organization, Lyon, France, p. 345-389, 1982.
50 Irons, R.D., W.S. Stillman, D.B. Colagiovanni, and
V.A. Henry, Synergistic action of the benzene metabolite
hydroquinone on myelopoietic stimulating activity of granulocyte/
macrophage colony-stimulating factor in vitro, Proc. Natl. Acad.
Sci. 89:3691-3695, 1992.
51 Environmental Protection Agency, Carcinogenic
Effects of Benzene: An Update, National Center for Environmental
Assessment, Washington, DC. 1998.
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b. 1,3-Butadiene
Highway mobile sources account for 42 percent of the annual
emissions of 1,3-butadiene and HDVs account for 15 percent of the
highway vehicle portion. Today's program will play an important role in
reducing in the mobile contribution of 1,3-butadiene. Reproductive and/
or developmental effects have been observed in mice and rats following
inhalation exposure to 1,3-butadiene.52 No information is
available on developmental/reproductive effects in humans following
exposure to 1,3-butadiene. In the EPA1998 draft Health Risk Assessment
of 1,3-Butadiene, that was reviewed by the SAB, EPA proposed that 1,3-
butadiene is a known human carcinogen based on human epidemiologic,
laboratory animal data, and supporting data such as the genotoxicity of
1,3-butadiene metabolites.53 The Environmental Health
Committee of EPA's Scientific Advisory Board (SAB), reviewed the draft
document in August 1998 and recommended that 1,3-butadiene be
classified as a probable human carcinogen, stating that designation of
1,3-butadiene as a known human carcinogen should be based on
observational studies in humans, without regard to mechanistic or other
information.54 In applying the 1996 proposed Guidelines for
Carcinogen Risk Assessment, the Agency relies on both observational
studies in humans as well as experimental evidence demonstrating
causality and therefore the designation of 1,3-butadiene as a known
human carcinogen remains applicable.55 The Agency has
revised the draft Health Risk Assessment of 1,3-Butadiene based on the
SAB and public comments. The draft Health Risk Assessment of 1,3-
Butadiene will undergo the Agency consensus review, during which time
additional changes may be made prior to its public release and
placement on the Integrated Risk Information System (IRIS).
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\52\ Environmental Protection Agency. Draft Health Risk
Assessment of 1,3-Butadiene, National Center for Environmental
Assessment, Office of Research and Development, U.S. EPA, EPA/600/P-
98/001A, February 1998.
\53\ An SAB Report: Review of the Health Risk Assessment of 1,3-
Butadiene. EPA-SAB-EHC-98, August, 1998.
\54\ Scientific Advisory Board. 1998. An SAB Report: Review of
the Health Risk Assessment of 1,3-Butadiene. EPA-SAB-EHC-98, August,
1998.
\55\ [55]: EPA 1996. Proposed guidelines for carcinogen risk
assessment. Federal Register 61(79):17960-18011.
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c. Formaldehyde
Highway mobile sources contribute 24 percent of the national
emissions of formaldehyde, and HDVs account for 36 percent of the
highway portion. EPA has classified formaldehyde as a probable human
carcinogen based on evidence in humans and in rats, mice, hamsters, and
monkeys.56 Epidemiological studies in occupationally exposed
workers suggest that long-term inhalation of formaldehyde may be
associated with tumors of the nasopharyngeal cavity (generally the area
at the back of the mouth near the nose), nasal cavity, and sinus.
Formaldehyde exposure also causes a range of noncancer health effects,
including irritation of the eyes (tearing of the eyes and increased
blinking) and mucous membranes. Sensitive individuals may experience
these adverse effects at lower concentrations than the general
population and in persons with bronchial asthma, the upper respiratory
irritation caused by formaldehyde can precipitate an acute asthmatic
attack. The agency is currently conducting a reassessment of risk from
inhalation exposure to formaldehyde.
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\56\ Environmental Protection Agency, Assessment of Health Risks
to Garment Workers and Certain Home Residents from Exposure to
Formaldehyde, Office of Pesticides and Toxic Substances, April 1987.
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d. Acetaldehyde
Highway mobile sources contribute 29 percent of the national
acetaldehyde emissions and HDVs are responsible for approximately 33
percent of these highway mobile source emissions. Acetaldehyde is
classified as a probable human carcinogen and is considered moderately
toxic by the inhalation, oral, and intravenous routes. The primary
acute effect of exposure to acetaldehyde vapors is irritation of the
eyes, skin, and respiratory tract. At high concentrations, irritation
and pulmonary effects can occur, which could facilitate the uptake of
other contaminants. The agency is currently conducting a reassessment
of

[[Page 5025]]

risk from inhalation exposure to acetaldehyde.
e. Acrolein
Highway mobile sources contribute 16 percent of the national
acrolein emissions and HDVs are responsible for approximately 39
percent of these highway mobile source emissions. Acrolein is extremely
toxic to humans when inhaled, with acute exposure resulting in upper
respiratory tract irritation and congestion. The Agency has developed a
reference concentration for inhalation (RfC) of acrolein of 0.02
micrograms/m3.57 Although no information is
available on its carcinogenic effects in humans, based on laboratory
animal data, EPA considers acrolein a possible human carcinogen.
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\57\ U.S. EPA (1993) Environmental Protection Agency, Integrated
Risk Information System (IRIS), National Center for Environmental
Assessment, Cincinnati, OH.
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f. Dioxins
Recent studies have confirmed that dioxins are formed by and
emitted from heavy-duty diesel trucks and are estimated to account for
1.2 percent of total dioxin emissions in 1995. In the environment, the
pathway of immediate concern is the food pathway (e.g., human ingestion
of certain foods, e.g. meat and dairy products contaminated by dioxin)
which may be affected by deposition of dioxin from the atmosphere. EPA
classified dioxins as probable human carcinogens in 1985. Recently EPA
has proposed, and the Scientific Advisory Board has concurred, to
classify one dioxin compound, 2,3,7,8-tetrachlorodibenzo-p-dioxin as a
human carcinogen and the complex mixtures of dioxin-like compounds as
likely to be carcinogenic to humans using the draft 1996 carcinogen
risk assessment guidelines.58 Using the 1986 cancer risk
assessment guidelines, the hazard characterization for 2,3,7,8-
tetrachlorodibenzo-p-dioxin is ``known'' human carcinogen and the
hazard characterization for complex mixtures of dioxin-like compounds
is ``probable'' human carcinogens. Acute and chronic noncancer effects
have also been reported for dioxin.
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\58\ U.S. EPA (2000) Exposure and Human Health Reassessment of
2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds.
Part III: Integrated Summary and Risk Characterization for 2,3,7,8-
Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds. External
Review Draft. EPA/600/P-00/001Ag.
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7. Other Welfare and Environmental Effects
Some commenters challenged the Agency's use of adverse welfare and
environmental effects associated with emissions from heavy-duty
vehicles as a partial basis for this rulemaking. Other commenters went
to great lengths to support the Agency's inclusion of these welfare and
environmental effects. Additional information has been added since the
proposal in order to update and clarify the available information on
welfare and environmental impacts of heavy-duty vehicle emissions. The
following section presents information on four categories of public
welfare and environmental impacts related to heavy-duty vehicle
emissions: acid deposition, eutrophication of water bodies, POM
deposition, and impairment of visibility.
a. Acid Deposition
Acid deposition, or acid rain as it is commonly known, occurs when
SO2 and NOX react in the atmosphere with water,
oxygen, and oxidants to form various acidic compounds that later fall
to earth in the form of precipitation or dry deposition of acidic
particles.59 It contributes to damage of trees at high
elevations and in extreme cases may cause lakes and streams to become
so acidic that they cannot support aquatic life. In addition, acid
deposition accelerates the decay of building materials and paints,
including irreplaceable buildings, statues, and sculptures that are
part of our nation's cultural heritage. To reduce damage to automotive
paint caused by acid rain and acidic dry deposition, some manufacturers
use acid-resistant paints, at an average cost of $5 per vehicle--a
total of $61 million per year if applied to all new cars and trucks
sold in the U.S.
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\59\ Much of the information in this subsection was excerpted
from the EPA document, Human Health Benefits from Sulfate Reduction,
written under Title IV of the 1990 Clean Air Act Amendments, U.S.
EPA, Office of Air and Radiation, Acid Rain Division, Washington, DC
20460, November 1995.
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Acid deposition primarily affects bodies of water that rest atop
soil with a limited ability to neutralize acidic compounds. The
National Surface Water Survey (NSWS) investigated the effects of acidic
deposition in over 1,000 lakes larger than 10 acres and in thousands of
miles of streams. It found that acid deposition was the primary cause
of acidity in 75 percent of the acidic lakes and about 50 percent of
the acidic streams, and that the areas most sensitive to acid rain were
the Adirondacks, the mid-Appalachian highlands, the upper Midwest and
the high elevation West. The NSWS found that approximately 580 streams
in the Mid-Atlantic Coastal Plain are acidic primarily due to acidic
deposition. Hundreds of the lakes in the Adirondacks surveyed in the
NSWS have acidity levels incompatible with the survival of sensitive
fish species. Many of the over 1,350 acidic streams in the Mid-Atlantic
Highlands (mid-Appalachia) region have already experienced trout losses
due to increased stream acidity. Emissions from U.S. sources contribute
to acidic deposition in eastern Canada, where the Canadian government
has estimated that 14,000 lakes are acidic. Acid deposition also has
been implicated in contributing to degradation of high-elevation spruce
forests that populate the ridges of the Appalachian Mountains from
Maine to Georgia. This area includes national parks such as the
Shenandoah and Great Smoky Mountain National Parks.
A recent study of emissions trends and acidity of waterbodies in
the Eastern United States by the General Accounting Office (GAO) found
that sulfates declined in 92 percent of a representative sample of
lakes from 1992 to 1999, and nitrate levels increased in 48 percent of
the lakes sampled.60 The decrease in sulfates is consistent
with emissions trends, but the increase in nitrates is inconsistent
with the stable levels of nitrogen emissions and deposition. The study
suggests that the vegetation and land surrounding these lakes have lost
some of their previous capacity to use nitrogen, thus allowing more of
the nitrogen to flow into the lakes and increase their acidity.
Recovery of acidified lakes is expected to take a number of years, even
where soil and vegetation have not been ``nitrogen saturated,'' as EPA
called the phenomenon in a 1995 study.61 This situation
places a premium on reductions of SOX and especially
NOX from all sources, including HDVs, in order to reduce the
extent and severity of nitrogen saturation and acidification of lakes
in the Adirondacks and throughout the United States.
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\60\ Acid Rain: Emissions Trends and Effects in the Eastern
United States, US General Accounting Office, March, 2000 (GOA/RCED-
00-47).
\61\ Acid Deposition Standard Feasibility Study: Report to
Congress, EPA 430R-95-001a, October, 1995.
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The SOX and NOX reductions from today's
action will help reduce acid rain and acid deposition, thereby helping
to reduce acidity levels in lakes and streams throughout the country
and help accelerate the recovery of acidified lakes and streams and the
revival of ecosystems adversely affected by acid deposition. Reduced
acid deposition levels will also help reduce stress on forests, thereby
accelerating reforestation efforts and improving timber production.
Deterioration of our

[[Page 5026]]

historic buildings and monuments, and of buildings, vehicles, and other
structures exposed to acid rain and dry acid deposition also will be
reduced, and the costs borne to prevent acid-related damage may also
decline. While the reduction in sulfur and nitrogen acid deposition
will be roughly proportional to the reduction in SOX and
NOX emissions, respectively, the precise impact of today's
action will differ across different areas.
b. Eutrophication and Nitrification
Eutrophication is the accelerated production of organic matter,
particularly algae, in a water body. This increased growth can cause
numerous adverse ecological effects and economic impacts, including
nuisance algal blooms, dieback of underwater plants due to reduced
light penetration, and toxic plankton blooms. Algal and plankton blooms
can also reduce the level of dissolved oxygen, which can also adversely
affect fish and shellfish populations.
In 1999, NOAA published the results of a five year national
assessment of the severity and extent of estuarine eutrophication. An
estuary is defined as the inland arm of the sea that meets the mouth of
a river. The 138 estuaries characterized in the study represent more
than 90 percent of total estuarine water surface area and the total
number of US estuaries. The study found that estuaries with moderate to
high eutrophication conditions represented 65 percent of the estuarine
surface area. Eutrophication is of particular concern in coastal areas
with poor or stratified circulation patterns, such as the Chesapeake
Bay, Long Island Sound, or the Gulf of Mexico. In such areas, the
``overproduced'' algae tends to sink to the bottom and decay, using all
or most of the available oxygen and thereby reducing or eliminating
populations of bottom-feeder fish and shellfish, distorting the normal
population balance between different aquatic organisms, and in extreme
cases causing dramatic fish kills.
Severe and persistent eutrophication often directly impacts human
activities. For example, losses in the nation's fishery resources may
be directly caused by fish kills associated with low dissolved oxygen
and toxic blooms. Declines in tourism occur when low dissolved oxygen
causes noxious smalls and floating mats of algal blooms create
unfavorable aesthetic conditions. Risks to human health increase when
the toxins from algal blooms accumulate in edible fish and shellfish,
and when toxins become airborne, causing respiratory problems due to
inhalation. According to the NOAA report, more than half of the
nation's estuaries have moderate to high expressions of at least one of
these symptoms--an indication that eutrophication is well developed in
more than half of U.S. estuaries.
In recent decades, human activities have greatly accelerated
nutrient inputs, such as nitrogen and phosphorous, causing excessive
growth of algae and leading to degraded water quality and associated
impairments of freshwater and estuarine resources for human
uses.62 Since 1970, eutrophic conditions worsened in 48
estuaries and improved in 14. In 26 systems, there was no trend in
overall eutrophication conditions since 1970.63 On the New
England coast, for example, the number of red and brown tides and
shellfish problems from nuisance and toxic plankton blooms have
increased over the past two decades, a development thought to be linked
to increased nitrogen loadings in coastal waters. Long-term monitoring
in the United States, Europe, and other developed regions of the world
shows a substantial rise of nitrogen levels in surface waters, which
are highly correlated with human-generated inputs of nitrogen to their
watersheds.
---------------------------------------------------------------------------

\62\ Deposition of Air Pollutants to the Great Waters, Third
Report to Congress, June, 2000.
\63\ Deposition of Air Pollutants to the Great Waters, Third
Report to Congress, June, 2000. Great Waters are defined as the
Great Lakes, the Chesapeake Bay, Lake Champlain, and coastal waters.
The first report to Congress was delivered in May, 1994; the second
report to Congress in June, 1997.
---------------------------------------------------------------------------

On a national basis, the most frequently recommended control
strategies by experts surveyed by National Oceanic and Atmospheric
Administration (NOAA) between 1992-1997 were agriculture, wastewater
treatment, urban runoff, and atmospheric deposition.64 In
its Third Report to Congress on the Great Waters, EPA reported that
atmospheric deposition contributes from 2 to 38 percent of the nitrogen
load to certain coastal waters.65 A review of peer reviewed
literature in 1995 on the subject of air deposition suggests a typical
contribution of 20 percent or higher.66 Human-caused
nitrogen loading to the Long Island Sound from the atmosphere was
estimated at 14 percent by a collaboration of federal and state air and
water agencies in 1997.67 The National Exposure Research
Laboratory, US EPA, estimated based on prior studies that 20 to 35
percent of the nitrogen loading to the Chesapeake Bay is attributable
to atmospheric deposition.68 The mobile source portion of
atmospheric NOX contribution to the Chesapeake Bay was
modeled at about 30 percent of total air deposition.69
---------------------------------------------------------------------------

\64\ Bricker, Suzanne B., et al., National Estuarine
Eutrophication Assessment, Effects of Nutrient Enrichment in the
Nation's Estuaries, National Ocean Service, National Oceanic and
Atmospheric Administration, September, 1999.
\65\ Deposition of Air Pollutants to the Great Waters, Third
Report to Congress, June, 2000.
\66\ Valigura, Richard, et al., Airsheds and Watersheds II: A
Shared Resources Workshop, Air Subcommittee of the Chesapeake Bay
Program, March, 1997.
\67\ The Impact of Atmospheric Nitrogen Deposition on Long
Island Sound, The Long Island Sound Study, September, 1997.
\68\ Dennis, Robin L., Using the Regional Acid Deposition Model
to Determine the Nitrogen Deposition Airshed of the Chesapeake Bay
Watershed, SETAC Technical Publications Series, 1997.
\69\ Dennis, Robin L., Using the Regional Acid Deposition Model
to Determine the Nitrogen Deposition Airshed of the Chesapeake Bay
Watershed, SETAC Technical Publications Series, 1997.
---------------------------------------------------------------------------

Deposition of nitrogen from heavy-duty vehicles contributes to
elevated nitrogen levels in waterbodies. In the Chesapeake Bay region,
modeling shows that mobile source deposition occurs in relatively close
proximity to highways, such as the 1-95 corridor which covers part of
the Bay surface. The new standards for heavy-duty vehicles will reduce
total NOX emissions by 2.6 million tons in 2030. The
NOX reductions will reduce the airborne nitrogen deposition
that contributes to eutrophication of watersheds, particularly in
aquatic systems where atmospheric deposition of nitrogen represents a
significant portion of total nitrogen loadings.
c. Polycyclic Organic Matter Deposition
EPA's Great Waters Program has identified 15 pollutants whose
deposition to water bodies has contributed to the overall contamination
loadings to the these Great Waters.70 One of these 15
pollutants, a group known as polycyclic organic matter (POM), are
compounds that are mainly adhered to the particles emitted by mobile
sources and later fall to earth in the form of precipitation or dry
deposition of particles. The mobile source contribution of the 7 most
toxic POM is at least 62 tons/year and represents only those POM that
adhere to mobile source particulate emissions.71 The
majority of these emissions are produced by diesel engines.
---------------------------------------------------------------------------

\70\ Deposition of Air Pollutants to the Great Waters--Third
Report to Congress, June, 2000, Office of Air Quality Planning and
Standards Deposition of Air Pollutants to the Great Waters--Second
Report to Congress, Office of Air Quality Planning and Standards,
June 1997, EPA-453/R-97-011.
\71\ The 1996 National Toxics Inventory, Office of Air Quality
Planning and Standards, October 1999.

---------------------------------------------------------------------------

[[Page 5027]]

POM is generally defined as a large class of chemicals consisting
of organic compounds having multiple benzene rings and a boiling point
greater than 100 degrees C. Polycyclic aromatic hydrocarbons are a
chemical class that is a subset of POM. POM are naturally occurring
substances that are byproducts of the incomplete combustion of fossil
fuels and plant and animal biomass (e.g., forest fires). Also, they
occur as byproducts from steel and coke productions and waste
incineration. Evidence for potential human health effects associated
with POM comes from studies in animals (fish, amphibians, rats) and in
human cells culture assays. Reproductive, developmental, immunological,
and endocrine (hormone) effects have been documented in these systems.
Many of the compounds included in the class of compounds known as POM
are classified by EPA as probable human carcinogens based on animal
data.
Evidence for potential human health effects associated with POM
comes from studies in animals (fish, amphibians, rats) and in human
cells culture assays. Reproductive, developmental, immunological, and
endocrine (hormone) effects have been documented in these systems. Many
of the compounds included in the class of compounds known as POM are
classified by EPA as probable human carcinogens based on animal data.
The particulate reductions from today's action will help reduce not
only the particulate emissions from highway diesel engines but also the
deposition of the POM adhering to the particles, thereby helping to
reduce health effects of POM in lakes and streams, accelerate the
recovery of affected lakes and streams, and revive the ecosystems
adversely affected.
d. Visibility and Regional Haze
Visibility impairment, also called regional haze, is a complex
problem caused by a variety of sources, both natural and anthropogenic
(e.g., motor vehicles). Regional haze masks objects on the horizon and
reduces the contrast of nearby objects. The formation, extent, and
intensity of regional haze are functions of meteorological and chemical
processes, which sometimes cause fine particle loadings to remain
suspended in the atmosphere for several days and to be transported
hundreds of kilometers from their sources (NRC, 1993).
Visibility has been defined as the degree to which the atmosphere
is transparent to visible light (NRC, 1993). Visibility impairment is
caused by the scattering and absorption of light by particles and gases
in the atmosphere. Fine particles (0.1 to 2.5 microns in diameter) are
more effective per unit mass concentration at impairing visibility than
either larger or smaller particles (NAPAP, 1991). Most of the diesel
particle mass emitted by diesel engines falls within this fine particle
size range. Light absorption is often caused by elemental carbon, a
product of incomplete combustion from activities such as burning diesel
fuel or wood. These particles cause light to be scattered or absorbed,
thereby reducing visibility.
Heavy-duty vehicles contribute a significant portion of the
emissions of direct PM, NOX, and SOX that result
in ambient PM that contributes to regional haze and impaired
visibility. The Grand Canyon Visibility Transport Commission's report
found that heavy-duty diesel vehicles contribute 41 percent of fine
elemental carbon or soot, 20 percent of NOX, 7 percent of
fine organic carbon, and 6 percent of SOX. The report also
found that reducing total mobile source emissions is an essential part
of any program to protect visibility in the Western U.S. The Commission
identified mobile source pollutants of concern as VOC, NOX,
and elemental and organic carbon. The Western Governors Association, in
later commenting on the Regional Haze Rule and on protecting the 16
Class I areas on the Colorado Plateau, stated that the federal
government, and particularly EPA, must do its part in regulating
emissions from mobile sources that contribute to regional haze in these
areas. As described more fully later in this section, today's action
will result in large reductions in these pollutants. These reductions
are expected to provide an important step towards improving visibility
across the nation. Emissions reductions being achieved to attain the 1-
hour ozone and PM10 NAAQS will assist in visibility
improvements. Moreover, the timing of the reductions from the standards
fits very well with the goals of the regional haze program. We will
work with the regional planning bodies to make sure they have the
information to take account of the reductions from this final rule in
their planning efforts.
The Clean Air Act contains provisions designed to protect national
parks and wilderness areas from visibility impairment. In 1999, EPA
promulgated a rule that will require States to develop plans to
dramatically improve visibility in national parks. Although it is
difficult to determine natural visibility levels, we believe that
average visual range in many Class I areas in the United States is
significantly less (about 50-66 percent of natural visual range in the
West, about 20 percent of natural visual range in the East) than the
visual range that will exist without anthropogenic air pollution. The
final Regional Haze Rule establishes a 60-year time period for planning
purposes, with several near term regulatory requirements, and is
applicable to all 50 states. One of the obligations is for States to
representative conduct visibility monitoring in mandatory Class I
Federal areas and determine baseline conditions using data for year
2000 to 2004. Reductions of particles, NOX, sulfur, and VOCs
from this rulemaking will have a significant impact on moving all
states towards achieving long-term visibility goals, as outlined in the
1999 Regional Haze Rule.

C. Contribution from Heavy-Duty Vehicles

Nationwide, heavy-duty vehicles are projected to contribute about
15 percent of the total NOX inventory, and 28 percent of the
mobile source inventory in 2007. Heavy-duty NOX emissions
also contribute to fine particulate concentrations in ambient air due
to the transformation in the atmosphere to nitrates. The NOX
reductions resulting from today's standards will therefore have a
considerable impact on the national NOX inventory. All
highway vehicles account for 34 percent and heavy-duty highway vehicles
account for 20 percent of the mobile source portion of national
PM10 emissions in 2007. The heavy-duty portion of the
inventory is often greater in the cities, and the reductions in this
rulemaking will have a relatively greater benefit in those areas.
1. NOX Emissions
Heavy-duty vehicles are important contributors to the national
inventories of NOX emissions. Without NOX
reductions from this rule, HDVs are expected to contribute
approximately 18 percent of annual NOX emissions in 1996.
The HDV contribution is predicted to fall to 15 percent in 2007 and 14
percent in 2020 due to reductions from the 2004 heavy-duty rulemaking,
and then rise again to 16 percent of total NOX inventory by
2030 (Table II.C-1). Annual NOX reductions from this rule
are expected to total 2.6 million tons in 2030.

[[Page 5028]]

Table II.C-1--NOX Emissions From HDVs With and Without Reductions From This Rule
----------------------------------------------------------------------------------------------------------------
Without this rule (base case) With this rule
---------------------------------------------------------------------------------------------- (control case)
------------------
HDV annual NOX HDV annual NOX Reductions in
Year tons tons as a percent annual HDV NOX
of total NOX tons
----------------------------------------------------------------------------------------------------------------
1996................................................... 4,810,000 18 n/a
2007................................................... 3,040,000 15 58,000
2020................................................... 2,560,000 14 1,820,000
2030................................................... 2,960,000 16 2,570,000
----------------------------------------------------------------------------------------------------------------

The contribution of heavy-duty vehicles to NOX
inventories in many MSAs is significantly greater than that reflected
in the national average. For example, HDV contributions to total annual
NOX is greater than the national average in the eight
metropolitan statistical areas listed in Table II.C-2. Examples of
major cities with a history of persistent ozone violations that are
heavily impacted by NOX emissions from HDVs include: Los
Angeles, Washington, DC, San Diego, Hartford, Atlanta, Sacramento. As
presented in the table below, HDV's contribute from 22 percent to 33
percent of the total NOX inventories in these selected
cities. NOX emissions also contribute to the formation of
fine particulate matter, especially in the West. In all areas,
NOX also contributes to environmental and welfare effects
such as regional haze, and eutrophication and nitrification of water
bodies.

Table II.C-2--Heavy-Duty Vehicle Percent Contribution to NOX Inventories
in Selected Urban Areas in 2007
------------------------------------------------------------------------
HDV NOX as
HDV NOX as portion of
MSA, CMSA / State portion of mobile
total NOX source NOX
(%) (%)
------------------------------------------------------------------------
National.................................... 15 28
Sacramento, CA.............................. 33 37
Hartford, CT................................ 28 38
San Diego, CA............................... 25 28
San Francisco, CA........................... 24 29
Atlanta, GA................................. 22 34
Los Angeles................................. 22 26
Dallas...................................... 22 28
Washington-Baltimore, MSA................... 22 36
------------------------------------------------------------------------

2. PM Emissions
Nationally, we estimate that primary emissions of PM10
to be about 33 million tons/year in 2007. Fugitive dust, other
miscellaneous sources and crustal material (wind erosion) constitute
approximately 90 percent of the 2007 PM10 inventory.
However, there is evidence from ambient studies that emissions of these
materials may be overestimated and/or that once emitted they have less
of an influence on monitored PM concentration than this inventory share
would suggest. Mobile sources account for 22 percent of the
PM10 inventory (excluding the contribution of miscellaneous
and natural sources) and highway heavy-duty engines, the subject of
today's action, account for 20 percent of the mobile source portion of
national PM10 emissions in 2007.
The contribution of heavy-duty vehicle emissions to total PM
emissions in some metropolitan areas is substantially higher than the
national average. This is not surprising, given the high density of
these engines operating in these areas. For example, in Los Angeles,
Atlanta, Hartford, San Diego, Santa Fe, Cincinnati, and Detroit, the
estimated 2007 highway heavy-duty vehicle contribution to mobile source
PM10 ranges from 25 to 38 percent, while the national
percent contribution to mobile sources for 2007 is projected to be
about 20 percent. As illustrated in Table II.C-3, heavy-duty vehicles
operated in El Paso, Indianapolis, San Francisco, and Minneapolis also
account for a higher portion of the mobile source PM inventory than the
national average. These data are based on updated inventories developed
for this rulemaking. Importantly, these estimates do not include the
contribution from secondary PM, which is an important component of
diesel PM.

Table II.C-3--2007 Heavy-Duty Vehicle Contribution to Urban Mobile
Source PM Inventories
------------------------------------------------------------------------
HDV PM
Contribution
MSA, State to mobile
source PMGa
------------------------------------------------------------------------
National (48 State)....................................... 20
Atlanta, GA MSA........................................... 25
Cincinnati-Hamilton, OH-KY-IN CMSA........................ 26
Detroit-Ann Arbor-Flint, MI CMSA.......................... 25
El Paso, TX MSA........................................... 23
Hartford, CT MSA.......................................... 30
Indianapolis, IN MSA...................................... 23
Los Angeles-Riverside-Orange County, CA CMSA.............. 25
Minneapolis-St. Paul, MN-WI MSA........................... 23
San Diego, CA MSA......................................... 27
San Francisco-Oakland-San Jose, CA CMSA................... 24
Santa Fe, NM MSA.......................................... 38
------------------------------------------------------------------------
a Direct exhaust emissions only; excludes secondary PM.

The city-specific emission inventory analysis and investigations of
ambient PM2.5 summarized in the RIA indicate that the
contribution of diesel engines to PM inventories in several urban areas
around the U.S. is much higher than indicated by the national PM
emission inventories only. One possible explanation for this is the
concentrated use of diesel engines in certain local or regional areas
which is not well represented by the national, yearly average presented
in national PM emission inventories. Another reason may be
underestimation of the in-use diesel PM emission rates. Our current
modeling incorporates deterioration only as would be experienced in
properly maintained, untampered vehicles. We are currently in the
process of reassessing the rate of in-use deterioration of diesel
engines and vehicles which could significantly increase the
contribution of HDVs to diesel PM.

[[Page 5029]]

3. Environmental Justice
Environmental justice is a priority for EPA. The Federal government
stated its concern, in part, over this issue through issuing Executive
Order 12898, Federal Actions To Address Environmental Justice in
Minority Populations and Low-Income Populations (February 11, 1994).
This Order requires that federal agencies make achieving environmental
justice part of their mission. Similarly, the EPA created an Office of
Environmental Justice (originally the Office of Environmental Equity)
in 1992, commissioned a task force to address environmental justice
issues, oversees a Federal Advisory Committee addressing environmental
justice issues (the National Environmental Justice Advisory Council),
and has developed an implementation strategy as required under
Executive Order 12898.
Application of environmental justice principles as outlined in the
Executive Order advances the fair treatment of people of all races,
income, and culture with respect to the development, implementation,
and enforcement of environmental laws, regulations, and policies. Fair
treatment implies that no person or group of people should shoulder a
disproportionate share of any negative environmental impacts resulting
from the execution of this country's domestic and foreign policy
programs.
For the last several years, environmental organizations and
community-based citizens groups have been working together to phase out
diesel buses in urban areas. For example, the Natural Resources Defense
Council initiated a ``Dump Dirty Diesel'' campaign in the 1990s to
press for the phase out of diesel buses in New York City. Other
environmental organizations operating in major cities such as Boston,
Newark, and Los Angeles have joined this campaign. The Coalition for
Clean Air worked with NRDC and other experts to perform exposure
monitoring in communities located near distribution centers where
diesel truck traffic is heavy. These two organizations concluded that
facilities with heavy truck traffic are exposing local communities to
diesel exhaust concentrations far above the average levels in outdoor
air. The report states: ``These affected communities, and the workers
at these distribution facilities with heavy diesel truck traffic, are
bearing a disproportionate burden of the health risks.'' 72
Other diesel ``hot spots'' identified by the groups are bus terminals,
truck and bus maintenance facilities, retail distribution centers, and
busy streets and highways.
---------------------------------------------------------------------------

\72\ Exhausted by Diesel: How America's Dependence on Diesel
Engines Threatens Our Health, Natural Resources Defense Council,
Coalition for Clean Air, May 1998.
---------------------------------------------------------------------------

While there is currently a limited understanding of the
relationship of environmental exposures to the onset of asthma, the
environmental triggers of asthma attacks for children with asthma have
become increasingly well characterized.73 Asthma's burden
falls hardest on the poor, inner city residents, and children. Among
children up to 4 years of age, asthma prevalence increased 160 percent
since 1980.74 African-American children have an annual rate
of hospitalization three times that for white children, and are four
times as likely to seek care at an emergency room.75 In
1995, the death rate from asthma in African-American children, 11.5 per
million, was over four times the rate in white American children, 2.6
per million.76
---------------------------------------------------------------------------

\73\ Asthma and the Environment: A Strategy to Protect Children,
President's Task Force on Environmental Health Risks and Safety
Risks to Children, January 28, 1999, Revised May, 2000.
\74\ Asthma Statistics, National Institutes of Health, National
Heart, Lung and Blood Institute, January, 1999.
\75\ Asthma and the Environment: A Strategy to Protect Children,
President's Task Force on Environmental Health Risks and Safety
Risks to Children, January 28, 1999, Revised May, 2000. The Task
Force was formed in conjunction with Executive Order 13045 (April
21, 1997), is co-chaired by Department of Health and Human Services
and EPA, and is charged with recommending strategies for protecting
children's environmental health and safety. In April, 1998, the Task
Force identified childhood asthma as one of its top four priorities
for immediate attention.
\76\ Id.
---------------------------------------------------------------------------

Local community groups and private citizens testified at public
hearings held for this rule that the residents of their communities
suffer greatly, and disproportionally, from air pollution in general,
and emissions from heavy-duty vehicles in particular. For example, a
testifier in New York pointed out that ``since Northern Manhattan and
the South Bronx experience asthma mortality and morbidity rates at
three to five times greater than the citywide average, New York City's
problem is Northern Manhattan's crisis.'' 77
---------------------------------------------------------------------------

\77\ Testimony by Peggy Shepard, Executive Director, West Harlem
Environmental Action, June 19th, 2000.
---------------------------------------------------------------------------

The new standards established in this rulemaking are expected to
improve air quality across the country and will provide increased
protection to the public against a wide range of health effects,
including chronic bronchitis, respiratory illnesses, and aggravation of
asthma symptoms. These air quality and public health benefits could be
expected to mitigate some of the environmental justice concerns related
to heavy-duty vehicles since the rule will provide relatively larger
benefits to heavily impacted urban areas.

D. Anticipated Emissions Benefits

This subsection presents the emission benefits we anticipate from
heavy-duty vehicles as a result of our new NOX, PM, and NMHC
emission standards for heavy-duty engines. The graphs and tables that
follow illustrate the Agency's projection of future emissions from
heavy-duty vehicles for each pollutant. The baseline case represents
future emissions from heavy-duty vehicles at present standards
(including the MY2004 standards). The controlled case quantifies the
future emissions of heavy-duty vehicles once the new standards in this
FRM are implemented.
We use the same baseline inventory as is used in the county-by-
county, hour-by-hour air quality analyses associated with this rule.
However, we made a slight modification to the controlled inventory to
incorporate the changes between the proposed and final standards.
Because the detailed air quality analyses took several months to
perform, we had to use the proposed standards for the air quality
analysis. Since beginning this analysis, we updated the control case
emission inventories to reflect the final phase-in of the
NOX standard, slight changes to the timing of the HDGV
standards, a temporary compliance option for introducing the low sulfur
fuel requirements, and various hardship provisions for refiners in our
emission inventory projections. The emission inventory calculations are
presented in detail in the Regulatory Impact Analysis.
1. NOX Reductions
The Agency expects substantial NOX reductions on both a
percentage and a tonnage basis from the new standards. The RIA provides
additional projections between 2007 and 2030. As stated previously,
HDVs contribute about 15 percent to the national NOX
inventory for all sources in 2007. Figure II.D-1 shows our national
projections of total NOX emissions with and without the
engine controls finalized today. Table II.D-1 presents the total
reductions.78 This includes both exhaust and crankcase
emissions.79 The standards

[[Page 5030]]

should result in close to a 90 percent reduction in NOX from
new engines.
---------------------------------------------------------------------------

\78\ The baseline used for this calculation is the 2004 HDV
standards (64 FR 58472). These reductions are in addition to the
NOX emissions reductions projected to result from the
2004 HDV standards.
79 We include in the NOX projections
excess emissions, developed by the EPA's Office of Enforcement and
Compliance, that were emitted by many model year 1998-98 diesel
engines. This is described in more detail in Chapter 2 of the RIA.

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Table II.D-1.--Estimated Reductions in NOX
------------------------------------------------------------------------
NOX
reduction
Calendar year [thousand
short tons]
------------------------------------------------------------------------
2007....................................................... 58
2010....................................................... 419
2015....................................................... 1,260
2020....................................................... 1,820
2030....................................................... 2,570
------------------------------------------------------------------------

2. PM Reductions
As stated previously, HDVs will contribute about 20 percent to the
2007 national PM10 inventory for mobile sources. The
majority of the projected PM reductions are directly a result of the
exhaust PM standard. However, a modest amount of PM reductions will
come from reducing sulfur in the fuel. For the existing fleet of heavy-
duty vehicles, a small fraction of the sulfur in diesel fuel is emitted
directly into the atmosphere as direct sulfate, and a portion of the
remaining fuel sulfur is transformed in the atmosphere into sulfate
particles, referred to as indirect sulfate. Reducing sulfur in the fuel
decreases the amount of direct sulfate PM emitted from heavy-duty
diesel engines and the amount of heavy-duty diesel engine SOx emissions
that are transformed into indirect sulfate PM in the
atmosphere.80 For engines meeting the new standards, we
consider low sulfur fuel to be necessary to enable the PM control
technology. In other words, we do not claim an additional benefit
beyond the new exhaust standard for reductions in direct sulfate PM for
new engines. However, once the low sulfur fuel requirements go into
effect, many pre-2007 model year engines would also be using low sulfur
fuel. Because these pre-2007 model year engines are certified with
higher sulfur fuel, they will achieve reductions in PM beyond their
certification levels.
---------------------------------------------------------------------------

\80\ Sulfate forms a significant portion of total fine
particulate matter in the Northeast Chemical speciation data in the
Northeast collected in 1995 shows that the sulfate fraction of fine
particulate matter ranges from 20 and 27 percent of the total fine
particle mass. Determination of Fine Particle and Concentrations and
Chemical Composition in the Northeastern United States. 1995.
NESCAUM, prepared by Cass, et al., September 1999.
---------------------------------------------------------------------------

Figure II.D-2 shows our national projections of total HDV PM (TPM)
emissions with and without the new engine controls. This figure
includes brake and tire wear, crankcase emissions and the direct
sulfate PM (DSPM) benefits due to the use of low sulfur fuel by the
existing fleet. These direct sulfate PM benefits from the existing
fleet are also graphed separately. The new standards will result in
about a 90 percent reduction in exhaust PM from new heavy-duty diesel
engines. The low sulfur fuel should result in more than a 95 percent
reduction in direct sulfate PM from pre-2007 heavy-duty diesel engines.
Due to complexities of the conversion and removal processes of sulfur
dioxide, we do not attempt to quantify the indirect sulfate reductions
that would be derived from this rulemaking in the inventory analysis.
Nevertheless, we recognize that these indirect sulfate PM reductions
contribute significant additional benefits to public health and
welfare, and we include this effect in our more detailed air quality
analysis.
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[[Page 5032]]

Table II.D-2.--Estimated Reductions in PM
------------------------------------------------------------------------
PM
reduction
Calendar year [thousand
short tons]
------------------------------------------------------------------------
2007....................................................... 11
2010....................................................... 36
2015....................................................... 61
2020....................................................... 82
2030....................................................... 109
------------------------------------------------------------------------

3. NMHC Reductions
The standards described in Section III are designed to be feasible
for both gasoline and diesel heavy-duty vehicles. Although the
standards give manufacturers the same phase-in for NMHC as for
NOX, we model the NMHC reductions for diesel vehicles to be
fully in place in 2007 due to the application of particulate control
technology. We believe the use of aftertreatment for PM control will
cause the NMHC levels to be below the standards as soon as the PM
standard goes into effect in 2007.
HDVs account for about 3 percent of national VOC and 8 percent from
mobile sources in 2007. Figure II.D-3 shows our national projections of
total NMHC emissions with and without the new engine controls. This
includes both exhaust emissions and evaporative emissions. Table II.D-3
presents the projected reductions of NMHC due to the new standards.

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[[Page 5033]]

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[[Page 5034]]

Table II.D-3.--Estimated Reductions in NMHC
------------------------------------------------------------------------
NMHC
reduction
Calendar year [thousand
short tons]
------------------------------------------------------------------------
2007....................................................... 2
2010....................................................... 21
2015....................................................... 54
2020....................................................... 83
2030....................................................... 115
------------------------------------------------------------------------

4. Additional Emissions Benefits
This subsection looks at tons/year emission inventories of CO,
SOX, and air toxics from HDEs. Although we are not including
stringent standards for these pollutants in this action, we believe the
standards will result in reductions in CO, SOX, and air
toxics. Here, we present our anticipated benefits.
a. CO Reductions
In 2007, HDVs are projected to contribute to approximately 5
percent of national CO and 9 percent of CO from mobile sources.
Although it does not include new CO emission standards, today's action
would nevertheless be expected to result in a considerable reduction in
CO emissions from heavy-duty vehicles. CO emissions from heavy-duty
diesel vehicles, although already very low, would likely be reduced by
an additional 90 percent due to the operation of emissions control
systems that will be necessary to achieve today's new standards for
hydrocarbons and particulate matter. CO emissions from heavy-duty
gasoline vehicles would also likely decline as the NMHC emissions are
decreased. Table II.D-4 presents the projected reductions in CO
emissions from HDVs.

Table II.D-4.--Estimated Reductions in CO
------------------------------------------------------------------------
CO
reduction
Calendar year [thousand
short tons]
------------------------------------------------------------------------
2007....................................................... 56
2010....................................................... 317
2015....................................................... 691
2020....................................................... 982
2030....................................................... 1,290
------------------------------------------------------------------------

b. SOX Reductions
HDVs are projected to emit approximately 0.5 percent of national
SOX and 8 percent of mobile source SOX in 2007.
We are requiring significant reductions in diesel fuel sulfur to enable
certain emission control devices to function properly. We expect
SOX emissions to decline as a direct benefit of low sulfur
diesel fuel. The majority of these benefits will be from heavy-duty
highway diesel vehicles; however, some benefits will also come from
highway fuel burned in other applications such as light-duty diesel
vehicles and nonroad engines. As discussed in greater detail in the
section on PM reductions, the amount of sulfate particles (direct and
indirect) formed as a result of diesel exhaust emissions will decline
for all HD diesel engines operated on low sulfur diesel fuel, including
the current on-highway HD diesel fleet, and those non-road HD diesel
engines that may operate on low sulfur diesel fuel in the future. Table
II.D-5 presents our estimates of SOX reductions resulting
from the low sulfur fuel.

Table II.D-5.--Estimated Reductions In SOX Due To Low Sulfur Fuel
------------------------------------------------------------------------
SOX
reduction
Calendar year [thousand
short tons]
------------------------------------------------------------------------
2007....................................................... 79
2010....................................................... 107
2015....................................................... 117
2020....................................................... 126
2030....................................................... 142
------------------------------------------------------------------------

c. Air Toxics Reductions
This FRM establishes new non-methane hydrocarbon standards for all
heavy-duty vehicles and a formaldehyde standard for complete heavy-duty
vehicles. Hydrocarbons are a broad class of chemical compounds
containing carbon and hydrogen. Many forms of hydrocarbons, such as
formaldehyde, are directly hazardous and contribute to what are
collectively called ``air toxics.'' Air toxics are pollutants known to
cause or suspected of causing cancer or other serious human health
effects or ecosystem damage. The Agency has identified at least 20
compounds emitted from on-road gasoline vehicles that have
toxicological potential, 19 of which are emitted by diesel vehicles, as
well as an additional 20 compounds which have been listed as toxic air
contaminants by California ARB.81 82 This action
also will reduce emissions of diesel exhaust and diesel particulate
matter (see Section II.B for a discussion of health effects).
---------------------------------------------------------------------------

\81\ National Air Quality and Emissions Trends Report, 1997,
(EPA 1998), p. 74.
\82\ California Environmental Protection Agency (1998) Report to
the Air Resources Board on the Proposed Identification of Diesel
Exhaust as a Toxic Air Contaminant. Appendix III, Part A: Exposure
Assessment. April 1998.
---------------------------------------------------------------------------

Our assessment of heavy-duty vehicle (gasoline and diesel) air
toxics focuses on the following compounds with cancer potency estimates
that have significant emissions from heavy-duty vehicles: benzene,
formaldehyde, acetaldehyde, and 1,3-butadiene. These compounds are an
important, but limited, subset of the total number of air toxics that
exist in exhaust and evaporative emissions from heavy-duty vehicles.
The reductions in air toxics quantified in this section represent only
a fraction of the total number and amount of air toxics reductions
expected from the new hydrocarbon standards.
For this analysis, we estimate that air toxic emissions are a
constant fraction of hydrocarbon exhaust emissions from future engines.
Because air toxics are a

[[Page 5035]]

subset of hydrocarbons, and new emission controls are not expected to
preferentially control one type of air toxic over another, the selected
air toxics chosen for this analysis are expected to decline by the same
percentage amount as hydrocarbon exhaust emissions. We have not
performed a separate analysis for the new formaldehyde standard since
compliance with the hydrocarbon standard should result in compliance
with the formaldehyde standard for all petroleum-fueled engines. The
RIA provides more detail on this analysis. Table II.D-6 shows the
estimated air toxics reductions associated with the reductions in
hydrocarbons.

Table II.D-6.--Estimated Reductions In Air Toxics (short tons)
----------------------------------------------------------------------------------------------------------------
Calendar year Benzene Formaldehyde Acetaldehyde 1,3-Butadiene
----------------------------------------------------------------------------------------------------------------
2007............................................ 24 181 67 14
2010............................................ 356 1,670 608 135
2015............................................ 965 4,720 1,720 384
2020............................................ 1,340 7,080 2,600 567
2030............................................ 1,960 10,200 3,730 823
----------------------------------------------------------------------------------------------------------------

E. Clean Heavy-Duty Vehicles and Low-Sulfur Diesel Fuel are Critically
Important for Improving Human Health and Welfare

Despite continuing progress in reducing emissions from heavy-duty
engines, emissions from these engines continue to be a concern for
human health and welfare. Ozone continues to be a significant public
health problem, and affects not only people with impaired respiratory
systems, such as asthmatics, but healthy children and adults as well.
Ozone also causes damage to plants and has an adverse impact on
agricultural yields. Particulate matter, like ozone, has been linked to
a range of serious respiratory health problems, including premature
mortality, aggravation of respiratory and cardiovascular disease,
aggravated asthma, acute respiratory symptoms, and chronic bronchitis.
Importantly, EPA has concluded that diesel exhaust is likely to be
carcinogenic to humans by inhalation at occupational and environmental
levels of exposure.
Today's action will reduce NOX, VOC, CO, PM, and
SOX emissions from these heavy-duty vehicles substantially.
These reductions will help reduce ozone levels nationwide and reduce
the frequency and magnitude of predicted exceedances of the ozone
standard. These reductions will also help reduce PM levels, both by
reducing direct PM emissions and by reducing emissions that give rise
to secondary PM. The NOX and SOX reductions will
help reduce acidification problems, and the NOX reductions
will help reduce eutrophication problems. The PM and NOX
standard enacted today will help improve visibility. All of these
reductions are expected to have a beneficial impact on human health and
welfare by reducing exposure to ozone, PM, diesel exhaust and other air
toxics and thus reducing the cancer and noncancer effects associated
with exposure to these substances.

III. Heavy-Duty Engine and Vehicle Standards

In this section, we describe the vehicle and engine standards we
are finalizing today to respond to the serious air quality needs
discussed in Section II. Specifically, we discuss:
The CAA and why we are finalizing new heavy-duty
standards.
The technology opportunity for heavy-duty vehicles and
engines.
Our new HDV and HDE standards, and our phase-in of those
standards.
Why we believe the stringent standards being finalized
today are feasible in conjunction with the low sulfur gasoline required
under the recent Tier 2 rule and the low sulfur diesel fuel being
finalized today.
The effects of diesel fuel sulfur on the ability to meet
the new standards, and what happens if high sulfur diesel fuel is used.
Plans for future review of the status of heavy-duty diesel
NOX emission control technology.

A. Why Are We Setting New Heavy-Duty Standards?

We are finalizing new heavy-duty vehicle and engine standards and
related provisions under section 202(a)(3) of the CAA, which authorizes
EPA to establish emission standards for new heavy-duty motor vehicles.
(See 42 U.S.C. 7521(a)(3).) Section 202(a)(3)(A) requires that such
standards ``reflect the greatest degree of emission reduction
achievable through the application of technology which the
Administrator determines will be available for the model year to which
such standards apply, giving appropriate consideration to cost, energy,
and safety factors associated with the application of such
technology.'' Section 202(a)(3)(B) allows EPA to take into account air
quality information in revising such standards. Because heavy-duty
engines contribute greatly to a number of serious air pollution
problems, especially the health and welfare effects of ozone, PM, and
air toxics, and because millions of Americans live in areas that exceed
the national air quality standards for ozone or PM, we believe the air
quality need for tighter heavy-duty standards is well founded. This,
and our belief that a significant degree of emission reduction from
heavy-duty vehicles and engines is achievable, giving appropriate
consideration to cost, energy, and safety factors, through the
application of new diesel emission control technology, further
refinement of well established gasoline emission controls, and
reductions of diesel fuel sulfur levels, leads us to believe that new
emission standards are warranted.

B. Emission Control Technologies for Heavy-Duty Vehicles and Engines

For the past 30 or more years, emission control development for
gasoline vehicles and engines has concentrated most aggressively on
exhaust emission control devices. These devices currently provide as
much as or more than 95 percent of the emission control on a gasoline
vehicle. In contrast, the emission control development work for diesels
has concentrated on improvements to the engine itself to limit the
emissions leaving the combustion chamber.
However, during the past 15 years, more development effort has been
put into diesel exhaust emission control devices, particularly in the
area of PM control. Those developments, and recent developments in
diesel NOX control devices, make the widespread commercial
use of diesel exhaust emission controls feasible. Through use of these
devices, we believe emissions control similar to that attained by
gasoline applications will be possible with diesel applications.
However, without low sulfur diesel fuel, these technologies cannot be
implemented on heavy-duty diesel applications. Low sulfur diesel fuel
will at the same time

[[Page 5036]]

also allow these technologies to be implemented on light-duty diesel
applications.
As discussed at length in the preamble to our proposal, several
exhaust emission control devices have been or are being developed to
control harmful diesel exhaust pollutants. Of these, we believe that
the catalyzed diesel particulate trap and the NOX adsorber
are the most likely candidates to be used to meet the very low diesel
exhaust emission standards adopted today on the variety of applications
in the heavy-duty diesel market. While other technologies exist that
have the potential to provide significant emission reductions, such as
selective catalytic reduction systems for NOX control, and
development of these technologies is being pursued to varying degrees,
we believe that the catalyzed diesel particulate trap and the
NOX adsorber will be the only likely broadly applicable
technology choice by the makers of engines and vehicles for the
national fleet in this timeframe. However, as discussed in detail in
the Final RIA, we strongly believe that none of these technologies can
be brought to market on diesel engines and vehicles unless the kind of
low sulfur diesel fuel adopted in this rule is available.
As for gasoline engines and vehicles, improvement continues to be
made to gasoline emissions control technology. This includes
improvement to catalyst designs in the form of improved washcoats and
improved precious metal dispersion. Much effort has also been put into
improved cold start strategies that allow for more rapid catalyst
light-off. This can be done by retarding the spark timing to increase
the temperature of the exhaust gases, and by using air-gap manifolds,
exhaust pipes, and catalytic converter shells to decrease heat loss
from the system.
These improvements to gasoline emission controls will be made in
response to the California LEV-II standards and the federal Tier 2
standards.83 These improvements should transfer well to the
heavy-duty gasoline segment of the fleet. With such migration of light-
duty technology to heavy-duty vehicles and engines, we believe that
considerable improvements to heavy-duty gasoline emissions can be
realized, thus allowing vehicles to meet the much more stringent
standards adopted today.
---------------------------------------------------------------------------

\83\ See Chapter IV.A of the final Tier 2 Regulatory Impact
Analysis, contained in Air Docket A-97-10, and McDonald, Joseph, and
Jones, Lee, ``Demonstration of Tier 2 Emission Levels for Heavy
Light-Duty Trucks,'' SAE 2001-01-1957.
---------------------------------------------------------------------------

The following discussion provides more detail on the technologies
we believe are most capable of meeting very stringent heavy-duty
emission standards. The goal of this discussion is to describe the
emission reduction capability of these emission control technologies
and their critical need for diesel fuel sulfur levels as low as those
being finalized today. But first, we present the details of the new
emission standards being finalized today.

C. What Engine and Vehicle Standards Are We Finalizing?

1. Heavy-Duty Engine Exhaust Emissions Standards
a. FTP Standards 84
---------------------------------------------------------------------------

\84\ The Phase 1 heavy-duty rule recently promulgated by EPA
specified two supplemental sets of standards for heavy-duty diesel
engines. (See 65 FR 59896, October 6, 2000.) Manufacturers of heavy-
duty diesel engines must meet these supplemental standards, the
Supplemental Emission Test (SET, formerly referred to as the
Supplemental Steady-State (SSS) test) and the Not-to-Exceed (NTE)
standards, beginning in model year 2007, in addition to meeting the
preexisting standards, which must be met using the preexisting
federal test procedure (FTP). For the purposes of this preamble, we
refer to the standards met using the preexisting FTP as the FTP
standards, though the SET and NTE test procedures have now been
added to the regulations establishing the various federal test
procedures for heavy-duty diesel engines.
---------------------------------------------------------------------------

The emission standards finalized today for heavy-duty engines are
summarized in Table III.C-1. For reasons explained below, the phase-in
schedule for these standards differs from the proposed schedule. We are
also finalizing an incentive provision to encourage the early
introduction of engines meeting these new standards. This incentive
provision is explained in section III.D. In addition, we have altered
our Averaging, Banking, and Trading (ABT) provisions from what was
proposed. The final ABT provisions are discussed in detail in section
VI.

Table III.C-1.--Full Useful Life Heavy-Duty Engine Exhaust Emissions Standards and Phase-Ins for Incomplete
Vehicles
----------------------------------------------------------------------------------------------------------------
Phase-In by Model Year a
Standard ---------------------------------------------------
(g/bhp-hr) 2007 2008 2009 2010
----------------------------------------------------------------------------------------------------------------
Diesel............................ NOX 0.20 50% 50% 50% 100%
NMHC 0.14 50% 50% 50% 100%
PM 0.01 100% 100% 100% 100%
Gasoline.......................... NOX 0.20 0% 50% 100% 100%
NMHC 0.14 0% 50% 100% 100%
PM 0.01 0% 50% 100% 100%
----------------------------------------------------------------------------------------------------------------
a Percentages represent percent of sales.

With respect to PM, this new standard represents a 90 percent
reduction for most heavy-duty diesel engines from the current PM
standard. The current PM standard for most heavy-duty engines, 0.10 g/
bhp-hr, was implemented in the 1994 model year; the PM standard for
urban buses implemented in that same year was 0.05 g/bhp-hr; these
standards are not changing when other standards change in the 2004
model year timeframe. The new PM standard of 0.01 g/bhp-hr being
finalized today is projected to require the addition of highly
efficient PM traps to diesel engines, including those diesel engines
used in urban buses; it is not expected to require the addition of any
new hardware for gasoline engines.
With respect to NMHC and NOX, these new standards
represent significant reductions from the 2004 diesel engine standard
which is either 2.4 g/bhp-hr NOX+NMHC, or 2.5 g/bhp-hr
NOX+NMHC with a cap on NMHC of 0.5 g/bhp-hr. We generally
expect that 2004 diesel engines will meet those standards with emission
levels around 2.2 g/bhp-hr NOX and 0.2 g/bhp-hr NMHC. Like
the PM standard, the new NOX standard is projected to
require the addition of a highly efficient NOX emission
control system to diesel engines which, with help from the PM trap,
will need to be optimized to control NMHC emissions. For gasoline

[[Page 5037]]

engines, the 2005 model year standard recently finalized in the Phase 1
heavy-duty rule is 1.0 g/bhp-hr NOX+NMHC. (See 65 FR 59896,
October 6, 2000.) There is a direct trade off between NOX
and NMHC emissions with a gasoline engine, but we would generally
expect NOX levels over 0.5 g/bhp-hr and NMHC levels below
that. Regardless of the NOX and NMHC split, today's
standards represent significant reductions for 2008 and later engines
that will require substantial improvement in the effectiveness of
heavy-duty gasoline emission control technology.
We proposed a new formaldehyde standard of 0.016 g/bhp-hr for both
heavy-duty diesel and gasoline engines. However, we have decided not to
finalize those standards. We proposed the formaldehyde (HCHO) standard
because it is a hazardous air pollutant that is emitted by heavy-duty
engines and other mobile sources. In the proposal, we stated our belief
that formaldehyde emissions from gasoline and diesel engines are and
will remain inherently low, but having the standard would ensure that
excess emissions would not occur. Several commenters took issue with
our proposed standard claiming that the benefits were nonexistent, that
we should address toxic emissions in our toxics rulemaking, and that we
had shown neither its technological feasibility nor its measurability.
After further consideration we do believe that the proposed
formaldehyde standard is not necessary because the NMHC standard we are
promulgating today will almost certainly result in formaldehyde
emissions well below our proposed formaldehyde standard. As a result,
other comments on this issue such as those concerning technological
feasibility and measurability are no longer relevant to this rule. We
will continue to evaluate this issue to ensure that formaldehyde
emissions do not become a problem in the future and may take action to
consider standards if warranted.
We believe a phase-in of the diesel NOX standard is
appropriate. With a phase-in, manufacturers are able to introduce the
new technology on a portion of their engines, thereby gaining valuable
experience with the technology prior to implementing it on their entire
fleet. Also, we are requiring that the NOX, and NMHC
standards be phased-in together for diesel engines. That is, engines
will be expected to meet both of these new standards, not just one or
the other. We are requiring this because the standard finalized in the
Phase 1 heavy-duty rule is a combined NMHC+NOX standard.
With separate NOX and NMHC phase-ins, say 50/50/50/100 for
NOX and 100 percent in 2007 for NMHC, the 2.5 gram engines
being phased-out would have a 2.5 gram NOX+NMHC standard and
a new 0.14 gram NMHC standard with which to comply. While this could be
done, we believe that it introduces unnecessary compliance complexity
to the program.
In our NPRM, we requested comment on a range of possible phase-in
schedules for NOX including anything from our primary
proposal of 25/50/75/100 percent phase-in to a possible requirement for
100 percent compliance in the 2007 model year. We have determined that
a 50/50/50/100 percent phase-in schedule is the most appropriate
schedule for several reasons.
Some commenters argued that we should require 100 percent
compliance in the 2007 model year because of the 0.20 gram standard was
both technologically feasible and critical given the nation's air
quality needs. Other commenters were concerned that 100 percent
compliance to the 0.20 gram NOX standard in the first year
of the program was ill advised as it would provide little opportunity
for industry to ``field test'' new NOX control technologies.
These commenters also expressed concern over workload burdens on
industry members needing to redesign all of their new engines and
vehicles in one year. Some commenters were concerned that a 25/50/75/
100 percent phase-in schedule would introduce competitiveness issues
whereby those vehicles equipped with new NOX control
technology may be less attractive to some buyers than vehicles without
the technology, making them difficult for manufacturers to sell.
We set standards and implementation schedules based on many factors
including technological feasibility, cost, energy, and safety.
Considering these factors, we believe that industry should be provided
the flexibility of having a phase-in of the new NOX
standard. As discussed in section III.E below, we believe the 0.20 gram
NOX standard is feasible in the 2007 time frame. However, we
believe a phase-in is appropriate for a couple of reasons. First, the
phase-in will provide industry with the flexibility to roll out the
NOX control technology on only a portion of their fleet.
This will allow them to focus their resources on that half of their
fleet being brought into compliance in 2007. This ability to focus
their efforts will increase both the efficiency and the effectiveness
of those efforts. Second, a phase-in allows industry the ability to
introduce the new technology on those engines it believes are best
suited for a successful implementation which, in turn, provides a
valuable opportunity to refine that technology on only a portion of
their product line prior to the next push toward full implementation.
Another concern with respect to our proposed phase-in schedule was
raised by several commenters and pertains to its interaction with the
final implementation schedule for the new supplemental requirements
(the Supplemental Emission Test, SET, and the Not-to-Exceed, NTE).
These requirements, finalized in the Phase 1 heavy-duty final rule,
will be implemented in the 2007 model year on all heavy-duty diesel
engines. (See 65 FR 59896, October 6, 2000.) Under a 25/50/75/100
percent phase-in schedule of new diesel engine emission requirements,
25 percent of engines in the 2007 model year would meet 0.20 and 0.01
g/bhp-hr NOX and PM, while 75 percent would meet 2.5 and
0.01 g/bhp-hr NOX and PM. Further, all of those engines
would be required, beginning in the 2007 model year, to meet the
supplemental requirements based on the FTP emission standards to which
they were certified. A 25/50/75/100 percent phase-in schedule would
change the supplemental requirements for those 25 percent of engines in
the 2008 model year that would have to change to meet the new 50
percent compliance requirement. This change would be required even
though the supplemental requirements on those 25 percent of engines
were first implemented only one model year earlier, in model year 2007.
Commenters have questioned whether this is consistent with section
202(a)(3)(c) of the Clean Air Act, which requires that standards for
heavy-duty vehicles and engines apply for no less than three model
years without revision. Under this argument, the supplemental
requirements implemented in the 2007 model year must be allowed three
model years of stability, meaning that no changes can be required to
those standards until the 2010 model year.
The final phase-in schedule, 50/50/50/100 percent, addresses any
concerns about violating the stability requirement of the Act and
addresses the technology and lead time benefits of a phase-in as
discussed above.85 While this phase-in does not provide
certain commenters with their goal of 100 percent implementation of
very low NOX engines in 2007, we believe it is

[[Page 5038]]

appropriate for the technology, cost, and other reasons described
above. This 50/50/50/100 percent phase-in schedule does provide a more
rapid implementation of low NOX engines and, more
importantly, provides more air quality benefits in 2007 than would our
proposed phase-in schedule. We are also finalizing provisions that
would encourage manufacturers to introduce clean technology, both
diesel and gasoline, earlier than required in return for greater
flexibility during the later years of our phase-in. These optional
early incentive provisions are analogous to those included in our
light-duty Tier 2 rule and are discussed in more detail in section
III.D. We have also revised our Averaging, Banking, and Trading program
to increase flexibility as discussed further in section VI.
---------------------------------------------------------------------------

\85\ EPA need not determine, at this time, whether the 25/50/75/
100 percent phase-in schedule violates section 202(a)(3)(c), as the
50/50/50/100 percent phase-in schedule clearly does not and is
available to all manufacturers.
---------------------------------------------------------------------------

For gasoline engines, we proposed 100 percent compliance in the
2007 model year. However, since the proposal was published, we have set
new standards for heavy-duty gasoline engines that take effect in the
2005 model year. Therefore, the three year stability requirement of the
CAA requires that today's new standards not apply until the 2008 model
year at the earliest. Further, while we had not proposed a phase-in for
gasoline standards, based on comments received we believe that a phase-
in should be provided. The phase-in will allow manufacturers to
implement improved gasoline control technologies on their heavy-duty
gasoline engines in the same timeframe as they implement those
technologies on their Tier 2 medium-duty passenger vehicles (MDPV).
This consistency with Tier 2 is discussed in more detail below in
section III.C.2 on vehicle standards. Note that the gasoline engine
phase-in schedule is the same as but separate from the gasoline vehicle
phase-in schedule discussed below. As we have done for diesel engines,
we have also revised our Averaging, Banking, and Trading program for
gasoline engines to increase flexibility as discussed further in
section VI.
For a discussion of why we believe these standards are
technologically feasible in the time frame required, refer to section
III.E below and for a more detailed discussion refer to the RIA
contained in the docket. The averaging, banking, and trading (ABT)
provisions associated with today's standards are discussed in Section
VI of this preamble. The reader should refer to that section for more
details.
b. Supplemental Provisions for HD Diesel Engines (SET & NTE)
In addition to the new FTP standards for HD diesel engines
contained in today's final action, we are also finalizing the
supplemental emission standards we proposed to apply to the new HDDEs,
with a number of changes as discussed in this section. The supplemental
provisions will help ensure that HD diesel engines achieve the expected
in-use emission reductions over a wide range of vehicle operation and a
wide range of ambient conditions, not only the test cycle and
conditions represented by the traditional FTP. The Agency has
historically relied upon the FTP and the prohibition of defeat devices
to ensure that HDDE emission control technologies which operate during
the laboratory test cycle continue to operate in-use. The supplemental
provisions are a valuable addition to the FTP and the defeat device
prohibition to ensure effective in-use emission control. The
supplemental provisions for HD diesel engines consist of two principal
requirements, the supplemental emission test and associated standards
(SET),86 and the not-to-exceed test and associated standards
(NTE). The supplemental emission standards finalized today for heavy-
duty diesel engines are summarized in Table III.C-2.
---------------------------------------------------------------------------

\86\ In the Phase 1 rulemaking, the Supplemental Emission Test
was referred to as the supplemental steady state test. As discussed
in the Phase 1 rule, the supplemental steady state test is based on
and is consistent with the European Commissions ``EURO III ESC''
test. (See 65 FR 59915.) In this final rule we have renamed the
supplemental steady state test the Supplemental Emission Test (SET).

Table III.C-2.--Full Useful Life Heavy-Duty Diesel Engine Supplemental
Exhaust Emissions Standards
------------------------------------------------------------------------
Requirements for NOX, NMHC,
Supplemental test PM
------------------------------------------------------------------------
Supplemental emission test................ 1.0 x FTP standard (or
FEL).
Not-to-exceed test........................ 1.5 x FTP standard (or
FEL).
------------------------------------------------------------------------

The SET and NTE test procedures were recently adopted for 2007 on-
highway HD diesel engines. (See 65 FR 59896, October 6, 2000.) In the
recent HD Phase 1 rulemaking which promulgated the SET and NTE, the
supplemental provisions were finalized in the context of the emission
control technology expected to be used to meet the 2004 FTP standards,
i.e., injection timing strategies and cooled EGR. In this final action,
we are finalizing a number of changes to the supplemental provisions to
address specific technical issues raised by commenters and which result
from the expected application of high efficiency exhaust emission
control devices on HD diesel engines and vehicles to meet today's new
standards. These changes are minor in nature and will not impact the
emission reductions we expect from the Phase 2 standards. These changes
are discussed in the following sections. Additional discussion
regarding the supplemental provisions for HDDEs is contained in the RIA
and the Response to Comments (RTC) for this final rule, as well as in
Section III.E of this preamble (``Feasibility of the New Engine and
Vehicle Standards'').
i. Supplemental Emission Test
We are finalizing supplemental emission test provisions for HD
diesel engines and vehicles certified to the new FTP standards
contained in this final rule. The SET emission standard is equal to 1.0
times the FTP standard or FEL for HD diesel engines. Emission results
from this test must meet the numerical standards for the FTP. The SET
requirements are phased-in beginning with the 2007 model year,
consistent with the phase-in of the new FTP standards. The supplemental
emission test duty cycle consists of 13 modes of speed and torque,
primarily covering the typical highway cruise operating range of heavy-
duty diesel engines. The emission results from each of the modes are
weighted by defined factors in the regulations, and the final weighted
emission value for each pollutant must meet the SET standard. In
addition, several of the 13 individual modes are in the NTE control
zone, and must meet the applicable NTE requirements. The SET test is a
laboratory test performed using an engine dynamometer under the same
conditions which apply to the FTP, as specified in the regulations.
(See 40 CFR 86.1360.)
The regulations for the SET in model year 2007 as they apply to the
2004 FTP emission standards contain additional steady-state test point
emission limits. The Phase 1 supplemental requirements define a
``Maximum Allowable Emission Limit'' (MAEL) which the engines must
comply with. The Phase 1 regulations allowed EPA to randomly select up
to three steady-state test points prior to certification which the
manufacturer would test to show compliance with the MAEL. These test
points are referred to as ``mystery points''. In this final rule we
have eliminated the MAEL for engines certified to the Phase 2
standards. The MAEL assures that an engine is calibrated to maintain
emission control similar to the SET test under steady state conditions
across the engine map, not just at the pre-defined 13 test points

[[Page 5039]]

which comprise the SET test. For Phase 1 engines the MAEL was necessary
to ensure this potential for gaming did not occur because the
difference between the FTP standard and the NTE standard could be
large, for example, 0.625 g/bhp-hr for NMHC + NOX. However,
for Phase 2 engines the NTE requirements are a mere 0.10 g/bhp-hr
NOX greater than the FTP standard. Considering this small
increment, we have eliminated the MAEL for Phase 2 engines because it
is redundant with the NTE. For the same reasons, we have eliminated the
certification ``mystery points'' for engines complying with today's
diesel engine standards.
ii. Not-to-Exceed
We are also finalizing revisions to the not-to-exceed emission
standards for HD diesel engines certified to the Phase 2 FTP standards
contained in this final rule. These NTE procedures apply under engine
operating conditions within the range specified in the NTE test
procedure that could reasonably be expected to be seen in normal
vehicle operation and use. (See 40 CFR 86.1370.) The NTE procedure
defines limited and specific engine operating regions (i.e., speed and
torque conditions) and ambient operating conditions (i.e., altitude,
temperature, and humidity conditions) which are subject to the NTE
emission standards. Emission results from this test procedure must be
less than or equal to 1.5 times the FTP standards (or FEL) for
NOX, NMHC, and PM. The new NTE requirements are phased-in
starting with the 2007 model year, consistent with the new FTP
standards.
The Not-To-Exceed (NTE) provisions were recently finalized for
HDDEs certified to the 2004 FTP emission standards with implementation
beginning in model year 2007. (See 65 FR 59896, October 6, 2000.) The
NTE approach establishes an area (the ``NTE control area'') under the
torque curve of an engine where emissions must not exceed a specified
value for any of the regulated pollutants.87 The NTE
requirements would apply under engine operating conditions that could
reasonably be expected to be seen in normal vehicle operation and use
which occur during the conditions specified in the NTE test procedure.
(See 40 CFR 86.1370.) This test procedure covers a specific range of
engine operation and ambient operating conditions (i.e., temperature,
altitude, and humidity). The NTE control area, emissions standards,
ambient conditions and test procedures for HDDEs are described in the
regulations.
---------------------------------------------------------------------------

\87\ Torque is a measure of rotational force. The torque curve
for an engine is determined by an engine ``mapping'' procedure
specified in the Code of Federal Regulations. The intent of the
mapping procedure is to determine the maximum available torque at
all engine speeds. The torque curve is merely a graphical
representation of the maximum torque across all engine speeds.
---------------------------------------------------------------------------

The NTE multiplier promulgated in the previous final rulemaking for
HD diesel engines certified to the 2004 FTP standards is 1.25 x FTP
standard (e.g., 1.25 x 2.5g/bhp-hr NMHC+NOX and 1.25 x
0.1 g/bhp-hr PM). We believe the NTE cap finalized today (1.5 x the
Phase 2 FTP standards or FEL) allows sufficient headroom above the FTP
standard to accommodate the technical challenges necessary to meet the
NTE standard which must be met over a broader range of ambient
conditions, a shorter time period, and a wider variety of operating
conditions, than the FTP or the SET. While the 1.5 NTE multiplier we
are finalizing is greater than what we proposed, in absolute terms the
NTE requirement for Phase 2 engines is much smaller than for Phase 1
engines (i.e., the magnitude of the cap in g/bhp-hr emissions), and the
Phase 2 NTE cap will help ensure the emission reductions we expect from
the Phase 2 standards will occur in-use. The NTE requirements have been
modified from what we proposed based on our assessment of the emission
performance of the exhaust emission control devices that will be used
to meet the new FTP standards (e.g., catalyzed particulate traps and
NOX adsorbers). Under the program finalized today, an NTE
limit of 1.5 x the NOX FEL would apply to 2007 and later
model year engines certified with FELs less than 1.5 g/bhp-hr
NOX. As discussed throughout this notice, the stringent 2007
PM standard, 0.01 g/bhp-hr, can be met with the use of catalyzed
particulate traps. Because of the very low particulate matter emissions
which will be emitted by engines meeting the PM standard, this final
rule also establishes a minimum PM NTE requirement for engines
certified with FELs below 0.01 g/bhp-hr at 1.5 x the FTP standard,
not the FEL. Based on our assessment of the expected exhaust emission
control devices and their performance, the NTE standard of 1.5 x FTP
standard is both technologically feasible and appropriate. A detailed
discussion of the feasibility of the NTE requirements is contained in
the RIA for this final rule.
Today's action allows the NTE deficiency provisions we recently
finalized for 2007 HDDEs meeting the 2004 FTP standards to be used by
HDDEs meeting the standards contained in today's final rule (See 40 CFR
86.007-11(a)(4)(iv) in the regulations, and 65 FR 59914 of the Phase 1
rule for a detailed discussion of the NTE deficiencies.). These
deficiency provisions are similar to the deficiency provisions which
currently apply to LD and HD on-board diagnostic systems. This will
allow the Administrator to accept a HDDE as compliant with the NTE even
though some specific requirements are not fully met. This provision
will be available for manufacturers through 2013, though it will be
more limited after 2009 as described below. In the Phase 1 rule, the
Agency finalized deficiency provisions which were allowed through model
year 2009. In this rule, it is appropriate to extend the availability
of the NTE deficiency provisions beyond 2009. Given the nature of the
phase-in requirements in this rule, manufacturers may be introducing
new engine families certified to the Phase 2 NOX and NMHC
standards as late as model year 2010, and these families may need
limited access to a NTE deficiency for a few years after their
introduction. Therefore, we have extended the availability of
deficiencies through model year 2013, but with one constraint. Given
the considerable lead time available, we have limited the number of
deficiencies to three per engine family for 2010 through 2013.
In addition, we have made a number of changes to the NTE
requirements to address specific technical issues which arise from the
application of high efficiency exhaust emission control devices to
HDDEs. These provisions will only be summarized here. A detailed
discussion is contained in the RIA and the RTC for this final rule.
These changes include: engine start-up provisions; exhaust emission
control device warm-up provisions; modifications of the NTE control
zone; and adjustments to the NTE minimum emissions sample time.
Under this final rule, the NTE requirements will not apply during
engine start-up conditions. EPA intended to include the provision
excluding start-up provisions from the NTE requirements under the Phase
1 rulemaking, and it was discussed in the preamble for both the Phase 1
proposal and final rule. However, this provision was inadvertently left
out of the regulations. We have corrected this in today's rule for both
Phase 1 and Phase 2 engines. In addition, with the application of
advanced exhaust emission control devices, an exhaust emission control
device warm-up provision is a necessary criterion for the NTE.
Specifically, until the exhaust gas temperature on the outlet side of
the exhaust emission control device(s)

[[Page 5040]]

achieves 250 degrees Celsius, the engine is not subject to the NTE.
Additional discussion of this provision is contained in the RIA.
We have made three changes to the NTE engine control zone. First,
we have expanded the NTE engine control zone for engines certified to
the new 0.01 g/bhp-hr PM standard. The NTE requirements as specified in
the regulations for engines certified to the 2004 FTP standards provide
specific ``PM carve-outs'' to the NTE control zone. These carve-outs
define an area of the engine operating regime (speed and torque area)
to which the NTE does not apply for PM emissions. (See 65 FR 59961.)
The PM only carve-outs were specified because, under certain engine
operating regions, the NTE requirements for PM could not be met with
the technology projected to be used to meet the 2004 FTP standards.
However, as discussed in the RIA, the advanced PM trap technology that
will be used to meet the PM standard contained in today's final rule is
very efficient at controlling PM emissions across the entire NTE
control zone. Due to the high PM reduction capabilities of catalyzed PM
traps, there is no need for the PM specific carve-outs. Therefore, we
have eliminated the NTE PM carve-outs for Phase 2 engines. Second, we
have added a provision which would allow a manufacturer to exclude
defined regions of the NTE engine control zone from NTE compliance if
the manufacturer could demonstrate that the engine, when installed in a
specified vehicle(s), is not capable of operating in such regions.
Finally, we have added a provision which would allow a manufacturer to
petition the Agency to limit testing in a defined region of the NTE
engine control zone during NTE testing. This optional provision would
require the manufacturer to provide the Agency with in-use operation
data which the manufacturer could use to define a single, continuous
region of the NTE control zone. This single area of the control zone
must be specified such that operation within the defined region
accounts for 5 percent or less of the total in-use operation of the
engine, based on the supplied data. Further, to protect against gaming
by manufacturers, the defined region must generally be elliptical or
rectangular in shape, and share a boundary with the NTE control zone.
If approved by EPA, the regulations then disallow testing with sampling
periods in which operation within the defined region constitutes more
than 5.0 percent of the time-weighted operation within the sampling
period.
We have also changed the minimum emissions sample time approach for
NTE testing to address technical issues specific to the advanced
exhaust emission control devices anticipated to be used to meet the NTE
requirements. We proposed that the minimum emission sample time for the
NTE was 30 seconds, which is what we recently finalized for engines
certified to the Phase 1 standards. This short sample time was
sufficient to ensure that momentary spikes in emissions (e.g., such as
could occur in a two or three second time frame) could not be isolated
for determining compliance with the NTE (e.g., an NTE test must be no
shorter than a 30 second average). However, the use of highly efficient
exhaust emission control devices complicates the minimum sample time
requirements because of the potential for short-duration emission
increases during regeneration events. We have adjusted the minimum
sample time requirements to address this issue as follows (a detailed
discussion of the need for this change is contained in the RIA). The
regulations specify that the NTE sample time can be as short as 30
seconds provided no regeneration events occur within the sample period.
However, if a regeneration event is included in the sample time, the
sample time must include the period of time from the start of one
regeneration event to the start of the next regeneration event, for
each regeneration included in the sample. A regeneration event is
determined by the engine manufacturer. This second provision regarding
the minimum NTE sample time also cannot be shorter than 30 seconds.
This sample time provision applies to any HDDE engine equipped with an
exhaust emission control device which requires discreet regeneration
events, regardless of the nature of the regeneration (e.g.,
NOX regeneration, desulfation).
c. Crankcase Emissions Control
Crankcase emissions are the pollutants that are emitted in the
gases that are vented from an engine's crankcase. These gases are also
referred to as ``blowby gases'' because they result from engine exhaust
from the combustion chamber ``blowing by'' the piston rings into the
crankcase. These gases are vented to prevent high pressures from
occurring in the crankcase. Our emission standards have historically
prohibited crankcase emissions from all highway engines except
turbocharged heavy-duty diesel engines. The most common way to
eliminate crankcase emissions has been to vent the blowby gases into
the engine air intake system, so that the gases can be recombusted. We
made the exception for turbocharged heavy-duty diesel engines in the
past because of concerns about fouling that could occur by routing the
diesel particulates (including engine oil) into the turbocharger and
aftercooler. Our concerns are now alleviated by newly developed closed
crankcase filtration systems, specifically designed for turbocharged
heavy-duty diesel engines. These new systems (discussed more fully in
Section III.E below and in Chapter III of the Final RIA) are already
required for new on-highway diesel engines under the EURO III emission
standards.
In today's action, we are eliminating the exception for
turbocharged heavy-duty diesel engines starting in the 2007 model year.
Manufacturers will be required to control crankcase emissions from
these engines, preferably by routing them back to the engine intake or
to the exhaust stream upstream of the exhaust emission control devices.
However, in response to the manufacturers' comments, we are finalizing
the crankcase control requirement to allow manufacturers to treat
crankcase emissions from these engines the same as other exhaust
emissions (i.e., we provide a performance requirement and leave the
design to the manufacturer). Under this allowance, manufacturers could
potentially discharge some or all of the crankcase emissions to the
atmosphere, but only if they were able to keep the combined total of
the crankcase emissions and the other exhaust emissions below the
applicable exhaust emission standards. They could do this by routing
the crankcase gases into the exhaust stream downstream of the exhaust
emission control devices, or by continuing the current practice of
venting the gases to the engine compartment. But, they could take
either of these approaches only if they make sure that the combined
total of the crankcase emissions and the other exhaust emissions are
below the applicable exhaust emission standards. Also, the manufacturer
would have to ensure that the crankcase emissions were readily
measurable during laboratory and in-use field testing.88
Despite this allowance made at the request of commenters, given the low
levels of today's final standards we believe that manufacturers will
have to close the crankcases of all of their

[[Page 5041]]

engines by either routing the crankcase emissions into the engine
intake or by routing them into the exhaust upstream of the exhaust
emission control devices.
---------------------------------------------------------------------------

\88\ During laboratory testing, the crankcase emissions would
need to be vented in a controlled manner so that they could be
routed into the dilution tunnel to ensure their proper measurement
and inclusion in the tested emission level.
---------------------------------------------------------------------------

d. On-Board Diagnostics (OBD)
The Phase 1 heavy-duty final rule put into place OBD requirements
for heavy-duty diesel and gasoline engines weighing 14,000 pounds or
less. (See 65 FR 59896, October 6, 2000.) In that rule, the OBD
thresholds for malfunction identification are based on multiples of the
applicable FTP emission standards to which the engine is certified.
Given the structure of the 2004 FTP emission standards (2005 FTP
emission standards for gasoline engines), which are combined
NMHC+NOX standards, the OBD thresholds are based on a
multiple of the combined FTP standards. However, the structure of the
2007 FTP standards (2008 for gasoline engines) finalized today is not a
combined NMHC+NOX standard, but is instead a separate
NOX and a separate NMHC standard.
Therefore, today's final rule is revising the existing section of
the regulations to link OBD thresholds to whatever the appropriate
standards are whether they are the combined FTP standards or the new
separate FTP standards finalized today. This is consistent with the
intent of our OBD requirements since inception--that the OBD thresholds
be based on the FTP standards to which the vehicle or engine has been
certified.
We are also revising the phase-in for the OBD requirements
finalized in the Phase 1 rule. (See 65 FR 59896.) In that rule, OBD
systems were required to phase-in on a schedule of 60/80/100 percent
beginning in the 2005 model year. At least one commenter claimed that
the OBD phase-in may require multiple changes to OBD systems in
consecutive years, because OBD systems are tied to the FTP standards to
which they are certified.89 We have decided, for diesel
engine OBD systems, to revise the 60/80/100 percent phase-in to 50/50/
100 percent beginning in the 2005 model year. This revised phase-in not
only alleviates the commenter's concerns, but also makes the OBD phase-
in consistent with the implementation of new emission standards.
---------------------------------------------------------------------------

\89\ EPA does not believe there would be any legal stability
concern even if we had kept the OBD phase-in as finalized in the
Phase 1 rule. However, EPA agrees with the commenter that the phase-
in as finalized in the Phase 1 rule would have complicated
compliance unnecessarily.
---------------------------------------------------------------------------

In addition, we have decided, for gasoline engine OBD systems, to
revise the 60/80/100 percent phase-in to 60/80/80/100 percent beginning
in the 2005 model year.90 As with the new diesel OBD phase-
in, this gasoline engine OBD phase-in alleviates the commenter's
concerns, and it also makes the gasoline OBD phase-in more consistent
with the implementation of new emission standards while maximizing the
percentage of gasoline engines designed to meet the OBD requirements.
---------------------------------------------------------------------------

\90\ For those manufacturers choosing compliance Options 1 or 2
as part of the Phase 1 program, the gasoline engine OBD phase-in
will become 40/60/80/80/100 percent beginning in model year 2004.
(See 65 FR 59896, October 6, 2000.)
---------------------------------------------------------------------------

We also received comments suggesting that we commit to making any
necessary changes to the OBD requirements based on the outcome of
future rulemaking efforts by the California Air Resources Board (ARB).
While we cannot make any such commitment, nor do we believe the
commenter truly would want us to commit to making changes solely
because ARB made changes, we do intend to continue our normal practice
of working closely with ARB and harmonizing our OBD requirements where
appropriate. Of course, any changes to our OBD requirements could only
be done via rulemaking.91
---------------------------------------------------------------------------

\91\ This comment also pertained to gasoline vehicle-based OBD
systems. Our statements made here pertain to those requirements as
well but are not repeated below in section III.2.c.
---------------------------------------------------------------------------

2. Heavy-Duty Vehicle Exhaust Emissions Standards 92
---------------------------------------------------------------------------

\92\ As noted above, vehicle and engine standards apply to all
vehicles and engines, even if they are alternative fueled vehicles
and engines.
---------------------------------------------------------------------------

a. FTP Standards
The emission standards being finalized today for heavy-duty
gasoline vehicles are summarized in Table III.C-3. We have already
required that all complete heavy-duty gasoline vehicles, whether for
transporting passengers or for work, be chassis certified. (See 65 FR
59896, October 6, 2000.) Current federal regulations do not require
that complete diesel vehicles over 8,500 pounds be chassis certified;
instead, our regulations have traditionally required certification of
their engines. Today's final rule allows, as an option, chassis
certification of complete heavy-duty diesel vehicles under 14,000
pounds. This option is discussed in more detail later in this section.
The Tier 2 final rule created a new vehicle category called
``medium-duty passenger vehicles.'' 93 These vehicles, both
gasoline and diesel, are required to meet requirements of the Tier 2
program, which carries with it a chassis certification requirement. As
a result, diesel medium-duty passenger vehicles must certify using the
chassis certification test procedure.94 Today's heavy-duty
vehicle based standards, or chassis standards, for 2008 and later model
year heavy-duty gasoline vehicles would apply to the remaining complete
gasoline vehicles under 14,000 pounds and those complete diesel
vehicles under 14,000 pounds choosing the chassis certification option;
these complete vehicles are typically used for commercial, non-
passenger applications. The standards shown in Table III.C-3 are, we
believe, comparable in stringency to the diesel and gasoline engine
standards shown in Table III.C-1.
---------------------------------------------------------------------------

\93\ Medium-duty passenger vehicles are defined as any complete
vehicle between 8,500 and 10,000 pounds GVWR designed primarily for
the transportation of persons. The definition specifically excludes
any vehicle that (1) has a capacity of more than 12 persons total
or, (2) is designed to accommodate more than 9 persons in seating
rearward of the driver's seat or, (3) has a cargo box (e.g., pick-up
box or bed) of six feet or more in interior length. (See the Tier 2
final rulemaking, 65 FR 6698, February 10, 2000.)
\94\ The Tier 2 final rule did make a limited allowance for
engine certification of diesel MDPVS through the 2007 model year.
The reader should refer to the Tier 2 final rule for details on that
allowance. (See 65 FR 6750, February 10, 2000.)

[[Page 5042]]

Table III.C-3.--Full Useful Life Heavy-Duty Vehicle Exhaust Emissions Standards and Phase-Ins for Complete
Vehicles a
[Grams/mile]
----------------------------------------------------------------------------------------------------------------
Phase-in by model year b
Weight range (GVWR) Standard (g/mi) --------------------------------------
2008 2009
----------------------------------------------------------------------------------------------------------------
8,500 to 10,000 lbs NOX 0.2 .................. .................
NMHC 0.195 .................. .................
HCHO 0.032 .................. .................
PM 0.02 .................. .................
10,001 to 14,000 lbs NOX 0.4 50% 100%
NMHC 0.230 .................. .................
HCHO 0.040 .................. .................
PM 0.02 .................. .................
----------------------------------------------------------------------------------------------------------------
a Does not include medium-duty passenger vehicles.
b Percentages represent percent of sales.

These NOX standards represent a 78 percent reduction and
a 60 percent reduction from the standards for 8,500-10,000 pound and
10,000-14,000 pound vehicles, respectively, finalized for the 2005
model year. The 2005 model year standards are equivalent to the
California LEV-I NOX standards of 0.9 g/mi and 1.0 g/mi,
respectively. The NOX standards shown in Table III.C-3 are
consistent with the CARB LEV-II NOX standards for low
emission vehicles (LEVs) in each respective weight range. The
NOX standard is slightly higher for the 10,000 to 14,000
pound vehicles for several reasons: these vehicles are tested at a
heavier payload; they generally have a larger frontal area which
creates more drag on the engine and requires it to work harder; and
their in-use duty cycle tends to be more severe. The increased weight
results in using more fuel per mile than vehicles tested at lighter
payloads; therefore, they tend to emit slightly more grams of pollutant
per mile than lighter vehicles.95
---------------------------------------------------------------------------

\95\ Engine standards, in contrast, are stated in terms of grams
per unit of work rather than grams per mile. Therefore, engine
emission standards need not increase with weight because heavier
engines do not necessarily emit more per unit of work produced. In
contrast, heavier vehicles, due to their greater mass, tend to emit
more per mile due to the increased load placed on the engine which
requires the engine to do more work to travel each mile.
---------------------------------------------------------------------------

The NMHC standards finalized today represent a 30 percent reduction
from the 2005 standards for 8500-10,000 and 10,000-14,000 pound
vehicles. The 2005 model year standards require such vehicles to meet
NMHC standard levels of 0.28 g/mi and 0.33 g/mi, respectively (equal to
the California LEV-I nonmethane organic gases (NMOG) standard levels).
These new NMHC standards are consistent with the CARB LEV-II NMOG
standards for LEVs in each respective weight class. The NMHC standard
for 10,000-14,000 pound vehicles is higher than for 8,500-10,000 pound
vehicles for the same reason as stated above for the higher
NOX standard for such vehicles.
The formaldehyde (HCHO) standards shown in Table III.C-3 are not
the standards we proposed. The standards we are finalizing are
equivalent to the California LEV-II LEV category standards. This
approach is being taken to maintain consistency with the approach taken
on NOX and NMHC standards. Although we are not finalizing
formaldehyde standards for engine certified systems, because all the
exhaust emission standards for complete vehicles are consistent with
the CARB LEV II standards, we believe it is appropriate to maintain the
formaldehyde standard for gasoline vehicles. Formaldehyde is a
hazardous air pollutant that is emitted by heavy-duty vehicles and
other mobile sources, and we are finalizing these formaldehyde
standards to prevent excessive formaldehyde emissions. These standards
are especially important for any methanol-fueled vehicles because
formaldehyde is chemically similar to methanol and is one of the
primary byproducts of incomplete combustion of methanol. Formaldehyde
is also emitted by vehicles using petroleum fuels (i.e., gasoline or
diesel fuel), but to a lesser degree than is typically emitted by
methanol-fueled vehicles. We expect that petroleum-fueled vehicles able
to meet the NMHC standards should comply with the formaldehyde
standards with large compliance margins. Based upon our analysis of the
similar Tier 2 standards for passenger vehicles, we believe that
formaldehyde emissions from petroleum-fueled vehicles when complying
with the new PM, NMHC and NOX standards should be as much as
90 percent below the standards.96 Thus, to reduce testing
costs, we are finalizing a provision that permits manufacturers of
petroleum-fueled vehicles to demonstrate compliance with the
formaldehyde standards based on engineering analysis. This provision
requires manufacturers to make a demonstration in their certification
application that vehicles having similar size and emission control
technology have been shown to exhibit compliance with the applicable
formaldehyde standard for their full useful life. This demonstration is
expected to be similar to that required to demonstrate compliance with
the Tier 2 formaldehyde standards.
---------------------------------------------------------------------------

\96\ See the Tier 2 Response to Comments document contained in
Air Docket A-97-10.
---------------------------------------------------------------------------

The PM standard is 80 percent lower than the CARB LEV-II LEV
category PM standard of 0.12 g/mi, which actually applies only to
diesel vehicles. Note that the PM standard shown in Table III.C-3
represents not only a stringent PM level, but a new standard for
federal HDVs where none existed before. Both the California LEV II
program for heavy-duty diesel vehicles and the federal Tier 2 standards
for over 8,500 pound gasoline and diesel vehicles designed for
transporting passengers contain PM standards. The PM standard finalized
today is consistent with the light-duty Tier 2 bins 7 and 8 level of
0.02 g/mi.
The timing for our final gasoline vehicle standards differs from
what we had proposed. Our proposal had no phase-in, requiring 100
percent compliance in the 2007 model year. However, since the proposal
was published, we have set new standards for heavy-duty gasoline
complete vehicles that take effect in the 2005 model year. Therefore,
the three year stability requirement of the CAA requires that today's
new standards not apply until the 2008 model year at the earliest.
Further, based on comments

[[Page 5043]]

received, we believe that a phase-in should be provided. The phase-in
will allow manufacturers to implement improved gasoline control
technologies on their heavy-duty gasoline vehicles in the same
timeframe as they implement those technologies on their Tier 2 medium-
duty passenger vehicles (MDPV). The MDPVs generally use the same
engines and emission control systems as do the heavy-duty versions of
those vehicles. MDPVs must comply with our light-duty Tier 2 program at
50 percent beginning in the 2008 model year and then 100 percent in the
2009 model year. As a result of this MDPV phase-in, and the stability
requirements of the CAA, and because we believe it provides the
greatest emission control considering costs, we are finalizing a
gasoline phase-in of 50/100 percent beginning in the 2008 model year.
Commenters suggested a 40/80/100 percent phase-in beginning in the 2008
model year, but we believe that a 50/100 percent phase-in allows
appropriate leadtime and synergy with the MDPV requirements of our Tier
2 program. It is worth clarifying that this phase-in excludes
California complete heavy-duty vehicles, which are already required to
be certified to the California emission standards. It also excludes
vehicles sold in any state that has adopted California emission
standards for complete heavy-duty vehicles. It would be inappropriate
to allow manufacturers to ``double-count'' the vehicles by allowing
them to count those vehicles both as part of their compliance with this
phase-in and for compliance with California requirements. We would
handle heavy-duty engines similarly if California were to adopt
different emission standards than those being established by this rule.
We are also finalizing provisions that would encourage
manufacturers to introduce clean technology earlier than required in
return for greater flexibility during the later years of our phase-in.
These optional early incentive provisions are analogous to those
included in our light-duty Tier 2 rule and are discussed in more detail
in section III.D.
As we have done for diesel and gasoline engines, we have revised
our Averaging, Banking, and Trading program for gasoline vehicles and
engines to increase flexibility as discussed further in section VI. The
reader should refer to that section for more details. Note that the
gasoline vehicle phase-in schedule is the same as but separate from the
gasoline engine phase-in schedule discussed above. For a discussion of
why we believe these standards are technologically feasible in the time
frame required, refer to section III.E below, and for a more detailed
discussion refer to the RIA contained in the docket.
We are also allowing complete heavy-duty diesel vehicles under
14,000 pounds to certify to the heavy-duty vehicle standards. The issue
of chassis certification of diesels was raised as part of the Phase 1
rule. At that time, manufacturers expressed little interest in such a
provision. Because the heavy-duty diesel industry is largely not a
vertically-integrated industry, in that one company makes the engine
and another makes the vehicle, chassis certification is not an
immediately attractive or practical option for diesel engine
manufacturers. Nonetheless, some manufacturers have begun to express
interest in diesel chassis certification.97 Also, the
California Air Resources Board allows complete diesel vehicles to
chassis certify. We like the idea of diesel chassis certification
because it allows us to more easily evaluate such vehicles in-use. A
chassis certified diesel could be acquired easily by EPA and tested in
its vehicle configuration without the need to remove the engine for an
engine test.
---------------------------------------------------------------------------

\97\ See memorandum from Todd Sherwood to Air Docket A-99-06,
dated December 6, 2000, Item #IV-E-47.
---------------------------------------------------------------------------

Therefore, while we fully expect that manufacturers will continue
to certify the engines intended for complete diesel vehicles to the
engine standards, we will allow the option to chassis certify such
vehicles. Any chassis-certified complete diesel vehicles must meet the
applicable Phase 2 emission standards for complete vehicles (i.e., this
option is not available to diesels certified to the Phase 1 standards).
In addition, while complete diesel vehicles would count against the
phase-in requirements for diesel engines, they would not be allowed in
the Averaging, Banking, and Trading program. Therefore, a chassis-
certified diesel vehicle can neither use nor earn ABT credits, but
counts as part of the 50 percent phase-in. Further, complete diesels
choosing the chassis certification option would be required to comply
with our federal OBD vehicle-based requirements for monitoring of
exhaust emission control devices, even if choosing the option to
demonstrate OBD compliance using the California OBD II requirements.
Lastly, diesel vehicles choosing this option would be certified under
subpart S which applies to chassis certified complete vehicles, but the
evaporative emissions provisions of that subpart would not apply for
diesel vehicles.
b. Supplemental Federal Test Procedure
We did not propose new supplemental FTP (SFTP) standards for heavy-
duty vehicles. The SFTP standards control off-cycle emissions in a
manner somewhat analogous to the NTE requirements for engines. We
believe that the SFTP standards are an important part of our light-duty
program just as we believe the NTE requirements will be an important
part of our heavy-duty diesel engine program. Although we did not
propose SFTP standards for heavy-duty vehicles, we stated an intention
to do so via a separate rulemaking. We requested comment on such an
approach, and on appropriate SFTP levels for heavy-duty vehicles along
with supporting data.
We received unanimous support from industry commenters to address
SFTP standards for heavy-duty vehicles in a separate rulemaking. In our
Tier 2 final rule, we stated that we are currently contemplating a new
SFTP rulemaking that would consider ``Tier 2'' SFTP standards for all
Tier 2 vehicles, including MDPVs. California is also interested in
developing more stringent SFTP standards within the context of their
LEV II program and we are coordinating with California on these new
SFTP standards. Given our concern over ``off cycle'' emissions, we
believe it is appropriate that SFTP standards apply to all chassis
certified vehicles, heavy-duty and light-duty. As part of the SFTP rule
being contemplated, we expect to examine not only those issues stated
in the Tier 2 rule (e.g., the SFTP test cycles and different SFTP
standards for different vehicles sizes) but also the issue of heavy-
duty SFTP standards.
c. On-Board Diagnostics (OBD)
The Phase 1 heavy-duty rule finalized OBD requirements for heavy-
duty diesel engines, heavy-duty gasoline engines, and heavy-duty
complete vehicles weighing 14,000 pounds or less. (See 65 FR 59896,
October 6, 2000.) In that rulemaking, the final regulatory language
stated the OBD catalyst thresholds for complete vehicles as multiples
of a combined NMHC+NOX emission standard. However, the
emission standards for complete vehicles are not combined, as are the
engine standards in that final rule. Therefore, the OBD catalyst
thresholds for complete vehicles were not stated properly in the
applicable sections of the regulations.
Today's final rule corrects that regulatory error by revising the
appropriate regulatory language to link the OBD thresholds to a
separate, rather than combined, set of FTP exhaust

[[Page 5044]]

emission standards. This is consistent with the Phase 1 heavy-duty
proposal which correctly linked the proposed OBD thresholds to the
separate FTP exhaust emission standards. (See 64 FR 58472, October 29,
1999.) It is also consistent with the preamble to the Phase 1 final
rule, which stated the catalyst monitor threshold correctly. This
change makes the OBD thresholds for complete vehicle certifications
consistent with the structure used since implementation of the federal
OBD requirements. (See 58 FR 9468, February 19, 1993.)
Consistent with the changes already discussed in section III.C.1,
we are also revising the phase-in for complete vehicle OBD requirements
finalized in the Phase 1 rule. (See 65 FR 59896.) In that rule, OBD
systems were required to phase-in on a schedule of 60/80/100 percent
beginning in the 2005 model year. At least one commenter pointed out
that the OBD phase-in may require multiple changes to OBD systems in
consecutive years because OBD systems are tied to the FTP standards to
which they are certified. We have decided, for gasoline vehicle OBD
systems, to revise the 60/80/100 percent phase-in to 60/80/80/100
percent beginning in the 2005 model year.98 This revised OBD
phase-in alleviates the commenter's concerns, and it makes the gasoline
OBD phase-in more consistent with the implementation of new emission
standards while maximizing the percentage of gasoline vehicles designed
to meet the OBD requirements.
---------------------------------------------------------------------------

\98\ For those manufacturers choosing compliance Options 1 or 2
as part of the Phase 1 program, the gasoline vehicle OBD phase-in
will become 40/60/80/80/100 percent beginning in model year 2004.
(See 65 FR 59896.)
---------------------------------------------------------------------------

3. Heavy-Duty Evaporative Emissions Standards
We are finalizing new evaporative emission standards for heavy-duty
vehicles and engines. The new standards are shown in Table III.C-4.
These standards will apply to heavy-duty gasoline-fueled vehicles and
engines, and methanol-fueled heavy-duty vehicles and engines.
Consistent with existing standards, the standard for the two day
diurnal plus hot soak test sequence would not apply to liquid petroleum
gas (LPG) fueled and natural gas fueled HDVs.

Table III.C-4.--New Heavy-Duty Evaporative Emissions Standards a
[Grams per test]
------------------------------------------------------------------------
Supplemental
3 day 2 day
Category diurnal + diurnal +
hot soak hot soak b
------------------------------------------------------------------------
8,500-14,000 lbs............................. 1.4 1.75
>14,000 lbs.................................. 1.9 2.3
------------------------------------------------------------------------
a To be implemented on the same schedule as the gasoline engine and
vehicle exhaust emission standards shown in Tables III.C-1 and III.C-
3. These new standards do not apply to medium-duty passenger vehicles,
and do not apply to diesel fueled vehicles and engines.
b Does not apply to LPG or natural gas fueled HDVs.

These new standards represent more than a 50 percent reduction in
the numerical standards as they exist today. The Phase 1 heavy-duty
rule made no changes to the numerical value of the standard, but it did
put into place new evaporative emission test procedures for heavy-duty
complete gasoline vehicles.99 (See 65 FR 59896, October 6,
2000.) For establishing evaporative emission levels from complete
heavy-duty vehicles, the standards shown in Table III.C-4 presume the
test procedures required in the Phase 1 heavy-duty rule.
---------------------------------------------------------------------------

\99\ The test procedure changes codify a commonly approved
waiver allowing heavy-duty gasoline vehicles to use the light-duty
driving cycle for demonstrating evaporative emission compliance. The
urban dynamometer driving schedule (UDDS) used for heavy-duty
vehicles is somewhat shorter than that used for light-duty vehicles,
both in terms of mileage covered and minutes driven. This results in
considerably less time for canister purge under the heavy-duty
procedure than under the light-duty procedure. We recognize this
discrepancy and have routinely provided waivers under the enhanced
evaporative program that allow the use of the light-duty procedures
for heavy-duty certification testing. This is consistent with CARB's
treatment of equivalent vehicles.
---------------------------------------------------------------------------

The new standards for 8,500 to 14,000 pound vehicles are consistent
with the Tier 2 standards for medium-duty passenger vehicles (MDPV).
MDPVs are of consistent size and have essentially identical evaporative
emission control systems as the remaining work-oriented HDVs in the
8,500 to 10,000 pound weight range. Therefore, the evaporative emission
standards should be equivalent. We are requiring those same standards
for the 10,000 to 14,000 pound HDVs because, historically, the
evaporative emission standards have been consistent throughout the
8,500 to 14,000 pound weight range. We believe that the HDVs in the
10,000 to 14,000 pound range are essentially equivalent in evaporative
emission control system design as the lighter HDVs; therefore,
continuing this historical approach is appropriate.
We are finalizing slightly higher evaporative emission standards
for the over 14,000 pound HDVs because of their slightly larger fuel
tanks and for non-fuel emissions related to larger vehicle sizes. This
is consistent with past evaporative emission standards. The levels
chosen for the over 14,000 pound HDVs maintains the same ratio relative
to the 8,500 to 14,000 pound HDVs as exists with current evaporative
standards. To clarify, the current standards for the 3 day diurnal test
are 3 and 4 grams/test for the 8,500 to 14,000 and the over 14,000
pound categories, respectively. The ratio of 3:4 is maintained for the
new 2008 standards, 1.4:1.9.
The new standard levels are slightly higher than the California
LEV-II standard levels. The California standard levels are 1.0 and 1.25
for the 3-day and the 2-day tests, respectively. However, federal
vehicles are certified using the higher-volatility federal test
fuel.100 Arguably, the federal and California evaporative
emission standards are equivalent in stringency despite the difference
in standard levels. We believe that our standards are appropriate for
federal heavy-duty vehicles.
---------------------------------------------------------------------------

\100\ The federal test fuel specification for fuel volatility,
the Reid Vapor Pressure, is 8.7 to 9.2 psi. The California test fuel
specification is 6.7 to 7.0 psi.
---------------------------------------------------------------------------

We are requiring that the new evaporative emission standards be
implemented on the same schedule as the gasoline engine and vehicle
exhaust standards shown in Tables III.C-1 and III.C-3. This will allow
manufacturers to plan any needed changes to new vehicles at the same
time, although it is not necessary that the exhaust and evaporative
standards be phased-in on the same vehicles and engines. Also, we are
finalizing the revised durability provisions finalized in the Tier 2
rulemaking, which require durability demonstration using fuel
containing at least 10 percent alcohol. Alcohol can break down the
materials used in evaporative emission control systems. Therefore, a
worst case durability demonstration would include a worst case alcohol
level in the fuel (10 percent) because in some areas of the country
there is widespread use of alcohol fuels.

D. Incentives for Early Introduction of Clean Engines and Vehicles

In our proposal, we requested comment on alternative phase-in
approaches that could provide attractive implementation options to

[[Page 5045]]

manufacturers without compromising air quality. We requested comment on
a ``declining standard'' approach and a ``cumulative phase-in''
approach. We received only limited comment on those approaches with no
commenters expressing particularly strong support for them. We did
receive numerous comments suggesting that we provide some form of
incentive for manufacturers to introduce clean technology engines
earlier than required by the base program. We are finalizing the
approach discussed here as an incentive for manufacturers to introduce
clean diesel engines earlier than the 2007 model year (or the 2008
model year for gasoline engines and vehicles).
In our Tier 2 rule, we stated our belief that providing inducements
to manufacturers to certify vehicles early to very low levels is
appropriate. We believe that such inducements may help pave the way for
greater and/or more cost effective emission reductions from future
vehicles. We believe the program discussed here provides a strong
incentive for manufacturers to maximize their development and
introduction of the best available vehicle and engine emission control
technology. This, in turn, provides a stepping stone to the broader
introduction of this technology soon thereafter. Early production of
cleaner vehicles enhances the early benefits of our program. If a
manufacturer can be induced to certify to the new standards by the
promise of reasonable extra credits, the benefits of that decision to
the program may last for many years.
The incentive program finalized today is analogous to the
provisions set forth in the final Tier 2 rule. We are finalizing
provisions that permit manufacturers to take credit for diesel engines
certified to this rule's final standards prior to the 2007 model year
(prior to the 2008 model year for gasoline engines or vehicles) in
exchange for making fewer diesel engines certified to these standards
in or after the 2007 model year (2008 for gasoline engines or
vehicles). In other words, a clean engine sold earlier than required
displaces the requirement to sell a similar engine later. Note that the
emission standards must be met to earn the early introduction credit.
That is, emission credits earned under averaging, banking, and trading
cannot be used to demonstrate compliance. Therefore, the early
introduction engine credit is an alternative to the ABT program in that
any early engines or vehicles can earn either the engine credit or the
ABT emission credit, but not both. The purpose of the incentive is to
encourage introduction of clean technology engines earlier than
required in exchange for added flexibility during the phase-in years.
Any early engine credits earned for a diesel-fueled engine would,
of course, be predicated on the assurance by the manufacturer that the
engine would indeed be fueled with low sulfur diesel fuel in the
marketplace. We expect this would occur through selling such engines
into fleet applications, such as city buses, school buses, or any such
well-managed centrally-fueled fleet. For this reason, we believe that
any engines sold within this early incentive program would be sold
primarily in urban areas where more centrally-fueled fleets exist.
Because of the difficulty associated with low sulfur diesel fuel
availability prior to mid-2006, we believe it is necessary and
appropriate to provide a greater incentive for early introduction of
clean diesel technology. Therefore, we will count one early diesel
engine as 1.5 diesel engines later. This extra early credit for diesel
engines means that fewer clean diesel engines than otherwise would be
required may enter the market during the years 2007 and later. But,
more importantly, it means that emission reductions would be realized
earlier than under our base program. We believe that providing
incentives for early emission reductions is a worthwhile goal for this
program. Therefore, we are finalizing these provisions for
manufacturers willing to make the early investment in cleaner engines.
For gasoline engines and vehicles, the early engine credit will be a
one-for-one credit because the gasoline needed by the engine or vehicle
will be readily available.
We are providing this early introduction credit to diesel engines
that meet all of today's final standards (0.20 g/bhp-hr NOX,
0.14 g/bhp-hr NMHC, and 0.01 g/bhp-hr PM). We are also providing this
early introduction credit to diesel engines that pull-ahead compliance
with only the 0.01 g/bhp-hr PM standard. However, a PM-only early
engine can offset only PM compliant engines during the phase-in years,
not NOX, NMHC, and PM compliant engines.
An important aspect of the early incentive provision is that it
must be done on an engine or vehicle count basis. That is, a diesel
engine meeting new standards early counts as 1.5 such diesel engines
later and a gasoline engine or vehicle early counts as one gasoline
engine or vehicle later. This contrasts with a provision done on an
engine percentage basis which would count one percent of diesel engines
early as 1.5 percent of diesel engines later. Basing the incentive on
an engine count will alleviate any possible influence of fluctuations
in engine and vehicle sales in different model years.
Another important aspect of this program is that it is limited to
engines sold prior to the 2007 model year (2008 for gasoline). In other
words, diesel engines sold in the 2007 through 2009 model years that
exceed the required 50 percent phase-in will not be considered
``early'' introduction engines and will, therefore, receive no early
introduction credit. The same is true for gasoline engines and vehicles
sold in the 2008 model year. However, such engines and vehicles will
still be able to generate ABT credits. Note that early gasoline
vehicles can count for later gasoline vehicles, and early gasoline
engines can count for later gasoline engines, but early gasoline
vehicles cannot be traded for later gasoline engines and vice versa.
Table III.D-1 shows an example for a diesel engine manufacturer and
how it might use this incentive provision on an assumed fleet of 100
engine sales growing at one percent per year beginning in the 2004
model year.

Table III.D-1.--Example Engine Introduction Under Our Early Incentive Program
----------------------------------------------------------------------------------------------------------------
2004 2005 2006 2007 2008 2009 2010
----------------------------------------------------------------------------------------------------------------
Total Sales 100 101 102 103 104 105 106
----------------------------------------------------------------------------------------------------------------
Clean Engines under 0 0 0 52 52 53 106
Base program .......... .......... .......... .......... .......... .......... ..........
----------------------------------------------------------------------------------------------------------------
Clean Engines under 4 4 4 46 46 47 106
Incentive Program .......... .......... .......... .......... .......... .......... ..........
----------------------------------------------------------------------------------------------------------------

[[Page 5046]]

The four engines sold early in each of model years 2004 through
2006 generate a total credit of 18 engines (4 x 3 x 1.5=18). This
allows the manufacturer to reduce its compliant engine count in each of
model years 2007 through 2009 by six engines (18/3=6). This helps the
manufacturer by reducing total costs through requiring fewer total
engines at the low-emitting, clean engine level. But, more importantly,
it introduces clean technology engines early and, by 2010 in this
example, generates from four to six years of emission reductions that
otherwise would not have occurred.
As further incentive to introduce clean engines and vehicles early,
we are also finalizing a provision that would give manufacturers an
early introduction credit equal to two engines during the phase-in
years. This ``Blue Sky'' incentive would apply for diesel engines
meeting one-half of today's final NOX standard while also
meeting the NMHC and PM standards. For gasoline engines, the same early
introduction double engine credit would be available to engines sold
prior to 2008 and meeting one-half the NOX standard while
also meeting the NMHC, PM, and evaporative emission standards. For
gasoline vehicles, the double engine credit would be available to those
vehicles certified early to the California SULEV levels and today's PM
and evaporative emission standards.101 Due to the extremely
low emission levels to which these Blue Sky series engines and vehicles
would need to certify, we believe that the double engine count credit
is appropriate. Table III.D-2 shows the emission levels that would be
required prior to the 2007 model year for diesel engines and the 2008
model year for gasoline vehicles and engines to earn any early
introduction engine credits.
---------------------------------------------------------------------------

\101\ The California SULEV levels are, for 8,500 to 10,000 pound
vehicles, 0.1 g/mi NOX, 0.100 g/mi NMOG, 0.008 g/mi HCMO,
and 0.06 g/mi PM; and for 10,000 to 14,000 pound vehicles, 0.2 g/mi
NOX, 0.117 g/mi NMOG, 0.010 g/mi HCHO, and 0.06 g/mi PM.
With the exception of the PM standards, these emission levels are
half or roughly half of this rule's final gasoline vehicle
standards.

Table III.D-2.--Emission Levels and Credits Available for Early
Introduction Engines
------------------------------------------------------------------------
Early engine
Category Must meet a credit b
------------------------------------------------------------------------
Early Diesel PM-only c......... Phase 2 PM &........... 1.5-to-1
Phase 1 NOX + NMHC.....
Early Diesel Engine c.......... All Phase 2 Standards.. 1.5-to-1
Early Gasoline Engine or Phase 2 Exhaust 1-to-1
Vehicle--Exhaust. Standards.
Early Gasoline Engine or Phase 2 Evaporative 1-to-1
Vehicle--Evap. Standards.
Blue Sky Series Diesel c or 0.10 g/bhp-hr NOX & All 2-to-1
Gasoline Engine. other Phase 2
Standardsd.
Blue Sky Series Gasoline....... 0.02 g/mi PM & 2-to-1
California SULEV Level
Standardsd.
Vehicle
------------------------------------------------------------------------
a Phase 1 refers to standards required by 65 FR 59896, October 6, 2000;
Phase 2 refers to today's final standards.
b Engine count credits must be earned prior to the phase-in years of
2007 for diesel and 2008 for gasoline.
c Early diesel engines must also meet the Phase 2 crankcase emissions
requirements.
d For gasoline engines and vehicles, these must also meet the Phase 2
evaporative emission standards.

Alternative fueled vehicles and engines can also play a significant
role in this incentive program. Any alternative fueled diesel-cycle
engine certified to today's final standards prior to the 2007 model
year can generate a 1.5 diesel-cycle engine count credit during the
diesel phase-in years. Likewise, any alternative fueled Otto-cycle
engine certified to today's final standards prior to the 2008 model
year can generate one Otto-cycle engine count credit. Many commenters
suggested that EPA should do more than was put forward in our proposal
to encourage the introduction of alternative fuel technologies. To the
extent that alternative fueled vehicles and engines are cleaner than
diesels and gasolines, they may have an advantage within today's
program. We believe that this program and its structure provides
significant incentives for manufacturers to introduce alternative
fueled vehicles and engines.
One final aspect of the incentive program is its interaction with
our Tier 2 program. The Tier 2 final rule allows some MDPVs to be
equipped with engine-certified diesel engines through the 2007 model
year. Any such engines are required to comply with the diesel engine
standards that apply during the given model year. Given that they are
certified as heavy-duty diesel engines, any such engines that meet
today's final diesel standards prior to the 2007 model year would be
allowed within today's incentive program provided they in no way
generate any emission or engine count credits within the Tier 2
program. Further, any MDPVs, whether gasoline or diesel, certified on a
chassis dynamometer and being counted in any way as part of the Tier 2
program, cannot be used as part of today's incentive program because
they are not considered heavy-duty vehicles.

E. Feasibility of the New Engine and Vehicle Standards

For more detail on the information and analyses supporting our
assessment of the technological feasibility of today's standards,
please refer to the Final RIA in the docket for this rule. The
following discussion summarizes the more detailed discussion found in
the Final RIA and in the Summary and Analysis of Comments document.
1. Feasibility of Stringent Standards for Heavy-Duty Diesel
The designers and manufacturers of diesel engines have made
substantial progress over the last 20 years reducing NOX
emissions by 60 percent and PM emissions by almost 90 percent through
better engine design. We believe that, in response to our Phase 1
heavy-duty rule, industry will have implemented all promising engine-
based emission reduction technologies in order to meet the 2.5 g/bhp-hr
NOX+NMHC standard and the 0.1 g/bhp-hr PM standard. To get
the substantial PM and NOX reductions from diesel engines
needed to solve the air quality problems identified in section II, we
believe a new technology solution will be required. That solution is
the application of high efficiency exhaust emission control
technologies (catalysts) to diesel engines, analogous to the
application of catalyst technologies to passenger cars in the 1970s.
These high efficiency catalyst technologies, enabled by the use of
diesel fuel with sulfur content at or below 15 ppm, can reduce
NOX and PM emissions by more than 90 percent. This dramatic
reduction in emissions will

[[Page 5047]]

enable diesel powered vehicles to reach emission levels well below
today's gasoline emission levels. As detailed in the sections below,
these technologies are rapidly being developed and will be available
for application to diesel powered vehicles by, or even before, the 2007
model year provided the low sulfur diesel fuel required today is widely
available.
a. Meeting the PM Standard
Diesel PM consists of three primary constituents: Unburned carbon
particles (soot), which make up the largest portion of the total PM;
the soluble organic fraction (SOF), which consists of unburned
hydrocarbons that have condensed into liquid droplets or have condensed
onto unburned carbon particles; and sulfates, which result from
oxidation of fuel and oil derived sulfur in the engine's exhaust.
Several exhaust emission control devices have been developed to control
harmful diesel PM constituents--the diesel oxidation catalyst (DOC),
and the many forms of diesel particulate filters, sometimes called PM
traps. DOCs have been shown to be durable in use, but they effectively
control only the SOF portion of the total PM which, on a modern diesel
engine constitutes only 10 to 30 percent of the total PM. Therefore,
the DOC on its own would only offer a modest reduction in PM emissions,
and would not be able to meet the PM standard set here.
Diesel particulate filters were first investigated some twenty
years ago as a means to capture solid particles in diesel exhaust. A
variety of approaches to this technology have been developed most of
which provide excellent mechanical filtration of the solid particles
that make up the bulk of diesel PM (60 to 80 percent). The collected
PM, mostly carbon particles, must then be ``burned off'' of the filter
before the filter becomes plugged. This burning off of collected PM
(oxidation of the stored PM, releasing CO2) is referred to
as ``regeneration,'' and can occur either:
On a periodic basis by using base metal catalysts
(including fuel-borne base metal catalysts) or an active regeneration
system such as an electrical heater, a fuel burner, or a microwave
heater; or,
On a continuous basis by using precious metal catalysts.
Diesel particulate traps that regenerate on a periodic basis
(referred to here as either uncatalyzed or base metal catalytic PM
traps) demonstrated high PM trapping efficiencies many years ago, but
the level of the applicable PM standard was such that it could be met
through less costly ``in-cylinder'' control techniques. Un-catalyzed
diesel particulate filters will not be able to meet the 0.01 g/bhp-hr
PM standard finalized today as they are only moderately effective at
controlling the SOF fraction of the particulate. In addition, they
require active regeneration technology which must be engaged frequently
making the systems expensive to operate (increasing fuel consumption)
and less reliable.
We believe the kind of PM trap that would be able to meet the PM
standard in a reliable, durable, cost effective manner, and the type of
trap that will prove to the be the industry's technology of choice, is
one capable of regenerating on an essentially continuous basis. In
addition these PM traps will be able to achieve very low PM emissions
because:
They are highly efficient at controlling the solid carbon
portion of PM;
Unlike uncatalyzed filters, they are highly efficient at
oxidizing the SOF of diesel PM;
They employ precious metals to produce conditions that
reduce the temperature at which regeneration occurs, thereby allowing
for passive regeneration under normal operating conditions typical of a
diesel engine; 102
---------------------------------------------------------------------------

\102\ For PM trap regeneration without precious metals, exhaust
metals, exhaust temperatures in excess of 650 deg.C must be
obtained. At such high temperatures, carbon will burn (oxidize to
CO2) provided sufficient oxygen is present. Although the
largest heavy-duty diesels may achieve exhaust temperatures of
650 deg.C under some operating conditions, smaller diesel engines,
particularly light-duty and light heavy-duty diesel engines, will
rarely achieve such high temperatures. For example, exhaust
temperatures on the HDE Federal Test Procedure cycle typically range
from 100 deg.C to 450 deg.C. Precious metal catalyzed traps use
platinum to oxidize NO in the exhaust to No2, which is
capable of oxidizing carbon at temperatures as low as 250 deg.C to
300 deg.C.
---------------------------------------------------------------------------

Because they regenerate continuously, they have lower
average backpressure thereby reducing potential fuel economy impacts;
and,
Because of their passive regeneration characteristics,
they need no extra burners or heaters like what would be required by an
active regeneration system, thereby reducing potential failures and
fuel economy impacts.
These catalyzed PM traps are able to provide in excess of 90
percent control of diesel PM when operated on diesel fuel with sulfur
levels at or below 15 ppm. However, as discussed in detail in the RIA,
the catalyzed PM trap cannot regenerate properly with current fuel
sulfur levels, as such sulfur levels poison the catalytic function of
the PM trap inhibiting the necessary NO to NO2 reaction to
the point of stopping trap regeneration.103 Also, because
SO2 is so readily oxidized to SO3, the 0.01 g/
bhp-hr PM standard cannot be achieved with fuel sulfur levels above 15
ppm because of the resultant increase in sulfate PM emissions
(``sulfate make'').104
---------------------------------------------------------------------------

\103\ Cooper and Thoss, Johnson Matthey, SAE 890404.
\104\ See the RIA for more detail on the relationship of fuel
sulfur to sulfate make.
---------------------------------------------------------------------------

More than one exhaust emission control manufacturer is known to
have or be developing these precious metal catalyzed, passively
regenerating PM traps and to have them in broad field test programs in
areas where low sulfur diesel fuel is currently available. In field
trials since 1994, they have demonstrated highly efficient PM control
and good durability with some units accumulating in excess of 360,000
miles of field use.105 The experience gained in these field
tests also helps to clarify the need for low sulfur diesel fuel. In
Sweden, where below 10 ppm diesel fuel sulfur is readily available,
more than 3,000 catalyzed diesel particulate filters have been
introduced into retrofit applications without a single failure. These
retrofit applications include intercity trains, airport buses, mail
trucks, city buses and garbage trucks.106 The field
experience in areas where sulfur is capped at 50 ppm has been less
definitive. In regions without extended periods of cold ambient
conditions, such as the United Kingdom, field tests on 50 ppm sulfur
cap fuel have been positive, matching the durability at 10 ppm, but
would be unable to meet a 0.01 g/bhp-hr PM standard due to a
substantial increase in sulfate PM. However, field tests on 50 ppm
sulfur fuel in Finland where colder winter conditions are often
encountered (similar to northern parts of the United States) have
experienced a failure rate of 10 percent, due to trap plugging. This 10
percent failure rate has been attributed to insufficient trap
regeneration due to fuel sulfur in combination with low ambient
temperatures.107 Other possible reasons for the high failure
rate in Finland when contrasted with the Swedish experience appear to
be unlikely. The Finnish and Swedish fleets were substantially similar,
with both fleets consisting of transit buses powered by Volvo and
Scania engines in the 10 to 11 liter range. Further, the buses were
operated in city areas and none of the vehicles were operated in
northern extremes such as north of the

[[Page 5048]]

Arctic Circle.108 Given that the fleets in Sweden and
Finland were substantially similar, and given that ambient conditions
in Sweden are expected to be similar to those in Finland, we believe
that the increased failure rates noted here are due to the higher fuel
sulfur level in a 50 ppm cap fuel versus a 10 ppm cap
fuel.109 Testing on an even higher fuel sulfur level of 200
ppm was conducted in Denmark on a fleet of 9 vehicles. In less than six
months all of the vehicles in the Danish fleet had failed due to trap
plugging.110 We believe that this real world testing clearly
indicates that increasing diesel fuel sulfur levels limit trap
regeneration, leading to plugging of the PM trap even at fuel sulfur
levels as low as 50 ppm.
---------------------------------------------------------------------------

\105\ Allansson, et al. SAE 2000-01-0480.
\106\ Allansson, et al. SAE 2000-01-0480.
\107\ Letter from Dr. Barry Cooper to Don Kopinski, US EPA, Air
Docket A-99-06.
\108\ Telephone conversation between Dr. Barry Cooper, Johnson
Matthey, and Todd Sherwood, EPA, Air Docket A-99-06.
\109\ The average temperatrue in Helsinki, Finland, for the
month of January is 21 deg.F. The average temperature in Stockholm,
Sweden, for the month of January is 26 deg.F. The average
temperature at the University of Michigan in Ann Arbor, Michigan,
for the month of January is 24 deg.F. The temperature reported here
are from www.worldclimate.com based upon the Global Historical
Climatology Network (GHCN) produced jointly by the National Climatic
Data Center and Carbon Dioxide Information Analysis Center at Oak
Ridge National Laboratory (ORNL).
\110\ Letter from Dr. Barry Cooper to Don Kopinski US EPA, Air
Docket A-99-06.
---------------------------------------------------------------------------

From these results, we can further conclude that lighter
applications (such as large pick-up trucks and other light heavy-duty
applications), having lower exhaust temperatures than heavier
applications, may experience similar failure rates even in more
temperate climates and would, therefore, need lower sulfur fuel even in
the United Kingdom. These results are understood to be due to the
effect of sulfur on the trap's ability to create sufficient
NO2 to carry out proper trap regeneration. Without the
NO2, the trap continues to trap the PM at high efficiency,
but it is unable to oxidize, or regenerate, the trapped PM. The
possible result is a plugged trap. This vulnerability of the catalyzed
diesel particulate filter due to sulfur in the fuel and the
consequences of trap plugging are discussed fully in section III.F and
the RIA.
Several commenters raised concerns with our use of the extensive
fleet experience in Europe, to draw conclusions about the necessary
sulfur reductions required in order to ensure PM trap durability. Their
concerns focused generally around the fact that these fleets were made
up of retrofit applications, and that the nature of the fleet operation
did not represent a controlled experiment (ideally all things would
have been equal except for the fuel sulfur level). While we acknowledge
these limitations in the data, we believe they still provide reasonable
evidence of the need for low sulfur diesel fuel. The diversity of
applications, climates, fuel properties, NOX emission
levels, and sulfur levels help to show the relative robustness of the
technology. Further, we believe the PM trap manufacturer's analysis of
the failure mode (i.e., that cold ambient conditions coupled with
diminished NO to NO2 conversion due to sulfur led to the
failures that were experienced) is the most likely explanation of the
observed phenomena. Sulfur in diesel fuel is known to inhibit the
oxidation of NO to NO2 (as described in section III.F)
leading to reduced ability to regenerate the PM filter, especially
under low ambient conditions. For our detailed response to comments
surrounding catalyzed diesel particulate filter durability refer to the
RTC document.
Several progressive refineries have begun to produce diesel fuel
with sulfur content less than 15 ppm for limited markets in the United
States. The availability of this low sulfur diesel fuel makes it
possible to introduce diesel particulate filters into these limited
markets today. International Truck and Engine Corporation
(``International'') has announced its intent to commercialize its Green
Diesel Engine TechnologyTM in 2001 coupled with less than 15
ppm sulfur fuel to achieve our proposed MY 2007 NMHC and PM emissions
standards six years in advance of the requirement. International's
ability to bring a catalyzed diesel particulate filter technology to
commercialization in such a short period highlights the advanced state
of this technology.111
---------------------------------------------------------------------------

\111\ International Truck and Engine Corporation's comments on
the proposed 2007 heavy duty vehicle standards, Air Docket A-99-06,
page 2.
---------------------------------------------------------------------------

Modern catalyzed PM traps have been shown to be very effective at
reducing PM mass. In addition, recent data show that they are also very
effective at reducing the overall number of emitted particles when
operated on low sulfur fuel. Hawker, et. al., found that a modern
catalyzed PM trap reduced particle count by over 95 percent, including
some of the smallest measurable particles (50 nm), at most of the
tested conditions. The lowest observed efficiency in reducing particle
number was 86 percent. No generation of particles by the PM trap was
observed under any tested conditions.112 Kittelson, et al.,
confirmed that ultrafine particles can be reduced by a factor of ten by
oxidizing volatile organics, and by an additional factor of ten by
reducing sulfur in the fuel. Catalyzed PM traps efficiently oxidize
nearly all of the volatile organic PM precursors, and elimination of as
much fuel sulfur as possible will substantially reduce the number of
ultrafine PM emitted from diesel engines. The combination of catalyzed
PM traps with low sulfur fuel is expected to result in very large
reductions in both PM mass and the number of ultrafine particles.
---------------------------------------------------------------------------

\112\ Hawker, P., et al., Effect of a Continuously Regenerating
Diesel Particulate Filter on Non-Regulated Emissions and Particle
Size Distribution, SAE 980189.
---------------------------------------------------------------------------

The data currently available show that catalyzed particulate
filters can provide significant reductions in PM. Catalyzed particulate
filters, in conjunction with low sulfur fuel, have been shown to be
more than 90 percent efficient over the FTP and at most SET
modes.113 Testing completed as part of the Diesel Emission
Control Sulfur Effects (DECSE) program has demonstrated that a heavy
duty diesel engine can achieve less than 0.01 g/bhp-hr PM emissions
over the supplemental emission test when equipped with a catalyzed
diesel particulate filter and operated on diesel fuel with sulfur
content less than 15 ppm.114 Further testing at NVFEL has
demonstrated that FTP PM emissions can likewise be controlled below
0.01 g/bhp-hr provided less than 15 ppm sulfur diesel fuel is used with
a catalyzed PM trap.115 Based upon these test results,
extensive field experience throughout the world and International Truck
and Engine Corporation's commitment to produce vehicles with this
technology in 2001, we conclude that the 0.01 g/bhp-hr FTP PM standard
is feasible and that it represents the lowest emission level possible
having given consideration to cost, energy and safety factors.
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\113\ Demonstration of Advanced Emission Control Technologies
Enabling Diesel-Powered Heavy-Duty Engines to Achieve Low Emission
Levels, Manufacturers of Emissions Controls Association, June 1999.
\114\ Testing for the DECSE program was conducted on 3 ppm and
30 ppm diesel fuel. A straight-line fit to the results between 3 ppm
and 30 ppm shows that a 15 ppm cap fuel would have emissions less
than 0.01 g/bhp-hr. Diesel Emission Control Sulfur Effects (DECSE)
Program, Phase I Interim Data Report No. 4: Diesel Particulate
Filters--Final Report, January 2000.
\115\ Memorandum from Charles Schenk, EPA, to Air Docket A-99-
06, ``Summary of EPA PM Efficiency Data,'' May 8, 2000.
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With regard to the NTE PM requirements, there is the potential for
sulfate production during some operating modes covered by the NTE which
would likely exceed the FTP PM standard. However, the NTE PM standard
is equal to 1.5 x FTP standard. Even though the FTP standard of 0.01
g/bhp-hr PM is very low, the small additional head room provided by a

[[Page 5049]]

NTE multiplier of 1.5 will be sufficient to enable PM trap equipped
HDDEs to meet the NTE provisions, even when operated on 15 ppm sulfur
fuel. This is supported by data generated as part of the DECSE test
program, as well as data generated at our own laboratory, as discussed
in greater detail in the RIA.116 As discussed in the RIA,
the expanded ambient condition requirements of the NTE test procedure
will have little effect on the PM reduction capabilities of a PM trap.
The SET PM requirements have also been demonstrated in our laboratory
and are supported by the DECSE test program. A detailed discussion is
contained in the RIA. Based on this information and assessment, we
conclude that the PM supplemental requirements will be feasible in the
2007 time frame.
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\116\ Diesel Emission Control Sulfur Effects (DECSE) Program--
Phase II Interim Data Report No. 4, Diesel Particulate Filters--
Final Report, January 2000, Table C1, www.ott.doe.gov/decse.
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b. Meeting the NOX Standard
NOX emissions from gasoline-powered vehicles are
controlled to extremely low levels through the use of the three-way
catalyst technology first introduced in the 1970s. Today, an
advancement upon this well-developed three-way catalyst technology, the
NOX adsorber, has shown that it too can make possible
extremely low NOX emissions from lean-burn engines such as
diesel engines. The potential of the NOX adsorber catalyst
is limited only by its need for careful integration with the total
vehicle system (as was done for three-way catalyst equipped passenger
cars in the 1980s and 1990s) and by poisoning of the catalyst from
sulfur in the fuel. Just as the Tier 2 rulemaking enables advanced
three-way catalyst equipped vehicles to meet ultra low NOX
emission levels through the use of low sulfur gasoline, today's
rulemaking will enable NOX adsorbers through substantial
reductions in diesel fuel sulfur levels. The NOX adsorber
has already been commercially introduced in a number of stationary and
mobile source applications.

NOX Adsorbers in Power Generation

NOX adsorber catalysts were first introduced in the
power generation market less than five years ago. Since then,
NOX adsorber systems in stationary source applications have
enjoyed considerable success. In 1997, the South Coast Air Quality
Management District of California determined that a NOX
adsorber system provided the ``Best Available Control Technology''
NOX limit for gas turbine power systems.117
Average NOX control for these power generation facilities is
in excess of 92 percent.118 A NOX adsorber
catalyst applied to a natural gas fired powerplant has demonstrated
better than 99 percent reliability for more than 21,000 hours of
operation while controlling NOX by more than 90
percent.119
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\117\ Letter from Barry Wallerstein, Acting Executive Officer,
SCAQMD, to Robert Danziger, Goal Line Environmental Technologies,
dated December 8, 1997, www.glet.com.
\118\ Reyes and Cutshaw, SCONOX Catalytic Absorption
System, December 8, 1998, www.glet.com.
\119\ Danziger, R. et al. 21,000 Hour Performance Report on
SCONOX, 15 September 2000, Air Docket A-99-06.
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NOX Adsorbers in Lean-Burn Gasoline Vehicles

The NOX adsorber's ability to control NOX
under oxygen rich (fuel lean) operating conditions has led the industry
to begin applying NOX adsorber technology to lean-burn
engines in mobile source applications. NOX adsorber
catalysts have been developed and are now in production for lean-burn
gasoline vehicles in Japan, including several vehicle models sold by
Toyota Motor Corporation.120 The 2000 model year saw the
first U.S. application of this technology with the introduction of the
Honda Insight, certified to the California LEV-I ULEV category
standard. These lean burn gasoline applications are of particular
interest because they are similar to diesel vehicle applications in
terms of NOX storage under lean exhaust conditions and the
need for periodic NOX regeneration under transient driving
conditions. The substantial experience already gained and continuing to
be gained from NOX adsorber use in lean-burn gasoline
vehicles provides a firm basis from which diesel NOX
adsorber development is proceeding.
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\120\ Toyota requires that their lean burn gasoline engines
equipped with NOX adsorbers are fueled on premium
gasoline in Japan, which has an average sulfur content of 6 ppm.
(See Item IV-E-31 in Air Docket A-99-06.)
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NOX Adsorbers in Light-Duty Diesel Vehicles

This rapid development pace of the NOX adsorber
technology is not limited to gasoline applications but includes markets
where low sulfur diesel fuel is already available or has been mandated
to coincide with future emission standards. In Japan, Toyota Motor
Corporation has recently announced that it will begin introducing
vehicles using its Diesel Particulate-- NOX Reduction (DPNR)
system in 2003. This system uses a NOX adsorber catalyst
applied on the surface of a diesel particulate filter, providing
greater than 80 percent reductions in both PM and NOX.
Toyota notes however, that DPNR requires fuel with low sulfur content
in order to maintain high efficiency for a long duration.121
In Europe, both Daimler Chrysler and Volkswagen, driven by a need to
meet stringent Euro IV emission standards, have published results
showing how they would apply the NOX adsorber technology to
their diesel-powered passenger cars. Volkswagen reports that it has
already demonstrated NOX emissions of 0.137 g/km (0.22 g/
mi), a 71 percent reduction, on a diesel powered Passat passenger car
equipped with a NOX adsorber catalyst.122
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\121\ Revolutionary Diesel Aftertreatment System Simultaneously
Reduces Diesel Particulate Matter and Nitrogen Oxides, Toyota Motor
Corporation press release, July 25, 2000, contained in Air Docket A-
99-06.
\122\ Pott, E., et al., ``Potential of NOX-Trap
Catalyst Application for DI-Diesel Engines,'' Air Docket A-99-06.
---------------------------------------------------------------------------

US DOE Research Programs

The U.S. Department of Energy (DOE) has funded several test
programs at national laboratories and in partnership with industry to
investigate NOX adsorber technology. At Oak Ridge National
Laboratory, DOE researchers have shown that a NOX adsorber
and a laboratory regeneration system can reduce NOX by more
than 90 percent when used on a diesel powered Mercedes A-class
passenger car. Following 600 miles of driving with 150 ppm sulfur fuel,
the system performance degraded considerably.123 While the
system was not production ready, it does demonstrate that very high
efficiencies are achievable with advanced emission control systems
operating on low sulfur fuel.124 With additional system
development over the next several years we are confident that the
remaining design challenges such as long-term durability will be
solved.
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\123\ Diesel Vehicle Emission Control Sulfur Effects Project at
Oak Ridge National Laboratory, Phase 1 Overview. Pete Devlin, DOE
Office of Transportation Technologies, March 29, 2000, Air Docket A-
99-06.
\124\ Diesel Emission Control Sulfur Effects (DECSE) Program
Phase II Summary Report: NOX Adsorber Catalysts, October
2000, Air Docket A-99-06.
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EPA NVFEL Current Technology Evaluation Program

As part of an effort to evaluate the rapidly developing state of
this technology, the Manufacturers of Emission Control Association
(MECA) provided four different NOX adsorber catalyst
formulations to EPA for

[[Page 5050]]

evaluation. Testing of these catalysts at NVFEL revealed that all four
formulations were capable of reducing NOX emissions by more
than 90 percent over the broad range of operation in the supplemental
emission test (SET) procedure as summarized in Figure III-1. At
operating conditions representative of ``road-load'' operation for a
heavy duty on-highway truck, the catalysts showed NOX
reductions as high as 99 percent resulting in NOX emissions
well below 0.1 g/bhp-hr from an engine-out level of nearly 5 g/bhp-
hr.125 Testing on the FTP has shown similarly good results,
with hot start FTP NOX emissions reduced by more than 90
percent. These results demonstrate that significant NOX
reductions are possible over a broad range of operating conditions with
current NOX adsorber technology, as typified by the FTP and
the SET.
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\125\ For more information on testing conducted at NVFEL, refer
to the in-depth discussion given in the RIA, and to the initial test
report contained in Air Docket A-99-06, Item IV-A-29.
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BILLING CODE 6560-50-P

[[Continued on page 5051]]

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