Control of Hazardous Air Pollutants From Mobile Sources

[Federal Register: March 29, 2006 (Volume 71, Number 60)]
[Proposed Rules]
[Page 15803-15852]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr29mr06-33]
[[Page 15804]]

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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Parts 59, 80, 85 and 86
[EPA-HQ-OAR-2005-0036; FRL-8041-2]
RIN 2060-AK70

AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.

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SUMMARY: Today EPA is proposing controls on gasoline, passenger
vehicles, and portable gasoline containers (gas cans) that would
significantly reduce emissions of benzene and other hazardous air
pollutants (``mobile source air toxics''). Benzene is a known human
carcinogen, and mobile sources are responsible for the majority of
benzene emissions. The other mobile source air toxics are known or
suspected to cause cancer or other serious health effects.
We are proposing to limit the benzene content of gasoline to an
annual average of 0.62% by volume, beginning in 2011. We are also
proposing to limit exhaust emissions of hydrocarbons from passenger
vehicles when they are operated at cold temperatures. This standard
would be phased in from 2010 to 2015. For passenger vehicles we also
propose evaporative emissions standards that are equivalent to those in
California. Finally, we are proposing a hydrocarbon emissions standard
for gas cans beginning in 2009, which would reduce evaporation and
spillage of gasoline from these containers.
These controls would significantly reduce emissions of benzene and
other mobile source air toxics such as 1,3-butadiene, formaldehyde,
acetaldehyde, acrolein, and naphthalene. This proposal would result in
additional substantial benefits to public health and welfare by
significantly reducing emissions of particulate matter from passenger
vehicles.
We project annual nationwide benzene reductions of 35,000 tons in
2015, increasing to 65,000 tons by 2030. Total reductions in mobile
source air toxics would be 147,000 tons in 2015 and over 350,000 tons
in 2030. Passenger vehicles in 2030 would emit 45% less benzene. Gas
cans meeting the new standards would emit almost 80% less benzene.
Gasoline would have 37% less benzene overall. We estimate that these
reductions would have an average cost of less than 1 cent per gallon of
gasoline and less than $1 per vehicle. The average cost for gas cans
would be less than $2 per can. The reduced evaporation from gas cans
would result in significant fuel savings, which would more than offset
the increased cost for the gas can.

DATES: Comments must be received on or before May 30, 2006. Under the
Paperwork Reduction Act, comments on the information collection
provisions must be received by OMB on or before April 28, 2006.
Hearing: We will hold a public hearing on April 12, 2006. The
hearing will start at 10 a.m. local time and continue until everyone
has had a chance to speak. If you want to testify at the hearing,
notify the contact person listed under FOR FURTHER INFORMATION CONTACT
by April 3, 2006.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2005-0036, by one of the following methods:
? http://www.regulations.gov: Follow the on-line
instructions for submitting comments.
? Fax your comments to: (202) 566-1741.
? Mail: Air Docket, Environmental Protection Agency,
Mailcode: 6102T, 1200 Pennsylvania Ave., NW., Washington, DC 20460. In
addition, please mail a copy of your comments on the information
collection provisions to the Office of Information and Regulatory
Affairs, Office of Management and Budget (OMB), Attn: Desk Officer for
EPA, 725 17th St. NW., Washington, DC 20503.
? Hand Delivery: EPA Docket Center, (EPA/DC) EPA West, Room
B102, 1301 Constitution Ave., NW., Washington, DC 20004. Such
deliveries are only accepted during the Docket's normal hours of
operation, and special arrangements should be made for deliveries of
boxed information.
Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2005-0036. EPA's policy is that all comments received will be included
in the public docket without change and may be made available online at
http://www.regulations.gov, including any personal information provided,
unless the comment includes information claimed to be Confidential
Business Information (CBI) or other information whose disclosure is
restricted by statute. Do not submit information that you consider to
be CBI or otherwise protected through http://www.regulations.gov or e-mail.
The http://www.regulations.gov website is an ``anonymous access'' system,
which means EPA will not know your identity or contact information
unless you provide it in the body of your comment. If you send an e-
mail comment directly to EPA without going through http://www.regulations.gov
your e-mail address will be automatically captured and included as
part of the comment that is placed in the public docket and made available
on the Internet. If you submit an electronic comment, EPA recommends
that you include your name and other contact information in the body of
your comment and with any disk or CD-ROM you submit. If EPA cannot read
your comment due to technical difficulties and cannot contact you for
clarification, EPA may not be able to consider your comment. Electronic
files should avoid the use of special characters, any form of
encryption, and be free of any defects or viruses. For additional
information about EPA's public docket visit the EPA Docket Center
homepage at http://www.epa.gov/epahome/dockets.htm. For additional
instructions on submitting comments, go to section XI, Public
Participation, of the SUPPLEMENTARY INFORMATION section of this document.
Docket: All documents in the docket are listed in the
http://www.regulations.gov index. Although listed in the index,
some information is not publicly available, e.g., CBI or other information
whose disclosure is restricted by statute. Certain other material, such
as copyrighted material, will be publicly available only in hard copy.
Publicly available docket materials are available either electronically
in http://www.regulations.gov or in hard copy at the Air Docket, EPA/DC,
EPA West, Room B102, 1301 Constitution Ave., NW., Washington, DC. The
Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through
Friday, excluding legal holidays. The telephone number for the Public
Reading Room is (202) 566-1744, and the telephone number for the Air
Docket is (202) 566-1742.
Hearing: The public hearing will be held at Sheraton Crystal City
Hotel, 1800 Jefferson Davis Highway, Arlington, Virginia 22202,
Telephone: (703) 486-1111. See section XI, Public Participation, for
more information about public hearings.

FOR FURTHER INFORMATION CONTACT: Mr. Chris Lieske, U.S. EPA, Office of
Transportation and Air Quality, Assessment and Standards Division
(ASD), Environmental Protection Agency, 2000 Traverwood Drive, Ann
Arbor, MI 48105; telephone number: (734) 214-4584; fax number: (734)
214-4816; email address: lieske.christopher@epa.gov, or Assessment and
Standards Division

[[Page 15805]]

Hotline; telephone number: (734) 214-4636; e-mail address:
asdinfo@epa.gov.

SUPPLEMENTARY INFORMATION:

General Information

A. Does this Action Apply to Me?

Entities potentially affected by this action are those that produce
new motor vehicles, alter individual imported motor vehicles to address
U.S. regulation, or convert motor vehicles to use alternative fuels. It
would also affect you if you produce gasoline motor fuel or manufacture
portable gasoline containers. Regulated categories include:

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NAICS SIC codes
Category codes \a\ \b\ Examples of potentially affected entities
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Industry...................... 336111 3711 Motor vehicle manufacturers.
Industry...................... 335312 3621 Alternative fuel vehicle converters.
424720 5172
811198 7539
........... 7549 ......................................................
Industry...................... 811111 7538 Independent commercial importers.
811112 7533 ......................................................
811198 7549 ......................................................
Industry...................... 324110 2911 Gasoline fuel refiners.
Industry...................... 326199 3089 Portable fuel container manufacturers.
332431 3411 ......................................................
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\a\ North American Industry Classification System (NAICS).
\b\ Standard Industrial Classification (SIC) system code.

This table is not intended to be exhaustive, but rather provides a
guide for readers regarding entities likely to be regulated by this
action. This table lists the types of entities that EPA is now aware
could potentially be regulated by this action. Other types of entities
not listed in the table could also be regulated. To determine whether
your activities are regulated by this action, you should carefully
examine the applicability criteria in 40 CFR parts 59, 80, 85, and 86.
If you have any questions regarding the applicability of this action to
a particular entity, consult the person listed in the preceding FOR
FURTHER INFORMATION CONTACT section.

B. What Should I Consider as I Prepare My Comments for EPA?

1. Submitting CBI
Do not submit this information to EPA through http://www.regulations.gov
or e-mail. Clearly mark the part or all of the information that you
claim to be confidential business information (CBI). For CBI
information in a disk or CD ROM that you mail to EPA, mark the outside
of the disk or CD ROM as CBI and then identify electronically within
the disk or CD ROM the specific information that is claimed as CBI. In
addition to one complete version of the comment that includes
information claimed as CBI, a copy of the comment that does not contain
the information claimed as CBI must be submitted for inclusion in the
public docket. Information so marked will not be disclosed except in
accordance with procedures set forth in 40 CFR part 2.
2. Tips for Preparing Your Comments
When submitting comments, remember to:
? Explain your views as clearly as possible.
? Describe any assumptions that you used.
? Provide any technical information and/or data you used
that support your views.
? If you estimate potential burden or costs, explain how you
arrived at your estimate.
? Provide specific examples to illustrate your concerns.
? Offer alternatives.
? Make sure to submit your comments by the comment period
deadline identified.
? To ensure proper receipt by EPA, identify the appropriate
docket identification number in the subject line on the first page of
your response. It would also be helpful if you provided the name, date,
and Federal Register citation related to your comments.

Outline of This Preamble

I. Introduction
A. Summary
B. What Background Information is Helpful to Understand this Proposal?
1. What Are Air Toxics and Related Health Effects?
2. What is the Statutory Authority for Today's Proposal?
a. Clean Air Act Section 202(l)
b. Clean Air Act Section 183(e)
c. Energy Policy Act
3. What Other Actions Has EPA Taken Under Clean Air Act Section 202(l)?
a. 2001 Mobile Source Air Toxics Rule
b. Technical Analysis Plan
II. Overview of Proposal
A. Why Is EPA Making This Proposal?
1. National Cancer Risk from Air Toxics
2. Noncancer Health Effects
3. Exposure Near Roads and From Attached Garages
4. Ozone and Particulate Matter
B. What Is EPA Proposing?
1. Light-Duty Vehicle Emission Standards
2. Gasoline Fuel Standards
3. Portable Gasoline Container (Gas Can) Controls
III. What Are Mobile Source Air Toxics (MSATs) and Their Health Effects?
A. What Are MSATs?
B. Compounds Emitted by Mobile Sources and Identified in IRIS
C. Which Mobile Source Emissions Pose the Greatest Health Risk
at Current Levels?
1. National and Regional Risk Drivers in 1999 National-Scale Air
Toxics Assessment
2. 1999 NATA Risk Drivers with Significant Mobile Source Contribution
D. What Are the Health Effects of Air Toxics?
1. Overview of Potential Cancer and Noncancer Health Effects
2. Health Effects of Key MSATs
a. Benzene
b. 1,3-Butadiene
c. Formaldehyde
d. Acetaldehyde
e. Acrolein
f. Polycyclic Organic Matter (POM)
g. Naphthalene
h. Diesel Particulate Matter and Diesel Exhaust Organic Gases
E. Gasoline PM
F. Near-Roadway Health Effects
G. How Would This Proposal Reduce Emissions of MSATs?
IV. What Are the Air Quality and Health Impacts of Air Toxics, and
How do Mobile Sources Contribute?
A. What Is the Health Risk to the U.S. Population from
Inhalation Exposure to Ambient Sources of Air Toxics, and How Would
It be Reduced by the Proposed Controls?

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B. What is the Distribution of Exposure and Risk?
1. Distribution of National-Scale Estimates of Risk from Air Toxics
2. Elevated Concentrations and Exposure in Mobile Source-Impacted Areas
a. Concentrations Near Major Roadways
b. Exposures Near Major Roadways
i. Vehicles
ii. Homes and Schools
iii. Pedestrians and Bicyclists
c. Exposure and Concentrations in Homes with Attached Garages
d. Occupational Exposure
3. What Are the Size and Characteristics of Highly Exposed Populations?
4. What Are the Implications for Distribution of Individual Risk?
C. Ozone
1. Background
2. Health Effects of Ozone
3. Current and Projected 8-hour Ozone Levels
D. Particulate Matter
1. Background
2. Health Effects of PM
3. Current and Projected PM_2.5 Levels
4. Current PM₁₀ Levels
E. Other Environmental Effects
1. Visibility
a. Background
b. Current Visibility Impairment
c. Future Visibility Impairment
2. Plant Damage from Ozone
3. Atmospheric Deposition
4. Materials Damage and Soiling
V. What Are Mobile Source Emissions Over Time and How Would This
Proposal Reduce Emissions, Exposure and Associated Health Effects?
A. Mobile Source Contribution to Air Toxics Emissions
B. VOC Emissions from Mobile Sources
C. PM Emissions from Mobile Sources
D. Description of Current Mobile Source Emissions Control
Programs that Reduce MSATs
1. Fuels Programs
a. RFG
b. Anti-dumping
c. 2001 Mobile Source Air Toxics Rule (MSAT1)
d. Gasoline Sulfur
e. Gasoline Volatility
f. Diesel Fuel
g. Phase-Out of Lead in Gasoline
2. Highway Vehicle and Engine Programs
3. Nonroad Engine Programs
4. Voluntary Programs
E. Emission Reductions from Proposed Controls
1. Proposed Vehicle Controls
a. Volatile Organic Compounds (VOC)
b. Toxics
c. PM_2.5
2. Proposed Fuel Benzene Controls
3. Proposed Gas Can Standards
a. VOC
b. Toxics
4. Total Emission Reductions from Proposed Controls
a. Toxics
b. VOC
c. PM_2.5
F. How Would This Proposal Reduce Exposure to Mobile Source Air
Toxics and Associated Health Effects?
G. Additional Programs Under Development That Will Reduce MSATs
1. On-Board Diagnostics for Heavy-Duty Vehicles Over 14,000 Pounds
2. Standards for Small SI Engines
3. Standards for Locomotive and Marine Engines
VI. Proposed New Light-duty Vehicle Standards
A. Why are We Proposing New Standards?
1. The Clean Air Act and Air Quality
2. Technology Opportunities for Light-Duty Vehicles
3. Cold Temperature Effects on Emission Levels
a. How Does Temperature Affect Emissions?
b. What Are the Current Emissions Control Requirements?
c. Opportunities for Additional Control
B. What Cold Temperature Requirements Are We Proposing?
1. NMHC Exhaust Emissions Standards
2. Feasibility of the Proposed Standards
a. Currently Available Emission Control Technologies
b. Feasibility Considering Current Certification Levels,
Deterioration and Compliance Margin
c. Feasibility and Test Programs for Higher Weight Vehicles
3. Standards Timing and Phase-in
a. Phase-In Schedule
b. Alternative Phase-In Schedules
4. Certification Levels
5. Credit Program
a. How Credits Are Calculated
b. Credits Earned Prior to Primary Phase-In Schedule
c. How Credits Can Be Used
d. Discounting and Unlimited Life
e. Deficits Could Be Carried Forward
f. Voluntary Heavy-Duty Vehicle Credit Program
6. Additional Vehicle Cold Temperature Standard Provisions
a. Applicability
b. Useful Life
c. High Altitude
d. In-Use Standards for Vehicles Produced During Phase-in
7. Monitoring and Enforcement
C. What Evaporative Emissions Standards Are We Proposing?
1. Current Controls and Feasibility of the Proposed Standards
2. Evaporative Standards Timing
3. Timing for Multi-Fueled Vehicles
4. In-Use Evaporative Emission Standards
5. Existing Differences Between California and Federal
Evaporative Emission Test Procedures
D. Opportunities for Additional Exhaust Control Under Normal Conditions
E. Vehicle Provisions for Small Volume Manufacturers
1. Lead Time Transition Provisions
2. Hardship Provisions
3. Special Provisions for Independent Commercial Importers (ICIs)
VII. Proposed Gasoline Benzene Control Program
A. Overview of Today's Proposed Fuel Control Program
B. Description of the Proposed Fuel Control Program
C. Development of the Proposed Gasoline Benzene Standard
1. Why Are We Focusing on Controlling Benzene Emissions?
a. Other MSAT Emissions
b. MSAT Emission Reductions Through Lowering Gasoline Volatility
or Sulfur Content
i. Gasoline Sulfur Content
ii. Gasoline Vapor Pressure
c. Toxics Performance Standard
d. Diesel Fuel Changes
2. Why Are We Proposing To Control Benzene Emissions By
Controlling Gasoline Benzene Content?
a. Benzene Content Standard
b. Gasoline Aromatics Content Standard
c. Benzene Emission Standard
3. How Did We Select the Level of the Proposed Gasoline Benzene
Content Standard?
a. Current Gasoline Benzene Levels
b. The Need for an Average Benzene Standard
c. Potential Levels for the Average Benzene Standard
d. Comparison of Other Benzene Regulatory Programs
4. How Do We Address Variations in Refinery Benzene Levels?
a. Overall Reduction in Benzene Level and Variation
b. Consideration of an Upper Limit Standard
i. Per-Gallon Cap Standard
ii. Maximum Average Standard
5. How Would the Proposed Program Meet or Exceed Related
Statutory and Regulatory Requirements?
D. Description of the Proposed Averaging, Banking, and Trading
(ABT) Program
1. Overview
2. Standard Credit Generation (2011 and Beyond)
3. Credit Use
a. Credit Trading Area
b. Credit Life
4. Early Credit Generation (2007-2010)
a. Establishing Early Credit Baselines
b. Early Credit Reduction Criteria (Trigger Points)
c. Calculating Early Credits
5. Additional Credit Provisions
a. Credit Trading
b. Pre-Compliance Reporting Requirements
6. Special ABT Provisions for Small Refiners
E. Regulatory Flexibility Provisions for Qualifying Refiners
1. Hardship Provisions for Qualifying Small Refiners
a. Qualifying Small Refiners
i. Regulatory Flexibility for Small Refiners
ii. Rationale for Small Refiner Provisions
b. How Do We Propose to Define Small Refiners for the Purpose of
the Hardship Provisions?
c. What Options Would Be Available For Small Refiners?
i. Delay in Standards
ii. ABT Credit Generation Opportunities
iii. Extended Credit Life
iv. ABT Program Review
d. How Would Refiners Apply for Small Refiner Status?

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e. The Effect of Financial and Other Transactions on Small
Refiner Status and Small Refiner Relief Provisions
2. General Hardship Provisions
a. Temporary Waivers Based on Unforeseen Circumstances
b. Temporary Waivers Based on Extreme Hardship Circumstances
c. Early Compliance with the Proposed Benzene Standard
F. Technological Feasibility of Gasoline Benzene Reduction
1. Benzene Levels in Gasoline
2. Technologies for Reducing Gasoline Benzene Levels
a. Why is Benzene Found in Gasoline?
b. Benzene Control Technologies Related to the Reformer
i. Routing Around the Reformer
ii. Routing to the Isomerization Unit
iii. Benzene Saturation
iv. Benzene Extraction
c. Other Benzene Reduction Technologies
d. Impacts on Octane and Strategies for Recovering Octane Loss
e. Experience Using Benzene Control Technologies
f. What Are the Potential Impacts of Benzene Control on Other
Fuel Properties?
3. Feasible Level of Benzene Control
4. Lead time
5. Issues
a. Small Refiners
b. Imported Gasoline
G. How Does the Proposed Fuel Control Program Satisfy the
Statutory Requirements?
H. Effect on Energy Supply, Distribution, or Use
I. How Would the Proposed Gasoline Benzene Standard Be Implemented?
1. General provisions
a. What Are the Implementation Dates for the Proposed Program?
b. Which Regulated Parties Would Be Subject to the Proposed
Benzene Standards?
c. What Gasoline Would Be Subject to the Proposed Benzene Standards?
d. How Would Compliance With the Benzene Standard Be Determined?
2. Averaging, Banking and Trading Program
a. Early Credit Generation
b. How Would Refinery Benzene Baselines Be Determined?
c. Credit Generation Beginning in 2011
d. How Would Credits Be Used?
3. Hardship and Small Refiner Provisions
a. Hardship
b. Small Refiners
4. Administrative and Enforcement Related Provisions
a. Sampling/Testing
b. Recordkeeping/Reporting
c. Attest Engagements, Violations, Penalties
5. How Would Compliance With the Provisions of the Proposed
Benzene Program Affect Compliance With Other Gasoline Toxics Programs?
VIII. Gas Cans
A. Why Are We Proposing an Emissions Control Program for Gas Cans?
1. VOC Emissions
2. Technological Opportunities to Reduce Emissions from Gas Cans
3. State Experiences Regulating Gas Cans
B. What Emissions Standard is EPA Proposing, and Why?
1. Description of Emissions Standard
2. Determination of Best Available Control
3. Emissions Performance vs. Design Standard
4. Automatic Shut-Off
5. Consideration of Retrofits of Existing Gas Cans
6. Consideration of Diesel, Kerosene and Utility Containers
C. Timing of Standard
D. What Test Procedures Would Be Used?
1. Diurnal Test
2. Preconditioning to Ensure Durable In-Use Control
a. Durability cycles
b. Preconditioning Fuel Soak
c. Spout Actuation
E. What Certification and In-Use Compliance Provisions Is EPA Proposing?
1. Certification
2. Emissions Warranty and In-Use Compliance
3. Labeling
F. How Would State Programs Be Affected By EPA Standards?
G. Provisions for Small Gas Can Manufacturers
1. First Type of Hardship Provision
2. Second Type of Hardship Provision
IX. What are the Estimated Impacts of the Proposal?
A. Refinery Costs of Gasoline Benzene Reduction
1. Tools and Methodology
a. Linear Programming Cost Model
b. Refiner-by-Refinery Cost Model
c. Price of Chemical Grade Benzene
d. Applying the Cost Model to Special Cases
2. Summary of Costs
a. Nationwide Costs of the Proposed Program
b. Regional Distribution of Costs
c. Cost Effects of Different Standards
d. Effect on Cost Estimates of Higher Benzene Prices
3. Economic Impacts of MSAT Control Through Gasoline Sulfur and
RVP Control and a Total Toxics Standard
B. What Are the Vehicle Cost Impacts?
C. What Are The Gas Can Cost Impacts?
D. Cost Per Ton of Emissions Reduced
E. Benefits
1. Unquantified Health and Environmental Benefits
2. Quantified Human Health and Environmental Effects of the
Proposed Cold Temperature Vehicle Standard
3. Monetized Benefits
4. What Are the Significant Limitations of the Benefit Analysis?
5. How Do the Benefits Compare to the Costs of The Proposed Standards?
F. Economic Impact Analysis
1. What Is an Economic Impact Analysis?
2. What Is the Economic Impact Model?
3. What Economic Sectors Are Included in this Economic Impact Analysis?
4. What Are the Key Features of the Economic Impact Model?
5. What Are the Key Model Inputs?
6. What Are the Results of the Economic Impact Modeling?
X. Alternative Program Options
A. Fuels
B. Vehicles
C. Gas cans
XI. Public Participation
A. How Do I Submit Comments?
B. How Should I Submit CBI to the Agency?
C. Will There Be a Public Hearing?
D. Comment Period
E. What Should I Consider as I Prepare My Comments for EPA?
XII. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review
B. Paperwork Reduction Act
C. Regulatory Flexibility Act (RFA), as amended by the Small
Business Regulatory Enforcement Fairness Act of 1996 (SBREFA), 5
U.S.C. 601 et. seq
1. Overview
2. Background
3. Summary of Regulated Small Entities
a. Highway Light-Duty Vehicles
b. Gasoline Refiners
c. Portable Gasoline Container Manufacturers
4. Potential Reporting, Record Keeping, and Compliance
5. Relevant Federal Rules
6. Summary of SBREFA Panel Process and Panel Outreach
a. Significant Panel Findings
b. Panel Process
c. Small Business Flexibilities
i. Highway Light-Duty Vehicles
(a) Highway Light-Duty Vehicle Flexibilities
(b) Highway Light-Duty Vehicle Hardships
ii. Gasoline Refiners
(a) Gasoline Refiner Flexibilities
(b) Gasoline Refiner Hardships
iii. Portable Gasoline Containers
(a) Portable Gasoline Container Flexibilities
(b) Portable Gasoline Container Hardships
D. Unfunded Mandates Reform Act
E. Executive Order 13132: Federalism
F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
G. Executive Order 13045: Protection of Children from
Environmental Health and Safety Risks
H. Executive Order 13211: Actions that Significantly Affect
Energy Supply, Distribution, or Use
I. National Technology Transfer Advancement Act
J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income Populations
XIII. Statutory Provisions and Legal Authority

I. Introduction

A. Summary

Mobile sources emit air toxics that can cause cancer and other
serious health effects. Section III of this preamble and Chapter 1 of the

[[Page 15808]]

Regulatory Impact Analysis (RIA) for this rule describe these compounds
and their health effects. Mobile sources contribute significantly to
the nationwide risk from breathing outdoor sources of air toxics.
Mobile sources were responsible for about 44% of outdoor toxic
emissions, almost 50% of the cancer risk, and 74% of the noncancer risk
according to EPA's National-Scale Air Toxics Assessment (NATA) for
1999. In addition, people who live or work near major roads or live in
homes with attached garages are likely to have higher exposures and
risk, which are not reflected in NATA. Sections II.A and IV of this
preamble and Chapter 3 of the RIA provide more detail about NATA, as
well as our analysis of exposures near roadways.
According to NATA for 1999, there are a few mobile source air
toxics that pose the greatest risk based on current information about
ambient levels and exposure. These include benzene, 1,3-butadiene,
formaldehyde, acrolein, naphthalene, and polycyclic organic matter
(POM). All of these compounds are hydrocarbons except POM. Benzene is
the most significant contributor to cancer risk from all outdoor air
toxics, according to NATA for 1999. NATA does not include a
quantitative estimate of cancer risk for diesel exhaust, but it
concludes that diesel exhaust (specifically, diesel particulate matter
and diesel exhaust organic gases) is one of the pollutants that pose
the greatest relative cancer risk. Although we expect significant
reductions in mobile source air toxics in the future, cancer and
noncancer health risks will remain a public health concern, and
exposure to benzene will remain the largest contributor to this risk.
As discussed in detail in Section V of this preamble and Chapter 2
of the RIA, this proposal would significantly reduce emissions of the
many air toxics that are hydrocarbons, including benzene, 1,3-
butadiene, formaldehyde, acetaldehyde, acrolein, and naphthalene. The
proposed fuel benzene standard and hydrocarbon standards for vehicles
and gas cans would together reduce total emissions of mobile source air
toxics by 350,000 tons in 2030, including 65,000 tons of benzene.
Mobile sources were responsible for 68% of benzene emissions in 1999.
As a result of this proposal, in 2030 passenger vehicles would emit 45%
less benzene, gas cans would emit 78% less benzene, and the gasoline
would have 37% less benzene overall.
In addition, EPA has already taken significant steps to reduce
diesel emissions from mobile sources, which will result in a 70%
reduction between 1999 and 2020. We have adopted stringent standards
for diesel trucks and buses, and nonroad diesel engines (engines used,
for example, in construction, agricultural, and industrial
applications). We also have additional programs underway to reduce
diesel emissions, including voluntary programs and a proposal that is
being developed to reduce emissions from diesel locomotives and marine
engines.
The proposed reductions in mobile source air toxics emissions would
reduce exposure and predicted risk of cancer and noncancer health
effects, including in environments where exposure and risk may be
highest, such as near roads, in vehicles, and in homes with attached
garages. In addition, the hydrocarbon reductions from the vehicle and
gas can standards would reduce VOC emissions (which are a precursor to
ozone and PM_2.5) by over 1 million tons in 2030. The
proposed vehicle standards would reduce direct PM_2.5
emissions by 20,000 tons in 2030 and would also reduce secondary
formation of PM_2.5. Although ozone and PM_2.5 are
considered criteria pollutants rather than ``air toxics,'' reductions
in ozone and PM_2.5 are important co-benefits of this
proposal. More details on emissions, cancer risks, and adverse health
and welfare effects associated with ozone and PM are found in sections
II.A, IV and V of this preamble and Chapters 2 and 3 of the RIA.
Section II.B of this preamble provides an overview of the
regulatory program that EPA is proposing for passenger vehicles,
gasoline, and gas cans. We are proposing standards to limit the exhaust
hydrocarbons from passenger vehicles during cold temperature operation.
We are also proposing evaporative hydrocarbon emissions standards for
passenger vehicles. We are proposing to limit the average annual
benzene content of gasoline. Finally, we are proposing hydrocarbon
emissions standards for gas cans that would reduce evaporation,
permeation, and spillage from these containers. Detailed discussion of
each of these programs is in sections VI, VII, and VIII of the preamble
and Chapters 5, 6, and 7 of the RIA.
We estimate that the benefits of this proposal would be about $6
billion in 2030, based on the direct PM_2.5 reductions from
the vehicle standards, plus unquantified benefits from reductions in
mobile source air toxics and VOC. We estimate that the annual net
social costs of this proposal would be about $200 million in 2030
(expressed in 2003 dollars). These net social costs include the value
of fuel savings from the proposed gas can standards, which would be
worth $82 million in 2030.
The proposed reductions would have an average cost of 0.13 cents
per gallon of gasoline, less than $1 per vehicle, and less than $2 per
gas can. The reduced evaporation from gas cans would result in fuel
savings that would more than offset the increased cost for the gas can.
In 2030, the long-term cost per ton of the proposed standards (in
combination, and including fuel savings) would be $450 per ton of total
mobile source air toxics reduced; $2,400 per ton of benzene reduced;
and no cost for the hydrocarbon and PM reductions (because the vehicle
standards would have no cost in 2020 and beyond). Section IX of the
preamble and Chapters 8-13 of the RIA provide more details on the
costs, benefits, and economic impacts of the proposed standards. The
impacts on small entities and the flexibilities we are proposing are
discussed in section XII.C of this preamble and Chapter 14 of the RIA.

B. What Background Information is Helpful to Understand this Proposal?

1. What Are Air Toxics and Related Health Effects?
Air toxics, which are also known in the Clean Air Act as
``hazardous air pollutants,'' are those pollutants known or suspected
to cause cancer or other serious health or environmental effects. For
example, some of these pollutants are known to have negative effects on
people's respiratory, cardiovascular, neurological, immune,
reproductive, or other organ systems, and they may also have
developmental effects. They may pose particular hazards to more
susceptible and sensitive populations, such as children, the elderly,
or people with pre-existing illnesses.
Mobile source air toxics (MSATs) are those toxics emitted by motor
vehicles, nonroad engines (such as lawn and garden equipment, farming
and construction equipment, aircraft, locomotives, and ships), and
their fuels. Toxics are also emitted by stationary sources such as
power plants, factories, oil refineries, dry cleaners, gas stations,
and small manufacturers. They can also be produced by combustion of
wood and other organic materials. There are also indoor sources of air
toxics, such as solvent evaporation and outgassing from furniture and
building materials.
Some MSATs of particular concern include benzene, 1,3-butadiene,
formaldehyde, acrolein, naphthalene, and diesel particulate matter and
diesel exhaust organic gases. Benzene and 1,3-butadiene are both known human

[[Page 15809]]

carcinogens. Section III of this preamble provides more detail on the
health effects of each of these pollutants.
MSATs are emitted as a result of various processes. Some MSATs are
present in fuel or fuel additives and are emitted to the air when the
fuel evaporates or passes through the engine. Some MSATs are formed
through engine combustion processes. Some compounds, like formaldehyde
and acetaldehyde, are also formed through a secondary process when
other mobile source pollutants undergo chemical reactions in the
atmosphere. Finally, some air toxics, such as metals, result from
engine wear or from impurities in oil or fuel.
2. What is the Statutory Authority for Today's Proposal?
a. Clean Air Act Section 202(l)
Section 202(l)(2) of the Clean Air Act requires EPA to set
standards to control hazardous air pollutants from motor vehicles,
motor vehicle fuels, or both. These standards must reflect the greatest
degree of emission reduction achievable through the application of
technology which will be available, taking into consideration the motor
vehicle standards established under section 202(a) of the Act, the
availability and cost of the technology, and noise, energy and safety
factors, and lead time. The standards are to be set under Clean Air Act
sections 202(a)(1) or 211(c)(1), and they are to apply, at a minimum,
to benzene and formaldehyde emissions.
Section 202(a)(1) of the Clean Air Act directs EPA to set standards
for new motor vehicles or new motor vehicle engines which EPA judges to
cause or contribute to air pollution which may reasonably be
anticipated to endanger public health or welfare. We are proposing a
cold-temperature hydrocarbon emission standard for passenger vehicles
under this authority.
Section 211(c)(1)(A) of the Clean Air Act authorizes EPA (among
other things) to control the manufacture of fuel if any emission
product of such fuel causes or contributes to air pollution which may
reasonably be anticipated to endanger public health or welfare. We are
proposing a benzene standard for gasoline under this authority.
Clean Air Act section 202(l)(2) requires EPA to ``from time to time
revise'' its regulations controlling hazardous air pollutants from
motor vehicles and fuels. As described in more detail in section I.F.
below, EPA has previously set standards under section 202(l), and we
committed in that rule to engage in further rulemaking to implement
section 202(l). This proposal fulfills that commitment.
b. Clean Air Act Section 183(e)
Clean Air Act section 183(e)(3) requires EPA to list categories of
consumer or commercial products that the Administrator determines,
based on an EPA study of VOC emissions from such products, contribute
at least 80 percent of the VOC emissions from such products in areas
violating the national ambient air quality standard for ozone. EPA
promulgated this list at 60 FR 15264 (March 23, 1995). EPA plans to
publish a Federal Register notice announcing that EPA has added
portable gasoline containers to the list of consumer products to be
regulated. This action must be taken by EPA prior to issuing a final
rule for gas cans. EPA is required to develop rules reflecting ``best
available controls'' to reduce VOC emissions from the listed products.
``Best available controls'' are defined in section 183(e)(1)(A) as follows:

The term ``best available controls'' means the degree of
emissions reduction that the Administrator determines, on the basis
of technological and economic feasibility, health, environmental,
and energy impacts, is achievable through the application of the
most effective equipment, measures, processes, methods, systems, or
techniques, including chemical reformulation, product or feedstock
substitution, repackaging, and directions for use, consumption,
storage, or disposal.''

Section 183(e)(4) also allows these standards to be implemented by
means of ``any system or systems of regulation as the Administrator may
deem appropriate, including requirements for registration and labeling,
self-monitoring and reporting * * * concerning the manufacture,
processing, distribution, use, consumption, or disposal of the
product.'' We are proposing a hydrocarbon standard for gas cans under
the authority of section 183(e).
c. Energy Policy Act
Section 1504(b) of the Energy Policy Act of 2005 requires EPA to
adjust the toxics emissions baselines for reformulated gasoline to
reflect 2001-2002 fuel qualities. However, the Act provides that this
action becomes unnecessary if EPA takes action which results in greater
overall reductions of toxics emissions from vehicles in areas with
reformulated gasoline. As described in section VII of this preamble, we
believe today's proposed action would in fact result in greater
reductions than would be achieved by adjusting the baselines under the
Energy Policy Act. Accordingly, under the provisions of the Energy
Policy Act, this proposed action would obviate the need for readjusting
emissions baselines for reformulated gasoline.
3. What Other Actions Has EPA Taken Under Clean Air Act Section 202(l)?
a. 2001 Mobile Source Air Toxics Rule
EPA published a final rule under Clean Air Act section 202(l) on
March 29, 2001, entitled, ``Control of Emissions of Hazardous Air
Pollutants from Mobile Sources'' (66 FR 17230). This rule established
toxics emissions performance standards for gasoline refiners. These
standards were designed to ensure that the over compliance to the
standard seen in the in-use fuels produced in the years of 1998-2000
would continue in the future.
EPA adopted this anti-backsliding requirement as a near-term
control that could be implemented and take effect within a year or two.
We did not adopt long-term controls, those controls that require a
longer lead time to implement, because we lacked information to address
the costs and benefits of potential fuel controls in the context of the
fuel sulfur controls that we had finalized in February 2000. However,
the March 2001 rule did commit to additional rulemaking that would
evaluate the need for and feasibility of additional controls.\1\
Today's proposal fulfills that commitment, and represents the second
step of the two-step approach originally envisioned in the 2001 rule.
---------------------------------------------------------------------------

\1\ See Sierra Club v. EPA, 325 F. 3d 374, 380 (D.C. Cir. 2003),
which upholds this approach.
---------------------------------------------------------------------------

The 2001 rule did not set additional air toxics controls for motor
vehicles, because the technology-forcing Tier 2 light-duty vehicle
standards and 2007 heavy-duty engine and vehicle standards had just
been promulgated. We found that those standards represented the
greatest degree of toxics control achievable at that time under section
202(l).\2\
---------------------------------------------------------------------------

\2\ 66 FR 17241-17245 (March 29, 2001).
---------------------------------------------------------------------------

b. Technical Analysis Plan
The 2001 rulemaking also included a Technical Analysis Plan that
described toxics-related research and activities that would inform our
future rulemaking to evaluate the need for and appropriateness of
additional mobile source air toxic controls. Specifically, we
identified four critical areas where there were data gaps requiring
long-term efforts:
? Developing better air toxics emission factors for nonroad sources;
? Improving estimation of air toxics exposures in microenvironments;

[[Page 15810]]

? Improving consideration of the range of total public
exposures to air toxics; and
? Increasing our understanding of the effectiveness and
costs of vehicle, fuel and nonroad controls for air toxics.
EPA and other outside researchers have conducted significant
research in these areas since 2001. The findings of this research are
described in more detail in other sections of this preamble and in the
regulatory impact analysis for this proposal. Following are some
highlights of our activities.
Nonroad emissions testing. EPA has tested emissions of nonroad
diesel engines for a comprehensive suite of hydrocarbons and inorganic
compounds. These emissions tests employed steady-state as well as
transient test cycles, using typical nonroad diesel fuel and low-sulfur
nonroad diesel fuel. In addition, EPA tested small gasoline-powered
engines such as lawnmowers, leaf blowers, chainsaws and string trimmers.
Improved estimation of exposures in microenvironments and
consideration of the range of public exposures. EPA and other
researchers have conducted a substantial amount of research and
analysis in these areas, which is discussed in section IV of this
preamble and in the regulatory impact analysis. This research has
involved monitoring as well as the development and application of
enhanced modeling tools. For example, personal exposure monitoring and
ambient monitoring has been conducted at homes and schools near
roadways; in vehicles; in homes with attached garages; and in
occupational settings involving both diesel and gasoline nonroad
equipment. We have also applied dispersion modeling techniques with
greater spatial refinement to estimate gradients of toxic pollutants
near roadways. A variety of improvements to our emissions, dispersion,
and exposure modeling tools are improving our ability to consider the
range of exposure people experience. These include the MOBILE6
emissions model, improved spatial and temporal allocation of emissions,
development of the Community Multiscale Air Quality (CMAQ) model, and
updates to the HAPEM exposure model. Many of these improvements were
applied in EPA's National-Scale Air Toxics Assessment for 1999 and
other analyses EPA performed to support this proposal. In fact, EPA
developed a modification of the HAPEM exposure model to account for
higher pollutant concentrations near major roads.
Research in these areas is continuing both inside and outside EPA,
including work under the auspices of the Health Effects Institute and
the Mickey Leland National Urban Air Toxics Research Center.
Costs and effectiveness of vehicle, fuel, and nonroad controls for
air toxics. EPA's analysis of the costs and effectiveness of vehicle
and fuel controls is described in section IX of this preamble and in
the regulatory impact analysis. In addition, as described in section V,
EPA is currently developing rules that will examine controls of small
gasoline engines and diesel locomotive and marine engines.

II. Overview of Proposal

A. Why Is EPA Making This Proposal?

People experience elevated risk of cancer and other noncancer
health effects from exposure to air toxics. Mobile sources are
responsible for a significant portion of this risk. For example,
benzene is the most significant contributor to cancer risk from all
outdoor air toxics,\3\ and most of the nation's benzene emissions come
from mobile sources. These risks vary depending on where people live
and work and the kinds of activities in which they engage. People who
live or work near major roads, or people that spend a large amount of
time in vehicles, are likely to have higher exposures and higher risks.
Although we expect significant reductions in mobile source air toxics
in the future, predicted cancer and noncancer health risks will remain
a public health concern. Benzene will remain the largest contributor to
this risk. In addition, some mobile source air toxics contribute to the
formation of ozone and PM_2.5, which contribute to serious
public health problems, which are discussed further in section II.A.4.
---------------------------------------------------------------------------

\3\ Based on quantitative estimates of risk, which do not
include diesel particular matter and diesel exhaust organic gases.
---------------------------------------------------------------------------

Sections II.A.1-3 discuss the risks posed by outdoor toxics now and
in the future, based on national-scale estimates such as EPA's
National-Scale Air Toxics Assessment (NATA). EPA's NATA for 1999
provides some perspective on the average risk of cancer and noncancer
health effects resulting from breathing air toxics from outdoor
sources, and the contribution of mobile sources to these
risks.4 5 This assessment did not include indoor sources of
air toxics. Also, it estimates average concentrations within a census
tract, and therefore does not reflect elevated concentrations and
exposures near roadways within a census tract. Nevertheless, its
findings are useful in providing a perspective on the magnitude of
risks posed by outdoor sources of air toxics generally, and in
identifying what pollutants and sources are important contributors to
these health risks.
---------------------------------------------------------------------------

\4\ http://www.epa.gov/ttn/atw/nata 1999.
\5\ NATA does not include a quantitative estimate of cancer risk
for diesel particulate matter and diesel exhaust organic gases. EPA
has concluded that while diesel exhaust is likely to be a human
carcinogen, available data are not sufficient to develop a
confidential estimate of cancer unit risk.
---------------------------------------------------------------------------

EPA also performed a national-scale assessment for future years,
using the same modeling tools and approach as the 1999 NATA. Finally,
we also performed national-scale exposure modeling that accounts for
the higher toxics concentrations near roads. This latter modeling
provides a perspective on the mobile source contribution to risk from
air toxics that is not reflected in our other national-scale assessments.
1. National Cancer Risk from Air Toxics
According to NATA, the average national cancer risk in 1999 from
all outdoor sources of air toxics was 42 in a million. That is, 42 out
of one million people would be expected to contract cancer from a
lifetime of breathing air toxics at 1999 levels. Mobile sources were
responsible for 44% of outdoor toxic emissions and almost 50% of the
cancer risk. Considering only the subset of compounds emitted by mobile
sources (see Table IV.C-2), the national average cancer risk in 1999,
including the stationary source contribution to these pollutants, was
23 in a million.
Benzene is the largest contributor to cancer risk of all 133
pollutants quantitatively assessed in the 1999 NATA. The national
average cancer risk from benzene alone was 11 in a million. Over 120
million people in 1999 were exposed to a risk level above 10 in a
million due to chronic inhalation exposure to benzene. Mobile sources
were responsible for 68% of benzene emissions in 1999.
Although air toxics emissions are projected to decline in the
future as a result of standards EPA has previously adopted, cancer risk
will continue to be a public health concern. The predicted national
average cancer risk from MSATs in 2030 will be 18 in a million,
according to EPA analysis (described in more detail in section IV of
this preamble and Chapter 3 of the Regulatory Impact Analysis). In
fact, in 2030 there will be more people exposed to the highest levels
of risk. The number of Americans above the 10 in a million cancer risk
level from exposure to MSATs is projected to increase from 214 million
in 1999 to 240 million in 2030. Mobile sources will continue to be a
significant contributor to risk in the future, accounting for 22% of
total air

[[Page 15811]]

toxic emissions in 2020, and 44% of benzene emissions.
2. Noncancer Health Effects
According to the NATA for 1999, nearly the entire U.S. population
was exposed to an average level of air toxics that has the potential
for adverse respiratory health effects (noncancer).\6\ This will
continue to be the case in 2030, even though toxics levels will be lower.
---------------------------------------------------------------------------

\6\ That is, the respiratory hazard index exceeded 1. See
section III.D of this preamble for more information.
---------------------------------------------------------------------------

Mobile sources were responsible for 74% of the noncancer
(respiratory) risk from outdoor air toxics in 1999. The majority of
this risk was from acrolein, and formaldehyde also contributed to the
risk of respiratory health effects. Mobile sources will continue to be
responsible for the majority of noncancer risk from outdoor air toxics
in 2030.
Although not included in NATA's estimates of noncancer risk, PM
from gasoline and diesel mobile sources contribute significantly to the
health effects associated with ambient PM, for which EPA has
established a National Ambient Air Quality Standard. There is extensive
human data showing a wide spectrum of adverse health effects associated
with exposure to ambient PM.
3. Exposure Near Roads and From Attached Garages
The national-scale risks described above do not account for higher
exposures experienced by people who live near major roadways, or people
who live in homes with attached garages. A substantial number of
studies show elevated concentrations of multiple MSATs in close
proximity to major roads. We also conducted an exposure modeling study
for three geographically distinct states (Colorado, New York, and
Georgia) and found that when the elevated concentrations near roadways
are accounted for, the distribution of benzene exposure is broader,
with a larger fraction of the population exposed to higher
concentrations. The largest effect on personal exposure occurs for the
population living near major roads. A U.S. Census survey of housing
found that in 2003 12.6% of U.S. housing units were within 300 feet of
a major transportation source.\7\ The potential population exposed to
elevated concentrations near major roadways is therefore large. In
addition, our analysis indicates that benzene exposure experienced by
people living in homes with attached garages may be twice the national
average benzene exposure estimated by NATA for 1999. More details on
exposure near roads and from attached garages can be found in section
IV of this preamble.
---------------------------------------------------------------------------

\7\ United States Census Bureau. (2004) American Housing Survey
web page. [Online at
http://www.cenus.gov/hhes/www/housing/ahs/ahs03/ahs03.html] Table IA-6.

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

4. Ozone and Particulate Matter
Many MSATs are part of a larger category of mobile source emissions
known as volatile organic compounds (VOC), which contribute to the
formation of ozone and particulate matter (PM). In addition, some MSATs
are emitted directly as PM rather than being formed through secondary
processes. Thus, MSATs contribute to adverse health effects both as
individual pollutants, and as precursors to ozone and PM. Mobile
sources contribute significantly to national emissions of VOC and PM.
In addition, gas cans are a source of both VOC and benzene emissions.
Both ozone and PM contribute to serious public health problems,
including 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.
In addition, ozone and PM cause significant harm to public welfare.
Specifically, ozone causes damage to vegetation, which leads to crop
and forestry economic losses, as well as harm to national parks,
wilderness areas, and other natural systems. PM contributes to the
substantial impairment of visibility in many parts of the U.S.,
including national parks and wilderness areas. The deposition of
airborne particles can also reduce the aesthetic appeal of buildings
and culturally important articles through soiling, and can contribute
directly (or in conjunction with other pollutants) to structural damage
by means of corrosion or erosion.
Finally, atmospheric deposition and runoff of polycyclic organic
matter (POM), metals, and other mobile-source-related compounds
contribute to the contamination of water bodies such as the Great Lakes
and coastal waters (e.g., the Chesapeake Bay).

B. What Is EPA Proposing?

1. Light-Duty Vehicle Emission Standards
As described in more detail in section VI, we are proposing new
standards for both exhaust and evaporative emissions from passenger
vehicles. The new exhaust emissions standards would significantly
reduce non-methane hydrocarbon (NMHC) emissions from passenger vehicles
at cold temperatures. These hydrocarbons include many mobile source air
toxics (including benzene), as well as VOC.
Current vehicle emission standards require that the certification
testing of NMHC is performed at 75 [deg]F. Recent research and analysis
indicates that these standards are not resulting in robust control of
NMHC at lower temperatures. We believe that cold temperature NMHC
control can be substantially improved using the same technological
approaches that are generally already being used in the Tier 2 vehicle
fleet to meet the stringent standards at 75 [deg]F. These cold-
temperature NMHC controls would also result in lower direct PM
emissions at cold temperatures.
Accordingly, we are proposing that light-duty vehicles, light-duty
trucks, and medium-duty passenger vehicles would be subject to a new
non-methane hydrocarbon (NMHC) exhaust emissions standard at 20 [deg]F.
Vehicles at or below 6,000 pounds gross vehicle weight rating (GVWR)
would be subject to a sales-weighted fleet average NMHC level of 0.3
grams/mile. Vehicles between 6,000 and 8,500 pounds GVWR and medium-
duty passenger vehicles would be subject to a sales-weighted fleet
average NMHC level of 0.5 grams/mile. For lighter vehicles, the
standard would phase in between 2010 and 2013. For heavier vehicles,
the new standards would phase in between 2012 and 2015. We are also
proposing a credit program and other provisions designed to provide
flexibility to manufacturers, especially during the phase-in periods.
These provisions are designed to allow the earliest possible phase-in
of standards and help minimize costs and ease the transition to new
standards.
We are also proposing a set of nominally more stringent evaporative
emission standards for all light-duty vehicles, light-duty trucks, and
medium-duty passenger vehicles. The proposed standards are equivalent
to California's Low Emission Vehicle II (LEV II) standards, and they
reflect the evaporative emissions levels that are already being
achieved nationwide. The standards we are proposing today would codify
the approach that most

[[Page 15812]]

manufacturers are already taking for 50-state evaporative systems, and
the standards would thus prevent backsliding in the future. We are
proposing to implement the evaporative emission standards in 2009 for
lighter vehicles and in 2010 for the heavier vehicles.
Section VI provides details on the proposed exhaust and evaporative
standards and their implementation, and our rationale for proposing them.
2. Gasoline Fuel Standards
As described in more detail in section VII, we are proposing to
limit the benzene content of all gasoline, both reformulated and
conventional. We propose that beginning January 1, 2011, refiners would
meet an average gasoline benzene content standard of 0.62% by volume on
all their gasoline. We are not proposing a standard for California,
however, because it is already covered by a similar state program.
This proposed fuel standard would result in air toxics emissions
reductions that are greater than required under all existing gasoline
toxics programs. As a result, EPA is proposing that upon full
implementation in 2011, the regulatory provisions for the benzene
control program would become the single regulatory mechanism used to
implement the RFG and Anti-dumping annual average toxics requirements.
The current RFG and Anti-dumping annual average provisions thus would
be replaced by the proposed benzene control program. The MSAT2 benzene
control program would also replace the MSAT1 requirements. In addition,
the program would satisfy certain fuel MSAT conditions of the Energy
Policy Act of 2005 and obviate the need to revise toxics baselines for
reformulated gasoline otherwise required by the Energy Policy Act. In
all of these ways, we would significantly consolidate and simplify the
existing national fuel-related MSAT regulatory program.
We also propose that refiners could generate benzene credits and
use or transfer them as a part of a nationwide averaging, banking, and
trading (ABT) program. From 2007-2010 refiners could generate benzene
credits by taking early steps to reduce gasoline benzene levels.
Beginning in 2011 and continuing indefinitely, refiners could generate
credits by producing gasoline with benzene levels below the 0.62%
average standard. Refiners could apply the credits towards company
compliance, ``bank'' the credits for later use, or transfer (``trade'')
them to other refiners nationwide (outside of California) under the
proposed program. Under this program, refiners could use credits to
achieve compliance with the benzene content standard.
This proposed ABT program would allow us to set a more stringent
benzene standard than would otherwise be possible, and it would allow
implementation to occur earlier. Under this proposed benzene content
standard and ABT program, gasoline in all areas of the country would
have lower benzene levels than they have today. Overall benzene levels
would be 37% lower. This would reduce benzene emissions and exposure
nationwide.
Finally, we propose hardship provisions. Refiners approved as
``small refiners'' would be eligible for certain temporary relief
provisions. In addition, any refiner facing extreme unforeseen
circumstances or extreme hardship circumstances could apply for similar
temporary relief.
Section VII of this preamble provides a detailed explanation and
rationale for the proposed fuel program and its implementation. It also
discusses and seeks comment on a variety of alternatives that we considered.
3. Portable Gasoline Container (Gas Can) Controls
Portable gasoline containers, or gas cans, are consumer products
used to refuel a wide variety of gasoline-powered equipment, including
lawn and garden equipment, recreational equipment, and passenger
vehicles that have run out of gas. As described in section VIII, we are
proposing standards that would reduce hydrocarbon emissions from
evaporation, permeation, and spillage. These standards would
significantly reduce benzene and other toxics, as well as VOC more
generally. VOC is an ozone precursor.
We propose a performance-based standard of 0.3 grams per gallon per
day of hydrocarbons, based on the emissions from the can over a diurnal
test cycle. The standard would apply to gas cans manufactured on or
after January 1, 2009. We also propose test procedures and a
certification and compliance program, in order to ensure that gas cans
would meet the emission standard over a range of in-use conditions. The
proposed standards would result in the use of best available control
technologies, such as durable permeation barriers, automatically
closing spouts, and cans that are well-sealed.
California implemented an emissions control program for gas cans in
2001, and since then, several other states have adopted the program.
Last year, California adopted a revised program, which will take effect
July 1, 2007. The revised California program is very similar to the
program we are proposing. Although a few aspects of the program we are
proposing are different, we believe manufacturers would be able to meet
both EPA and California requirements with the same gas can designs.

III. What Are Mobile Source Air Toxics (MSATs) and Their Health Effects?

A. What Are MSATs?

Section 202(l) refers to ``hazardous air pollutants from motor
vehicles and motor vehicle fuels.'' We use the term ``mobile source air
toxics (MSATs)'' to refer to compounds that are emitted by mobile
sources and have the potential for serious adverse health effects.
There are a variety of ways in which to identify compounds that have
the potential for serious adverse health effects. For example, EPA's
Integrated Risk Information System (IRIS) is EPA's database containing
information on human health effects that may result from exposure to
various chemicals in the environment. In addition, Clean Air Act
section 112(b) contains a list of hazardous air pollutants that EPA is
required to control through regulatory standards; other agencies or
programs such as the Agency for Toxic Substances and Disease Registry
and the California EPA have developed health benchmark values for
various compounds; and the International Agency for Research on Cancer
and the National Toxicology Program have assembled evidence of
substances that cause cancer in humans and issue judgments on the
strength of the evidence. Each source of information has its own
strengths and limitations. For example, there are inherent limitations
on the number of compounds that have been investigated sufficiently for
EPA to conduct an IRIS assessment. There are some compounds that are
not listed in IRIS but are considered to be hazardous air pollutants
under Clean Air Act section 112(b) and are regulated by the Agency
(e.g., propionaldehyde, 2,2,4-trimethylpentane).

B. Compounds Emitted by Mobile Sources and Identified in IRIS

In its 2001 MSAT rule, EPA identified a list of 21 MSATs. We listed
a compound as an MSAT if it was emitted from mobile sources, and if the
Agency had concluded in IRIS that the compound posed a potential cancer
hazard and/or if IRIS contained an inhalation reference concentration
or ingestion reference dose for the compound. Since 2001, EPA has
conducted an extensive review of the

[[Page 15813]]

literature to produce a list of the compounds identified in the exhaust
or evaporative emissions from onroad and nonroad equipment, using
baseline as well as alternative fuels (e.g., biodiesel, compressed
natural gas). This list, the Master List of Compounds Emitted by Mobile
Sources (``Master List''), currently includes approximately 1,000
compounds. It is available in the public docket for this rule and on
the web (http://www.epa.gov/otaq/toxics.htm). Table III.B-1 lists those
compounds from the Master List that currently meet those 2001 MSAT
criteria, based on the current IRIS.
Table III.B-1 identifies all of the compounds from the Master List
that are present in IRIS with (a) a cancer hazard identification of
known, probable, or possible human carcinogens (under the 1986 EPA
cancer guidelines) or carcinogenic to humans, likely to be carcinogenic
to humans, or suggestive evidence of carcinogenic potential (under the
2005 EPA cancer guidelines); and/or (b) an inhalation reference
concentration or an ingestion reference dose. Although all these
compounds have been detected in emissions from mobile sources, many are
emitted in trace amounts and data are not adequate to develop an
inventory. Those compounds for which we have developed an emissions
inventory are summarized in Table IV.C-2. There are several compounds
for which IRIS assessments are underway and therefore are not included
in Table III.B-1. These compounds are: Cerium, copper, ethanol, ethyl
tertiary butyl ether (ETBE), platinum, propionaldehyde, and 2,2,4-
trimethylpentane.
The fact that a compound is listed in Table III.B-1 does not imply
a risk to public health or welfare at current levels, or that it is
appropriate to adopt controls to limit the emissions of such a compound
from motor vehicles or their fuels. In conducting any such further
evaluation, pursuant to sections 202(a) or 211(c) of the Act, EPA would
consider whether emissions of the compound from motor vehicles cause or
contribute to air pollution which may reasonably be anticipated to
endanger public health or welfare.

Table III.B-1.--Compounds Emitted by Mobile Sources That Are Listed in
IRIS*
------------------------------------------------------------------------

------------------------------------------------------------------------
1,1,1,2-Tetrafluoroethane... Cadmium............. Manganese.
1,1,1-Trichloroethane....... Carbon disulfide.... Mercury, elemental.
1,1-Biphenyl................ Carbon tetrachloride Methanol.
1,2-Dibromoethane........... Chlorine............ Methyl chloride.
1,2-Dichlorobenzene......... Chlorobenzene....... Methyl ethyl ketone
(MEK).
1,3-Butadiene............... Chloroform.......... Methyl isobutyl
ketone (MIBK).
2,4-Dinitrophenol........... Chromium III........ Methyl tert-butyl
ether (MTBE).
2-Methylnaphthalene......... Chromium VI......... Molybdenum.
2-Methylphenol.............. Chrysene............ Naphthalene.
4-Methylphenol.............. Crotonaldehyde...... Nickel.
Acenaphthene................ Cumene (isopropyl Nitrate.
benzene).
Acetaldehyde................ Cyclohexane......... N-
Nitrosodiethylamine
.
Acetone..................... Cyclohexanone....... N-
Nitrosodimethylamin
e.
Acetophenone................ Di(2- N-Nitroso-di-n-
ethylhexyl)phthalat butylamine.
e.
Acrolein (2-propenal)....... Dibenz[a,h]anthracen N-Nitrosodi-N-
e. propylamine.
Ammonia..................... Dibutyl phthalate... N-
Nitrosopyrrolidine.
Anthracene.................. Dichloromethane..... Pentachlorophenol.
Antimony.................... Diesel PM and Diesel Phenol.
exhaust organic
gases.
Arsenic, inorganic.......... Diethyl phthalate... Phosphorus.
Barium and compounds........ Ethylbenzene........ Phthalic anhydride.
Benz[a]anthracene........... Ethylene glycol Pyrene.
monobutyl ether.
Benzaldehyde................ Fluoranthene........ Selenium and
compounds.
Benzene..................... Fluorene............ Silver.
Benzo[a]pyrene (BaP)........ Formaldehyde........ Strontium.
Benzo[b]fluoranthene........ Furfural............ Styrene.
Benzo[k]fluoranthene........ Hexachlorodibenzo-p- Tetrachloroethylene.
dioxin, mixture
(dioxin/furans).
Benzoic acid................ n-Hexane............ Toluene.
Beryllium and compounds..... Hydrogen cyanide.... Trichlorofluorometha
ne.
Boron (Boron and Borates Hydrogen sulfide.... Vanadium.
only).
Bromomethane................ Indeno[1,2,3- Xylenes.
cd]pyrene.
Butyl benzyl phthalate...... Lead and compounds Zinc and compounds.
(inorganic).
------------------------------------------------------------------------
* Compounds listed in IRIS as known, probable, or possible human
carcinogens and/or pollutants for which the Agency has calculated a
reference concentration or reference dose.

C. Which Mobile Source Emissions Pose the Greatest Health Risk at
Current Levels?

The 1999 National-Scale Air Toxics Assessment (NATA) provides some
perspective on which mobile source emissions pose the greatest risk at
current estimated ambient levels.\8\ We also conducted a national-scale
assessment for future years, which is discussed more fully in section
IV of this preamble and Chapters 2 and 3 of the RIA. Our understanding
of what emissions pose the greatest risk will evolve over time, based
on our understanding of the ambient levels and health effects
associated with the compounds.\9\
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\8\ It is, of course, not necessary for EPA to show that a
compound is a national or regional risk driver to show that its
emission from motor vehicles may reasonably cause or contribute to
endangerment of public health or welfare. A showing that motor
vehicles contribute some non-trivial percentage of the inventory of
a compound known to be associated with adverse health effects would
normally be sufficient. Cf. Bluewater Network v. EPA, 370 F. 3d 1,
15 (D.C. Cir. 2004).
\9\ The discussion here considers risks other than those
attributed to ambient levels of criteria pollutants.
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1. National and Regional Risk Drivers in 1999 National-Scale Air Toxics
Assessment
The 1999 NATA evaluates 177 hazardous air pollutants currently
listed under CAA section 112(b), as well as

[[Page 15814]]

diesel PM.\10\ NATA is described in greater detail in Chapters 2 and 3
of the Regulatory Impact Analysis for this proposed rule. Additional
information can also be obtained from the NATA website (http://www.epa.gov/
ttn/atw/nata1999). Based on the assessment of inhalation
exposures associated with outdoor sources of these hazardous air
pollutants, NATA has identified cancer and noncancer risk drivers on a
national and regional scale (Table III.C-1). A cancer risk driver on a
national scale is a hazardous air pollutant for which at least 25
million people are exposed to risk greater than ten in one million.
Benzene is the only compound identified in the 1999 NATA as a national
cancer risk driver. A cancer risk driver on a regional scale is a
hazardous air pollutant for which at least one million people are
exposed to risk greater than ten in one million or at least 10,000
people are exposed to risk greater than 100 in one million. Twelve
compounds (or groups of compounds in the case of POM) were identified
as regional cancer risk drivers. The 1999 NATA concludes that diesel
particulate matter is among the substances that pose the greatest
relative risk, although the cancer risk cannot be quantified.
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\10\ NATA does not include a quantitative estimate of cancer
risk for diesel particulate matter and diesel exhaust organic gases.
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A noncancer risk driver at the national scale is a hazardous air
pollutant for which at least 25 million people are exposed at a
concentration greater than the inhalation reference concentration. The
RfC is an estimate (with uncertainty spanning perhaps an order of
magnitude) of a daily exposure to the human population (including
sensitive subgroups) that is likely to be without appreciable risk of
deleterious effects during a lifetime. Acrolein is the only compound
identified in the 1999 NATA as a national noncancer risk driver. A
noncancer risk driver on a regional scale is defined as a hazardous air
pollutant for which at least 10,000 people are exposed to an ambient
concentration greater than the inhalation reference concentration.
Sixteen regional-scale noncancer risk drivers were identified in the
1999 NATA (see Table III.C-1.).

Table III.C-1.--National and Regional Cancer and Noncancer Risk Drivers
in 1999 NATA
------------------------------------------------------------------------
Cancer \1\ Noncancer
------------------------------------------------------------------------
National drivers \2\...................... National drivers \4\
Benzene................................... Acrolein
Regional drivers \3\...................... Regional drivers \5\
Arsenic compounds......................... Antimony
Benzidine................................. Arsenic compounds
1,3-Butadiene............................. 1,3-Butadiene
Cadmium compounds......................... Cadmium compounds
Carbon tetrachloride...................... Chlorine
Chromium VI............................... Chromium VI
Coke oven................................. Diesel PM
Ethylene oxide............................ Formaldehyde
Hydrazine................................. Hexamethylene 1-6-
diisocyanate
Naphthalene............................... Hydrazine
Perchloroethylene......................... Hydrochloric acid
Polycyclic organic matter................. Maleic anhydride
Manganese compounds
Nickel compounds
2,4-Toluene diisocyanate
Triethylamine
------------------------------------------------------------------------
\1\ The list of cancer risk drivers does not include diesel particulate
matter. However, the 1999 NATA concluded that it was one of the
pollutants that posed the greatest relative cancer risk.
\2\ At least 25 million people exposed to risk >10 in 1 million.
\3\ At least 1 million people exposed to risk >10 in 1 million or at
least 10,000 people exposed to risk >100 in 1 million.
\4\ At least 25 million people exposed to a hazard quotient > 1.0.
\5\ At least 10,000 people exposed to a hazard quotient > 1.

2. 1999 NATA Risk Drivers with Significant Mobile Source Contribution

Among the national and regional-scale cancer and noncancer risk
drivers identified in the 1999 NATA, seven compounds have significant
contributions from mobile sources: benzene, 1,3-butadiene,
formaldehyde, acrolein, polycyclic organic matter (POM), naphthalene,
and diesel particulate matter and diesel exhaust organic gases (Table
III.C-2.). For example, mobile sources contribute 68% of the national
benzene inventory, with 49% from on-road sources and 19% from nonroad
sources.

Table III.C-2.--Mobile Source Contribution to 1999 NATA Risk Drivers
------------------------------------------------------------------------
Percent Percent
contribution contribution
1999 NATA risk drivers from all from on-road
mobile sources mobile sources
(percent) (percent)
------------------------------------------------------------------------
Benzene................................. 68 49
1,3-Butadiene........................... 58 41
Formaldehyde............................ 47 27
Acrolein................................ 25 14
Polycyclic organic matter *............. 6 3
Naphthalene............................. 27 21
Diesel PM and Diesel exhaust organic 100 38
gases..................................
------------------------------------------------------------------------
* This POM inventory includes the 15 POM compounds:
benzo[b]fluoranthene, benz[a]anthracene, indeno(1,2,3-c,d)pyrene,
benzo[k]fluoranthene, chrysene, benzo[a]pyrene, dibenz(a,h)anthracene,
anthracene, pyrene, benzo(g,h,i)perylene, fluoranthene,
acenaphthylene, phenanthrene, fluorene, and acenaphthene.

[[Page 15815]]

D. What Are the Health Effects of Air Toxics?

1. Overview of Potential Cancer and Noncancer Health Effects
Air toxics can cause a variety of cancer and noncancer health
effects. A number of the mobile source air toxic pollutants described
in section III are known or likely to pose a cancer hazard in humans.
Many of these compounds also cause adverse noncancer health effects
resulting from chronic,\11\ subchronic,\12\ or acute \13\ inhalation
exposures. These include neurological, cardiovascular, liver, kidney,
and respiratory effects as well as effects on the immune and
reproductive systems. Section III.D.2 discusses the health effects of
air toxic compounds listed in Table III.C-2, as well as acetaldehyde.
The compounds in Table III.C-2 were all identified as national and
regional-scale cancer and noncancer risk drivers in the 1999 National-
Scale Air Toxics Assessment (NATA), and have significant inventory
contributions from mobile sources. Acetaldehyde is included because it
is a likely human carcinogen, has a significant inventory contribution
from mobile sources, and was identified as a risk driver in the 1996
NATA. We are also including diesel particulate matter and diesel
exhaust organic gases in this discussion. Although 1999 NATA did not
quantify cancer risks associated with exposure to this pollutant, EPA
has concluded that diesel exhaust ranks with the other substances that
the national-scale assessment suggests pose the greatest relative risk.\14\
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\11\ Chronic exposure is defined in the glossary of the
Integrated Risk Information (IRIS) database (http://www.epa.gov/iris)
as repeated exposure by the oral, dermal, or inhalation route for more
than approximately 10 of the life span in humans (more than approximately
90 days to 2 years in typically used laboratory animal species).
\12\ Defined in the IRIS database as exposure to a substance
spanning approximately 10 of the lifetime of an organism.
\13\ Defined in the IRIS database as exposure by the oral,
dermal, or inhalation route for 24 hours or less.
\14\ http://www.epa.gov/ttn/atw/nata1999.

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Inhalation cancer risks are usually estimated by EPA as ``unit
risks,'' which represent the excess lifetime cancer risk estimated to
result from continuous exposure to an agent at a concentration of 1
[mu]g/m\3\ in air. Some air toxics are known to be carcinogenic in
animals but lack data in humans. These have been assumed to be human
carcinogens. Also, relationships between exposure and probability of
cancer are assumed to be linear. In addition, these unit risks are
typically upper bound estimates. Upper bound estimates are more likely
to overestimate than underestimate risk. Where there are strong
epidemiological data, a maximum likelihood (MLE) estimate may be
developed. An MLE is a best scientific estimate of risk. The benzene
unit risk is an MLE. A discussion of the confidence in a quantitative
cancer risk estimate is provided in the IRIS file for each compound.
The discussion of the confidence in the cancer risk estimate includes
an assessment of the source of the data (human or animal),
uncertainties in dose estimates, choice of the model used to fit the
exposure and response data and how uncertainties and potential
confounders are handled.
Potential noncancer chronic inhalation health risks are quantified
using reference concentrations (RfCs) and noncancer chronic ingestion
health risks are quantified using reference doses (RfDs). The RfC is an
estimate (with uncertainty spanning perhaps an order of magnitude) of a
daily exposure to the human population (including sensitive subgroups)
that is likely to be without appreciable risk of deleterious effects
during a lifetime. Sources of uncertainty in the development of the
RfCs and RfDs include intraspecies extrapolation (animal to human) and
interspecies extrapolation (average human to sensitive human).
Additional sources of uncertainty can be using a lowest observed
adverse effect level in place of a no observed adverse effect level,
and other data deficiencies. A statement regarding the confidence in
the RfC and/or RfD is developed to reflect the confidence in the
principal study or studies on which the RfC or RfD are based and the
confidence in the underlying database. Factors that affect the
confidence in the principal study include how well the study was
designed, conducted and reported. Factors that affect the confidence in
the database include an assessment of the availability of information
regarding identification of the critical effect, potentially susceptible
populations and exposure scenarios relevant to assessment of risk.
The RfC may be used to estimate a hazard quotient, which is the
environmental exposure to a substance divided by its RfC. A hazard
quotient greater than one indicates adverse health effects are
possible. The hazard quotient cannot be translated to a probability
that adverse health effects will occur, and is unlikely to be
proportional to risk. It is especially important to note that a hazard
quotient exceeding one does not necessarily mean that adverse effects
will occur. In NATA, hazard quotients for different respiratory
irritants were also combined into a hazard index (HI). A hazard index
is the sum of hazard quotients for substances that affect the same
target organ or organ system. Because different pollutants may cause
similar adverse health effects, it is often appropriate to combine
hazard quotients associated with different substances. However, the HI
is only an approximation of a combined effect because substances may
affect a target organ in different ways.
2. Health Effects of Key MSATs
a. Benzene
The EPA's IRIS database lists benzene, an aromatic hydrocarbon, as
a known human carcinogen (causing leukemia) by all routes of
exposure.\15\ A number of adverse noncancer health effects including
blood disorders and immunotoxicity have also been associated with long-
term occupational exposure to benzene.
---------------------------------------------------------------------------

\15\ U.S. EPA (2000). Integrated Risk Information System File
for Benzene. This material is available electronically at
http://www.epa.gov/iris/subst/0276.htm.

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Inhalation is the major source of human exposure to benzene in the
occupational and non-occupational setting. Long-term inhalation
occupational exposure to benzene has been shown to cause cancer of the
hematopoetic (blood cell) system in adults. Among these are acute
nonlymphocytic leukemia \16\ and chronic lymphocytic leukemia.17 18

[[Page 15816]]

Leukemias, lymphomas, and other tumor types have been observed in
experimental animals exposed to benzene by inhalation or oral
administration. Exposure to benzene and/or its metabolites has also
been linked with chromosomal changes in humans and animals 19 20 and
increased proliferation of mouse bone marrow cells.21 22
---------------------------------------------------------------------------

\16\ Leukemia is a blood disease in which the white blood cells
are abnormal in type or number. Leukemia may be divided into
nonlymphocytic (granulocytic) leukemias and lymphocytic leukemias.
Nonlymphocytic leukemia generally involves the types of white blood
cells (leukocytes) that are involved in engulfing, killing, and
digesting bacteria and other parasites (phagocytosis) as well as
releasing chemicals involved in allergic and immune responses. This
type of leukemia may also involve erythroblastic cell types
(immature red blood cells). Lymphocytic leukemia involves the
lymphocyte type of white blood cells that are responsible for the
immune responses. Both nonlymphocytic and lymphocytic leukemia may,
in turn, be separated into acute (rapid and fatal) and chronic
(lingering, lasting) forms. For example; in acute myeloid leukemia
there is diminished production of normal red blood cells
(erythrocytes), granulocytes, and platelets (control clotting),
which leads to death by anemia, infection, or hemorrhage. These
events can be rapid. In chronic myeloid leukemia (CML) the leukemic
cells retain the ability to differentiate (i.e., be responsive to
stimulatory factors) and perform function; later there is a loss of
the ability to respond.
\17\ U.S. EPA (1985) Environmental Protection Agency, Interim
quantitative cancer unit risk estimates due to inhalation of
benzene, prepared by the Office of Health and Environmental
Assessment, Carcinogen Assessment Group, Washington, DC, for the
Office of Air Quality Planning and Standards, Washington, DC, 1985.
\18\ U.S. EPA. (1993). Motor Vehicle-Related Air Toxics Study.
Office of Mobile Sources, Ann Arbor, MI.
http://www.epa.gov/otaq/regs/toxics/tox_archive.htm.
\19\ International Agency for Research on Cancer (IARC) (1982)
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.
\20\ U.S. EPA (1998) Environmental Protection Agency,
Carcinogenic Effects of Benzene: An Update, National Center for
Environmental Assessment, Washington, DC. EPA600-P-97-001F.
http://www.epa.gov/ncepihom/Catalog/EPA600P97001F.html.
\21\ Irons, R.D., W.S. Stillman, D.B. Colagiovanni, and V.A.
Henry (1992) 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.
\22\ U.S. EPA (1998) Environmental Protection Agency,
Carcinogenic Effects of Benzene: An Update, National Center for
Environmental Assessment, Washington, DC. EPA600-P-97-001F.
http://www.epa.gov/ncepihom/Catalog/EPA600P97001F.html.

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

The latest assessment by EPA places the excess risk of developing
acute nonlymphocytic leukemia from inhalation exposure to benzene at
2.2 x 10-\6\ to 7.8 x 10-\6\ per [mu]g/m\3\. In
other words, there is a risk of about two to eight excess leukemia
cases in one million people exposed to 1 [mu]g/m\3\ of benzene over a
lifetime.\23\ This range of unit risks are the MLEs calculated from
different exposure assumptions and dose-response models that are linear
at low doses. At present, the true cancer risk from exposure to benzene
cannot be ascertained, even though dose-response data are used in the
quantitative cancer risk analysis, because of uncertainties in the low-
dose exposure scenarios and lack of clear understanding of the mode of
action. A range of estimates of risk is recommended, each having equal
scientific plausibility. There are confidence intervals associated with
the MLE range that reflect random variation of the observed data. For
the upper end of the MLE range, the 5th and 95th percentile values are
about a factor of 5 lower and higher than the best fit value. The upper
end of the MLE range was used in NATA.
---------------------------------------------------------------------------

\23\ U.S. EPA (1998). Environmental Protection Agency,
Carcinogenic Effects of Benzene: An Update, National Center for
Environmental Assessment, Washington, DC. EPA600-P-97-001F.
http://www.epa.gov/ncepihom/Catalog/EPA600P97001F.html.

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

It should be noted that not enough information is known to
determine the slope of the dose-response curve at environmental levels
of exposure and to provide a sound scientific basis to choose any
particular extrapolation/exposure model to estimate human cancer risk
at low doses. EPA risk assessment guidelines suggest using an
assumption of linearity of dose response when (1) there is an absence
of sufficient information on modes of action or (2) the mode of action
information indicates that the dose-response curve at low dose is or is
expected to be linear.\24\ Since the mode of action for benzene
carcinogenicity is unknown, the current cancer unit risk estimate
assumes linearity of the low-dose response. Data that were considered
by EPA in its carcinogenic update suggested that the dose-response
relationship at doses below those examined in the studies reviewed in
EPA's most recent benzene assessment may be supralinear. They support
the inference that cancer risks are as high or are higher than the
estimates provided in the existing EPA assessment.\25\ Data discussed
in the EPA IRIS assessment suggest that genetic abnormalities occur at
low exposure in humans, and the formation of toxic metabolites plateaus
above 25 ppm (80,000 [mu]g/m3).\26\ More recent data on
benzene adducts in humans, published after the most recent IRIS
assessment, suggest that the enzymes involved in benzene metabolism
start to saturate at exposure levels as low as 1 ppm.\27\ Because there
is a transition from linear to saturable metabolism below 1 ppm, the
assumption of low-dose linearity extrapolated from much higher
exposures could lead to substantial underestimation of leukemia risks.
This is consistent with recent epidemiological data which also suggest
a supralinear exposure-response relationship and which ``[extend]
evidence for hematopoietic cancer risks to levels substantially lower
than had previously been established.'' 28 29 These data are
from the largest cohort study done to date with individual worker
exposure estimates. However, these data have not yet been formally
evaluated by EPA as part of the IRIS review process, and it is not
clear whether these data provide sufficient evidence to reject a linear
dose-response curve. A better understanding of the biological mechanism
of benzene-induced leukemia is needed.
---------------------------------------------------------------------------

\24\ U.S. EPA (2005) Guidelines for Carcinogen Risk Assessment.
Report No. EPA/630/P-03/001F.
http://cfpub.epa.gov/ncea/raf/recordisplay.cfm?deid=116283.
\25\ U.S. EPA (1998) Carcinogenic Effects of Benzene: An Update.
EPA/600/P-97/001F.
\26\ Rothman, N; Li, GL; Dosemeci, M; et al. (1996)
Hematotoxicity among Chinese workers heavily exposed to benzene. Am.
J. Indust. Med. 29:236-246.
\27\ Rappaport, S.M.; Waidyanatha, S.; Qu, Q.; Shore, R.; Jin,
X.; Cohen, B.; Chen, L.; Melikian, A.; Li, G.; Yin, S.; Yan, H.; Xu,
B.; Mu, R.; Li, Y.; Zhang, X.; and Li, K. (2002) Albumin adducts of
benzene oxide and 1,4-benzoquinone as measures of human benzene
metabolism. Cancer Research 62:1330-1337.
\28\ Hayes, R.B.; Yin, S.; Dosemeci, M.; Li, G.; Wacholder, S.;
Travis, L.B.; Li, C.; Rothman, N.; Hoover, R.N.; and Linet, M.S.
(1997) Benzene and the dose-related incidence of hematologic
neoplasms in China. J. Nat. Cancer Inst. 89:1065-1071.
\29\ Hayes, R.B.; Songnian, Y.; Dosemeci, M.; and Linet, M.
(2001) Benzene and lymphohematopoietic malignancies in humans. Am.
J. Indust. Med. 40:117-126.
---------------------------------------------------------------------------

Children may represent a subpopulation at increased risk from
benzene exposure, due to factors that could increase their
susceptibility. Children may have a higher unit body weight exposure
because of their heightened activity patterns which can increase their
exposures, as well as different ventilation tidal volumes and
frequencies, factors that influence uptake. This could entail a greater
risk of leukemia and other toxic effects to children if they are
exposed to benzene at similar levels as adults. There is limited
information from two studies regarding an increased risk to children
whose parents have been occupationally exposed to
benzene.30 31 Data from animal studies have shown benzene
exposures result in damage to the hematopoietic (blood cell formation)
system during development.32 33 34 Also, key changes related
to the development of childhood leukemia occur in the developing
fetus.\35\ Several studies have reported that genetic changes related
to eventual leukemia development occur before birth. For example, there
is one study of genetic changes in twins who developed T cell leukemia
at 9 years of

[[Page 15817]]

age.\36\ An association between traffic volume, residential proximity
to busy roads and occurrence of childhood leukemia has also been
identified in some studies, although some studies show no association.
---------------------------------------------------------------------------

\30\ Shu, X.O,; Gao, Y.T.; Brinton, L.A.; et al. (1988) A
population-based case-control study of childhood leukemia in
Shanghai. Cancer 62:635-644.
\31\ McKinney, P.A.; Alexander, F.E.; Cartwright, R.A.; et al.
(1991) Parental occupations of children with leukemia in west
Cumbria, north Humberside, and Gateshead, Br. Med. J. 302:681-686.
\32\ Keller, KA; Snyder, CA. (1986) Mice exposed in utero to low
concentrations of benzene exhibit enduring changes in their colony
forming hematopoietic cells. Toxicology 42:171-181.
\33\ Keller, KA; Snyder, CA. (1988) Mice exposed in utero to 20
ppm benzene exhibit altered numbers of recognizable hematopoietic
cells up to seven weeks after exposure. Fundam. Appl. Toxicol. 10:224-232.
\34\ Corti, M; Snyder, CA. (1996) Influences of gender,
development, pregnancy and ethanol consumption on the hematotoxicity
of inhaled 10 ppm benzene. Arch. Toxicol. 70:209-217.
\35\ U.S. EPA. (2002). Toxicological Review of Benzene
(Noncancer Effects). National Center for Environmental Assessment,
Washington, DC. Report No. EPA/635/R-02/001F.
http://www.epa.gov/iris/toxreviews/0276-tr[1].pdf.
\36\ Ford, AM; Pombo-de-Oliveira, MS; McCarthy, KP; MacLean, JM;
Carrico, KC; Vincent, RF; Greaves, M. (1997) Monoclonal origin of
concordant T-cell malignancy in identical twins. Blood 89:281-285.
---------------------------------------------------------------------------

A number of adverse noncancer health effects, including blood
disorders such as preleukemia and aplastic anemia, have also been
associated with long-term exposure to benzene.37 38 People
with long-term occupational exposure to benzene have experienced
harmful effects on the blood-forming tissues, especially in bone
marrow. These effects can disrupt normal blood production and suppress
the production of important blood components, such as red and white
blood cells and blood platelets, leading to anemia (a reduction in the
number of red blood cells), leukopenia (a reduction in the number of
white blood cells), or thrombocytopenia (a reduction in the number of
blood platelets, thus reducing the ability of blood to clot). Chronic
inhalation exposure to benzene in humans and animals results in
pancytopenia,\39\ a condition characterized by decreased numbers of
circulating erythrocytes (red blood cells), leukocytes (white blood
cells), and thrombocytes (blood platelets).40 41 Individuals
that develop pancytopenia and have continued exposure to benzene may
develop aplastic anemia, whereas others exhibit both pancytopenia and
bone marrow hyperplasia (excessive cell formation), a condition that
may indicate a preleukemic state.42 43 The most sensitive
noncancer effect observed in humans, based on current data, is the
depression of the absolute lymphocyte count in blood.44 45
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\37\ Aksoy, M. (1989) Hematotoxicity and carcinogenicity of
benzene. Environ. Health Perspect. 82:193-197.
\38\ Goldstein, B.D. (1988) Benzene toxicity. Occupational
medicine. State of the Art Reviews 3: 541-554.
\39\ Pancytopenia is the reduction in the number of all three
major types of blood cells (erythrocytes, or red blood cells,
thrombocytes, or platelets, and leukocytes, or white blood cells).
In adults, all three major types of blood cells are produced in the
bone marrow of the vertebra, sternum, ribs, and pelvis. The bone
marrow contains immature cells, known as multipotent myeloid stem
cells, that later differentiate into the various mature blood cells.
Pancytopenia results from a reduction in the ability of the red bone
marrow to produce adequate numbers of these mature blood cells.
\40\ Aksoy, M. (1991) Hematotoxicity, leukemogenicity and
carcinogenicity of chronic exposure to benzene. In: Arinc, E.;
Schenkman, J.B.; Hodgson, E., Eds. Molecular Aspects of
Monooxygenases and Bioactivation of Toxic Compounds. New York:
Plenum Press, pp. 415-434.
\41\ Goldstein, B.D. (1988) Benzene toxicity. Occupational
medicine. State of the Art Reviews 3: 541-554.
\42\ Aksoy, M., S. Erdem, and G. Dincol. (1974) Leukemia in
shoe-workers exposed chronically to benzene. Blood 44:837.
\43\ Aksoy, M. and K. Erdem. (1978) A follow-up study on the
mortality and the development of leukemia in 44 pancytopenic
patients associated with long-term exposure to benzene. Blood 52: 285-292.
\44\ Rothman, N., G.L. Li, M. Dosemeci, W.E. Bechtold, G.E.
Marti, Y.Z. Wang, M. Linet, L.Q. Xi, W. Lu, M.T. Smith, N. Titenko-
Holland, L.P. Zhang, W. Blot, S.N. Yin, and R.B. Hayes (1996)
Hematotoxicity among Chinese workers heavily exposed to benzene. Am.
J. Ind. Med. 29: 236-246.
\45\ EPA 2005 ``Full IRIS Summary for Benzene (CASRN 71-43-2)''
Environmental Protection Agency, Integrated Risk Information System
(IRIS), Office of Health and Environmental Assessment, Environmental
Criteria and Assessment Office, Cincinnati, OH
http://www.epa.gov/iris/subst/0276.htm.

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EPA's inhalation reference concentration (RfC) for benzene is 30
[mu]g/m3, based on suppressed absolute lymphocyte counts as
seen in humans under occupational exposure conditions. The overall
confidence in this RfC is medium. Since development of this RfC, there
have appeared human reports of benzene's hematotoxic effects in the
literature that provides data suggesting a wide range of hematological
endpoints that are affected at occupational exposures of less than 5
ppm (about 16 mg/m3) \46\ and even at air levels of 1 ppm
(about 3 mg/m3) or less among genetically susceptible
populations.\47\ One recent study found benzene metabolites in mouse
liver and bone marrow at environmental doses, indicating that even
concentrations in urban air can elicit a biochemical response in
rodents that indicates toxicity.\48\ EPA has not formally evaluated
these recent studies as part of the IRIS review process to determine
whether or not they will lead to a change in the current RfC. EPA does
not currently have an acute reference concentration for benzene. The
Agency for Toxic Substances and Disease Registry Minimal Risk Level for
acute exposure to benzene is 160 [mu]g/m3 for 1-14 days exposure.
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\46\ Qu, Q., R. Shore, G. Li, X. Jin, L.C. Chen, B. Cohen, et
al. (2002). Hematological changes among Chinese workers with a broad
range of benzene exposures. Am. J. Industr. Med. 42: 275-285.
\47\ Lan, Qing, Zhang, L., Li, G., Vermeulen, R., et al. (2004).
Hematotoxically in Workers Exposed to Low Levels of Benzene. Science
306: 1774-1776.
\48\ Turtletaub, K.W. and Mani, C. (2003). Benzene metabolism in
rodents at doses relevant to human exposure from Urban Air. Res Rep
Health Effect Inst 113.
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b. 1,3-Butadiene
EPA has characterized 1,3-butadiene, a hydrocarbon, as a
leukemogen, carcinogenic to humans by inhalation.49 50 The
specific mechanisms of 1,3-butadiene-induced carcinogenesis are
unknown; however, it is virtually certain that the carcinogenic effects
are mediated by genotoxic metabolites of 1,3-butadiene. Animal data
suggest that females may be more sensitive than males for cancer
effects; nevertheless, there are insufficient data from which to draw
any conclusions on potentially sensitive subpopulations. The upper
bound cancer unit risk estimate is 0.08 per ppm or 3x10-5
per [mu]g/m3 (based primarily on linear modeling and
extrapolation of human data). In other words, it is estimated that
approximately 30 persons in one million exposed to 1 [mu]g/
m3 of 1,3-butadiene continuously for their lifetime would
develop cancer as a result of this exposure. The human incremental
lifetime unit cancer risk estimate is based on extrapolation from
leukemias observed in an occupational epidemiologic study.\51\ This
estimate includes a two-fold adjustment to the epidemiologic-based unit
cancer risk applied to reflect evidence from the rodent bioassays
suggesting that the epidemiologic-based estimate (from males) may
underestimate total cancer risk from 1,3-butadiene exposure in the
general population, particularly for breast cancer in females.
Confidence in the excess cancer risk estimate of 0.08 per ppm is moderate.
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\49\ U.S. EPA. (2002). Health Assessment of 1,3-Butadiene.
Office of Research and Development, National Center for
Environmental Assessment, Washington Office, Washington, DC. Report
No. EPA600-P-98-001F.
http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=54499.
\50\ U.S. EPA (1998). A Science Advisory Board Report: Review of
the Health Risk Assessment of 1,3-Butadiene. EPA-SAB-EHC-98.
\51\ Delzell, E, N. Sathiakumar, M. Macaluso, et al. (1995). A
follow-up study of synthetic rubber workers. Submitted to the
International Institute of Synthetic Rubber Producers. University of
Alabama at Birmingham. October 2, 1995.
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1,3-Butadiene also causes a variety of reproductive and
developmental effects in mice; no human data on these effects are
available. The most sensitive effect was ovarian atrophy observed in a
lifetime bioassay of female mice.\52\ Based on this critical effect and
the benchmark concentration methodology, an RfC was calculated. This
RfC for chronic health effects is 0.9 ppb, or about 2 [mu]g/
m3. Confidence in the inhalation RfC is medium.
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\52\ Bevan, C.; Stadler, J.C.; Elliot, G.S.; et al. (1996)
Subchronic toxicity of 4-vinylcyclohexene in rats and mice by
inhalation. Fundam. Appl. Toxicol. 32:1-10.
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c. Formaldehyde
Since 1987, EPA has classified formaldehyde, a hydrocarbon, as a

[[Page 15818]]

probable human carcinogen based on evidence in humans and in rats,
mice, hamsters, and monkeys.\53\ Recently released research conducted
by the National Cancer Institute (NCI) found an increased risk of
nasopharyngeal cancer among workers exposed to
formaldehyde.54 55 A recent National Institute of
Occupational Safety and Health (NIOSH) study of garment workers also
found increased risk of death due to leukemia among workers exposed to
formaldehyde.\56\ In 2004, the working group of the International
Agency for Research on Cancer concluded that formaldehyde is
carcinogenic to humans (Group 1 classification), on the basis of
sufficient evidence in humans and sufficient evidence in experimental
animals--a higher classification than previous IARC evaluations. In
addition, the National Institute of Environmental Health Sciences
recently nominated formaldehyde for reconsideration as a known human
carcinogen under the National Toxicology Program. Since 1981 it has
been listed as a ``reasonably anticipated human carcinogen.''
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\53\ U.S. EPA (1987). Assessment of Health Risks to Garment
Workers and Certain Home Residents from Exposure to Formaldehyde,
Office of Pesticides and Toxic Substances, April 1987.
\54\ Hauptmann, M.; Lubin, J. H.; Stewart, P. A.; Hayes, R. B.;
Blair, A. 2003. Mortality from lymphohematopoetic malignancies among
workers in formaldehyde industries. Journal of the National Cancer
Institute 95: 1615-1623.
\55\ Hauptmann, M.; Lubin, J. H.; Stewart, P. A.; Hayes, R. B.;
Blair, A. 2004. Mortality from solid cancers among workers in
formaldehyde industries. American Journal of Epidemiology 159: 1117-1130.
\56\ Pinkerton, L. E. 2004. Mortality among a cohort of garment
workers exposed to formaldehyde: an update. Occup. Environ. Med. 61: 193-200.
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In the past 15 years there has been substantial research on the
inhalation dosimetry for formaldehyde in rodents and primates by the
CIIT Centers for Health Research, with a focus on use of rodent data
for refinement of the quantitative cancer dose-response
assessment.57 58 59 CIIT's risk assessment of formaldehyde
incorporated mechanistic and dosimetric information on formaldehyde.
The risk assessment analyzed carcinogenic risk from inhaled
formaldehyde using approaches that are consistent with EPA's draft
guidelines for carcinogenic risk assessment. In 2001, Environment
Canada relied on this cancer dose-response assessment in their
assessment of formaldehyde.\60\ In 2004, EPA also relied on this cancer
unit risk estimate during the development of the plywood and composite
wood products national emissions standards for hazardous air pollutants
(NESHAPs).\61\ In these rules, EPA concluded that the CIIT work
represented the best available application of the available mechanistic
and dosimetric science on the dose-response for portal of entry cancers
due to formaldehyde exposures. EPA is reviewing the recent work cited
above from the NCI and NIOSH, as well as the analysis by the CIIT
Centers for Health Research and other studies, as part of a reassessment
of the human hazard and dose-response associated with formaldehyde.
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\57\ Conolly, RB, JS Kimbell, D Janszen, PM Schlosser, D
Kalisak, J Preston, and FJ Miller. 2003. Biologically motivated
computational modeling of formaldehyde carcinogenicity in the F344
rat. Tox. Sci. 75: 432-447.
\58\ Conolly, RB, JS Kimbell, D Janszen, PM Schlosser, D
Kalisak, J Preston, and FJ Miller. 2004. Human respiratory tract
cancer risks of inhaled formaldehyde: Dose-response predictions
derived from biologically-motivated computational modeling of a
combined rodent and human dataset. Tox. Sci. 82: 279-296.
\59\ Chemical Industry Institute of Toxicology (CIIT). 1999.
Formaldehyde: Hazard characterization and dose-response assessment
for carcinogenicity by the route of inhalation. CIIT, September 28,
1999. Research Triangle Park, NC.
\60\ Health Canada. 2001. Priority Substances List Assessment
Report. Formaldehyde. Environment Canada, Health Canada, February 2001.
\61\ U.S. EPA. 2004. National Emission Standards for Hazardous
Air Pollutants for Plywood and Composite Wood Products Manufacture:
Final Rule. (69 FR 45943, 7/30/04).
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Noncancer effects of formaldehyde have been observed in humans and
several animal species and include irritation to eye, nose and throat
tissues in conjunction with increased mucous secretions.
d. Acetaldehyde
Acetaldehyde, a hydrocarbon, is classified in EPA's IRIS database
as a probable human carcinogen and is considered moderately toxic by
inhalation.\62\ Based on nasal tumors in rodents, the upper confidence
limit estimate of a lifetime extra cancer risk from continuous
acetaldehyde exposure is about 2.2x10-\6\ per [mu]g/m\3\. In
other words, it is estimated that about 2 persons in one million
exposed to 1 [mu]g/m\3\ acetaldehyde continuously for their lifetime
(70 years) would develop cancer as a result of their exposure, although
the risk could be as low as zero. In short-term (4 week) rat studies,
compound-related histopathological changes were observed only in the
respiratory system at various concentration levels of
exposure.63 64 Data from these studies showing degeneration
of the olfactory epithelium were found to be sufficient for EPA to
develop an RfC for acetaldehyde of 9 [mu]g/m\3\. Confidence in the
principal study is medium and confidence in the database is low, due to
the lack of chronic data establishing a no observed adverse effect
level and due to the lack of reproductive and developmental toxicity
data. Therefore, there is low confidence in the RfC. The agency is
currently conducting a reassessment of risk from inhalation exposure to
acetaldehyde.
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\62\ U.S. EPA. 1988. Integrated Risk Information System File of
Acetaldehyde. This material is available electronically at
http://www.epa.gov/iris/subst/0290.htm.
\63\ Appleman, L. M., R. A. Woutersen, V. J. Feron, R. N.
Hooftman, and W. R. F. Notten. (1986). Effects of the variable
versus fixed exposure levels on the toxicity of acetaldehyde in
rats. J. Appl. Toxicol. 6: 331-336.
\64\ Appleman, L.M., R.A. Woutersen, and V.J. Feron. (1982).
Inhalation toxicity of acetaldehyde in rats. I. Acute and subacute
studies. Toxicology. 23: 293-297.
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The primary acute effect of exposure to acetaldehyde vapors is
irritation of the eyes, skin, and respiratory tract.\65\ Some
asthmatics have been shown to be a sensitive subpopulation to
decrements in functional expiratory volume (FEV1 test) and
bronchoconstriction upon acetaldehyde inhalation.\66\
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\65\ U.S. EPA (1988). Integrated Risk Information System File of
Acetaldehyde. This material is available electronically at
http://www.epa.gov/iris/subst/0290.htm.
\66\ Myou, S.; Fujimura, M.; Nishi K.; Ohka, T.; and Matsuda, T.
(1993) Aerosolized acetaldehyde induces histamine-mediated
bronchoconstriction in asthmatics. Am. Rev. Respir.Dis.148(4 Pt 1): 940-3.
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e. Acrolein
Acrolein, a hydrocarbon, is intensely irritating to humans when
inhaled, with acute exposure resulting in upper respiratory tract
irritation and congestion. The Agency has developed an RfC for acrolein
of 0.02 [mu]g/m\3\.\67\ The overall confidence in the RfC assessment is
judged to be medium. The Agency is also currently in the process of
conducting an assessment of acute health effects for acrolein. EPA
determined in 2003 using the 1999 draft cancer guidelines that the
human carcinogenic potential of acrolein could not be determined
because the available data were inadequate. No information was
available on the carcinogenic effects of acrolein in humans and the
animal data provided inadequate evidence of carcinogenicity.
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\67\ U.S. Environmental Protection Agency (2003) Integrated Risk
Information System (IRIS) on Acrolein. National Center for
Environmental Assessment, Office of Research and Development,
Washington, D.C. 2003. This material is available electronically at
http://www.epa.gov/iris/subst/0364.htm.

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f. Polycyclic Organic Matter (POM)
POM is generally defined as a large class of organic compounds
which have multiple benzene rings and a boiling point greater than 100
degrees Celsius. 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. One

[[Page 15819]]

of these compounds, naphthalene, is discussed separately below.
Polycyclic aromatic hydrocarbons (PAHs) are a chemical subset of
POM. In particular, EPA frequently obtains data on 16 of these POM
compounds. Recent studies have found that maternal exposures to PAHs in
a population of pregnant women were associated with several adverse
birth outcomes, including low birth weight and reduced length at
birth.\68\ These studies are discussed in the Regulatory Impact Analysis.
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\68\ Perara, F.P.; Rauh, V.; Tsai, W-Y.; et al. (2002) Effect of
transplacental exposure to environmental pollutants on birth outcomes in a
multiethnic population. Environ Health Perspect. 111: 201-205.
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g. Naphthalene
Naphthalene is a PAH compound consisting of two benzene rings fused
together with two adjacent carbon atoms common to both rings. In 2004,
EPA released an external review draft (External Review Draft, IRIS
Reassessment of the Inhalation Carcinogenicity of Naphthalene, U.S.
EPA. http://www.epa.gov/iris) of a reassessment of the inhalation
carcinogenicity of naphthalene.\69\ The draft reassessment completed
external peer review in 2004 by Oak Ridge Institute for Science and
Education.\70\ Based on external comments, additional analyses are
being considered. California EPA has also released a new risk
assessment for naphthalene with a cancer unit risk estimate of
3x10-\5\ per [mu]g/m\3\.\71\ The California EPA value was
used in the 1999 NATA and in the analyses done for this rule. In
addition, IARC has reevaluated naphthalene and re-classified it as
Group 2B: possibly carcinogenic to humans.\72\ The cancer data form the
basis of an inhalation RfC of 3 [mu]g/m\3\.\73\ A low to medium
confidence rating was given to this RfC, in part because it cannot be
said with certainty that this RfC will be protective for hemolytic
anemia and cataracts, the more well-known human effects from
naphthalene exposure.
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\69\ U.S. EPA. (2004) External Review Draft, IRIS Reassessment
of the Inhalation Carcinogenicity of Naphthalene. http://www.epa.gov/iris
\70\ Oak Ridge Institute for Science and Education. (2004)
External Peer Review for the IRIS Reassessment of the Inhalation
Carcinogenicity of Naphthalene. August 2004.
http://cfpub2.epa.gov/ncea/cfm/recordisplay.cfm?deid=86019
\71\ California EPA. (2004) Long Term Health Effects of Exposure
to Naphthalene. Office of Environmental Health Hazard Assessment.
http://www.oehha.ca.gov/air/toxic_contaminants/draftnaphth.html
\72\ International Agency for Research on Cancer (IARC). (2002)
Monographs on the Evaluation of the Carcinogenic Risk of Chemicals
for Humans. Vol. 82. Lyon, France.
\73\ EPA 2005 ``Full IRIS Summary for Naphthalene (CASRN 91-20-
3)'' Environmental Protection Agency, Integrated Risk Information
System (IRIS), Office of Health and Environmental Assessment,
Environmental Criteria and Assessment Office, Cincinnati, OH
http://www.epa.gov/iris/subst/0436.htm.

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h. Diesel Particulate Matter and Diesel Exhaust Organic Gases
In EPA's Diesel Health Assessment Document (HAD),\74\ diesel
exhaust was classified as likely to be carcinogenic to humans by
inhalation at environmental exposures, in accordance with the revised
draft 1996/1999 EPA cancer guidelines. A number of other agencies
(National Institute for Occupational Safety and Health, the
International Agency for Research on Cancer, the World Health
Organization, California EPA, and the U.S. Department of Health and
Human Services) have made similar classifications. EPA concluded in the
Diesel HAD that it is not possible currently to calculate a cancer unit
risk for diesel exhaust due to a variety of factors that limit the
current studies, such as limited quantitative exposure histories in
occupational groups investigated for lung cancer.
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\74\ U.S. EPA (2002) Health Assessment Document for Diesel
Engine Exhaust. EPA/600/8-90/057F Office of Research and
Development, Washington DC. This document is available
electronically at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=29060.

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However, in the absence of a cancer unit risk, the EPA Diesel HAD
sought to provide additional insight into the significance of the
cancer hazard by estimating possible ranges of risk that might be
present in the population. The possible risk range analysis was
developed by comparing a typical environmental exposure level for
highway diesel sources to a selected range of occupational exposure
levels. The occupationally observed risks were then proportionally
scaled according to the exposure ratios to obtain an estimate of the
possible environmental risk. A number of calculations are needed to
accomplish this, and these can be seen in the EPA Diesel HAD. The
outcome was that environmental risks from diesel exhaust exposure could
range from a low of 10-\4\ to 10-\5\ to as high as 10-\3\, reflecting the
range of occupational exposures that could be associated with the relative
and absolute risk levels observed in the occupational studies. Because of
uncertainties, the analysis acknowledged that the risks could be lower
than 10-\4\ or 10-\5\, and a zero risk from diesel exhaust exposure was
not ruled out.
The acute and chronic exposure-related effects of diesel exhaust
emissions are also of concern to the Agency. EPA derived an RfC from
consideration of four well-conducted chronic rat inhalation studies
showing adverse pulmonary effects.75 76 77 78 The RfC is 5
[mu]g/m\3\ for diesel exhaust as measured by diesel PM. This RfC does
not consider allergenic effects such as those associated with asthma or
immunologic effects. There is growing evidence, discussed in the Diesel
HAD, that diesel exhaust can exacerbate these effects, but the
exposure-response data are presently lacking to derive an RfC.
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\75\ Ishinishi, N; Kuwabara, N; Takaki, Y; et al. (1988) Long-
term inhalation experiments on diesel exhaust. In: Diesel exhaust
and health risks. Results of the HERP studies. Ibaraki, Japan:
Research Committee for HERP Studies; pp. 11-84.
\76\ Heinrich, U; Fuhst, R; Rittinghausen, S; et al. (1995)
Chronic inhalation exposure of Wistar rats and two different strains
of mice to diesel engine exhaust, carbon black, and titanium
dioxide. Inhal. Toxicol. 7:553-556.
\77\ Mauderly, JL; Jones, RK; Griffith, WC; et al. (1987) Diesel
exhaust is a pulmonary carcinogen in rats exposed chronically by
inhalation. Fundam. Appl. Toxicol. 9:208-221.
\78\ Nikula, KJ; Snipes, MB; Barr, EB; et al. (1995) Comparative
pulmonary toxicities and carcinogenicities of chronically inhaled
diesel exhaust and carbon black in F344 rats. Fundam. Appl. Toxicol.
25:80-94.
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The Diesel HAD also briefly summarizes health effects associated
with ambient PM and the EPA's annual National Ambient Air Quality
Standard (NAAQS) of 15 [mu]g/m\3\. There is a much more extensive body
of human data showing a wide spectrum of adverse health effects
associated with exposure to ambient PM, of which diesel exhaust is an
important component. The RfC is not meant to say that 5 [mu]g/m\3\
provides adequate public health protection for ambient PM_2.5. In fact,
there may be benefits to reducing diesel PM below 5 [mu]g/m\3\ since
diesel PM is a major contributor to ambient PM_2.5.

E. Gasoline PM

Beyond the specific areas of quantifiable risk discussed above in
section III.C, EPA is also currently investigating gasoline PM.
Gasoline exhaust is a complex mixture that has not been evaluated in
EPA's IRIS, in contrast to diesel exhaust, which has been evaluated in
IRIS. However, there is evidence for the mutagenicity and cytotoxicity
of gasoline exhaust and gasoline PM. Seagrave et al. investigated the
combined particulate and semivolatile organic fractions of gasoline
engine emissions.\79\ Their results demonstrate that emissions from
gasoline engines are mutagenic and can induce inflammation and have
cytotoxic effects. Gasoline exhaust is a ubiquitous

[[Page 15820]]

source of particulate matter, contributing to the health effects
observed for ambient PM which is discussed extensively in the EPA
Particulate Matter Criteria Document.\80\ The PM Criteria Document
notes that the PM components of gasoline and diesel engine exhaust are
hypothesized, important contributors to the observed increases in lung
cancer incidence and mortality associated with ambient
PM_2.5.\81\ Gasoline PM is also a component of near-roadway
emissions that may be contributing to the health effects observed in
people who live near roadways (see section III.F).
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\79\ Seagrave, J.; McDonald, J.D.; Gigliotti, A.P.; Nikula,
K.J.; Seilkop, S.K.; Gurevich, M. and Mauderly, J.L. (2002)
Mutagenicity and in Vivo Toxicity of Combined Particulate and
Semivolatile Organic Fractions of Gasoline and Diesel Engine
Emissions. Toxicological Sciences 70:212-226.
\80\ U.S. Environmental Protection Agency (2004) Air Quality
Criteria for Particulate Matter. Research Triangle Park, NC:
National Center for Environmental Assessment--RTP Office; Report No.
EPA/600/P-99/002aF (PM Criteria Document).
\81\ PM Criteria Document, p. 8-318.
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EPA is working to improve the understanding of PM emissions from
gasoline engines, including the potential range of emissions and
factors that influence emissions. EPA led a cooperative test program
that recently completed testing approximately 500 randomly procured
vehicles in the Kansas City metropolitan area. The purpose of this
study was to determine the distribution of gasoline PM emissions from
the in-use light-duty fleet. Results from this study are expected to be
available in 2006. Some source apportionment studies show gasoline and
diesel PM can result in larger contributions to ambient PM than
predicted by EPA emission inventories.82 83 These source
apportionment studies were one impetus behind the Kansas City study.
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\82\ Fujita, E.; Watson, M.J.; Chow, M.C.; et al. (1998)
Northern Front Range Air Quality Study, Volume C: Source
apportionment and simulation methods and evaluation. Prepared for
Colorado State University, Cooperative Institute for Research in the
Atmosphere, by Desert Research Institute, Reno, NV.
\83\ Schauer, J.J.; Rogge, W.F.; Hildemann, L.M.; et al. (1996)
Source apportionment of airborne particulate matter using organic
compounds as tracers. Atmos. Environ. 30(22):3837-3855.
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Another issue related to gasoline PM is the effect of gasoline
vehicles and engines on ambient PM, especially secondary PM. Ambient PM
is composed of primary PM emitted directly into the atmosphere and
secondary PM that is formed from chemical reactions in the atmosphere.
The issue of secondary organic aerosol formation from aromatic
precursors is an important one to which EPA and others are paying
significant attention. This is discussed in more detail in Section
1.4.1 of the RIA.

F. Near-Roadway Health Effects

Over the years there have been a large number of studies that have
examined associations between living near major roads and different
adverse health endpoints. These studies generally examine people living
near heavily-trafficked roadways, typically within several hundred
meters, where fresh emissions from motor vehicles are not yet fully
diluted with background air.
Several studies have measured elevated concentrations of pollutants
emitted directly by motor vehicles near road as compared to overall
urban background levels. These elevated concentrations generally occur
within approximately 200 meters of the road, although the distance may
vary depending on traffic and environmental conditions. Pollutants
measured with elevated concentrations include benzene, polycyclic
aromatic hydrocarbons, carbon monoxide, nitrogen dioxide, black carbon,
and coarse, fine, and ultrafine particulate matter. In addition,
concentrations of road dust, and wear particles from tire and brake use
also show concentration increases in proximity of major roadways.
The near-roadway health studies provide stronger evidence for some
health endpoints than others. Evidence of adverse responses to traffic-
related pollution is strongest for non-allergic respiratory symptoms,
cardiovascular effects, premature adult mortality, and adverse birth
outcomes, including low birth weight and size. Some evidence for new
onset asthma is available, but not all studies have significant
orrelations. Lastly, among studies of childhood cancer, in particular
childhood leukemia, evidence is inconsistent. Several small studies
report positive associations, though such effects have not been
observed in two larger studies. As described above, benzene and 1,3-
butadiene are both known human leukemogens in adults. As previously
mentioned, there is evidence of increased risk of leukemia among
children whose parents have been occupationally exposed to benzene.
Though the near-roadway studies are equivocal, taken together with the
laboratory studies and other exposure environments, the data suggest a
potentially serious children's health concern could exist. Additional
research is needed to determine the significance of this potential concern.
Significant scientific uncertainties remain in our understanding of
the relationship between adverse health effects and near-road exposure,
including the exposures of greatest concern, the importance of chronic
versus acute exposures, the role of fuel type (e.g. diesel or gasoline)
and composition (e.g., % aromatics), relevant traffic patterns, the
role of co-stressors including noise and socioeconomic status, and the
role of differential susceptibility within the ``exposed'' populations.
For a more detailed discussion, see Chapter 3 of the Regulatory Impact
Analysis.
These studies provide qualitative evidence that reducing emissions
from on-road mobile sources will provide public health benefits beyond
those that can be quantified using currently available information.

G. How Would This Proposal Reduce Emissions of MSATs?

The benzene and hydrocarbon standards proposed in this action would
reduce benzene, 1,3-butadiene, formaldehyde, acrolein, polycyclic
organic matter, and naphthalene, as well as many other hydrocarbon
compounds that are emitted by motor vehicles, including those that are
listed in Table III.B-1 and discussed in more detail in Chapter 1 of
the RIA. The emission reductions expected from today's controls are
reported in section V.E of this preamble and Chapter 2 of the RIA.
EPA believes that the emission reductions from the standards
proposed today for motor vehicles and their fuels, combined with the
standards currently in place, represent the maximum achievable
reductions of emissions from motor vehicles through the application of
technology that will be available, considering costs and the other
factors listed in section 202(l)(2). This conclusion applies whether
you consider just the compounds listed in Table III.B-1, or consider
all of the compounds on the Master List of emissions, given the breadth
of EPA's current and proposed control programs and the broad groups of
emissions that many of the control technologies reduce.
EPA has already taken significant steps to reduce diesel emissions
from mobile sources. We have adopted stringent standards for on-highway
diesel trucks and buses, and nonroad diesel engines (engines used, for
example, in construction, agricultural, and industrial applications).
We also have additional programs underway to reduce diesel emissions,
including voluntary programs and a proposal that is being developed to
reduce emissions from diesel locomotives and marine engines.
Emissions from motor vehicles can be chemically categorized as
hydrocarbons, trace elements (including metals) and a

[[Page 15821]]

few additional compounds containing carbon, nitrogen and/or halogens
(e.g., chlorine). For the hydrocarbons, which are the vast majority of
these compounds, we believe that with the controls proposed today, we
would control the emissions of these compounds from motor vehicles to
the maximum amount currently feasible or currently identifiable with
available information. Section VI of this preamble provides more
details about why the proposed and existing standards represent maximum
achievable reduction of hydrocarbons from motor vehicles. There are not
motor vehicle controls to reduce individual hydrocarbons selectively;
instead, the maximum emission reductions are achieved by controls on
hydrocarbons as a group. There are fuel controls that could selectively
reduce individual air toxics (e.g., formaldehyde, acetaldehyde, 1,3-
butadiene), as well as controls that reduce hydrocarbons more
generally. Section VII of this preamble describes why the standards we
are proposing today represent the maximum emission reductions
achievable through fuel controls, considering the factors required by
Clean Air Act section 202(l).
Motor vehicle emissions also contain trace elements, including
metals, which originate primarily from engine wear and impurities in
engine oil and gasoline or diesel fuel. EPA does not have authority to
regulate engine oil, and there are no feasible motor vehicle controls
to directly prevent engine wear. Nevertheless, oil consumption and
engine wear have decreased over the years, decreasing emission of
metals from these sources. Metals associated with particulate matter
will be captured in emission control systems employing a particulate
matter trap, such as heavy-duty vehicles meeting the 2007 standards. We
believe that currently, particulate matter traps, in combination with
engine-out control, represent the maximum feasible reduction of both
motor vehicle particulate matter and toxic metals present as a
component of the particulate matter.
The mobile source contribution to the national inventory for metal
compounds is generally small. In fact, the emission rate for most
metals from motor vehicles is small enough that quantitative
measurement requires state-of-the art analytical techniques that are
only recently being applied to this source category. We have efforts
underway to gather information regarding trace metal emissions,
including mercury emissions, from motor vehicles (see Chapter 1 of the
RIA for more details).
A few metals and other elements are used as fuel additives. These
additives are designed to reduce the emission of regulated pollutants
either in combination with or without an emission control device (e.g.,
a passive particulate matter trap). Clean Air Act section 211 provides
EPA with various authorities to regulate fuel additives in order to
reduce the risk to public health from exposure to their emissions. It
is under this section that EPA requires manufacturers to register
additives before their introduction into commerce. Registration
involves certain data requirements that enable EPA to identify products
whose emissions may pose an unreasonable risk to public health. In
addition, section 211 provides EPA with authority to require health
effects testing to fill any gaps in the data that would prevent a
determination regarding the potential for risk to the public. Clean Air
Act section 211(c) provides the primary mechanism by which EPA would
take actions necessary to minimize exposure to metals or other
additives to diesel and gasoline. It is under section 211 that EPA is
currently generating the information needed to update an assessment of
the potential human health risks related to having manganese in the
national fuel supply.
Existing regulations limit sulfur in gasoline and diesel fuel to
the maximum amount feasible and will reduce emissions of all sulfur-
containing compounds (e.g., hydrogen sulfide, carbon disulfide) to the
greatest degree achievable.84 85 86 For the remaining
compounds (e.g., chlorinated compounds), we currently have very little
information regarding emission rates and conditions that impact
emissions. This information would be necessary in order to evaluate
potential controls under section 202(l). Emissions of hydrocarbons
containing chlorine (e.g., dioxins/furans) would likely be reduced with
control measures that reduce total hydrocarbons, just as these
emissions were reduced with the use of catalytic controls that lowered
exhaust hydrocarbons.
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\84\ 65 FR 6697, February 10, 2000.
\85\ 66 FR 5001, January 18, 2001.
\86\ 69 FR 38958, June 29, 2004.
---------------------------------------------------------------------------

IV. What Are the Air Quality and Health Impacts of Air Toxics, and How
Do Mobile Sources Contribute?

A. What Is the Health Risk to the U.S. Population from Inhalation
Exposure to Ambient Sources of Air Toxics, and How Would It be Reduced
by the Proposed Controls?

EPA's National-Scale Air Toxics Assessment (NATA) assesses human
health impacts from chronic inhalation exposures to outdoor sources of
air toxics. It assesses lifetime risks assuming continuous exposure to
levels of air toxics estimated for a particular point in time. The most
recent NATA was done for the year 1999.\87\
---------------------------------------------------------------------------

\87\ http://www.epa.gov/ttn/atw/nata1999.

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

The NATA modeling framework has a number of limitations, but it
remains very useful in identifying air toxic pollutants and sources of
greatest concern. Among the significant limitations of the framework,
which are discussed in more detail in the regulatory impact analysis,
is that it cannot be used to reliably identify ``hot spots,'' such as
areas in immediate proximity to major roads, where the air
concentration, exposure and/or risk might be significantly higher
within a census tract \88\ or county. These ``hot spots'' are discussed
in more detail in section IV.B.2. The framework also does not account
for risk from sources of air toxics originating indoors, such as
stoves, out-gassing from building materials, or evaporative benzene
emissions from cars in attached garages. There are also limitations
associated with the dose-response values used to quantify risk; these
are discussed in Section I of the preamble. Importantly, it should be
noted that the 1999 NATA does not include default adjustments for early
life exposures recently recommended in the Supplemental Guidance for
Assessing Susceptibility from Early-Life Exposure to Carcinogens.\89\
These adjustments would be applied to compounds which act through a
mutagenic mode of action. EPA will determine as part of the IRIS
assessment process which substances meet the criteria for making
adjustments, and future assessments will reflect them. If warranted,
incorporation of such adjustments would lead to higher estimates of
risk assuming constant lifetime exposure.
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\88\ A census tract is a subdivision of a county that typically
contains roughly 4000 people. In urban areas, these tracts can be
very small, on the order of a city block, whereas in rural areas,
they can be large.
\89\ U. S. EPA. (2005) Supplemental Guidance for Assessing
Susceptibility from Early-Life Exposure to Carcinogens. Report No.
EPA/630/R-03/003F. Available electronically at
http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=116283.

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Because of its limitations, EPA notes that the NATA assessment
should not be used as the basis for developing risk reduction plans or
regulations to control specific sources or pollutants. Additionally,
this assessment should not be used for estimating risk at the local
level, for quantifying benefits of reduced air toxic emissions, or for
identifying localized hotspots. In this

[[Page 15822]]

rule, we have evaluated air quality, exposure, and risk impacts of
mobile source air toxics using the 1999 NATA, as well as projections of
risk to future years using the same tools as 1999 NATA. In addition, we
also evaluate more refined local scale modeling, measured ambient
concentrations, personal exposure measurements, and other data. This
information is discussed below, as well as in Chapter 3 of the RIA. It
serves as a perspective on the possible risk-related implications of
the rule.
Overall, the average nationwide lifetime population cancer risk in
1999 NATA was 42 in a million, assuming continuous exposure to 1999
levels. The average noncancer respiratory hazard index was 6.4.\90\
Highway vehicles and nonroad equipment account for almost 50% of the
average population cancer risk, and 74% of the noncancer risk These
estimates are based on the contribution of sources within 50 kilometers
of a given emission point and do not include the contribution to
ambient concentrations from transport beyond 50 kilometers. Ambient
concentrations from transport beyond 50 kilometers, referred to as
``background'' in NATA, are responsible for almost 50% of the average
cancer risk in NATA.
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\90\ A hazard index above 1 indicates the potential for adverse
health effects. It cannot be translated into a probability that an
adverse effect will occur, and is not likely to be proportional to
risk. A hazard index greater than one can be best described as only
indicating that a potential may exist for adverse health effects.
---------------------------------------------------------------------------

Section III.C.1 discusses the pollutants that the 1999 National-
Scale Air Toxics Assessment identifies as national and regional risk
drivers. As summarized in Table III.C-1, benzene is the only pollutant
described as a national cancer risk driver. Twenty-four percent of the
total cancer risk in the 1999 National-Scale Air Toxics Assessment was
due to benzene. In 1999, 68% of nationwide benzene emissions were
attributable to mobile sources. 1,3-Butadiene and naphthalene are
regional cancer risk drivers that have a large mobile source
contribution. As presented in Table III.C-2, 58% of nationwide 1,3-
butadiene emissions in 1999 came from mobile sources. Twenty-seven percent
of nationwide naphthalene emissions in 1999 came from mobile sources.
One compound, acrolein, was identified as a national risk driver
for noncancer health effects, and 25% of primary acrolein emissions
were attributable to mobile sources. Over 70% of the average ambient
concentration of acrolein is attributable to mobile sources. This is
due to the large contribution from mobile source 1,3-butadiene, which
is transformed to acrolein in the atmosphere.
Table III.C-2 provides additional information on the mobile source
contribution to emissions of national and regional risk drivers. The
standards proposed in this rule will reduce emissions of all these
pollutants.
In addition to the 1999 NATA, we have estimated future-year risks
for those pollutants included in the 1999 NATA whose emissions
inventories include a mobile source contribution (see Table IV.B-1).
This analysis indicates that cancer and noncancer risk will continue to
be a public health concern due to exposure to mobile-source-related
pollutants.
Figure IV.A-1 summarizes changes in average population inhalation
cancer risk for the MSATs in Table IV.A-1. Despite significant
reductions in risk from these pollutants, average inhalation cancer
risks are expected to remain well above 1 in 100,000. In addition,
because of population growth (using projected populations from the U.S.
Bureau of Census), the number of Americans above the 1 in 100,000
cancer risk level from exposure to these mobile source air toxics is
projected to increase from about 214 million in 1999 to 240 million in
2030. Benzene continues to account for a large fraction of the total
inhalation cancer risk from mobile source air toxics, decreasing
slightly from 45% of the risk in 1999 to 37% in 2030. Similarly,
although the average noncancer respiratory hazard index for MSATs
decreases from over 6 in 1999 to 3.2 in 2030, the population with a
hazard index above one increases from 250 million in 1999 to 273
million in 2030. That is, in 2030 nearly the entire U.S. population
will still be exposed to levels of these pollutants that have the
potential to cause adverse respiratory health effects (other than cancer).
These projected risks were estimated using the same tools and
methods as the 1999 NATA, but with future-year projected inventories.
More detailed information on the methods used to do these projections,
and associated limitations and uncertainties, can be found in Chapter 3
of the RIA for this rule. Projected risks assumed 1999 ``background''
levels. For MSATs, ``background'' accounts for slightly less than 20%
of the average cancer risk in 1999, increasing to 24% in 2030. However,
background levels should decrease along with emissions. A sensitivity
analysis of this assumption is presented in Chapter 3 of the RIA. It
should also be noted that the projected inventories used for this
modeling do not include some more recent revisions, such as higher
emissions of hydrocarbons, including gaseous air toxics, at cold
temperatures. These revisions are discussed in section V and increase
the overall magnitude of the inventory.

[[Page 15823]]
[GRAPHIC]
[TIFF OMITTED]
TP29MR06.000

Table IV.A-1.--Pollutants Included in Risk Modeling for Projection Years
*
------------------------------------------------------------------------

------------------------------------------------------------------------
1,3-Butadiene............................. Ethyl Benzene
2,2,4-Trimethylpentane.................... Fluoranthene **
Acenaphthene **........................... Fluorene **
Acenaphthylene **......................... Formaldehyde
Acetaldehyde.............................. Hexane
Acrolein.................................. Indeno(1,2,3,c,d)-pyrene **
Anthracene **............................. Manganese
Benzene................................... Methyl tert-butyl ether
(MTBE)
Benz(a)anthracene **...................... Naphthalene
Benzo(a)pyrene **......................... Nickel
Benzo(b)fluoranthene **................... Phenanthrene **
Benzo(g,h,i)perylene **................... Propionaldehyde
Benzo(k)fluoranthene **................... Pyrene **
Chromium (includes Chromium III, Chromium Styrene
VI, and non-speciated Chromium).
Chrysene **............................... Toluene
Dibenzo(a,h)anthracene **................. Xylenes
------------------------------------------------------------------------
* This list includes compounds from the 1999 National-Scale Air Toxics
Assessment with a mobile source emissions contribution, for which data
were sufficient to develop an emissions inventory.
** POM compound as discussed in Section III.

B. What Is the Distribution of Exposure and Risk?

1. Distribution of National-Scale Estimates of Risk From Air Toxics
National-scale modeling indicates that 95th percentile average
cancer risk from exposure to mobile source air toxics is more than
three times higher than median risk. In addition, the 95th percentile
cancer risk is more than 10 times higher than the 5th percentile risk.
This is true for all years modeled, from 1999 to 2030. Table IV.B-1
gives the median and 5th and 95th percentile cancer risk distributions
for mobile source air toxics. As previously mentioned, the tools used
in this assessment are inadequate for identifying ``hot spots'' and do
not account for significant sources of inhalation exposure, such as
benzene emissions within attached garages from vehicles, equipment, and
portable fuel containers. If these hot spots and additional sources of
exposure were accounted for, a larger percentage of the population
would be exposed to higher risk levels. (Sections IV.B.2-4 provides
more details on ``hot spots'' and the implications for distribution of
risk.) In addition, the modeling underestimates the contribution of
hydrocarbon and particulate matter emissions at cold temperatures. These
modeling results are discussed in more detail in Chapter 3 of the RIA.

[[Page 15824]]

Table IV.B--1.--Median and 5th and 95th Percentile Lifetime Inhalation Cancer Risk Distributions for Inhalation
Exposure to Outdoor Sources of Mobile Source Air Toxics
[Based on modeled average census tract risks]
----------------------------------------------------------------------------------------------------------------
1999 2020
Pollutant -----------------------------------------------------------------------
5th Median 95th 5th Median 95th
----------------------------------------------------------------------------------------------------------------
All MSATs............................... 4.0x10-6 1.9x10-5 5.9x10-5 3.6x10-6 1.3x10-5 4.4x10-5
Benzene................................. 2.4x10-6 8.9x10-6 2.5x10-5 2.1x10-6 5.6x10-6 1.4x10-5
1,3-Butadiene........................... 1.6x10-7 3.1x10-6 1.2x10-5 7.5x10-8 2.0x10-6 7.5x10-6
Acetaldehyde............................ 1.0x10-6 2.5x10-6 6.9x10-6 9.3x10-7 1.6x10-6 3.6x10-6
Naphthalene............................. 1.1x10-7 1.4x10-6 7.6x10-6 1.0x10-7 1.4x10-6 8.5x10-6
----------------------------------------------------------------------------------------------------------------

2. Elevated Concentrations and Exposure in Mobile Source-Impacted Areas
Air quality measurements near roads often identify elevated
concentrations of air toxic pollutants at these locations. The
concentrations of air toxic pollutants near heavily trafficked roads,
as well as the pollutant composition and characteristics, differ from
those measured distant from heavily trafficked roads. Exposures for
populations residing, working, or going to school near major roads are
likely higher than for other populations. The vehicle and fuel
standards proposed in this rule will reduce those elevated exposures.
Following is an overview of concentrations of air toxics and exposure
to air toxics in areas heavily impacted by mobile source emissions.
a. Concentrations Near Major Roadways
The 1999 NATA estimates average concentrations within a census
tract, but it does not differentiate between locations near roadways
and those further away (within the same tract). Local-scale modeling
can better characterize distributions of concentrations, using more
refined allocation of highway vehicle emissions. Urban-scale
assessments done in Houston, TX and Portland, OR illustrated steep
gradients of air toxic concentrations along major roadways, as well as
better agreement with monitor data.91-92 93 Results of the
Portland study show average concentrations of motor vehicle-related
pollutants are ten times higher at 50 meters from a road than they are
at greater than 400 meters a road. These findings are consistent with
pollutant dispersion theory, which predicts that pollutants emitted
along roadways will show highest concentrations nearest a road, and
concentrations exponentially decrease with increasing distance
downwind. These near-road pollutant gradients have been confirmed by
measurements of both criteria pollutants and air toxics, and they are
discussed in detail in Chapter 3 of the RIA.
---------------------------------------------------------------------------

\91-92\ Kinnee, E.J.; Touma, J.S.; Mason, R.; Thurman, J.;
Beidler, A., Bailey, C.; Cook, R. (2004) Allocation of onroad mobile
emissions to road segments for air toxics modeling in an urban area.
Transport. Res. Part D 9: 139-150.
\93\ Cohen, J.; Cook, R.; Bailey, C.R.; Carr, E. (2005)
Relationship between motor vehicle emissions of hazardous
pollutants, roadway proximity, and ambient concentrations in
Portland, Oregon. Environ. Modelling & Software 20: 7-12.
---------------------------------------------------------------------------

Air quality monitoring is another means of evaluating pollutant
concentrations at locations near sources such as roadways. It is also
used to evaluate model performance at a given point and, given adequate
data quality, can be statistically analyzed to determine associations
with different source types. EPA has been deploying fixed-site ambient
monitors that monitor concentrations of multiple air toxics, including
benzene, over time. Several studies have found that concentrations of
benzene and other mobile source air toxics are significantly elevated
near busy roads compared to ``urban background'' concentrations
measured at a fixed site. These studies are discussed in detail in
Chapter 3 of the RIA.
Ambient VOC concentrations were measured around residences in
Elizabeth, NJ, as part of the Relationship among Indoor, Outdoor, and
Personal Air (RIOPA) study. Data from that study was analyzed to assess
how concentrations are influenced by proximity to known ambient
emission sources.94 95 The ambient concentrations of
benzene, toluene, ethylbenzene, and xylene isomers (BTEX) were found to
be inversely associated with distances to interstate highways and major
urban roads, and with distance to gasoline stations. The data indicate
that BTEX concentrations around homes within 200 meters of roadways and
gas stations are 1.5 to 4 times higher than urban background levels.
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\94\ Kwon, J. (2005) Development of a RIOPA database and
evaluation of the effect of proximity on the potential residential
exposure to VOCs from ambient sources. Rutgers, the State University
of New Jersey and University of Medicine and Dentistry of New
Jersey. PhD dissertation. This document is available in Docket EPA-
HQ-OAR-2005-0036.
\95\ Weisel, C.P. (2004) Assessment of the contribution to
personal exposures of air toxics from mobile sources. Final report.
Submitted to EPA Office of Transportation and Air Quality.
Environmental & Occupational Health Sciences Institute, Piscataway,
NJ. This document is available in Docket EPA-HQ-OAR-2005-0036.
---------------------------------------------------------------------------

b. Exposures Near Major Roadways
The modeling assessments and air quality monitoring studies
discussed above have increased our understanding of ambient
concentrations of mobile source air toxics and potential population
exposures. Results from the following exposure studies reveal that
populations spending time near major roadways likely experience
elevated personal exposures to motor vehicle related pollutants. In
addition, these populations may experience exposures to differing
physical and chemical compositions of certain air toxic pollutants
depending on the amount of time spent in close proximity to motor
vehicle emissions. Following is a detailed discussion on exposed
populations near major roadways.
i. Vehicles
Several studies suggest that significant exposures may be
experienced while driving in vehicles. A recent in-vehicle monitoring
study was conducted by EPA and consisted of in-vehicle air sampling
throughout work shifts within ten police patrol cars used by the North
Carolina State Highway Patrol (smoking not permitted inside the
vehicles).\96\ Troopers operated their vehicles in typical patterns,
including highway and city driving and refueling. In-vehicle benzene
concentrations averaged 12.8 [mu]g/m3, while concentrations
measured at an ``ambient'' site located outside a nearby state
environmental office averaged 0.32 [mu]g/m3. The study also
found that the benzene concentrations were closely

[[Page 15825]]

associated with other fuel-related VOCs measured.
---------------------------------------------------------------------------

\96\ Riediker, M.; Williams, R.; Devlin, R.; et al. (2003)
Exposure to particulate matter, volatile organic compounds, and
other air pollutants inside patrol cars. Environ Sci. Technol. 37:
2084-2093.
---------------------------------------------------------------------------

In Boston, the exposure of commuters to VOCs during various
commuting modes was examined.\97\ For commuters driving a car, the mean
time-weighted concentrations of benzene, toluene, and xylenes in-
vehicle were measured at 17.0, 33.1, and 28.2 [mu]g/m3, respectively.
---------------------------------------------------------------------------

\97\ Chan C.-C., Spengler J. D., Ozkaynak H., and Lefkopoulou M.
(1991) Commuter Exposures to VOCs in Boston, Massachusetts. J. Air
Waste Manage. Assoc. 41: 1594-1600.
---------------------------------------------------------------------------

The American Petroleum Institute funded a screening study of high-
end exposure microenvironments as required by section 211(b) of the
Clean Air Act.\98\ The study included vehicle chase measurements and
measurements in several vehicle-related microenvironments in several
cities for benzene and other air toxics. In-vehicle microenvironments
(average benzene concentrations in parentheses) included the vehicle
cabin tested on congested freeways (17.5 [mu]g/m\3\), in parking
garages above-ground (155 [mu]g/m\3\) and below-ground (61.7 [mu]g/
m\3\), in urban street canyons (7.54 [mu]g/m\3\), and during refueling
(46.0 [mu]g/m\3\).
---------------------------------------------------------------------------

\98\ Zielinska, B.; Fujita, E.M.; Sagebiel, J.C.; et al. (2002)
Interim data report for Section 211(B) Tier 2 high end exposure
screening study of baseline and oxygenated gasoline. Prepared for
American Petroleum Institute. November 19, 2002. This document is
available in Docket EPA-HQ-OAR-2005-0036.
---------------------------------------------------------------------------

In 1998, the California Air Resources Board published an extensive
study of concentrations of in-vehicle air toxics in Los Angeles and
Sacramento, CA.\99\ The data set is large and included a variety of
sampling conditions. On urban freeways, benzene in-vehicle
concentrations ranged from 3 to 15 [mu]g/m\3\ in Sacramento and 10 to
22 [mu]g/m\3\ in Los Angeles. In comparison, ambient benzene
concentrations ranged from 1 to 3 [mu]g/m\3\ in Sacramento and 3 to 7
[mu]g/m\3\ in Los Angeles.
---------------------------------------------------------------------------

\99\ Rodes, C.; Sheldon, L.; Whitaker, D.; et al. (1998)
Measuring concentrations of selected air pollutants inside
California vehicles. Final report to California Air Resources Board.
Contract No. 95-339.
---------------------------------------------------------------------------

Similar findings of elevated concentrations of pollutants have also
been found in studies done in diesel buses.100 101 102
---------------------------------------------------------------------------

\100\ Fitz, D.R.; Winer, A.M.; Colome, S.; et al. (2003)
Characterizing the Range of Children's Pollutant Exposure During
School Bus Commutes. Prepared for the California Resources Board.
\101\ Sabin, L.D.; Behrentz, E.; Winer, A.M.; et al. (2005)
Characterizing the range of children's air pollutant exposure during
school bus commutes. J. Expos. Anal. Environ. Epidemiol. 15: 377-387.
\102\ Batterman, S.A.; Peng, C.Y.; and Braun, J. (2002) Levels
and composition of volatile organic compounds on commuting routes in
Detroit, Michigan. Atmos. Environ. 36: 6015-6030.
---------------------------------------------------------------------------

Overall, these studies show that concentrations experienced by
commuters and other roadway users are substantially higher than those
measured in typical urban air. As a result, the time a person spends in
a vehicle will significantly affect their overall exposure.
ii. Homes and Schools
The proximity of schools to major roads may result in elevated
exposures for children due to potentially increased concentrations
indoors and increased exposures during outdoor activities. Here we
discuss international studies in addition to the limited number of U.S.
studies, because while fleets and fuels outside the U.S. can differ
significantly, the spatial distribution of concentrations is relevant.
In the Fresno Asthmatic Children's Environment Study (FACES),
traffic-related pollutants were measured on selected days from July
2002 to February 2003 at a central site, and inside and outside of
homes and outdoors at schools of asthmatic children.\103\ Preliminary
data indicate that PAH concentrations are higher at elementary schools
located near primary roads than at elementary schools distant from
primary roads (or located near primary roads with limited access). PAH
concentrations also appear to increase with increase in annual average
daily traffic on nearest major collector. Remaining results regarding
the variance in traffic pollutant concentrations at schools in relation
to proximity to roadways and traffic density will be available in 2006.
---------------------------------------------------------------------------

\103\ Personal communication with FACES Investigators Fred
Lurmann, Paul Roberts, and Katharine Hammond. Data is currently
being prepared for publication.
---------------------------------------------------------------------------

The East Bay Children's Respiratory Health Study studied traffic-
related air pollution outside of schools near busy roads in the San
Francisco Bay Area in 2001.\104\ Concentrations of the traffic
pollutants PM₁₀, PM_2.5, black carbon, total
NO_X, and NO₂ were measured at 10 school sites in
neighborhoods that spanned a busy traffic corridor during the spring
and fall seasons. The school sites were selected to represent a range
of locations upwind and downwind of major roads. Differences were
observed in concentrations between schools nearby (< 300 m) versus
those more distant (or upwind) from major roads. Investigators found
spatial variability in exposure to black carbon, NO_X, NO,
and (to a lesser extent) NO₂, due specifically to roads with
heavy traffic within a relatively small geographic area.
---------------------------------------------------------------------------

\104\ Kim J.J.; Smorodinsky S.; Lipsett M.; et al. (2004)
Traffic-related air pollution near busy roads. Am. J. Respir. Crit.
Care Med. 170: 520-526.
---------------------------------------------------------------------------

A study to assess children's exposure to traffic-related air
pollution while attending schools near motorways was performed in the
Netherlands.\105\ Investigators measured PM_2.5,
NO₂ and benzene inside and outside of 24 schools located
within 400 m of motorways. The indoor average benzene concentration was
3.2 [mu]g/m\3\ with a range of 0.6-8.1 [mu]g/m\3\. The outdoor average
benzene concentration was 2.2 [mu]g/m\3\ with a range of 0.3-5.0 [mu]g/
m\3\. Overall results indicate that indoor pollutant concentrations are
significantly correlated with traffic density and composition,
percentage of time downwind, and distance from major roadways.
---------------------------------------------------------------------------

\105\ Janssen, N.A.H.; van Vliet, P.H.N.; Aarts, F.; et al.
(2001) Assessment of exposure to traffic related air pollution of
children attending schools near motorways. Atmos. Environ. 35: 3875-3884.
---------------------------------------------------------------------------

The Toxic Exposure Assessment--Columbia/Harvard (TEACH) study
measured the concentrations of VOCs, PM_2.5, black carbon,
and metals outside the homes of high school students in New York
City.\106\ The study was conducted during winter and summer of 1999 on
46 students and their homes. Average winter (and summer) indoor
concentrations exceeded outdoor concentrations by a factor of 2.3
(1.3). In addition, analyses of spatial and temporal patterns of MTBE
concentrations were consistent with traffic patterns. MTBE is a tracer
for motor vehicle pollution.
---------------------------------------------------------------------------

\106\ Kinney, P.L.; Chillrud, S.N.; Ramstrom, S.; et al. (2002)
Exposures to multiple air toxics in New York City. Environ Health
Perspect. 110 (Suppl 4): 539-546.
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Children are exposed to elevated levels of air toxics not only in
their homes, classrooms, and outside on school grounds, but also during
their commute to school. See the discussion of in-vehicle
concentrations of air toxics above and in Chapter 3 of the RIA.
iii. Pedestrians and Bicyclists
Researchers have noted that pedestrians and cyclists along major
roads experience elevated exposures to motor vehicle related
pollutants. Although commuting near roadways leads to higher levels of
exposure to traffic pollutants, the general consensus is that exposure
levels of those commuting by walking or biking is lower than for those
who travel by car or bus, (see discussion on in-vehicle exposure in
previous section above). These studies are discussed in Chapter 3 of
the RIA for this rule.

[[Page 15826]]

c. Exposure and Concentrations in Homes with Attached Garages
People living in homes with attached garages are potentially
exposed to substantially higher concentrations of benzene, toluene, and
other VOCs indoors. Homes with attached garages present a special
concern related to infiltration of components of fuel, exhaust, and
other materials stored in garages (including gasoline in gas cans). A
study from the early 1980's found that approximately 30% of an average
nonsmoker's benzene exposure originated from sources in attached
garages.\107\
---------------------------------------------------------------------------

\107\ Wallace, L. (1996) Environmental exposure to benzene: an
update. Environ Health Perspect. 104 (Suppl 6): 1129-1136.
---------------------------------------------------------------------------

Concentrations within garages are often substantially higher than
those found outdoors or indoors. A recently-completed study in Michigan
found that average concentrations in residential garages were 36.6
[mu]g/m\3\, compared to 0.4 [mu]g/m\3\ outdoors.\108\ A recent study in
Alaska, where fuel benzene concentrations are higher, cold start
emissions are higher, and homes are more tightly sealed than in most of
the U.S., found average garage concentrations of 101 [mu]g/m\3\.\109\
Air passing from these high-benzene locations can cause increased
concentrations indoors.
---------------------------------------------------------------------------

\108\ Batterman, S.; Hatzivasilis, G.; Jia, C. (2006)
Concentrations and emissions of gasoline and other vapors from
residential vehicle garages. Atmos. Environ. 30: 1828-1844.
\109\ George, M.; Kaluza, P.; Maxwell, B.; Moore, G.; Wisdom, S.
(2002) Indoor air quality & ventilation strategies in new homes in
Alaska. Alaska Building Science Network. http://www.cchrc.org.
This document is available in Docket EPA-HQ-OAR-2005-0036.
---------------------------------------------------------------------------

Measurement studies have found that homes with attached garages can
have significantly higher concentrations of benzene and other VOCs. One
study from Alaska found that in homes without attached garages, average
benzene concentrations were 8.6 [mu]g/m\3\, while homes with attached
garages had average concentrations of 70.8 [mu]g/m\3\.\110\ Another
showed that indoor CO and total hydrocarbon (THC) concentrations rose
sharply following a cold vehicle starting and pulling out of the
attached garage, persisting for an hour or more.\111\ The study also
showed that cold start emissions accounted for 13-85% of indoor non-
methane hydrocarbons (NMHC), while hot soak emissions accounted for 9-
71% of indoor NMHC. Numerous other studies have shown associations
between VOCs in indoor air and the presence of attached garages. These
studies are discussed in Chapter 3 of the RIA.
---------------------------------------------------------------------------

\110\ Schlapia, A.; Morris, S. (1998) Architectural, behavioral,
and environmental factors associated with VOCs in Anchorage homes.
Proceedings of the Air & Waste Management Associations 94th Annual
Conference. Paper 98-A504.
\111\ Graham, L.A.; Noseworthy, L.; Fugler, D.; O'Leary, K.;
Karman, D.; Grande, C. (2004) Contribution of vehicle emissions from
an attached garage to residential indoor air pollution levels. J.
Air & Waste Manage. Assoc. 54: 563-584.
---------------------------------------------------------------------------

EPA has conducted a modeling analysis to examine the influence of
attached garages on personal exposure to benzene.\112\ The analysis
modeled the air flow between the outdoor environment, indoor
environment, and the garage, and accounted for the fraction of home air
intake from the garage. Compared to national average exposure
concentrations of 1.36 [mu]g/m\3\ modeled for 1999 in the National-
Scale Air Toxics Assessment, which do not account for emissions
originating in attached garages, average exposure concentrations for
people with attached garages could more than double. For additional
details, see Chapter 3 of the RIA.
---------------------------------------------------------------------------

\112\ Bailey, C. (2005) Additional contribution to benzene
exposure from attached garages. Memorandum to the Docket. This
document is available in Docket EPA-HQ-OAR-2005-0036.
---------------------------------------------------------------------------

Overall, emissions of VOCs within attached garages result in
substantially higher concentrations of benzene and other pollutants
indoors. Proposed reductions in fuel benzene content, new standards for
cold temperature exhaust emissions during vehicle starts, and reduced
emissions from gas cans are all expected to significantly reduce this
major source of exposure.
d. Occupational Exposure
Occupational settings can be considered a microenvironment in which
exposure to benzene and other air toxics can occur. Occupational
exposures to benzene from mobile sources or fuels can be several orders
of magnitude greater than typical exposures in the non-occupationally
exposed population. Several key occupational groups include workers in
fuel distribution, storage, and tank remediation; handheld and non-
handheld equipment operators; and workers who operate gasoline-powered
engines such as snowmobiles and ATV's. Exposures in these occupational
settings are discussed in Chapter 3 of the RIA.
In addition, some occupations require that workers spend
considerable time in vehicles, which increases the time they spend in a
higher-concentration microenvironment. In-vehicle concentrations are
discussed in a previous section above.
3. What Are the Size and Characteristics of Highly Exposed Populations?
A study of the populations in three states (Colorado, Georgia, and
New York) indicated that more than half of the population lives within
200 meters of a major road.\113\ In addition, analysis of data from the
Census Bureau's American Housing Survey suggests that approximately 37
million people live within 300 feet of a 4- or more lane highway,
railroad, or airport. American Housing Survey statistics, as well as
epidemiology studies, indicate that those houses sited near major
transportation sources are more likely to be lower in income or have
minority residents than houses not located near major transportation
sources. These data are discussed in detail in Chapter 3 of the RIA.
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\113\ Major roads are defined as those roads defined by the U.S.
Census as one of the following: ``limited access highway,''
``highway,'' ``major road,'' or ``ramp.''
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Other population studies also indicate that a significant fraction
of the population resides in locations near major roads. At present,
the available studies use different indicators of ``major road'' and of
``proximity,'' but the estimates range from 12.4% of student enrollment
in California attending schools within 150 meters of roads with 25,000
vehicles per day or more, to 13% of Massachusetts veterans living
within 50 meters of a road with at least 10,000 vehicles per
day.114 115 Using a more general definition of a ``major
road,'' between 22% and 51% of different study populations live near
such roads.
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\114\ Green, R.S.; Smorodinsky, S.; Kim, J.J.; McLaughlin, R.;
Ostro, B. (2004) Proximity of California public schools to busy
roads. Environ. Health Perspect. 112: 61-66.
\115\ Garshick, E.; Laden, F.; Hart, J.E.; Caron, A. (2003)
Residence near a major road and respiratory symptoms in U.S.
veterans. Epidemiol. 14: 728-736.
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4. What Are the Implications for Distribution of Individual Risk?
We have made revisions to HAPEM5, which is the exposure model used
in our national-scale modeling, in order to account for near-road
impacts. The effect of the updated model is best understood as widening
the distribution of exposure, with a larger fraction of the population
being exposed to higher benzene concentrations. Including the effects
of residence locations near roads can result in exposures to some
individuals that are up to 50% higher than those predicted by HAPEM5.
The revised model, HAPEM6, was run for three states representing
different parts of the country. These areas are intended to represent
different

[[Page 15827]]

geographies, development patterns, and housing densities. The states
modeled include Georgia, Colorado, and New York. Overall, these study
results indicate that proximity to major roads can significantly
increase personal exposure for populations living near major roads.
These modeling tools will be extended to a national scale for the final
rulemaking.
For details on the modeling study with HAPEM6, refer to Chapter 3.2
of the RIA. We used geographic information systems to estimate the
population within each U.S. census tract living at various distances
from a major road (within 75 meters; between 75 and 200 meters; or
beyond 200 meters). An exposure gradient was determined for people
living in each zone, based on dispersion modeling.\116\ These gradients
were confirmed with monitoring studies funded by EPA.\117\ The HAPEM5
model was updated to account for elevated concentrations within these
defined distances from roadways and the population living in these areas.
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\116\ Cohen, J.; Cook, R.; Bailey, C.R.; Carr, E. (2005)
Relationship between motor vehicle emissions of hazardous
pollutants, roadway proximity, and ambient concentrations in
Portland, Oregon. Environ Modelling & Software 20: 7-12.
\117\ Kwon, J. (2005) Development of a RIOPA database and
evaluation of the effect of proximity on the potential residential
exposure to VOCs from ambient sources. PhD Dissertation. Rutgers,
The State University of New Jersey and University of Medicine and
Dentistry of New Jersey. Written under direction of Dr. Clifford
Weisel. This document is available in Docket EPA-HQ-OAR-2005-0036.
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C. Ozone

While the focus of this rule is on air toxics, the proposed vehicle
and gas can standards will also help reduce volatile organic compounds
(VOCs), which are precursors to ozone.
1. Background
Ground-level ozone, the main ingredient in smog, is formed by the
reaction of VOCs and nitrogen oxides (NO_X) in the atmosphere
in the presence of heat and sunlight. These pollutants, often referred
to as ozone precursors, are emitted by many types of pollution sources,
such as highway and nonroad motor vehicles and engines, power plants,
chemical plants, refineries, makers of consumer and commercial
products, industrial facilities, and smaller ``area'' sources. VOCs can
also be emitted by natural sources such as vegetation. The gas can
controls proposed in this action would help reduce VOC emissions by
reducing evaporation, permeation and spillage from gas cans. The
proposed vehicle controls will also reduce VOC emissions; however,
because these reductions will occur at cold temperatures the ozone
benefits will be limited.
The science of ozone formation, transport, and accumulation is
complex.\118\ Ground-level ozone is produced and destroyed in a
cyclical set of chemical reactions, many of which are sensitive to
temperature and sunlight. When ambient temperatures and sunlight levels
remain high for several days and the air is relatively stagnant, ozone
and its precursors can build up and result in more ozone than typically
would occur on a single high-temperature day. Further complicating
matters, ozone also can be transported into an area from pollution
sources found hundreds of miles upwind, resulting in elevated ozone
levels even in areas with low VOC or NO_X emissions. As a
result, differences in VOC and NO_X emissions contribute to
daily, seasonal, and yearly differences in ozone concentrations across
different locations.
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\118\ U.S. EPA (1996). Air Quality Criteria for Ozone and
Related Photochemical Oxidants, EPA600-P-93-004aF. This document is
available in Docket EPA-HQ-OAR-2005-0036.
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The current ozone National Ambient Air Quality Standards (NAAQS)
has an 8-hour averaging time. The 8-hour ozone NAAQS, established by
EPA in 1997, is based on well-documented science demonstrating that
more people were experiencing adverse health effects at lower levels of
exertion, over longer periods, and at lower ozone concentrations than
addressed by the previous one-hour ozone NAAQS. It addresses ozone
exposures of concern for the general population and populations most at
risk, including children active outdoors, outdoor workers, and
individuals with pre-existing respiratory disease, such as asthma. The
8-hour ozone NAAQS is met at an ambient air quality monitoring site
when the average of the annual fourth-highest daily maximum 8-hour
average ozone concentration over three years is less than or equal to
0.084 ppm.
2. Health Effects of Ozone
The health and welfare effects of ozone are well documented and are
critically assessed in the EPA ozone criteria document (CD) and EPA
staff paper.119 120 In August 2005, the EPA released the
second external review draft of a new ozone CD which is scheduled to be
released in final form in February 2006.\121\ This document summarizes
the findings of the 1996 ozone criteria document and critically
assesses relevant new scientific information which has emerged in the
past decade. Additional information on health and welfare effects of
ozone can also be found in the draft RIA for this proposal.
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\119\ U.S. EPA (1996). Air Quality Criteria for Ozone and
Related Photochemical Oxidants, EPA600-P-93-004aF. This document is
available in Docket EPA-HQ-OAR-2005-0036.
\120\ U.S. EPA (1996) Review of National Ambient Air Quality
Standards for Ozone, Assessment of Scientific and Technical
Information, OAQPS Staff Paper, EPA-452/R-96-007. This document is
available in Docket EPA-HQ-OAR-2005-0036.
\121\ U.S. EPA (2005) Air Quality Criteria for Ozone and Related
Photochemical Oxidants (Second External Review Draft). This document
is available in Docket EPA-HQ-OAR-2005-0036.
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Ozone can irritate the respiratory system, causing coughing, throat
irritation, and/or uncomfortable sensation in the chest. Ozone can
reduce lung function and make it more difficult to breathe deeply, and
breathing may become more rapid and shallow than normal, thereby
limiting a person's normal activity. Ozone can also aggravate asthma,
leading to more asthma attacks that require a doctor's attention and/or
the use of additional medication. In addition, ozone can inflame and
damage the lining of the lungs, which may lead to permanent changes in
lung tissue, irreversible reductions in lung function, and a lower
quality of life if the inflammation occurs repeatedly over a long time
period. People who are of particular concern with respect to ozone
exposures include children and adults who are active outdoors. Those
people particularly susceptible to ozone effects are people with
respiratory disease (e.g., asthma), people with unusual sensitivity to
ozone, and children.
There has been new research that suggests additional serious health
effects beyond those that had been known when the 1996 ozone CD was
published. Since then, over 1,700 new ozone-related health and welfare
studies have been published in peer-reviewed journals.\122\ Many of
these studies have investigated the impact of ozone exposure on such
health effects as changes in lung structure and biochemistry,
inflammation of the lungs, exacerbation and causation of asthma,
respiratory illness-related school absence, hospital and emergency room
visits for asthma and other respiratory causes, and premature

[[Page 15828]]

mortality. EPA is currently in the process of evaluating these and
other studies as part of the ongoing review of the air quality criteria
document and NAAQS for ozone. Key new health information falls into
four general areas: development of new-onset asthma, hospital admissions
for young children, school absence rate, and premature mortality.
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\122\ New Ozone Health and Environmental Effects References,
Published Since Completion of the Previous Ozone AQCD, National
Center for Environmental Assessment, Office of Research and
Development, U.S. Environmental Protection Agency, Research Triangle
Park, NC 27711 (7/2002). This document is available in Docket EPA-
HQ-OAR-2005-0036.
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Aggravation of existing asthma resulting from short-term ambient
ozone exposure was reported prior to the 1997 NAAQS standard and has
been observed in studies published subsequently.123 124 In
addition, a relationship between long-term ambient ozone concentrations
and the incidence of new-onset asthma in adult males (but not in
females) was reported by McDonnell et al. (1999).\125\ Subsequently, an
additional study suggests that incidence of new diagnoses of asthma in
children is associated with heavy exercise in communities with high
concentrations (i.e., mean 8-hour concentration of 59.6 parts per
billion (ppb) or greater) of ozone.\126\ This relationship was
documented in children who played 3 or more sports and thus spent more
time outdoors. It was not documented in those children who played one
or two sports.
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\123\ Thurston, G.D.; Lippman, M.L.; Scott, M.B.; Fine, J.M.
(1997) Summertime Haze Air Pollution and Children with Asthma.
American Journal of Respiratory Critical Care Medicine 155: 654-660.
\124\ Ostro, B.; Lipsett, M.; Mann, J.; Braxton-Owens, H.;
White, M. (2001) Air pollution and exacerbation of asthma in
African-American children in Los Angeles. Epidemiology 12(2): 200-208.
\125\ McDonnell, W.F.; Abbey, D.E.; Nishino, N.; Lebowitz, M.D.
(1999) ``Long-term ambient ozone concentration and the incidence of
asthma in nonsmoking adults: the AHSMOG study.'' Environmental
Research 80(2 Pt 1): 110-121.
\126\ McConnell, R.; Berhane, K.; Gilliland, F.; London, S.J.;
Islam, T.; Gauderman, W.J.; Avol, E.; Margolis, H.G.; Peters, J.M.
(2002) Asthma in exercising children exposed to ozone: a cohort
study. Lancet 359: 386-391.
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Previous studies have shown relationships between ozone and
hospital admissions in the general population. A study in Toronto
reported a significant relationship between 1-hour maximum ozone
concentrations and respiratory hospital admissions in children under
the age of two.\127\ Given the relative vulnerability of children in
this age category, there is particular concern about these findings.
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\127\ Burnett, R.T.; Smith-Doiron, M.; Stieb, D.; Raizenne,
M.E.; Brook, J.R.; Dales, R.E.; Leech, J.A.; Cakmak, S.; Krewski, D.
(2001) Association between ozone and hospitalization for acute
respiratory diseases in children less than 2 years of age. Am. J.
Epidemiol. 153: 444-452.
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Increased rates of illness-related school absenteeism have been
associated with 1-hour daily maximum and 8-hour average ozone
concentrations in studies conducted in Nevada \128\ in kindergarten to
6th grade and in Southern California in grades four through six.\129\
These studies suggest that higher ambient ozone levels may result in
increased school absenteeism.
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\128\ Chen, L.; Jennison, B.L.; Yang, W.; Omaye, S.T. (2000)
Elementary school absenteeism and air pollution. Inhalation Toxicol.
12: 997-1016.
\129\ Gilliland, F.D.; Berhane, K.; Rappaport, E.B.; Thomas,
D.C.; Avol, E.; Gauderman, W.J.; London, S.J.; Margolis, H.G.;
McConnell, R.; Islam, K.T.; Peters, J.M. (2001) The effects of
ambient air pollution on school absenteeism due to respiratory
illnesses. Epidemiology 12:43-54.
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The air pollutant most clearly associated with premature mortality
is PM, with many studies reporting such an association. However, recent
analyses provide evidence that short term ozone exposure is associated
with increased premature mortality. Bell et al. (2004) published new
analyses of the 95 cities in the National Morbidity, Mortality, and Air
Pollution Study (NMMAPS) data sets, showing associations between daily
mortality and the previous week's ozone concentrations which were
robust to adjustment for particulate matter, weather, seasonality, and
long-term trends.\130\ Although earlier analyses undertaken as part of
the NMMAPS did not report an effect of ozone on total mortality across
the full year, in those earlier studies the NMMAPS investigators did
observe an effect after limiting the analysis to summer, when ozone
levels are highest.131 132 Another recent study from 23
cities throughout Europe (APHEA2) also found an association between
ambient ozone and daily mortality.\133\ Similarly, other studies have
shown associations between ozone and mortality.134 135
Specifically, Toulomi et al. (1997) found that 1-hour maximum ozone
levels were associated with daily numbers of deaths in four cities
(London, Athens, Barcelona, and Paris), and a quantitatively similar
effect was found in a group of four additional cities (Amsterdam,
Basel, Geneva, and Zurich).
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\130\ Bell, M.L.; McDermott, A.; Zeger, S.L.; Samet, J.M.;
Dominici, F. Ozone and short-term mortality in 95 U.S. urban
communities, 1987-2000. JAMA 292(19): 2372-2378.
\131\ Samet, J.M.; Zeger, S.L.; Dominici, F.; Curriero, F.;
Coursac, I.; Dockery, D.W.; 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. This document is available in Docket EPA-
HQ-OAR-2005-0036.
\132\ Samet, J.M.; Zeger, S.L.; Dominici, F.; Curriero, F.;
Coursac, I.; Zeger, S. (2000) Fine Particulate Air Pollution and
Mortality in 20 U.S. Cities, 1987-1994. The New England Journal of
Medicine 343(24): 1742-1749.
\133\ Gryparis, A.; Forsberg, B.; Katsouyanni, K.; Analitis, A.;
Touloumi, G.; Schwartz, J.; Samoli, E.; Medina, S.; Anderson, H.R.;
Niciu, E.M.; Wichmann, H.E.; Kriz, B.; Kosnik, M.; Skorkovsky, J.;
Vonk, J.M.; Dortbudak, Z. (2004) Acute effects of ozone on mortality
from the ``Air Pollution and Health: A European Approach'' project.
Am. J. Respir. Crit. Care Med. 170: 1080-1087.
\134\ Thurston, G.D.; Ito, K. (2001) Epidemiological studies of
acute ozone exposures and mortality. J. Exposure Anal. Environ.
Epidemiol. 11: 286-294.
\135\ Touloumi, G.; Katsouyanni, K.; Zmirou, D.; Schwartz, J.;
Spix, C.; Ponce de Leon, A.; Tobias, A.; Quennel, P.; Rabczenko, D.;
Bacharova, L.; Bisanti, L.; Vonk, J.M.; Ponka, A. (1997) Short-term
effects of ambient oxidant exposure on mortality: A combined
analysis within the APHEA project. Am. J. Epidemiol. 146: 177-185.
---------------------------------------------------------------------------

In all, the new studies that have become available since the 8-hour
ozone standard was adopted in 1997 continue to demonstrate the harmful
effects of ozone on public health, and the need to attain and maintain
the ozone NAAQS.
3. Current and Projected 8-Hour Ozone Levels
Currently, ozone concentrations exceeding the level of the 8-hour
ozone NAAQS occur over wide geographic areas, including most of the
nation's major population centers.\136\ As of September 2005 there are
approximately 159 million people living in 126 areas designated as not
in attainment with the 8-hour ozone NAAQS. There are 474 full or
partial counties that make up the 8-hour ozone nonattainment areas.
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\136\ A map of the 8-hour ozone nonattainment areas is included
in the RIA for this proposed rule.
---------------------------------------------------------------------------

EPA has already adopted many emission control programs that are
expected to reduce ambient ozone levels. These control programs include
the Clean Air Interstate Rule (70 FR 25162, May 12, 2005), as well as
many mobile source rules (many of which are described in section V.D).
As a result of these programs, the number of areas that fail to achieve
the 8-hour ozone NAAQS is expected to decrease.
Based on the recent ozone modeling performed for the CAIR analysis
\137\, barring additional local ozone precursor controls, we estimate
37 Eastern counties (where 24 million people are projected to live)
will exceed the 8-hour ozone NAAQS in 2010. An additional 148 Eastern
counties (where 61 million people are projected to live) are expected
to be within 10 percent of violating the 8-hour ozone NAAQS in 2010.
---------------------------------------------------------------------------

\137\ Technical Support Document for the Final Clean Air
Interstate Rule Air Quality Modeling. This document is available in
Docket EPA-HQ-OAR-2005-0036.
---------------------------------------------------------------------------

States with 8-hour ozone nonattainment areas will be required to

[[Page 15829]]

take action to bring those areas into compliance in the future. Based
on the final rule designating and classifying 8-hour ozone
nonattainment areas (69 FR 23951, April 30, 2004), most 8-hour ozone
nonattainment areas will be required to attain the 8-hour ozone NAAQS
in the 2007 to 2013 time frame and then be required to maintain the 8-
hour ozone NAAQS thereafter.\138\ We also expect many of the 8-hour
ozone nonattainment areas to adopt additional emission reduction
programs, but we are unable to quantify or rely upon future reductions
from additional state and local programs that have not yet been
adopted. The expected ozone inventory reductions from the standards
proposed in this action may be useful to states in attaining or
maintaining the 8-hour ozone NAAQS.
---------------------------------------------------------------------------

\138\ The Los Angeles South Coast Air Basin 8-hour ozone
nonattainment area will have to attain before June 15, 2021.
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A metamodeling tool developed at EPA, the ozone response surface
metamodel, was used to estimate the effects of the proposed emission
reductions. The ozone response surface metamodel was created using
multiple runs of the Comprehensive Air Quality Model with Extensions
(CAMx). Base and proposed control CAMx metamodeling was completed for
two future years (2020, 2030) over a modeling domain that includes all
or part of 37 Eastern U.S. states. For more information on the response
surface metamodel, please see the RIA for this proposal or the Air
Quality Modeling Technical Support Document (TSD).
We have made estimates using the ozone response surface metamodel
to illustrate the types of change in future ozone levels that we would
expect to result from this proposed rule, as described in Chapter 3 of
the draft RIA. The proposed gas can controls are projected to result in
a very small net improvement in future ozone, after weighting for
population. Although the net future ozone improvement is small, some
VOC-limited areas in the Eastern U.S. are projected to have non-
negligible improvements in projected 8-hour ozone design values due to
the proposed gas can controls. As stated in Section VII.E.3, we view
these improvements as useful in meeting the 8-hour ozone NAAQS. These
net ozone improvements are in addition to reductions in levels of
benzene due to the proposed gas can controls.

D. Particulate Matter

The cold temperature vehicle controls proposed here will result in
reductions of primary PM being emitted by vehicles. In addition, both
the proposed vehicle controls and the proposed gas can controls will
reduce VOCs that react in the atmosphere to form secondary PM_2.5, namely
organic carbonaceous PM_2.5.
1. Background
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. PM is further described
by breaking it down into size fractions. PM₁₀ refers to
particles with an aerodynamic diameter less than or equal to a nominal
10 micrometers ([mu]m). PM_2.5 refers to fine particles,
those particles with an aerodynamic diameter less than or equal to a
nominal 2.5 [mu]m. Coarse fraction particles refer to those particles
with an aerodynamic diameter less than or equal to a nominal 10 [mu]m.
Inhalable (or ``thoracic'') coarse particles refer to those particles
with an aerodynamic diameter greater than 2.5 [mu]m but less than or
equal to 10 [mu]m. Ultrafine PM refers to particles with diameters of
less than 100 nanometers (0.1 [mu]m). Larger particles (>10 [mu]m) tend
to be removed by the respiratory clearance mechanisms, whereas smaller
particles are deposited deeper in the lungs. Ambient fine particles are
a complex mixture including sulfates, nitrates, chlorides, organic
carbonaceous material, elemental carbon, geological material, and
metals. Fine particles can remain in the atmosphere for days to weeks
and travel through the atmosphere hundreds to thousands of kilometers,
while coarse particles generally tend to deposit to the earth within
minutes to hours and within tens of kilometers from the emission source.
EPA has NAAQS for both PM_2.5 and PM₁₀. Both
the PM_2.5 and PM₁₀ NAAQS consist of a short-term
(24-hour) and a long-term (annual) standard. The 24-hour
PM_2.5 NAAQS is set at a level of 65 [mu]g/m\3\ based on the
98th percentile concentration averaged over three years. The annual
PM_2.5 NAAQS specifies an expected annual arithmetic mean not
to exceed 15 [mu]g/m\3\ averaged over three years. The 24-hour
PM₁₀ NAAQS is set at a level of 150 [mu]g/m\3\ not to be
exceeded more than once per year. The annual PM₁₀ NAAQS
specifies an expected annual arithmetic mean not to exceed 50 [mu]g/m\3\.
EPA has recently proposed to amend the PM NAAQS.\139\ The proposal
includes lowering the level of the primary 24-hour fine particle
standard from the current level of 65 micrograms per cubic meter
([mu]g/m\3\) to 35 [mu]g/m\3\, retaining the level of the annual fine
standard at 15 [mu]g/m\3\, and setting a new primary 24-hour standard
for certain inhalable coarse particles (the indicator is qualified so
as to include any ambient mix of PM_10-2.5 that is dominated
by resuspended dust from high-density traffic on paved roads and PM
generated by industrial and construction sources, and excludes any
ambient mix of PM_10-2.5 dominated by rural windblown dust
and soils and PM generated by agricultural and mining sources) at 70
[mu]g/m\3\. The Agency is also requesting comment on various other
standards for fine and inhalable coarse PM (71 FR 2620, Jan. 17, 2006).
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\139\ U.S. EPA, National Ambient Air Quality Standards for
Particulate Matter (71 FR 2620, Jan. 17, 2006). This document is
also available on the web at:
http://www.epa.gov/air/particlepollution/actions.html
2. Health Effects of PM
Scientific studies show ambient PM is associated with a series of
adverse health effects. These health effects are discussed in detail in
the 1997 PM criteria document, the recent 2004 EPA Criteria Document
for PM as well as the 2005 PM Staff Paper.140 141 142
Further discussion of health effects associated with PM can also be
found in the draft RIA for this proposal.
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\140\ U.S.EPA (1996) Air Quality Criteria for Particulate
Matter, EPA 600-P-95-001aF, EPA 600-P-95-001bF. This document is
available in Docket EPA-HQ-OAR-2005-0036.
\141\ U.S. EPA (2004) Air Quality Criteria for Particulate
Matter (Oct 2004), Volume I Document No. EPA600/P-99/002aF and
Volume II Document No. EPA600/P-99/002bF. This document is available
in Docket EPA-HQ-OAR-2005-0036.
\142\ U.S. EPA (2005) Review of the National Ambient Air Quality
Standard for Particulate Matter: Policy Assessment of Scientific and
Technical Information, OAQPS Staff Paper. EPA-452/R-05-005. This
document is available in Docket EPA-HQ-OAR-2005-0036.
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As described in the documents listed above, health effects
associated with short-term variation (e.g. hours to days) in ambient
PM_2.5 include premature mortality, hospital admissions,
heart and lung diseases, increased cough, lower-respiratory symptoms,
decrements in lung function and changes in heart rate rhythm and other
cardiac effects. Studies examining populations exposed to different
levels of air pollution over a number of years, including the Harvard
Six Cities Study and the American Cancer Society Study, show
associations between long-term exposure to ambient PM_2.5 and
premature mortality, including deaths attributed to cardiovascular
changes and lung cancer.

[[Page 15830]]

Recently, several studies have highlighted the adverse effects of
PM specifically from mobile sources.143 144 Studies have
also focused on health effects due to PM exposures on or near
roadways.\145\ Although these studies include all air pollution
sources, including both spark-ignition (gasoline) and diesel powered
vehicles, they indicate that exposure to PM emissions near roadways,
thus dominated by mobile sources, are associated with health effects.
The proposed vehicle controls may help to reduce exposures to mobile
source related PM_2.5. Additional information on near roadway
health effects can be found in Section III of this preamble.
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\143\ Laden, F.; Neas, L.M.; Dockery, D.W.; Schwartz, J. (2000)
Association of Fine Particulate Matter from Different Sources with
Daily Mortality in Six U.S. Cities. Environmental Health
Perspectives 108: 941-947.
\144\ Janssen, N.A.H.; Schwartz, J.; Zanobetti, A.; Suh, H.H.
(2002) Air Conditioning and Source-Specific Particles as Modifiers
of the Effect of PM₁₀ on Hospital Admissions for Heart
and Lung Disease. Environmental Health Perspectives 110: 43-49.
\145\ Riekider, M.; Cascio, W.E.; Griggs, T.R.; Herbst, M.C.;
Bromberg, P.A.; Neas, L.; Williams, R.W.; Devlin, R.B. (2003)
Particulate Matter Exposures in Cars is Associated with
Cardiovascular Effects in Healthy Young Men. Am. J. Respir. Crit.
Care Med. 169: 934-940.
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3. Current and Projected PM_2.5 Levels
EPA has recently finalized PM_2.5 nonattainment
designations (70 FR 943, Jan 5. 2005).\146\ As can be seen from the
designations, ambient PM_2.5 levels exceeding the level of
the PM_2.5 NAAQS are widespread throughout the country. There
are approximately 88 million people living in 39 areas (which include
all or part of 208 counties) designated as not in attainment with the
PM_2.5 NAAQS.
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\146\ US EPA, Air Quality Designations and Classifications for
the Fine Particles (PM_2.5) National Ambient Air Quality
Standards, December 17, 2004. (70 FR 943, Jan 5, 2005) This document
is also available on the web at: http://www.epa.gov/pmdesignations/.

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EPA has already adopted many emission control programs that are
expected to reduce ambient PM levels. These rules include the Clean Air
Interstate Rule (70 FR 25162, May 12, 2005), as well as many mobile
source rules. Section V.D details many of these mobile source
rules.\147\ As a result of these programs, the number of areas that
fail to achieve the 1997 PM_2.5 NAAQS is expected to
decrease. Based on modeling performed for the CAIR analysis, we
estimate that 28 Eastern counties (where 19 million people are
projected to live) will exceed the PM_2.5 standard in
2010.\148\ In addition, 56 Eastern counties (where 24 million people
are projected to live) are expected to be within 10 percent of
violating the PM_2.5 in 2010.
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\147\ The Clean Air Interstate Rule (CAIR) will reduce emissions
of SO₂ and NO_X from power plants in the
Eastern 37 states, reducing interstate transport of nitrogen oxides
and sulfur dioxide and helping cities and states in the East meet
the ozone and PM NAAQS. (70 FR 25162) (May 12, 2005).
\148\ Technical Support Document for the Final Clean Air
Interstate Rule Air Quality Modeling. This document is available in
Docket EPA-HQ-OAR-2005-0036.
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While the final implementation process for bringing the nation's
air into attainment with the 1997 PM_2.5 NAAQS is still being
completed in a separate rulemaking action, we expect that most areas
will need to attain the 1997 PM_2.5 NAAQS in the 2009 to 2014
time frame, and then be required to maintain the NAAQS thereafter. The
expected PM and VOC inventory reductions from the standards proposed in
this action will be useful to states in attaining or maintaining the
PM_2.5 NAAQS.
4. Current PM₁₀ Levels
Air quality monitoring data indicates that as of September 2005
approximately 29 million people live in 55 designated PM₁₀
nonattainment areas, which include all or part of 54 counties. The RIA
for this proposed rule lists the PM₁₀ nonattainment areas
and their populations.
Based on section 188 of the Act, we expect that most areas will
attain the PM₁₀ NAAQS no later than December 31, 2006,
depending on an area's classification and other factors, and then be
required to maintain the PM₁₀ NAAQS thereafter. The expected
PM and VOC inventory reductions from the standards proposed in this action
could be useful to states in maintaining the PM₁₀ NAAQS.\149\
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\149\ As mentioned above, the EPA has recently proposed to amend
the PM NAAQS, by establishing a new indicator for certain inhalable
coarse particles, and a new primary 24-hour standard for coarse
particles described by that indicator. EPA also proposed to revoke
the current 24-hour PM₁₀ standard in all areas of the
country except in those areas with a population of at least 100,000
people and which contain at least one monitor violating the 24-hour
PM₁₀ standard, based on the most recent 3 years of air
quality data. In addition, EPA proposed to revoke upon promulgation
of this rule the current annual PM₁₀ standard if EPA finalizes the
proposed primary standard for PM_10-2.5 (71 FR 2620, Jan. 17, 2006).
---------------------------------------------------------------------------

E. Other Environmental Effects

1. Visibility
a. Background
Visibility can be defined as the degree to which the atmosphere is
transparent to visible light.\150\ Visibility is important because it
has direct significance to people's enjoyment of daily activities in
all parts of the country. Individuals value good visibility for the
well-being it provides them directly, where they live and work, and in
places where they enjoy recreational opportunities. Visibility is also
highly valued in significant natural areas such as national parks and
wilderness areas, because of the special emphasis given to protecting
these lands now and for future generations. For more information on
visibility see the recent 2004 EPA Criteria Document for PM as well as
the 2005 PM Staff Paper.151 152
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\150\ National Research Council, 1993. Protecting Visibility in
National Parks and Wilderness Areas. National Academy of Sciences
Committee on Haze in National Parks and Wilderness Areas. National
Academy Press, Washington, DC. This document is available in Docket
EPA-HQ-OAR-2005-0036. This book can be viewed on the National
Academy Press Website at http://www.nap.edu/books/0309048443/html.

\151\ U.S. EPA (2004) Air Quality Criteria for Particulate
Matter (Oct 2004), Volume I Document No. EPA600/P-99/002aF and
Volume II Document No. EPA600/P-99/002bF. This document is available
in Docket EPA-HQ-OAR-2005-0036.
\152\ U.S. EPA (2005) Review of the National Ambient Air Quality
Standard for Particulate Matter: Policy Assessment of Scientific and
Technical Information, OAQPS Staff Paper. EPA-452/R-05-005. This
document is available in Docket EPA-HQ-OAR-2005-0036.
---------------------------------------------------------------------------

To address the welfare effects of PM on visibility, EPA set
secondary PM_2.5 standards in 1997 which would act in
conjunction with the establishment of a regional haze program. EPA
concluded that PM_2.5 causes adverse effects on visibility in
various locations, depending on PM concentrations and factors such as
chemical composition and average relative humidity and the secondary
(welfare-based) PM_2.5 NAAQS was established as equal to the
suite of primary (health-based) NAAQS (62 FR 38669, July 18, 1997).
Furthermore, Section 169 of the Act provides additional authorities to
remedy existing visibility impairment and prevent future visibility
impairment in the 156 national parks, forests and wilderness areas
categorized as mandatory Federal class I areas (62 FR 38680-81, July
18, 1997).\153\ In July 1999 the regional haze rule (64 FR 35714) was
put in place to protect the visibility in mandatory Federal class I
areas. Visibility can be said to be impaired in both PM_2.5
nonattainment areas and mandatory Federal class I areas.\154\
---------------------------------------------------------------------------

\153\ These areas are defined in section 162 of the Act as those
national parks exceeding 6,000 acres, wilderness areas and memorial
parks exceeding 5,000 acres, and all international parks which were
in existence on August 7, 1977.
\154\ As mentioned above, the EPA has recently proposed to amend
the PM NAAQS (71 FR 2620, Jan. 17, 2006). The proposal would set the
secondary NAAQS equal to the primary standards for both
PM_2.5 and PM_10-2.5. EPA also is taking comment
on whether to set a separate PM_2.5 standard, designed to
address visibility (principally in urban areas), on potential levels
for that standard within a range of 20 to 30 [mu]g/m3,
and on averaging times for the standard within a range of four to
eight daylight hours.

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[[Page 15831]]

b. Current Visibility Impairment
Data showing PM_2.5 nonattainment areas, and visibility
levels above background at the Mandatory Class I Federal Areas
demonstrate that unacceptable visibility impairment is experienced
throughout the U.S., in multi-state regions, urban areas, and remote
mandatory Federal class I areas.155 156 The mandatory
federal class I areas are listed in Chapter 3 of the draft RIA for this
action. The areas that have design values above the PM_2.5
NAAQS are also listed in Chapter 3 of the draft RIA for this action.
---------------------------------------------------------------------------

\155\ US EPA, Air Quality Designations and Classifications for
the Fine Particles (PM_2.5) National Ambient Air Quality
Standards, December 17, 2004. (70 FR 943, Jan 5. 2005) This document
is also available on the web at: http://www.epa.gov/pmdesignations/.
\156\ US EPA. Regional Haze Regulations, July 1, 1999. (64 FR
35714, July 1, 1999).
---------------------------------------------------------------------------

c. Future Visibility Impairment
Recent modeling for the Clean Air Interstate Rule (CAIR) was used
to project visibility conditions in mandatory Federal class I areas
across the country in 2015. The results for the mandatory Federal Class
I areas suggest that these areas are predicted to continue to have
annual average deciview levels above background in the future.\157\
Modeling done for the CAIR also projected PM_2.5 levels in
the Eastern U.S. in 2010. These projections include all sources of
PM_2.5, including the engines covered in this proposal, and
suggest that PM_2.5 levels above the 1997 NAAQS will persist
into the future.\158\
The vehicles that would be subject to the proposed standards
contribute to visibility concerns in these areas through both their
primary PM emissions and their VOC emissions, which contribute to the
formation of secondary PM_2.5. The gas cans that would be
subject to the proposed standards also contribute to visibility
concerns through their VOC emissions. Reductions in these direct PM and
VOC emissions will help to improve visibility across the nation,
including mandatory Federal class I areas.
---------------------------------------------------------------------------

\157\ The deciview metric describes perceived visual changes in
a linear fashion over its entire range, analogous to the decibel
scale for sound. A deciview of 0 represents pristine conditions. The
higher the deciview value, the worse the visibility, and an
improvement in visibility is a decrease in deciview value.
\158\ EPA recently proposed to revise the current secondary PM
NAAQS standards by making them identical to the suite of proposed
primary standards for fine and coarse particles (71 FR 2620, Jan. 17, 2006).
---------------------------------------------------------------------------

2. Plant Damage From Ozone
Ozone contributes to many environmental effects, with damage to
plants and ecosystems 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.
Prolonged ozone concentrations of 100 ppb can be phytotoxic to a large
number of plant species, and can produce acute injury and reduced crop
yield and biomass production. Ozone concentrations within the range of
50 to 100 ppb have the potential over a longer duration to create
chronic stress on vegetation that can result in reduced plant growth
and yield, shifts in competitive advantages in mixed populations,
decreased vigor, and injury. Ozone effects on vegetation are presented
in more detail in the 1996 Criteria Document and the 2005 draft
Criteria Document.
3. Atmospheric Deposition
Wet and dry deposition of ambient particulate matter delivers a
complex mixture of metals (e.g., mercury, zinc, lead, nickel, aluminum,
cadmium), organic compounds (e.g., POM, dioxins, furans) and inorganic
compounds (e.g., nitrate, sulfate) to terrestrial and aquatic
ecosystems. EPA's Great Waters Program has identified 15 pollutants
whose deposition to water bodies has contributed to the overall
contamination loadings to these Great Waters. These 15 compounds
include several heavy metals and a group known as polycyclic organic
matter (POM). Within POM are the polycyclic aromatic hydrocarbons
(PAHs). PAHs in the environment may be present in the gas or particle
phase, although the bulk will be adsorbed onto airborne particulate
matter. In most cases, human-made sources of PAHs account for the
majority of PAHs released to the environment. The PAHs are usually the
POMs of concern as many PAHs are probable human carcinogens.\159\ For
some watersheds, atmospheric deposition represents a significant input
to the total surface water PAH burden.160 161 Emissions from
mobile sources have been found to account for a percentage of the
atmospheric deposition of PAHs. For instance, recent studies have
identified gasoline and diesel vehicles as the major contributors in
the atmospheric deposition of PAHs to Chesapeake Bay, Massachusetts Bay
and Casco Bay.162 163 The vehicle controls being proposed
may help to reduce deposition of heavy metals and POM.
---------------------------------------------------------------------------

\159\ Deposition of Air Pollutants to the Great Waters-Third
Report to Congress, Office of Air Quality Planning and Standards,
June 2000, EPA453-R-00-005. This document is available in Docket
EPA-HQ-OAR-2005-0036.
\160\ Simcik, M.F.; Eisenrich, S.J.; Golden, K.A.; Liu, S.;
Lipiatou, E.; Swackhamer, D.L.; and Long, D.T. (1996) Atmospheric
Loading of Polycyclic Aromatic Hydrocarbons to Lake Michigan as
Recorded in the Sediments. Environ. Sci. Technol. 30:3039-3046.
\161\ Simcik, M.F.; Eisenrich, S.J.; and Lioy, P.J. (1999)
Source Apportionment and Source/Sink Relationships of PAHs in the
Coastal Atmosphere of Chicago and Lake Michigan. Atmospheric
Environment 33: 5071-5079.
\162\ Dickhut, R.M.; Canuel, E.A.; Gustafson, K.E.; Liu, K.;
Arzayus, K.M.; Walker, S.E.; Edgecombe, G.; Gaylor, M.O.; and
McDonald, E.H. (2000) Automotive Sources of Carcinogenic Polycyclic
Aromatic Hydrocarbons Associated with Particulate Matter in the
Chesapeake Bay Region. Environ. Sci. Technol. 34: 4635-4640.
\163\ Golomb, D.; Barry, E.; Fisher, G.; Varanusupakul, P.;
Koleda, M.; amd Rooney, T. (2001) Atmospheric Deposition of
Polycyclic Aromatic Hydrocarbons near New England Coastal Waters.
Atmospheric Environment 35: 6245-6258.
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4. Materials Damage and Soiling
The deposition of airborne particles can also reduce the aesthetic
appeal of buildings and culturally important articles through soiling,
and can contribute directly (or in conjunction with other pollutants)
to structural damage by means of corrosion or erosion.\164\ Particles
affect materials principally by promoting and accelerating the
corrosion of metals, by degrading paints, and by deteriorating building
materials such as concrete and limestone. Particles contribute to these
effects because of their electrolytic, hygroscopic, and acidic
properties, and their ability to sorb corrosive gases (principally
sulfur dioxide). The rate of metal corrosion depends on a number of
factors, including the deposition rate and nature of the pollutant; the
influence of the metal protective corrosion film; the amount of
moisture present; variability in the electrochemical reactions; the
presence and concentration of other surface electrolytes; and the
orientation of the metal surface.
---------------------------------------------------------------------------

\164\ U.S. EPA (2005) Review of the National Ambient Air Quality
Standards for Particulate Matter: Policy Assessment of Scientific
and Technical Information, OAQPS Staff Paper. This document is
available in Docket EPA-HQ-OAR-2005-0036.
---------------------------------------------------------------------------

V. What Are Mobile Source Emissions Over Time and How Would This
Proposal Reduce Emissions, Exposure and Associated Health Effects?

A. Mobile Source Contribution to Air Toxics Emissions

In 1999, based on the National Emissions Inventory (NEI), mobile
sources accounted for 44% of total

[[Page 15832]]

emissions of 188 hazardous air pollutants (on the Clean Air Act section
112(b) list of hazardous air pollutants). Diesel particulate matter
(PM) is not included in this list of 188 pollutants. Sixty-five percent
of the mobile source tons in this inventory were attributable to
highway mobile sources, and the remainder to nonroad sources.
Furthermore, over 90% of mobile source emissions of air toxics (not
including diesel PM) are attributable to gasoline vehicles and equipment.
Recently, EPA projected trends in air toxic emissions (not
including diesel PM) to 2020, using the 1999 National Emissions
Inventory (NEI) as a baseline.\165\ Overall, air toxic emissions are
projected to decrease from 5,030,000 tons in 1999 to 4,010,000 tons in
2020, as a result of emission controls on major, area, and mobile
sources. In the absence of Clean Air Act emission controls currently in
place, EPA estimates air toxic emissions would total 11,590,000 tons in
2020.
---------------------------------------------------------------------------

\165\ Strum, M., R. Cook, J. Thurman, D. Ensley, A. Pope, T.
Palma, R. Mason, H. Michaels, and S. Shedd. 2005. Projection of
Hazardous Air Pollutant Emissions to Future Years. Science of the
Total Environment, in press.
---------------------------------------------------------------------------

Figure V.A-1 depicts the contributions of source categories to air
toxic emissions between 1990 and 2020.\166\ As indicated in Figure V.A-
1, mobile source air toxic emissions will be reduced 60% between 1999
and 2020, from 2.2 million to 880,000 tons. This reduction will occur
despite a projected 57% increase in vehicle miles traveled, and a
projected 63% increase in nonroad activity, based on units of work
called horsepower-hours. It should be noted, however, that EPA
anticipates mobile source air toxic emissions will begin to increase
after 2020, from about 880,000 tons in 2020 to 920,000 tons in 2030.
This is because, after 2020, reductions from control programs will be
outpaced by increases in activity.
---------------------------------------------------------------------------

\166\ It should be noted that after 2010, stationary source
emissions are based only on economic growth, and do not account for
reductions from ongoing toxics programs such as the urban air toxics
program, residual risk standards and area source program, which are
expected to further reduce toxics.
---------------------------------------------------------------------------

In 1999, 29% of air toxic emissions were from highway vehicles and
15% from nonroad equipment. Moreover, 54% of air toxic emissions from
highway vehicles were emitted by light-duty gasoline vehicles (LDGVs)
and 37% by light-duty trucks (LDGTs) (see Table V.A-1). EPA projects
that in 2020, only 27% of highway vehicle toxic emissions will be from
LDGVs and 63% will be from LDGTs. Air toxic emissions from nonroad
equipment are dominated by lawn and garden equipment, recreational
equipment, and pleasure craft, which collectively accounted for almost
80% of nonroad toxic emissions in 1999 and 2020 (see Table V.A-2).
Figure V.A-1Contribution of Source Categories to Air Toxic
Emissions, 1990 to 2020 (not including diesel particulate matter).
Note: Dashed line represents projected emissions without Clean Air Act
controls.

[[Page 15833]]
[GRAPHIC]
[TIFF OMITTED]
TP29MR06.001

If diesel PM emissions were added to the mobile source total,
mobile sources would account for 48% of a total 5,398,000 tons in 1999.
Figure V.A.-2 summarizes the trend in diesel PM between 1999 and 2020,
by source category. Diesel PM emissions will be reduced from 368,000
tons in 1999 to 114,000 tons in 2020, a decrease of 70%. As controls on
highway diesel engines and nonroad diesel engines phase in, diesel-
powered locomotives and commercial marine vessels increase from 11% of
the inventory in 1999 to 27% in 2020.
Subsequent to the development of these projected inventories for
mobile source air toxics, a number of inventory revisions have
occurred. Data EPA has collected indicate that the MOBILE6.2 emission
factor model is under predicting hydrocarbon emissions (including air
toxics) and PM emissions at lower temperatures, from light-duty
vehicles meeting National Low Emission Vehicle (NLEV) and Tier 2
tailpipe standards. The inventories presented in sections V.B, V.C.,
and V.E. reflect these enhancements.

Table V.A-1.--Percent Contribution of Vehicle Classes to Highway Vehicle Air Toxic Emissions, 1999 to 2020
[Not including diesel particulate matter]
----------------------------------------------------------------------------------------------------------------
Vehicle 1999 (%) 2007 (%) 2010 (%) 2015 (%) 2020 (%)
----------------------------------------------------------------------------------------------------------------
Light-Duty Gasoline Vehicles................... 54 41 37 31 27
Light-Duty Gasoline Trucks..................... 37 49 53 59 63
Heavy-Duty Gasoline Vehicles................... 6 5 4 4 3
Heavy-Duty Diesel Vehicles..................... 3 4 4 4 5
Other (motorcycles and light-duty diesel 1 1 1 2 2
vehicles and trucks)..........................
----------------------------------------------------------------------------------------------------------------

[[Page 15834]]

Table V.A-2.--Contribution of Equipment Types to Nonroad Air Toxic Emissions, 1999 to 2020
----------------------------------------------------------------------------------------------------------------
Equipment type 1999 (%) 2007 (%) 2010 (%) 2015 (%) 2020 (%)
----------------------------------------------------------------------------------------------------------------
Lawn and Garden................................ 26 18 17 21 25
Pleasure Craft................................. 34 27 25 25 25
Recreational................................... 19 38 40 35 29
All Others..................................... 21 17 18 19 21
----------------------------------------------------------------------------------------------------------------
[GRAPHIC]
[TIFF OMITTED]
TP29MR06.002

B. VOC Emissions From Mobile Sources

Table V.B-1 presents 48-State VOC emissions from key mobile source
sectors in 1999, 2010, 2015, and 2020, not including the effects of
this proposed rule. The 1999 inventory estimates for nonroad equipment
were obtained from the National Emissions Inventory, and the 2010 and
later year estimates were obtained from the inventories developed for
the Clean Air Interstate Air Quality Rule (CAIR). The table provides
emissions for nonroad equipment such as commercial marine vessels,
locomotives, aircraft, lawn and garden equipment, recreational vehicles
and boats, industrial equipment, and construction equipment. The
estimates for highway vehicle classes were developed for this rule. The
estimates for light-duty gasoline vehicles reflect revised estimates of
hydrocarbon emissions at low temperatures.

Table V.B-1.--48-State VOC Emissions (Tons) From Key Mobile Source Sectors in 1999, 2010, 2015, and 2020
[Without this proposed rule]
----------------------------------------------------------------------------------------------------------------
Category 1999 2010 2015 2020
----------------------------------------------------------------------------------------------------------------
Light Duty Gasoline Vehicles and Trucks......... 4,873,000 2,896,000 2,566,000 2,486,000

[[Page 15835]]

Heavy Duty and Other Highway Vehicles........... 672,000 255,000 212,000 200,000
Nonroad Equipment............................... 2,785,000 1,739,000 1,500,000 1,387,000
----------------------------------------------------------------------------------------------------------------

VOC emissions from highway vehicles are about twice those from
nonroad equipment in 1999. Emissions from both highway vehicles and
nonroad equipment decline substantially between 1999 and 2020 as a
result of EPA control programs that are already adopted. The VOC
emission reductions associated with this proposed rule are presented in
section V.E, below.

C. PM Emissions From Mobile Sources

Table V.C-1 presents 48-State PM_2.5 \167\ emissions from
key mobile source sectors in 1999, 2010, 2015, and 2020, not including
the effects of this proposed rule. The estimates in Table V.C-1 come
from the same sources as the VOC estimates in section V.B. EPA is
considering revisions to estimates of the PM emissions inventory for
motor vehicles. Recent data suggest PM emissions are significantly
higher than currently estimated in the MOBILE6 emissions model. In
addition, testing done for this rule demonstrates that PM emissions are
elevated at cold temperatures. The estimates in Table V.C-1 do not
account for the effects of cold temperature.
---------------------------------------------------------------------------

\167\ PM_2.5 is particulate matter under 2.5 microns
in diameter. Over 85% of the mass of PM from mobile sources is PM_2.5.

Table V.C-1--48-State PM2.5 Emissions (Tons) from Key Mobile Source Sectors in 1999, 2010, 2015, and 2020
[Without this proposed rule]
----------------------------------------------------------------------------------------------------------------
Category 1999 2010 2015 2020
----------------------------------------------------------------------------------------------------------------
Light-Duty Gasoline Vehicles and Trucks......... 48,000 33,000 36,000 39,000
Heavy-Duty and Other Highway Vehicles........... 136,000 51,000 28,000 20,000
Nonroad Equipment............................... 332,000 232,000 201,000 178,000
----------------------------------------------------------------------------------------------------------------

Section V.E, below, presents estimates of PM emission reductions
associated with the proposed cold-temperature vehicle standards.

D. Description of Current Mobile Source Emissions Control Programs That
Reduce MSATs

As described in section V.A, existing mobile source control
programs will reduce MSAT emissions (not including diesel PM) by 60%
between 1999 and 2020. Diesel PM from mobile sources will be reduced by
70% between 1999 and 2020. The mobile source programs include controls
on fuels, highway vehicles, and nonroad equipment. These programs are
also reducing hydrocarbons and PM more generally, as well as oxides of
nitrogen. The sections immediately below provide general descriptions
of these programs, as well as voluntary programs to reduce mobile
source emissions, such as the National Clean Diesel Campaign and Best
Workplaces for Commuters. A more detailed description of mobile source
programs is provided in Chapter 2 of the RIA.
1. Fuels Programs
Several federal fuel programs reduce MSAT emissions. Some of these
programs directly control air toxics, such as the reformulated gasoline
(RFG) program's benzene content limit and required reduction in total
toxics emissions, and the anti-backsliding requirements of the anti-
dumping and current MSAT programs, which require that gasoline cannot
get dirtier with respect to toxics emissions. Others, such as the
gasoline sulfur program, control toxics indirectly by reducing
hydrocarbon and related toxics emissions.
a. RFG
The RFG program contains two direct toxics control requirements.
The first is a fuel benzene standard, requiring RFG to average no
greater than 0.95 volume percent benzene annually (on a refinery or
importer basis). The RFG benzene requirement includes a per-gallon cap
on fuel benzene level of 1.3 volume percent. In 1990, when the Clean
Air Act was amended to require reformulated gasoline, fuel benzene
averaged 1.60 volume percent. For a variety of reasons, including other
regulations, chemical product prices and refining efficiencies, most
refiners and importers have achieved significantly greater reductions
in benzene than required by the program. In 2003, RFG benzene content
averaged 0.62 percent. The RFG benzene requirement includes a per-
gallon cap on fuel benzene level of 1.3 volume percent.
The second RFG toxics control requires that RFG achieve a specific
level of toxics emissions reduction. The requirement has increased in
stringency since the RFG program began in 1995, when the requirement
was that RFG annually achieve a 16.5% reduction in total (exhaust plus
evaporative) air toxics emissions. Currently, a 21.5% reduction is
required. These reductions are determined using the Complex Model. As
mentioned above, for a variety of reasons most regulated parties have
overcomplied with the required toxics emissions reductions. During
1998-2000, RFG achieved, on average, a 27.5% reduction in toxics emissions.
b. Anti-Dumping
The anti-dumping regulations were intended to prevent the dumping
of ``dirty'' gasoline components, which

[[Page 15836]]

were removed to produce RFG, into conventional gasoline (CG). Since the
dumping of ``dirty'' gasoline components, for example, benzene or
benzene-containing blending streams, would show up as increases in
toxics emissions, the anti-dumping regulations require that a refiner's
or importer's CG be no more polluting with respect to toxics emissions
than the refiner's or importer's 1990 gasoline. The anti-dumping
program considers only exhaust toxics emissions and does not include
evaporative emissions.\168\ Refiners and importers have either a unique
individual anti-dumping baseline or they have the statutory anti-
dumping baseline if they did not fulfill the minimum requirements for
developing a unique individual baseline. In 1990, average exhaust
toxics emissions (as estimated by the Complex Model) were 104.5 mg/
mile; \169\ in 2004, CG exhaust toxics emissions averaged 90.7 mg/mile.
Although CG has no benzene limit, benzene levels have declined
significantly from the 1990 level of 1.6 volume percent to 1.1 volume
percent for CG in 2004.
---------------------------------------------------------------------------

\168\ See RFG rule for why evaporative emissions are not
included in the anti-dumping toxics determination.
\169\ Phase II.
---------------------------------------------------------------------------

c. 2001 Mobile Source Air Toxics Rule (MSAT1)
As discussed above, both RFG and CG have, on average, exceeded
their respective toxics control requirements. In 2001, EPA issued a
mobile source air toxics rule (MSAT1, for the purposes of this second
proposal), as discussed in section I.D. The intent of MSAT1 is to
prevent refiners and importers from backsliding from the toxics
performance that was being achieved by RFG and CG. In order to lock in
superior levels of control, the rule requires that the annual average
toxics performance of gasoline must be at least as clean as the average
performance of the gasoline produced or imported during the three-year
period 1998-2000. The period 1998-2000 is called the baseline period.
Toxics performance is determined separately for RFG and CG, in the same
manner as the toxics determinations required by the RFG \170\ and anti-
dumping rules.
---------------------------------------------------------------------------

\170\ 40 CFR Part 80, Subpart D.
---------------------------------------------------------------------------

Like the anti-dumping provisions, MSAT1 utilizes an individual
baseline against which compliance is determined. The average 1998-2000
toxics performance level, or baseline, is determined separately for
each refinery and importer.\171\ To establish a unique individual MSAT1
baseline, EPA requires each refiner and importer to submit
documentation supporting the determination of the baseline. Most
refiners and many importers in business during the baseline period had
sufficient data to establish an individual baseline. An MSAT1 baseline
volume is associated with each unique individual baseline value. The
MSAT1 baseline volume reflects the average annual volume of such
gasoline produced or imported during the baseline period. Refiners and
importers who did not have sufficient refinery production or imports
during 1998-2000 to establish a unique individual MSAT1 baseline must
use the default baseline provided in the rule.
---------------------------------------------------------------------------

\171\ Except for those who comply with the anti-dumping
requirements for conventional gasoline on an aggregate basis, in
which case the MSAT1 requirements for conventional gasoline must be
met on the same aggregate basis (40 CFR Part 80, Subpart E).
---------------------------------------------------------------------------

The MSAT1 program began with the annual averaging period beginning
January 1, 2002. Since then, the toxics performance for RFG has
improved from a baseline period average of 27.5% reduction to 29.5%
reduction in 2003. Likewise, CG toxics emissions have decreased from an
average of 95 mg/mile during 1998-2000 to 90.7 mg/mile in 2003.
d. Gasoline Sulfur
EPA's gasoline sulfur program \172\ requires, beginning in 2006,
that sulfur levels in gasoline can be no higher in any one batch than
80 ppm, and must average 30 ppm annually. When fully effective,
gasoline will have 90 percent less sulfur than before the program.
Reduced sulfur levels are necessary to ensure that vehicle emission
control systems are not impaired. These systems effectively reduce non-
methane organic gas (NMOG) emissions, of which some are air toxics.
With lower sulfur levels, emission control technologies can work longer
and more efficiently. Both new and older vehicles benefit from reduced
gasoline sulfur levels.
---------------------------------------------------------------------------

\172\ 65 FR 6822 (February 10, 2000).
---------------------------------------------------------------------------

e. Gasoline Volatility
A fuel's volatility defines its evaporation characteristics. A
gasoline's volatility is commonly referred to as its Reid vapor
pressure, or RVP. Gasoline summertime RVP ranges from about 6-9 psi,
and wintertime RVP ranges from about 9-14 psi, when additional vapor is
required for starting in cold temperatures. Gasoline vapors contain a
subset of the liquid gasoline components, and thus can contain toxics
compounds such as benzene. EPA has controlled summertime gasoline RVP
since 1989 primarily as a VOC and ozone precursor control, which also
results in some toxics pollutant reductions.
f. Diesel Fuel
In early 2001, EPA issued rules requiring that diesel fuel for use
in highway vehicles contain no more than 15 ppm sulfur beginning June
1, 2006.\173\ This program contains averaging, banking and trading
provisions, as well as other compliance flexibilities. In June 2004,
EPA issued rules governing the sulfur content of diesel fuel used in
nonroad diesel engines.\174\ In the nonroad rule, sulfur levels are
limited to a maximum of 500 ppm sulfur beginning in 2007 (current
levels are approximately 3000 ppm). In 2010, nonroad diesel sulfur
levels must not exceed 15 ppm.
---------------------------------------------------------------------------

\173\ 66 FR 5002 (January 18, 2001) http://www.epa.gov/otaq/diesel.html.
\174\ 69 FR 38958 (June 29, 2004).
---------------------------------------------------------------------------

EPA's diesel fuel requirements are part of a comprehensive program
to combine engine and fuel controls to achieve the greatest emission
reductions. The diesel fuel provisions enable the use of advanced
emission-control technologies on diesel vehicles and engines. The
diesel fuel requirements will also provide immediate public health
benefits by reducing PM emissions from current diesel vehicles and engines.
g. Phase-Out of Lead in Gasoline
One of the first programs to control toxic emissions from motor
vehicles was the removal of lead from gasoline. Beginning in the mid-
1970s, unleaded gasoline was phased in to replace leaded gasoline. The
phase-out of leaded gasoline was completed January 1, 1996, when lead
was banned from motor vehicle gasoline. The removal of lead from
gasoline has essentially eliminated on-highway mobile source emissions
of this highly toxic substance.
2. Highway Vehicle and Engine Programs
The 1990 Clean Air Act Amendments set specific emission standards
for hydrocarbons and for PM. Air toxics are present in both of these
pollutant categories. As vehicle manufacturers develop technologies to
comply with the hydrocarbon (HC) and particulate standards (e.g., more
efficient catalytic converters), air toxics are reduced as well. Since
1990, we have developed a number of programs to address exhaust and
evaporative hydrocarbon emissions and PM emissions.
Two of our recent initiatives to control emissions from motor vehicles

[[Page 15837]]

and their fuels are the Tier 2 control program for light-duty vehicles
and the 2007 heavy-duty engine rule. Together these two initiatives
define a set of comprehensive standards for light-duty and heavy-duty
motor vehicles and their fuels. In both of these initiatives, we treat
vehicles and fuels as a system. The Tier 2 control program establishes
stringent tailpipe and evaporative emission standards for light-duty
vehicles and a reduction in sulfur levels in gasoline fuel beginning in
2004.\175\ The 2007 heavy-duty engine rule establishes stringent
exhaust emission standards for new heavy-duty engines and vehicles for
the 2007 model year as well as reductions in diesel fuel sulfur levels
starting in 2006.\176\ Both of these programs will provide substantial
emissions reductions through the application of advanced technologies.
We expect 90% reductions in PM from new diesel engines compared to
engines under current standards.
---------------------------------------------------------------------------

\175\ 65 FR 6697, February 10, 2000.
\176\ 66 FR 5001, January 18, 2001.
---------------------------------------------------------------------------

Some of the key earlier programs controlling highway vehicle and
engine emissions are the Tier 1 and NLEV standards for light-duty
vehicles and trucks; enhanced evaporative emissions standards; the
supplemental federal test procedures (SFTP); urban bus standards; and
heavy-duty diesel and gasoline standards for the 2004/2005 time frame.
3. Nonroad Engine Programs
There are various categories of nonroad engines, including land-
based diesel engines (e.g., farm and construction equipment), small
land-based spark-ignition (SI) engines (e.g., lawn and garden
equipment, string trimmers), large land-based SI engines (e.g.,
forklifts, airport ground service equipment), marine engines (including
diesel and SI, propulsion and auxiliary, commercial and recreational),
locomotives, aircraft, and recreational vehicles (off-road motorcycles,
``all terrain'' vehicles and snowmobiles). Chapter 2 of the RIA
provides more information about these programs. As with highway
vehicles, the VOC standards we have established for nonroad engines
will also significantly reduce VOC-based toxics from nonroad engines.
In addition, the standards for diesel engines (in combination with the
stringent sulfur controls on nonroad diesel fuel) will significantly
reduce diesel PM and exhaust organic gases, which are mobile source air
toxics.
In addition to the engine-based emission control programs described
below, fuel controls will also reduce emissions of air toxics from
nonroad engines. For example, restrictions on gasoline formulation (the
removal of lead, limits on gasoline volatility and RFG) are projected
to reduce nonroad MSAT emissions because most gasoline-fueled nonroad
vehicles are fueled with the same gasoline used in on-highway vehicles.
An exception to this is lead in aviation gasoline. Aviation gasoline,
used in general (as opposed to commercial) aviation, is a high octane
fuel used in a relatively small number of aircraft (those with piston
engines). Such aircraft are generally used for personal transportation,
sightseeing, crop dusting, and similar activities.
4. Voluntary Programs
In addition to the fuel and engine control programs described
above, we are actively promoting several voluntary programs to reduce
emissions from mobile sources, such as the National Clean Diesel
Campaign, anti-idling measures, and Best Workplaces for Commuters.
While the stringent emissions standards described above apply to new
highway and nonroad diesel engines, it is also important to reduce
emissions from the existing fleet of about 11 million diesel engines.
EPA has launched a comprehensive initiative called the National Clean
Diesel Campaign, one component of which is to promote the reduction of
emissions in the existing fleet of engines through a variety of cost-
effective and innovative strategies. The goal of the Campaign is to
reduce emissions from the 11 million existing engines by 2014. Emission
reduction strategies include switching to cleaner fuels, retrofitting
engines through the addition of emission control devices, and engine
replacement. For example, installing a diesel particulate filter
achieves diesel particulate matter reductions of approximately 90
percent (when combined with the use of ultra low sulfur diesel fuel).
The Energy Policy Act of 2005 includes grant authorizations and other
incentives to help facilitate voluntary clean diesel actions nationwide.
The National Clean Diesel Campaign is focused on leveraging local,
state, and federal resources to retrofit or replace diesel engines,
adopt best practices, and track and report results. The Campaign
targets five key sectors: School buses, ports, construction, freight,
and agriculture.
Reducing vehicle idling provides important environmental benefits.
As a part of their daily routine, truck drivers often keep their
vehicles at idle during stops to provide power, heat and air
conditioning. EPA's SmartWay Transport Partnership is helping the
freight industry to adopt innovative idle reduction technologies and
take advantage of proven systems that provide drivers with basic
necessities without using the engine. To date, there are 50 stationary
anti-idling projects, and mobile technology has been installed on
nearly 20,000 trucks. The SmartWay Transport Partnership also works
with the freight industry to reduce fuel use (with a concomitant
reduction in emissions) by promoting a wide range of new technologies
such as advanced aerodynamics, single-wide tires, weight reduction
speed control and intermodal shipping.
Daily commuting represents another significant source of emissions
from motor vehicles. EPA's Best Workplaces for CommutersSM
program is working with employers across the country to reverse the
trend of longer, single-occupancy vehicle commuting. OTAQ has created a
national list of the Best Workplaces for Commuters to formally
recognize employers that offer superior commuter benefits such as free
transit passes, subsidized vanpools/carpools, and flexi-place, or work-
from-home, programs. More than 1,300 employers representing 2.8 million
U.S. workers have been designated Best Workplaces for Commuters.
Much of the growth in the Best Workplaces for Commuters program has
been through metro area-wide campaigns. Since 2002, EPA has worked with
coalitions in 14 major metropolitan areas to increase the penetration
of commuter benefits in the marketplace and the visibility of the
companies that have received the BWC designation. Another significant
path by which the program has grown is through Commuter Districts
including corporate and industrial business parks, shopping malls,
business improvement districts and downtown commercial areas. To date
EPA has granted the Best Workplaces for Commuters ``District''
designation to twenty locations across the country including downtown
Denver, Houston, Minneapolis and Tampa.

E. Emission Reductions From Proposed Controls

1. Proposed Vehicle Controls
We are proposing a hydrocarbon standard for gasoline passenger
vehicles at cold temperatures. This standard will reduce VOC at
temperatures below 75 [deg]F, including air toxics such as benzene,
1,3-butadiene, formaldehyde, acetaldehyde, acrolein and naphthalene,
and will also reduce emissions of direct and secondary PM. We are also
proposing new evaporative emissions standards for Tier 2 vehicles
starting in

[[Page 15838]]

2009. These new evaporative standards reflect the emissions levels
already being achieved by manufacturers.
a. Volatile Organic Compounds (VOC)
Table V.E-1 shows the VOC exhaust emission reductions from light-
duty gasoline vehicles and trucks that would result from our proposed
standards. The proposed standards would reduce VOC emissions in 2030 by
32%. Overall VOC exhaust emissions from these vehicles would be reduced
by 81% between 1999 and 2030 (including the effects of the proposed
standards as well as standards already in place, such as Tier 2).

Table V.E-1.--Estimated National Reductions in Exhaust VOC Emissions From Light-Duty Gasoline Vehicles and
Trucks, 1999 to 2030
----------------------------------------------------------------------------------------------------------------
1999 2015 2020 2030
----------------------------------------------------------------------------------------------------------------
VOC Without Rule (tons)......................... 4,899,891 2,625,076 2,556,751 2,899,269
VOC With Proposed Vehicle Standards (tons)...... N.A 2,305,202 2,020,267 1,985,830
VOC Reductions from Proposed Vehicle Standards N.A 319,874 536,484 913,439
(tons).........................................
Percentage Reduction............................ N.A 12 21 32
----------------------------------------------------------------------------------------------------------------

b. Toxics
In 2030, we estimate that the proposed vehicle standards would
result in a 38% reduction in benzene emissions and 37% reduction in
total emissions of the MSATs \177\ from light-duty vehicles and trucks
(see Tables V.E-2 and V.E-3).
---------------------------------------------------------------------------

\177\ Table IV.A-1 lists the MSATs included in this analysis.

Table V.E-2.--Estimated National Reductions in Benzene Exhaust Emissions From Light-Duty Gasoline Vehicles and
Trucks, 1999 to 2030
----------------------------------------------------------------------------------------------------------------
1999 2015 2020 2030
----------------------------------------------------------------------------------------------------------------
Benzene Without Rule (tons)..................... 171,154 101,355 106,071 124,897
Benzene With Proposed Vehicle Standards (tons).. N.A. 84,496 77,966 77,208
Benzene Reductions from Proposed Vehicle N.A. 16,859 28,105 47,689
Standards (tons)...............................
Percentage Reduction............................ N.A. 17 26 38
----------------------------------------------------------------------------------------------------------------

Table V.E-3.--Estimated National Reductions in Exhaust MSAT Emissions From Light-Duty Gasoline Vehicles and
Trucks, 1999 to 2030
----------------------------------------------------------------------------------------------------------------
1999 2015 2020 2030
----------------------------------------------------------------------------------------------------------------
MSATs Without Rule (tons)....................... 1,341,572 707,877 724,840 844,366
MSATs With Proposed Vehicle Standards (tons).... N.A. 599,492 543,332 535,479
MSAT Reductions from Proposed Vehicle Standards N.A. 108,385 181,509 308,887
(tons).........................................
Percentage Reduction............................ N.A. 15 25 37
----------------------------------------------------------------------------------------------------------------

c. PM_2.5
EPA expects that the proposed cold-temperature vehicle standards
would reduce exhaust emissions of direct PM_2.5 by over
20,000 tons in 2030 nationwide (see Table V.E-4 below). Our analysis of
the data from vehicles meeting Tier 2 emission standards indicate that
PM emissions follow a monotonic relationship with temperature, with
lower temperatures corresponding to higher vehicle emissions.
Additionally, the analysis shows the ratio of PM to total non-methane
hydrocarbons (NMHC) to be independent of temperature.\178\ Our testing
indicates that strategies which reduce NMHC start emissions at cold
temperatures also reduce direct PM emissions. Based on these findings,
direct PM emissions at cold temperatures were estimated using a
constant PM to NMHC ratio. PM emission reductions were estimated by
assuming that NMHC reductions will result in proportional reductions in
PM. This assumption is supported by test data. For more detail, see
Chapter 2.1 of the RIA.
---------------------------------------------------------------------------

\178\ U.S. EPA. 2005. Cold-temperature exhaust particulate
matter emissions. Memorandum from Chad Bailey to docket EPA-HQ-OAR-
2005-0036.

Table V.E-4.--Estimated National Reductions in Direct PM2.5 Exhaust Emissions From Light-Duty Gasoline Vehicles
and Trucks, 2015 to 2030
----------------------------------------------------------------------------------------------------------------
2015 2020 2030
----------------------------------------------------------------------------------------------------------------
PM2.5 Reductions from Proposed Vehicle Standards (tons)......... 7,037 11,803 20,096
----------------------------------------------------------------------------------------------------------------

2. Proposed Fuel Benzene Controls
The proposed fuel benzene controls would reduce benzene exhaust and
evaporative emissions from both on-road and nonroad mobile sources that
are fueled by gasoline. In addition, the proposed fuel benzene standard
would reduce evaporative emissions from gasoline distribution and gas cans.

[[Page 15839]]

Impacts on 1,3-butadiene, formaldehyde, and acetaldehyde emissions are
not significant, but are presented in Chapter 2 of the RIA. We do not
expect the fuel benzene standard to have quantifiable impacts on any
other air toxics, total VOCs, or PM.
Table V.E-5 shows national estimates of total benzene emissions
from these source sectors with and without the proposed fuel benzene
standard. These estimates do not include effects of the proposed
vehicle or gas can standards (see section V.E.4 for the combined
effects of the controls). The proposed fuel benzene standard would
reduce total benzene emissions from on-road and nonroad gasoline mobile
sources, gas cans, and gasoline distribution by 12% in 2015.

Table V.E-5.--Estimated Reductions in Benzene Emissions From Proposed Gasoline Standard by Sector in 2015
----------------------------------------------------------------------------------------------------------------
Gasoline on- Gasoline
road mobile nonroad mobile Gas cans Gasoline Total
sources sources distribution
----------------------------------------------------------------------------------------------------------------
Benzene Without Rule (tons)..... 103,797 37,747 2,262 5,999 149,805
Benzene With Proposed Gasoline 92,513 33,247 1,359 4,054 131,173
Standard (tons)................
Benzene Reductions from Proposed 11,284 4,500 903 1,945 18,632
Gasoline Standard (tons).......
Percentage Reduction............ 11 12 40 32 12
----------------------------------------------------------------------------------------------------------------

3. Proposed Gas Can Standards
a. VOC
Table V.E-6 shows the reductions in VOC emissions that we expect
from the proposed gas can standard. In 2015, VOC emissions from gas
cans would be reduced by 60% because of reduced permeation, spillage,
and evaporative losses. These estimates do not include the effects of a
fuel benzene standard (see section V.E.4 for the combined effects of
the proposed controls).

Table V.E-6.--Estimated National Reductions in VOC Emissions From Gas Cans, 2010 to 2030
----------------------------------------------------------------------------------------------------------------
1999 2010 2015 2020 2030
----------------------------------------------------------------------------------------------------------------
VOC Without Rule (tons)......... 318,596 279,374 296,927 318,384 362,715
VOC With Proposed Gas Can N.A. 250,990 116,431 125,702 144,634
Standard (tons)................
VOC Reductions from Proposed Gas N.A. 28,384 180,496 192,683 218,080
Can Standard (tons)............
Percentage Reduction............ N.A. 10 61 61 60
----------------------------------------------------------------------------------------------------------------

b. Toxics
The proposed gas can standard would reduce emissions of benzene,
naphthalene, toluene, xylenes, ethylbenzene, n-hexane, 2,2,4-
trimethylpentane, and MTBE. We estimate that benzene emissions from gas
cans would be reduced by 65% (see Table V.E-7) and, more broadly, air
toxic emissions by 61% (see Table V.E-8) in year 2015. These reductions
do not include effects of the proposed fuel benzene standard (see
section V.E.4 for the combined effects of the proposed controls).
Chapter 2 of the RIA provides details on the emission reductions of the
other toxics.

Table V.E-7.--Estimated National Reductions in Benzene Emissions From Gas Cans, 2010 to 2030
----------------------------------------------------------------------------------------------------------------
1999 2010 2015 2020 2030
----------------------------------------------------------------------------------------------------------------
Benzene Without Rule (tons)..... 2,229 2,118 2,262 2,423 2,757
Benzene With Proposed Gas Can N.A. 1,885 794 856 985
Standard (tons)................
Benzene Reductions from Proposed N.A. 233 1,468 1,567 1,772
Gas Can Standard (tons)........
Percentage Reduction............ N.A. 11 65 65 64
----------------------------------------------------------------------------------------------------------------

Table V.E-8.--Estimated National Reductions in Total MSAT Emissions From Gas Cans, 2010 to 2030
----------------------------------------------------------------------------------------------------------------
1999 2010 2015 2020 2030
----------------------------------------------------------------------------------------------------------------
MSATs Without Rule (tons)....... 39,581 34,873 37,076 39,751 45,284
MSATs With Proposed Gas Can N.A. 31,312 14,445 15,593 17,942
Standard (tons)................
MSAT Reductions from Proposed N.A. 3,561 22,631 24,158 27,342
Gas Can Standard (tons)........
Percentage Reduction............ N.A. 10 61 61 60
----------------------------------------------------------------------------------------------------------------

Chapter 2 of the RIA describes how we estimated emissions from gas
cans, including the key assumptions used and uncertainties in the
analysis. We request comments on the emissions inventory methodology
used by EPA and we encourage commenters to provide relevant data where
possible.
4. Total Emission Reductions From Proposed Controls
Sections V.E.1 through V.E.3 present the emissions impacts of each
of the

[[Page 15840]]

proposed controls individually. This section presents the combined
emissions impacts of the proposed controls.
a. Toxics
Air toxic emissions from light-duty vehicles depend on both fuel
benzene content and vehicle hydrocarbon emission controls. Similarly,
the air toxic emissions from gas cans depend on both fuel benzene
content and the gas can emission controls. Tables V.E-9 and V.E-10
below summarize the expected reductions in benzene and MSAT emissions,
respectively, from our proposed vehicle, fuel, and gas can controls. In
2030, annual benzene emissions from gasoline on-road mobile sources
would be 44% lower as a result of this proposal (see Figure V.E-1).
Annual benzene emissions from gasoline light-duty vehicles would be 45%
lower in 2030 as a result of this proposal. Likewise, this proposal
would reduce annual emissions of benzene from gas cans by 78% in 2030
(see Figure V.E-2). For MSATs from on-road mobile sources, Figure V.E-3
below shows a 33% reduction in MSAT emissions in 2030.

Table V.E-9.--Estimated Reductions in Benzene Emissions From Proposed Control Measures by Sector, 2015 to 2030
--------------------------------------------------------------------------------------------------------------------------------------------------------
2015 2020 2030
-----------------------------------------------------------------------------------------------------------
Benzene 1999 Without Without Without
rule With rule Reductions rule With rule Reductions rule With rule Reductions
(tons) (tons) (tons) (tons) (tons) (tons) (tons) (tons) (tons)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Gasoline On-road Mobile Sources. 178,465 103,798 77,155 26,643 108,256 71,326 36,930 127,058 70,682 56,376
Gasoline Nonroad Mobile Sources. 58,710 37,747 33,247 4,500 36,440 32,018 4,422 39,162 34,400 4,762
Gas Cans........................ 2,229 2,262 492 1,770 2,423 531 1,892 2,757 610 2,147
Gasoline Distribution........... 5,502 5,999 4,054 1,945 6,207 4,210 1,997 6,207 4,210 1,997
-----------------------------------------------------------------------------------------------------------------------
Total....................... 244,905 149,806 114,948 34,858 153,326 108,085 45,241 175,184 109,902 65,282
--------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 15841]]
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Table V.E-10.--Estimated Reductions in MSAT Emissions From Proposed Control Measures by Sector, 2015 to 2030
--------------------------------------------------------------------------------------------------------------------------------------------------------
2015 2020 2030
-----------------------------------------------------------------------------------------------------------
MSAT 1999 Without Without Without
rule With rule Reductions rule With rule Reductions rule With rule Reductions
(tons) (tons) (tons) (tons) (tons) (tons) (tons) (tons) (tons)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Gasoline On-road Mobile Sources. 1,415,502 731,283 613,227 118,056 745,769 555,541 190,228 865,767 548,298 317,469
Gasoline Nonroad Mobile Sources. 673,922 432,953 428,506 4,447 390,468 386,095 4,373 405,119 400,408 4,711
Gas Cans........................ 39,581 37,076 14,143 22,933 39,751 15,268 24,483 45,284 17,567 27,717
Gasoline Distribution........... 50,625 62,804 60,859 1,945 64,933 62,936 1,997 64,933 62,936 1,997
-----------------------------------------------------------------------------------------------------------------------
Total....................... 2,179,630 1,264,116 1,116,735 147,381 1,240,921 1,019,840 221,081 1,381,103 1,029,209 351,894
--------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 15842]]
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b. VOC
VOC emissions would be reduced by the hydrocarbon emission
standards for both light-duty vehicles and gas cans. As seen in the
table and accompanying figure below, annual VOC emission reductions
from both of these sources would be 35% lower in 2030 because of
proposed control measures.

Table V.E-11.--Estimated Reductions in VOC Emissions from Light-Duty Gasoline Vehicles and Gas Cans, 2015 to
2030
----------------------------------------------------------------------------------------------------------------
2015 2020 2030
----------------------------------------------------------------------------------------------------------------
VOC Without Rule (tons)......................................... 2,922,003 2,875,135 3,261,984
VOC With Proposed Vehicle and Gas Can Standards (tons).......... 2,421,633 2,145,969 2,130,464
VOC Reduction (tons)............................................ 500,370 729,168 1,131,520
----------------------------------------------------------------------------------------------------------------
[GRAPHIC]
[TIFF OMITTED]
TP29MR06.005

c. PM_2.5
We expect that only the proposed vehicle control would reduce
emissions of direct PM_2.5. As shown in Table V.E-4, we
expect this control to reduce direct PM_2.5 emissions by
about 20,000 tons in 2030. In addition, the VOC reductions from the
proposed vehicle and gas can standards would also reduce secondary
formation of PM_2.5.

F. How Would This Proposal Reduce Exposure to Mobile Source Air Toxics
and Associated Health Effects?

The proposed benzene standard for gasoline would reduce both
evaporative and exhaust emissions from motor vehicles and nonroad
equipment. It would also reduce emissions from gas cans and stationary
source emissions associated with gasoline distribution. Therefore, it
would reduce exposure to benzene for the general population, and also
for people near roadways, in

[[Page 15843]]

vehicles, in homes with attached garages, operating nonroad equipment,
and living or working near sources of gasoline distribution emissions
(such as bulk terminals, bulk plants, tankers, marine vessels, and
service stations). Section IV.B.2 of this preamble provides more
details on these types of exposures.
We performed national-scale air quality, exposure, and risk
modeling in order to quantitatively assess the impacts of the proposed
fuel benzene standard. However, in addition to the limitations of the
national-scale modeling tools (discussed in section IV.A), this
modeling did not account for the elevated hydrocarbon emissions from
motor vehicles at cold temperatures, which we recently discovered and
are further described in section VI and the RIA. The modeling also
examined the gasoline benzene standard alone, without the proposed
vehicle or gas can standards. Nevertheless, the modeling is useful as a
preliminary assessment of the impacts of the fuel standard.
The fuel benzene standard being proposed in this rule would reduce
both the number of people above the 1 in 100,000 increased cancer risk
level, and the average population cancer risk, by reducing exposures to
benzene from mobile sources. The number of people above the 1 in
100,000 cancer risk level due to exposure to all mobile source air
toxics from all sources would decrease by over 3 million in 2020 and by
about 3.5 million in 2030, based on average census tract risks. The
number of people above the 1 in 100,000 increased cancer risk level
from exposure to benzene from all sources would decrease by over 4
million in 2020 and 5 million in 2030. It should be noted that if it
were possible to estimate impacts of the proposed standard on
``background'' concentrations, the estimated overall risk reductions
would be even larger. The proposed standard would have little impact on
the number of people above various respiratory hazard index levels,
since this potential non-cancer risk is dominated by exposure to acrolein.
Table V.F-1 depicts the impact on the mobile source contribution to
nationwide average population cancer risk from benzene in 2020.
Nationwide, the cancer risk attributable to mobile source benzene would
be reduced by over 8%. Reductions in areas not subject to reformulated
gasoline controls are almost 13 percent relative to risks without the
proposed control; and in some states with high fuel benzene levels,
such as Minnesota and Washington, the risk reduction would exceed 17
percent. In Alaska, which has the highest fuel benzene levels in the
country, reductions would exceed 30%. Reductions for other modeled
years are similar. The methods and assumptions used to model the impact
of the proposed control are described in more detail in the Regulatory
Impact Analysis. Although not quantified in the risk analyses for this
rule, controls proposed for portable fuel containers will also reduce
exposures and risk from benzene, and cold temperature hydrocarbon
standards for exhaust emissions will reduce cancer and noncancer risks
for all gaseous mobile source air toxics. These reductions will vary
geographically since reductions from vehicle control are higher at
colder temperatures, and reductions from gas can controls are higher at
higher temperatures.

Table V.F-1.--Impact of Proposed Fuel Benzene Control on the Mobile Source Contribution to Nationwide Average
Population Cancer Risk in 2020
----------------------------------------------------------------------------------------------------------------
U.S. RFG areas Non-RFG areas
----------------------------------------------------------------------------------------------------------------
Without Proposal............................................... 2.57x10-6 3.64x10-6 1.96x10-6
0.62% Benzene Standard.......................................... 2.35x10-6 3.51x10-6 1.72x10-6
% Reduction.................................................... 8.6 3.6 12.2
----------------------------------------------------------------------------------------------------------------

Table V.F-2 summarizes the change in median and 95th percentile
benzene inhalation cancer risk from all outdoor sources in 2015, 2020,
and 2030, with the fuel benzene controls proposed in this rule. The
reductions in risk would be larger if the modeling fully accounted for
a number of factors, including: benzene emissions at cold temperature;
exposure to benzene emissions from vehicles, equipment, and gas cans in
attached garages; near-road exposures; and the impacts of the control
program on ``background'' levels attributable to transport.

Table V.F-2.--Change in Median and 95th Percentile Benzene Inhalation Cancer Risk From Outdoor Sources in 2015, 2020, and 2030 With the Fuel Benzene
Controls Proposed in this Rule
--------------------------------------------------------------------------------------------------------------------------------------------------------
2015 2020 2030
-----------------------------------------------------------------------------------------------
median 95th median 95th median 95th
--------------------------------------------------------------------------------------------------------------------------------------------------------
Current Controls........................................ 5.73x10-6 1.38x10-5 5.61x10-6 1.35x10-5 5.75x10-6 1.41x10-5
Proposed Benzene Standard............................... 5.49x10-6 1.32x10-5 5.39x10-6 1.29x10-5 5.51x10-6 1.35x10-5
Percent Change.......................................... 4.2 4.3 3.9 4.4 4.2 4.3
--------------------------------------------------------------------------------------------------------------------------------------------------------

We did not model the air quality, exposure, and risk impacts of the
proposed vehicle and gas can standards. However, the proposed vehicle
standards would reduce exposure to several MSATs, including benzene.
Like the proposed fuel standard, the vehicle standards would reduce the
general population's exposure to MSATs, as well as people near roadways
and in vehicles. Since motor vehicle emissions are ubiquitous across
the U.S. and widely dispersed, reductions in exposure and risk will be
approximately proportional to reductions in emissions.
The gas can standard will reduce evaporative emissions of several
MSATs, including benzene. We expect that these standards would
significantly reduce concentrations of benzene and other MSATs in
attached garages and inside homes with attached garages. Accordingly,
exposure to benzene and other MSATs would be significantly reduced. As
discussed in section IV.B.2, exposures to emissions occurring in
attached garages can be quite high.

[[Page 15844]]

The proposed vehicle and gas can standards would also reduce
precursors to ozone and PM. We have modeled the ozone impacts of the
proposed gas can standard and the PM health benefits that would be
associated with the direct PM reductions from the proposed vehicle
standards. These results are discussed in sections IV.D and IX, respectively.

G. Additional Programs Under Development That Will Reduce MSATs

1. On-Board Diagnostics for Heavy-Duty Vehicles Over 14,000 Pounds
We are planning to propose on-board diagnostics (OBD) requirements
for heavy-duty vehicles over 14,000 pounds. In general, OBD systems
monitor the operation of key emissions controls to detect major
failures that would lead to emissions well above the standards during
the life of the vehicle. Given the nature of the heavy-duty trucking
industry, 50-state harmonization of emissions requirement is an
important consideration. In order to work towards this goal, the Agency
signed a Memorandum of Agreement in 2004 with the California Air
Resources Board which expresses both agencies' interest in working
towards a single, nationwide program for heavy-duty OBD. Since that
time, California has established their heavy-duty OBD program, which
will begin implementation in 2010. We expect the Agency's program will
also begin in the 2010 time frame. These requirements would help ensure
that the emission reductions we projected in the 2007 rulemaking for
heavy-duty engines occur in-use.
2. Standards for Small SI Engines
We are developing a proposal for Small SI engines (those typically
used in lawn and garden equipment) and recreational marine engines.
This proposal is being developed in response to Section 428 of the
Omnibus Appropriations Bill for 2004, which requires EPA to propose
regulations under Clean Air Act section 213 for new nonroad spark-
ignition engines under 50 horsepower. We plan to propose standards that
would further reduce the emissions for these nonroad categories, and we
anticipate that the new standards would provide significant further
reductions in HC (and VOC-based toxics) emissions.
3. Standards for Locomotive and Marine Engines
In addition, we are planning to propose more stringent standards
for large diesel engines used in locomotive and marine applications, as
discussed in a recent Advance Notice of Proposed Rulemaking.\179\ New
standards for marine diesel engines would apply to engines less than 30
liters per cylinder in displacement (all engine except for Category 3).
We are considering standards modeled after our Tier 4 nonroad diesel
engine program, which achieve substantial reductions in PM, HC, and
NO_X emissions. These standards would be based on the use of
high efficiency catalyst aftertreatment and would also require fuel
sulfur control. As discussed in our recent ANPRM, we are considering
implementation as early as 2011.
---------------------------------------------------------------------------

\179\ 69 FR 39276, June 29, 2004.
---------------------------------------------------------------------------

VI. Proposed New Light-Duty Vehicle Standards

A. Why Are We Proposing New Standards?

1. The Clean Air Act and Air Quality
As described in section V of this preamble, the U.S. has made
significant progress in reducing emissions from passenger cars and
light trucks since the passage of the 1990 Clean Air Act Amendments.
Many emission control programs adopted to implement the 1990 Clean Air
Act Amendments are reducing and will continue to reduce air toxics from
light-duty vehicles. These include our reformulated gasoline (RFG)
program, our Supplemental Federal Test Procedure (SFTP) standards, our
national low emission vehicle program (NLEV), and, most recently, our
Tier 2 motor vehicle emissions standards and gasoline sulfur control
requirements.\180\ While these vehicle programs were put in place
primarily to reduce ambient concentrations of criteria pollutants and
their precursors (NO_X, VOC, CO, and PM), they have reduced
and will continue to significantly reduce light-duty vehicle emissions
of air toxics. For example, there are numerous chemicals that make up
total VOC emissions, including several gaseous toxics (e.g., benzene,
formaldehyde, 1,3-butadiene, and acetaldehyde). These toxics are all
reduced by VOC emissions standards. It is the stringent control of
hydrocarbons in particular that results in stringent control of gaseous
toxics. There are no vehicle-based technologies of which we are aware
that reduce these air toxics individually.
---------------------------------------------------------------------------

\180\ Unless otherwise noted, we use ``light-duty vehicles'' or
``vehicles'' to generally refer to passenger vehicles, light-duty
trucks such as sport utility vehicles (SUVs) and pick-ups, and
medium-duty passenger vehicles (MDPVs) which includes larger SUVs
and passenger vans up to 10,000 pounds Gross Vehicle Weight Rating.
---------------------------------------------------------------------------

At the time of our 2001 MSAT rule, we had recently finalized the
Tier 2 emissions standards and gasoline sulfur control requirements
(described in more detail below in section V.D). As explained earlier,
we concluded then under section 202(l) that the Tier 2 standards
represented the greatest degree of emissions control achievable for
those vehicles. However, we also committed to continue to consider the
feasibility of additional vehicle-based MSAT controls in the future.
2. Technology Opportunities for Light-Duty Vehicles
Since the 2001 MSAT rule, we have identified potential situations
where further reductions of light-duty vehicle hydrocarbon emissions--
and, therefore, mobile source air toxics--are technically feasible,
cost-effective, and do not have adverse energy or safety implications.
First, recent research and analytical work shows that the Tier 2
exhaust emission standards for hydrocarbons (which are typically tested
at 75[deg] F) do not, in the case of many vehicles, result in robust
control of hydrocarbon emissions at lower temperatures. We believe that
cold temperature hydrocarbon control can be substantially improved
using the same technological approaches generally already in use in the
Tier 2 vehicle fleet to meet the stringent standards at 75[deg] F.
Second, we believe that harmonization of evaporative emission standards
with California would prevent backsliding by codifying current industry
practices. Sections VI.B.1 and VI.B.2, below, provide our rationale for
proposing new cold temperature and evaporative controls and describe
the detailed provisions of our proposal. We request comment on all
aspects of these proposals and encourage commenters to provide detailed
rationales and supporting data where possible.
Aside from these proposed standards, we continue to believe that
the remaining Tier 2 exhaust emission standards (i.e., those that apply
over the standard Federal Test Procedure at temperatures between
68[deg] F and 86[deg] F) represent the greatest emissions reductions
achievable as required under Clean Air Act section 202(l). We therefore
are not proposing further emission reductions from these vehicles.
(Please see section VI.D for further discussion.)
3. Cold Temperature Effects on Emission Levels
a. How Does Temperature Affect Emissions?
With the possible exception of high-load operation, Tier 2
gasoline-powered vehicles emit the overwhelming

[[Page 15845]]

majority of hydrocarbon emissions in the first few minutes of operation
following a cold start (i.e., starting the vehicles after the engine
has stabilized to the ambient temperatures, such as overnight). This is
true at all cold start temperatures, and the general trend is that
hydrocarbon emissions progressively increase as engine start
temperatures decrease. The level of hydrocarbon emissions produced by
the engine will vary with start temperature, engine hardware design and
most importantly, engine management control strategies. Furthermore,
due to the heavy dependence on the aftertreatment system to perform the
main emission reducing functions, any delayed or non-use of emission
controls (hardware or software) will further increase the amount of
hydrocarbon emissions emitted from the vehicle following the cold start.
Elevated hydrocarbon levels at cold temperatures, specifically, the
non-methane hydrocarbons (NMHC) portion of total hydrocarbons (THC),
also indicate higher emissions of gaseous air toxics. A detailed
description of the relationship between NMHC and air toxics can be
found in Chapter 2 of the RIA. Recent EPA research studies \181\ on
Tier 2 gasoline vehicles, and past EPA studies \182\ on older
generation gasoline vehicles, demonstrate that many air toxics (e.g.,
benzene) are a relatively constant fraction of NMHC. This relationship
is observed regardless of vehicle type, NMHC emissions level, or
temperature. The relationship remains relatively constant for different
vehicles with different levels of NMHC emissions, and for the same
vehicle at colder temperatures. Therefore, it can be concluded that
reductions in NMHC will result in proportional reductions in gaseous
air toxics which are components of HC. These observations and findings
indicate that controlling NMHC is an effective approach to reducing
toxics which are a component of NMHC, including benzene emissions.
---------------------------------------------------------------------------

\181\ ``VOC/PM Cold Temperature Characterization and Interior
Climate Control Emissions/Fuel Economy Impact,'' Volume I and II,
October 2005.
\182\ ``Characterization of Emissions from Malfunctioning
Vehicles fueled with Oxygenated Gasoline-Ethanol (E10) Fuel,'' Part
I, II and III.
---------------------------------------------------------------------------

In addition to control of air toxics, another benefit of regulating
NMHC at cold temperatures is reductions in particulate matter (PM). PM
is a criteria pollutant and for gasoline-fueled vehicles is an emerging
area of interest on which we are continuing to collect data (see
sections III.E and IV.F for more details on PM). We have limited data
indicating that PM emissions can be significantly higher at cold
temperatures compared to emissions at the 68-86[deg] F testing
temperatures used in the FTP. Data also indicate that HC and direct PM
emissions correlate fairly well as temperature changes and that some
direct PM emissions reductions can be expected when VOCs are reduced.
Also, from a technological standpoint, we can expect reductions in PM
as manufacturers reduce over-fueling at cold temperatures for NMHC
control. Although section 202(l) deals with control of air toxics, and
not criteria pollutants like PM, this co-benefit of cold temperature
control is significant.
b. What Are the Current Emissions Control Requirements?
There are several requirements currently in place that have
resulted in significant NMHC reductions and provided experience with
control strategies that apply across a broad range of in-use driving
conditions, including cold temperatures. These requirements include the
Tier 2 standards, the Supplemental Federal Test Procedure (SFTP)
standards, the cold temperature carbon monoxide (CO) standard, and the
California 50[deg] F hydrocarbon standard.
The Tier 2 program (and, before that, the NLEV program) contains
stringent new standards for light-duty vehicles that have resulted in
significant hydrocarbon reductions. To meet these standards, vehicle
manufacturers have responded with emissions control hardware and
control strategies that have very effectively minimized emissions,
particularly immediately following the vehicle start-up. In addition,
the SFTP rule (effective beginning in model year 2001) significantly
expanded the area of operation where stringent emission control was
required, by adding a high load/speed cycle (US06) and an air
conditioning cycle (SC03). Vehicle manufacturers responded with
additional control strategies across a broader range of in-use driving
conditions to successfully meet SFTP requirements.
We also have cold temperature carbon monoxide (CO) standards which
began in model year 1994 for light-duty vehicles (LDVs) and light-duty
trucks (LDTs).\183\ This program requires manufacturers to comply with
a 20[deg] F CO standard. The 20[deg] F cold CO test replicates the
75[deg] F FTP drive cycle, but at the colder temperature. While the
recent Tier 2 program is primarily designed to reduce ozone, the cold
CO requirement was enacted to address exceedances of the national
ambient air quality standards (NAAQS) for CO, which were mostly
occurring during the cold weather months. While the cold CO standard
was considered challenging at its introduction, manufacturers quickly
developed emission control strategies and today comply with the
standard with generally large compliance margins. This indicates that
manufacturers do in fact have experience with emission control
strategies at colder temperatures.
---------------------------------------------------------------------------

\183\ 57 FR 31888 ``Control of Air Pollution from New Motor
Vehicles and New Motor Vehicle Engines: Cold Temperature Carbon
Monoxide Emissions from 1994 and Later Model Year Gasoline-Fueled
Light-Duty Vehicles and Light-Duty Trucks'', Final Rule, July 17, 1992.
---------------------------------------------------------------------------

Under the Low Emission Vehicle (LEV) programs, California
implemented stringent emissions standards for a 50[deg] F FTP test
condition in addition to stringent 75[deg] F standards. By creating a
unique 50[deg] F standard, California ensures that emission control
strategies successfully used at 75[deg] F are also utilized at the
slightly cooler temperatures that encompass a larger range of
California's expected climates. The 50[deg] F non-methane organic gases
(NMOG) standards are directly proportional to the 75[deg] F
certification standard; that is, they are two times the 75[deg] F
standard. These standards have resulted in proportional emissions
improvements at 50[deg] F for vehicles certified to the California
standards, as observed in the manufacturer certification data.
Manufacturers have met the standards and have successfully obtained
these proportional improvements at 50[deg] F by implementing the same
emission control strategies developed for 75[deg] F requirements.
c. Opportunities for Additional Control
As emissions standards have become more stringent from Tier 1 to
NLEV, and now to Tier 2, manufacturers have concentrated primarily on
emissions performance just after the start of the engine in order to
further reduce emissions. To comply with stringent hydrocarbon emission
standards at 75[deg] F, manufacturers developed new emission control
strategies and practices that resulted in significant emissions
reductions at that start temperature. For California, the LEV II
program contains a standard at 50[deg] F (as just explained), which
essentially requires proportional control of hydrocarbon emissions down
to that temperature. On the national level, even though there is no
explicit requirement, we expected that proportional reductions in
hydrocarbon emissions would occur at other colder start temperatures--
including the 20[deg] F Cold CO test point--as a result of the more
stringent NLEV and Tier 2 standards. We believe that there is no

[[Page 15846]]

engineering reason why proportional control should not be occurring on
a widespread basis.
However, reported annual manufacturer certification results
(discussed in the next paragraph) indicate that for many engine
families, very little improvement in hydrocarbon emissions was realized
at the colder 20[deg] F Cold CO test conditions, despite the improved
emission control systems designed for the vehicle under normal 75[deg]
F test conditions. Thus although all vehicle manufacturers have been
highly successful at reducing emissions at the required FTP start
temperature range, in general, they do not appear to be capitalizing on
NMHC emission control strategies and technologies at lower temperatures.
Certification reports submitted by manufacturers for recent model
years of light duty vehicles in fact show a sharp rise in hydrocarbon
\184\ emissions at 20[deg] F when compared to the reported 75[deg] F
hydrocarbon emission levels. Any rise in hydrocarbon emissions,
specifically NMHC, will result in proportional rise in VOC-based air
toxics \185\. While some increase in NMHC emissions can be expected
simply due to combustion limitations of gasoline engines at colder
temperatures, the reported levels of hydrocarbon emissions seem to
indicate a significantly diminished use of hydrocarbon emissions
controls occurring at colder temperatures. For example, on recent Tier
2 certified vehicles, the reported 20[deg] F hydrocarbon levels on
average were 10 to 12 times higher than the equivalent vehicle's
measured 75[deg] F hydrocarbon levels. Some vehicles which were
certified to more stringent Tier 2 bins (bins 2, 3, and 4) demonstrated
20[deg] F hydrocarbon levels no different than less stringent Tier 2
bins (bins 5, 6, 7, and 8), likewise suggesting no discernable attempt
to use the 75[deg] F hydrocarbon controls at the 20[deg] F temperature.
On the other hand, in some select cases, individual vehicles did
demonstrate proportional improvements in hydrocarbon emission results
at 20[deg] F relative to their 75[deg] F results, confirming our belief
that proportional control is feasible and indeed is occasionally
practiced. One manufacturer's certification results reflected
proportional improvements across almost its entire vehicle lines
(including vehicles up to 5665 GVWR), further supporting that
proportional control is feasible.
---------------------------------------------------------------------------

\184\ Most certification 20[deg] F hydrocarbon levels are
reported as THC, but NMHC accounts for approximately 95% of THC as
seen in results with both THC and NMHC levels reported. This
relationship also is confirmed in EPA test programs supporting this
rule-making.
\185\ ``VOC/PM Cold Temperature Characterization and Interior
Climate Control Emissions/Fuel Economy Impact'', Volume I and II,
October 2005.
---------------------------------------------------------------------------

B. What Cold Temperature Requirements Are We Proposing?

1. NMHC Exhaust Emissions Standards
We are proposing a set of standards that will achieve proportional
NMHC control from the 75[deg] F Tier 2 standards to the 20[deg] F test
point. The proposed standard would achieve the greatest degree of
hydrocarbon emissions reductions feasible by fully utilizing the
substantial existing emission control hardware required to meet Tier 2
standards. We believe these standards would be achievable through
calibration and software control strategies on Tier 2 level vehicles
without use of additional hardware. The proposed standards are shown in
Table VI.B-1.

Table VI.B-1.--Proposed 20[deg]
F FTP Exhaust Emission Standards
------------------------------------------------------------------------
NMHC sales-
weighted
fleet
Vehicle GVWR and category average
standard
(grams/
mile)
------------------------------------------------------------------------
< = 6000 lbs: Light-duty vehicles (LDV) & Light light-duty 0.3
trucks (LLDT).............................................
> 6000 lbs: Heavy light-duty trucks (HLDT) up to 8,500 lbs 0.5
& Medium-duty passenger vehicles (MDPV) up to 10,000 lbs..
------------------------------------------------------------------------

We are proposing two separate sales-weighted fleet average NMHC
levels: (1) 0.3 g/mile for vehicles at or below 6,000 pounds GVWR and
(2) 0.5 g/mile for vehicles over 6,000 pounds, including MDPVs.\186\
The new standard would not require additional certification testing
beyond what is required today with ``worst case'' model selection of a
durability test group.\187\ NMHC emissions would be measured during the
Cold CO test, which already requires hydrocarbon measurement.\188\
---------------------------------------------------------------------------

\186\ Tier 2 created the medium-duty passenger vehicle (MDPV)
category to include larger complete passenger vehicles, such as SUVs
and vans, with a GVWR of 8,501-10,000 pounds GVWR. Large pick-ups
above 8,500 pounds are not included in the MDPV category but are
included in the heavy-duty vehicle category.
\187\ The existing cold FTP test procedures are specified in 40
CFR Subpart C. In the proposed rule for fuel economy labeling,
recently signed on January 10, 2006 (71, FR 5426, February 1, 2006),
EPA is seeking comment on the issue of requiring manufacturers to
run the heater and/or defroster while conducting the cold FTP test.
As discussed in the fuel economy labeling proposed rule, we do not
believe this requirement would have a significant impact on emissions.
\188\ 40 CFR Subpart C, Sec. 86.244-94 requires the measurement
of all pollutants measured over the FTP except NO_X.
---------------------------------------------------------------------------

The separate fleet average standards are proposed to address
challenges related to vehicle weight. We examined the certification
data from interim non-Tier 2 vehicles (i.e., vehicles not yet phased in
to the final Tier 2 program, but meeting interim standards established
by Tier 2), and we determined that there was a general trend of
increasing hydrocarbon levels with heavier GVWR vehicles. Heavier
vehicles generally produce higher levels of emissions for several
reasons. First, added weight results in additional work required to
accelerate the vehicle mass. This generally results in higher
emissions, particularly early in the test right after engine start-up.
Second, the design of these vehicle emission control systems may
incorporate designs for heavy work (i.e., trailer towing) that may put
them at some disadvantage at 20[deg] F cold starts. For example, the
catalyst may be located further away from the engine so it is protected
from high exhaust temperatures. This catalyst placement may delay the
warm-up of the catalyst, especially at colder temperatures. Therefore,
we believe a standard that is higher than the 0.3 g/mile level proposed
for vehicles below 6,000 lbs GVWR, is what is technically feasible for
heavier vehicles. The proposed 0.5 g/mile standard would apply for
vehicles over 6000 lbs GVWR, which includes both HLDTs (6000 lbs to
8500 lbs) and MDPVs.
We are proposing the sales-weighted fleet average approach because
it achieves the greatest degree of emission control feasible for Tier 2
vehicles, while allowing manufacturers flexibility to certify different
vehicle groups to different levels and thus providing both lower cost
and feasible lead times. We believe this is an appropriate approach
because the base Tier 2 program is also based on emissions averaging,
and will result in a mix of emissions control strategies across the
fleet that would have varying cold temperature capabilities. These
capabilities won't be fully understood until manufacturers go through
the process of evaluating each Tier 2 package for cold temperature
emissions control potential. Also, Tier 2 is still being phased in and
some Tier 2 vehicle emissions control packages are still being
developed. A fleet average provides manufacturers with flexibility to
balance challenging vehicle families with ones that more easily achieve
the standards.

[[Page 15847]]

There are several ways fleet averaging can work. In Tier 2, we
established bins of standards to which individual vehicle families were
certified. Each bin contains a NO_X standard, and these
NO_X standards are then sales-weighted to demonstrate
compliance with the corporate average NO_X standard. In other
emissions control programs, such as the highway motorcycle program and
the highway and nonroad heavy-duty engine programs, we have established
a Family Emissions Limit (FEL) structure. In this approach,
manufacturers establish individual FELs for each group of vehicles
certified. These FELs serve as the standard for each individual group,
and the FELs are averaged together on a sales-weighted basis to
demonstrate overall compliance with the standards. For the proposed new
cold temperature NMHC standards, we are proposing to use the FEL-based
approach. We believe the FEL approach adds flexibility and should lead
to cost-effective improvements in vehicle emissions performance. The
FEL approach is discussed further in Section VI.B.4 below.
We are proposing to apply the new cold temperature NMHC standards
to Tier 2 gasoline-fueled vehicles. We are not proposing to apply the
standards to diesel vehicles, alternative-fueled vehicles, or heavy-
duty vehicles, in general, due to a lack of data on which to base
standards. Section VI.B., below, provides a detailed discussion of
applicability.
As discussed above, we are expecting PM reductions at cold
temperatures as a result of the control strategies we expect
manufacturers to meet under the proposed cold temperature NMHC
standards. We may consider the need for a separate PM standard under
CAA section 202(a), as part of a future rulemaking, to further ensure
that PM reductions occur under cold temperature conditions. We also
request comments on what testing challenges exist for testing PM under
cold conditions. We request that comments be supported by data where
possible.
We request comments on the level of the new standards and the
averaging approach we are proposing, and we urge commenters to include
supporting information and data where possible.
2. Feasibility of the Proposed Standards
We believe the proposed standards are feasible, based on our
analysis of the stringency of the standard provided below and the lead
time and flexibilities described in section VI.B.3. We believe that the
proposed standards could be achieved using a number of the technologies
discussed in the following section, but that none of these potential
technologies performs markedly better than any other. Moreover, as
explained in section VI.D, we do not believe that additional reductions
would be feasible without significant changes in Tier 2 technology, and
we are not yet in a position to fully evaluate the achievability of
standards based on such technologies. We thus are not considering more
stringent cold temperature NMHC standards. We request comment on our
analysis of the feasibility of the proposed standards.
a. Currently Available Emission Control Technologies
We believe that the cold temperature NMHC standards being proposed
today for gasoline-fueled vehicles are challenging but within the reach
of Tier 2 level emission control technologies. Our proposed
determination of feasibility is based on the emission control hardware
and strategies that are already in use today on Tier 2 vehicles. These
emission control technologies are successfully used to meet the
stringent Tier 2 standards for HC at the FTP temperature range of
68[deg] F to 86[deg] F, but generally are not fully used or activated
at colder temperatures. As discussed in section VI.D, we are not
proposing standards that would force changes to Tier 2 technology at
this time. As discussed above, many current engine families are already
achieving emissions levels at or below the proposed emission standards
(see RIA Chapter 5), while other engine families are at levels greater
than twice the proposed standard. The only apparent reason for the
difference is the failure of some vehicles to use the Tier 2 control
technologies at cold temperatures. While manufacturers could always
choose to use additional hardware to facilitate compliance with the
proposed standard, many of the engine families already at levels below
the proposed standard do not necessarily contain any unique enabling
hardware. These vehicles appear to achieve their results through mainly
software and calibration control technologies. Thus, we believe our
proposed standards can be met by the application of calibration and
software approaches similar to those currently used at 50[deg] F and
75[deg] F, and we have estimated cost of control based on use of
calibration and software approaches. Estimated costs are provided in
section IX below, and in Chapter 8 of the RIA. As described in section
VI.B.2.c, our own feasibility testing of a vehicle over 6000 lbs GVWR
achieved NMHC reductions consistent with the proposed standard without
the use of new hardware.
In addition, a 20[deg] F cold hydrocarbon requirement has been in
place in Europe since approximately the 2002 model year.\189\ Many
manufacturers currently have common vehicle models offered in Europe
and the U.S. market. While the European standard is over a different
drive cycle, unique strategies have been developed to comply with this
standard. In fact, when the new European cold hydrocarbon standard was
implemented in conjunction with a new 75[deg] F standard (Euro4), many
manufacturers responded by implementing NLEV level hardware and
supplementing this hardware with advanced cold start emission control
strategies. Although we are proposing a sales-weighted fleet average
standard, the European standard is a fixed standard that cannot be
exceeded by any vehicle model. Like the standard we are proposing,
Europe also has made distinctions in the level of the standard
reflecting that heavier weight vehicles cannot achieve as stringent a
standard. Those manufacturers with European models shared with the U.S.
market have the opportunity to leverage their European models or
divisions in an attempt to transfer the emission control technologies
that are used today for 20[deg] F hydrocarbon control.
---------------------------------------------------------------------------

\189\ European Union (EU) Type VI Test (-7[deg] C) required for
new vehicle model certified as of 1/1/2002.
---------------------------------------------------------------------------

There are several different approaches or strategies used in the
vehicles that are achieving proportional improvements in NMHC emissions
at 20[deg] F FTP. Several European models sold in the U.S. market that
demonstrate excellent cold hydrocarbon performance are utilizing
secondary air systems at the 20[deg] F start temperature. These
secondary air systems, sometimes called air pumps, inject ambient air
into the exhaust immediately after the cold start. This performs
additional combustion of unburned hydrocarbons prior to the catalytic
converter and also accelerates the necessary heating of the catalytic
converter. In the past and even recently, these systems have been used
extensively to improve hydrocarbon performance at 75[deg] F starts. As
predicted in the Tier 2 Final Rule, a portion of the Tier 2 fleet is
being equipped with secondary air systems in order to comply with Tier
2 standards.
Some manufacturers that currently have these systems available on
their vehicles have indicated that they are simply not utilizing them
at temperatures below freezing due to past engineering issues. The
manufacturers that are using secondary air at 20[deg] F, mainly
European manufacturers, have indicated that these engineering

[[Page 15848]]

challenges have been addressed through design changes. The robustness
of these systems below freezing has also been confirmed with the
manufacturers and with the suppliers of the secondary air
components.\190\ While not necessarily producing 20[deg] F NMHC
emission results better than other available technologies, vehicles
equipped with this technology should be able to meet the proposed
20[deg] F standard by capitalizing on this hardware.
---------------------------------------------------------------------------

\190\ Memo to docket ``Discussions Regarding Secondary Air
System Usage at 20[deg] F with European Automotive Manufacturers and
Suppliers of Secondary Air Systems,'' December 2005.
---------------------------------------------------------------------------

Manufacturers have also used several other strategies to
successfully produce proportional improvements in hydrocarbon emissions
at 20[deg] F. These include lean limit fuel strategies, elevated idle
speeds, retarded spark timing, and accelerated closed loop times. Some
software design strategies include fuel injection strategies detailed
in past Society of Automotive Engineers (SAE) papers \191\ that
synchronize fuel injection timing with engine intake valve position to
provide optimal fuel preparation. Spark delivery strategies have also
been entertained that include higher energy levels and even redundant
spark delivery to possibly complete additional combustion of unburned
hydrocarbons. We expect that software and/or calibration changes, such
as previously described, will generally perform as well or better than
added hardware. This is because critical hardware such as the catalyst
may not be immediately usable directly following the cold start. See
RIA Chapter 5 for further discussion.
---------------------------------------------------------------------------

\191\ Meyer, Robert and John B. Heywood, ``Liquid Fuel Transport
Mechanisms into the Cylinder of a Firing Port-Injected SI Engine
During Start-up,'' SAE 970865, 1997.
---------------------------------------------------------------------------

b. Feasibility Considering Current Certification Levels, Deterioration
and Compliance Margin
Of the vehicles that were certified to Tier 2 and demonstrated
proportional improvements in hydrocarbon emissions, approximately 20%
of vehicles below 6,000 pounds GVWR had certification levels in the
range of two to three times the 75[deg] F Tier 2 bin 5 full useful life
standard (.18 g/mile to .27 g/mile). These reported hydrocarbon levels
are from Cold CO test results for certification test vehicles with
typically only 4,000 mile aged systems, without full useful life
deterioration applied. Due to rapid advances in emission control
hardware technology, deterioration factors used today by manufacturers
to demonstrate full useful life compliance are very low and typically
even indicate little or no deterioration over the life of the vehicle.
The deterioration factors generated today by manufacturers are common
across all required test cycles including cold temperature testing. The
standards we are proposing will have a full useful life of 120,000
miles, consistent with Tier 2 standards. Additionally, manufacturers
typically target certification emission levels that incorporate a 20%
to 30% compliance margin primarily to account for in-use issues that
may cause emissions variability. The 0.3 g/mile FEL standard would
leave adequate flexibility for compliance margins and any emissions
deterioration concerns. See RIA Chapter 5 for further discussion and
details regarding current certification levels.
Given enough lead time, we believe manufacturers would be able to
develop control strategies for each of their widely varying product
lines utilizing the approaches outlined above without fundamentally
changing the design of the vehicles.
c. Feasibility and Test Programs for Higher Weight Vehicles
While a few of the heavier vehicles achieved a standard similar to
the lighter weight class, there were limited certification results
available for Tier 2 compliant vehicles over 6000 lbs GVWR (due to the
later Tier 2 phase-in schedule for these vehicles). To further support
the feasibility of the standard for heavier vehicles, we conducted a
feasibility study for Tier 2 vehicles over 6000 lbs GVWR to assess
their capabilities with typical Tier 2 hardware. We were able to reduce
HC emissions for one vehicle with models above and below 6,000 pounds
GVWR by between 60-70 percent, depending on control strategy, from a
baseline level of about 1.0 g/mile. The results are well within the 0.5
g/mile standard including compliance margin, and we even achieved a 0.3
g/mile level on some tests. We achieved these reductions through
recalibration without the use of new hardware. The findings from the
study are provided in detail in the RIA.
We believe the proposed standards are feasible while at the same
time providing the greatest degree of emission reduction achievable
through the application of available technology. Our feasibility
assessment, provided above, is based on our analysis of the stringency
of the standard given current emission levels at certification
(considering deterioration, compliance margin, and vehicle weight);
available emission control techniques; and our own feasibility testing.
In addition, sections VI.B.3-6 describe the proposed lead time and
flexibility within the program structure, which also contribute to the
feasibility of the proposed standards. Chapter 8 of the RIA provides
our cost estimations per vehicle and on a nationwide basis, including
capital and development costs. We believe the estimated costs are
reasonable and the proposal is cost effective, as provided in section
IX, below. Given the emission control strategies we expect
manufacturers to utilize, we expect feasible implementation of
technologies without a significant impact on vehicle noise, energy
consumption, or safety factors. Although manufacturers would need to
employ new emissions control strategies at cold temperatures,
fundamental Tier 2 vehicle hardware and designs are not expected to
change. In addition, we are providing necessary lead time for
manufacturers to identify and resolve any related issues as part of
overall vehicle development. We request comment on our analysis of the
feasibility of the proposed standards.
3. Standards Timing and Phase-in
a. Phase-In Schedule
EPA must consider lead time in determining the greatest degree of
emission reduction achievable under section 202(l) of the CAA. We are
proposing to begin implementing the standard in the 2010 model year
(MY) for LDVs/LLDTs and 2012 MY for HLDTs/MDPVs. The proposed
implementation schedule, in Table VI.B-2, begins 3 model years after
Tier 2 phase-in is complete for both vehicle classes. Manufacturers
would demonstrate compliance with phase-in requirements through sales
projections, similar to Tier 2. The 3-year period between completion of
the Tier 2 phase-in and the start of the new cold NMHC standard should
provide vehicle manufacturers sufficient lead time to design their
compliance strategies and determine the product development plans
necessary to meet the new standards. We believe that this phase-in
schedule is needed to allow manufacturers to develop compliant vehicles
without significant disruptions in the product development cycles.
Also, for vehicles above 6,000 GVWR, section 202(a) of the Act requires
that four years of lead time be provided to manufacturers.
We recognize that the new cold temperature standards we are
proposing could represent a significant new challenge for manufacturers
and development time will be needed. The issue of NMHC control at cold
temperatures was not anticipated by

[[Page 15849]]

many entities, and research and development to address the issue is
consequently at a rudimentary stage. Lead time is therefore necessary
before compliance can be demonstrated. While certification will only
require one vehicle model of a durability group to be tested,
manufacturers must do development on all vehicle combinations to ensure
full compliance within the durability test group. We believe a phase-in
allows the program to begin sooner than would otherwise be feasible.

Table VI.B-2.--Proposed Phase-in Schedule for 20 [deg]F NMHC Standard by Model Year
----------------------------------------------------------------------------------------------------------------
Vehicle GVWR (category) 2010 2011 2012 2013 2014 2015
----------------------------------------------------------------------------------------------------------------
< = 6000 lbs (LDV/LLDT)............ 25% 50% 75% 100% ........... ...........
> 6000 lbs HLDT and MDPV.......... ........... ........... 25% 50% 75% 100%
----------------------------------------------------------------------------------------------------------------

In considering a phase-in period, manufacturers have raised
concerns that a rapid phase-in schedule would lead to a significant
increase in the demand for their cold testing facilities, which could
necessitate substantial capital investment in new cold test facilities
to meet development needs. This is because manufacturers would need to
use their cold testing facilities not only for certification but also
for vehicle development. If vehicle development is compressed into a
narrow time window, significant numbers of new facilities would be
needed. Manufacturers were further concerned that investment in new
test facilities would be stranded at the completion of the initial
development and phase-in period.
As stated earlier, durability test groups may be large and diverse
and therefore require significant development effort and cold test
facility usage for each model. Our proposed phase-in period
accommodates test facilities and work load concerns by distributing
these fleet phase-in percentage requirements over a 4-year period for
each vehicle weight category. The staggered start dates for the phase-
in schedule between the two weight categories should further alleviate
manufacturers' concerns with needing to construct new test facilities.
Some manufacturers may still determine that upgrades to their current
cold facility are needed to handle increased workload. Some
manufacturers have indicated that they would simply add additional
shifts to their facility work schedules that are not in place today.
Some manufacturers will already meet the first-year requirement based
on current certification reporting, essentially providing an additional
year for distributing the anticipated development test burden for the
remaining fleet. The 4-year phase-in period provides ample time for
vehicle manufacturers to develop a compliance schedule that is
coordinated with their future product plans and projected product sales
volumes of the different vehicle models.
We request comments on the proposed start date and duration of the
phase-in schedule. We also request comment on allowing a volume-based
offset during the phase-in period for cases where manufacturers
voluntarily certify heavy-duty vehicles above 8,500 pound GVWR to the
proposed cold temperature standards. This may provide incentive for
voluntary certification of these heavier vehicles.
b. Alternative Phase-In Schedules
Alternative phase-in schedules essentially credit the manufacturer
for its early or accelerated efforts and allow the manufacturer greater
flexibility in subsequent years during the phase-in. By introducing
vehicles earlier than required, manufacturers would earn the
flexibility to make offsetting adjustments, on a vehicle-year basis, to
the phase-in percentages in later years. Under these alternative
schedules, manufacturers would have to introduce vehicles that meet or
surpass the NHMC average standards before they are required to do so,
or else introduce vehicles that meet or surpass the standard in greater
quantities than required.
We are proposing that manufacturers may apply for an alternative
phase-in schedule that would still result in 100% phase-in by 2013 and
2015, respectively, for the lighter and heavier weight categories. As
with the primary phase-in, manufacturers would base an alternative
phase-in on their projected sales estimates. An alternate phase-in
schedule submitted by a manufacturer would be subject to EPA approval
and would need to provide the same emissions reductions as the primary
phase-in schedule. We propose that the alternative phase-in could not
be used to delay full implementation past the last year of the primary
phase-in schedule (2013 for LDVs/LDTs and 2015 for HLDTs/MDPVs).
An alternative phase-in schedule would be acceptable if it passes a
specific mathematical test. We have designed the test to provide
manufacturers a benefit from certifying to the standards early, while
ensuring that significant numbers of vehicles are introduced during
each year of the alternative phase-in schedule. Manufacturers would
multiply their percent phase-in by the number of years the vehicles are
phased in prior to the second full phase-in year. The sum of the
calculation would need to be greater than or equal to 500, which is the
sum from the primary phase-in schedule (4*25 + 3*50 + 2*75 +
1*100=500). For example, the equation for LDVs/LLDTs would be as follows:

(6xAPI₂₀₀₈) + (5xAPI ₂₀₀₉) + (4xAPI
₂₀₁₀) + (3xAPI ₂₀₁₁) + (2xAPI ₂₀₁₂) +
(1xAPI ₂₀₁₃) >= 500%,

Where:

API is the anticipated phase-in percentage for the referenced model year.

California used this approach to an alternative phase-in for the
LEVII program.\192\ It provides alternative phase-in credit for both
the number of vehicles phased in early and the number of years the
early phase-in occurs.
---------------------------------------------------------------------------

\192\ Title 13, California Code of Regulations, Section 1961(b)(2).
---------------------------------------------------------------------------

As described above, the final sum of percentages for both LDVs/LDTs
and HLDTs/MDPVs must equal or exceed 500--the sum that results from a
25/50/75/100 percent phase-in. For example, a 10/25/50/55/100 percent
phase-in for LDVs/LDTs that begins in 2009 will have a sum of 510
percent and is acceptable. A 10/20/40/70/100 percent phase-in that
begins the same year has a sum of 490 percent and is not acceptable.
To ensure that significant numbers of LDVs/LDTs are introduced in
the 2010 time frame (2012 for HLDTs/MDPVs), manufacturers would not be
permitted to use alternative phase-in schedules that delay the
implementation of the requirements, even if the sum of the phase-in
percentages ultimately meets or exceeds 500. Such a situation could
occur if a manufacturer delayed implementation of its compliant
production until 2011 and began an 80/85/100 percent phase-in that year for

[[Page 15850]]

LDVs/LDTs. To protect against this possibility, we are proposing that
for any alternative phase-in schedule, a manufacturer's phase-in
percentages*years factor from the 2010 and earlier model years sum to
at least 100 (2012 and earlier for HLDTs/MDPVs). The early phase-in
also encourages the early introduction of vehicles meeting the new
standard or the introduction of such vehicles in greater quantity than
required. This would achieve early emissions reductions and provide an
opportunity to gain experience in meeting the standards.
Phase-in schedules, in general, add little flexibility for
manufacturers with limited product offerings because a manufacturer
with only one or two test groups cannot take full advantage of a 25/50/
75/100 percent or similar phase-in. Therefore, consistent with the
recommendations of the Small Advocacy Review Panel (SBAR Panel), which
we discuss in more detail later in section VI.E, manufacturers meeting
EPA's definition of ``small volume manufacturer'' would be exempt from
the phase-in schedules and would be required to simply comply with the
final 100% compliance requirement. This provision would only apply to
small volume manufacturers and not to small test groups of larger
manufacturers.
4. Certification Levels
Manufacturers typically certify groupings of vehicles called
durability groups and test groups, and they have some discretion on
what vehicle models are placed in each group. A durability group is the
basic classification used by manufacturers to group vehicles to
demonstrate durability and predict deterioration. A test group is a
basic classification within a durability group used to demonstrate
compliance with FTP 75[deg] F standards.\193\ For Cold CO,
manufacturers certify on a durability group basis, whereas for 75[deg]
F FTP testing, manufacturers certify on a test group basis. In keeping
with the current cold CO standards, we are proposing to require testing
on a durability group basis for the cold temperature NMHC standard. We
also propose to allow manufacturers the option of certifying on the
smaller test group basis, as is allowed under current cold CO
standards. Testing on a test group basis would require more tests to be
run by manufacturers but may provide them with more flexibility within
the averaging program. In either case, the worst case vehicle within
the group from an NMHC emissions standpoint would be tested for
certification.
---------------------------------------------------------------------------

\193\ 40 CFR 86.1803-01.
---------------------------------------------------------------------------

For the new standard, manufacturers would declare a family emission
limit (FEL) for each group either at, above, or below the fleet
averaging standard. The FEL would be based on the certification NMHC
level, including deterioration factor, plus the compliance margin
manufacturers feel is needed to ensure in-use compliance. The FEL
becomes the standard for each group, and each group could have a
different FEL so long as the projected sales-weighted average level met
the fleet average standard at time of certification. Like the standard,
the certification resolution for the FEL would be one decimal point.
This FEL approach would be similar to having bins in 0.1 g/mile
intervals, with no upper limit. Similar to a bin approach,
manufacturers would compute a sales-weighted average for the NMHC
emissions at the end of the model year and then determine credits
generated or needed based on how much the average is above or below the
standard.
5. Credit Program
As described above, we are proposing that manufacturers average the
NMHC emissions of their vehicles and comply with a corporate average
NMHC standard. In addition, we are proposing that when a manufacturer's
average NMHC emissions of vehicles certified and sold falls below the
corporate average standard, it could generate credits that it could
save for later use (banking) or sell to another manufacturer (trading).
Manufacturers would consume any credits if their corporate average NMHC
emissions were above the applicable standard for the weight class.
EPA views the proposed averaging, banking, and trading (ABT)
provisions as an important element in setting emission standards
reflecting the greatest degree of emission reduction achievable,
considering factors including cost and lead time. If there are vehicles
that will be particularly costly or have a particularly hard time
coming into compliance with the standard, a manufacturer can adjust the
compliance schedule accordingly, without special delays or exceptions
having to be written into the rule. This is an important flexibility
especially given the current uncertainty regarding optimal technology
strategies for any given vehicle line. In addition, ABT allows us to
consider a more stringent emission standard than might otherwise be
achievable under the CAA, since ABT reduces the cost and improves the
technological feasibility of achieving the standard. By enhancing the
technological feasibility and cost effectiveness of the proposed
standard, ABT allows the standard to be attainable earlier than might
otherwise be possible.
Credits may be generated prior to, during, and after the phase-in
period. Manufacturers could certify LDVs/LLDTs to standards as early as
the 2008 model year (2010 for HLDTs/MDPVs) and receive early NMHC
credits for their efforts. They could use credits generated under these
``early banking'' provisions after the phase-in begins in 2010 (2012
for HLDTs/MDPVs).
a. How Credits Are Calculated
The corporate average for each weight class would be calculated by
computing a sales-weighted average of the NMHC levels to which each FEL
was certified. As discussed above, manufacturers group vehicles into
durability groups or test groups and establish an FEL for each group.
This FEL becomes the standard for that group. Consistent with FEL
practices in other programs, manufacturers may opt to select an FEL
above the test level. The FEL would be used in calculating credits. The
number of credits or debits would then be determined using the
following equation:

Credits or Debits = (Standard - Sales weighted average of FELs to
nearest tenth) x Actual Sales

If a manufacturer's average was below the 0.3 g/mi corporate
average standard for LDVs/LDTs, credits would be generated (below 0.5
g/mi for HLDTs/MDPVs). These credits could then be used in a future
model year when its average NMHC might exceed the 0.3 or the 0.5
standard. Conversely, if the manufacturer's fleet average was above the
corporate average standard, banked credits could offset the difference,
or credits could be purchased from another manufacturer.
b. Credits Earned Prior to Primary Phase-in Schedule
We propose that manufacturers could earn early emissions credits if
they introduce vehicles that comply with the new standards early and
the corporate average of those vehicles is below the applicable
standard. Early credits could be earned starting in 2008 for vehicles
meeting the 0.3 g/mile standard and in 2010 for vehicles meeting the
0.5 g/mile standard. These emissions credits generated prior to the
start of the phase-in could be used both during and after the phase-in
period and have all the same properties as credits generated by
vehicles subject to the primary phase-in schedule. As previously
mentioned, we are also proposing that manufacturers

[[Page 15851]]

may apply for an alternative phase-in schedule for vehicles that are
introduced early. The alternative phase-in and early credits provisions
would operate independent of one another.
c. How Credits Can Be Used
A manufacturer could use credits in any future year when its
corporate average was above the standard, or it could trade (sell) the
credits to other manufacturers. Because of separate sets of standards
for the different weight categories, we are proposing that
manufacturers compute their corporate NMHC averages separately for LDV/
LLDTs and HLDTs/MDPVs. Credit exchanges between LDVs/LLDTs and HLDTs/
MDPVs would be allowed. This will provide added flexibility for fuller-
line manufacturers who may have the greatest challenge in meeting the
new standards due to their wide disparity of vehicle types/weights and
emissions levels.
d. Discounting and Unlimited Life
Credits would allow manufacturers a way to address unexpected
shifts in their sales mix. The NMHC emission standards in this proposed
program are quite stringent and do not present easy opportunities to
generate credits. Therefore, we are not proposing to discount unused
credits. Further, the degree to which manufacturers invest the
resources to achieve extra NMHC reductions provides true value to the
manufacturer and the environment. We do not want to take measures to
reduce the incentive for manufacturers to bank credits, nor do we want
to take measures to encourage unnecessary credit use. Consequently we
are not proposing that the NMHC credits would have a credit life limit.
However, we are proposing that they only be used to offset deficits
accrued with respect to the proposed 0.3/0.5 g/mile cold temperature
standards. We request comment on the need for discounting of credits or
credit life limits and what those discount rates or limits, if any,
should be.
e. Deficits Could Be Carried Forward
When a manufacturer has an NMHC deficit at the end of a model
year--that is, its corporate average NMHC level is above the required
corporate average NMHC standard--we are proposing that the manufacturer
be allowed to carry that deficit forward into the next model year. Such
a carry-forward could only occur after the manufacturer used any banked
credits. If the deficit still existed and the manufacturer chose not
to, or was unable to, purchase credits, the deficit could be carried
over. At the end of that next model year, the deficit would need to be
covered with an appropriate number of credits that the manufacturer
generated or purchased. Any remaining deficit would be subject to an
enforcement action.
To prevent deficits from being carried forward indefinitely, we
propose that manufacturers would not be permitted to run a deficit for
two years in a row. We believe that it is reasonable to provide this
flexibility to carry a deficit for one year given the uncertainties
that manufacturers face with changing market forces and consumer
preferences, especially during the introduction of new technologies.
These uncertainties can make it hard for manufacturers to accurately
predict sales trends of different vehicle models.
f. Voluntary Heavy-Duty Vehicle Credit Program
In addition to MDPV requirements in Tier 2, we also currently have
chassis-based emissions standards for other complete heavy-duty
vehicles (e.g., large pick-ups and cargo vans) above 8,500 pound GVWR.
However, these standards do not include cold temperature CO standards.
As noted below in section VI.B.6.a, we are not proposing to apply cold
temperature NMHC standards to heavy-duty gasoline vehicles due to a
current lack of emissions data on which to base such standards. We plan
to revisit the need for and feasibility of standards as data become
available.
During discussions with manufacturers, we discussed a voluntary
program for chassis-certified complete heavy-duty vehicles. We believe
that there may be opportunities within the framework of a cold
temperature NMHC program to allow for emissions credits from chassis-
certified heavy-duty vehicles above 8,500 pounds GVWR to be used to
meet the proposed standards. It is possible that some control
strategies developed for meeting cold NMHC emissions standards could
also be applied to these vehicles above 8,500 pounds GVWR.
One approach would be to allow manufacturers to certify heavy-duty
vehicles voluntarily to the 0.5 g/mile cold NMHC standards proposed for
HLDTs/MDPVs. To the extent that heavy-duty vehicles achieve FELs below
the 0.5 g/mile standard, manufacturers could earn credits which could
be applied to any vehicle subject to the proposed standard. It is
unclear, however, if this approach would provide a meaningful
opportunity for credit generation, given the stringency of the
standard. We would expect that most heavy-duty vehicles would have
emissions well above the 0.5 g/mile level, based on the additional
weight of the vehicle. We request comment on this approach, as well as
others for voluntary certification and credit generation.
It may be possible to establish a voluntary standard above 0.5 g/
mile for purposes of generating credits, but we would need data on
which to base this level of the standard. Suggestions on an appropriate
level of a voluntary standard are welcomed, as well as any data that
support such a recommendation. Comments on testing protocols, such as
use of the vehicle's adjusted loaded vehicle weight (ALVW) or loaded
vehicle weight (LVW), are also encouraged. We believe such a voluntary
program could provide significant data that would help us evaluate the
feasibility of a future standard for these vehicles.
6. Additional Vehicle Cold Temperature Standard Provisions
We request comments on all of the following proposed provisions.
a. Applicability
We are proposing to apply the new cold temperature standards to all
gasoline-fueled light-duty vehicles and MDPVs sold nationwide. While we
have significant amounts of data on which to base our proposals for
gasoline-fueled light-duty vehicles, we have very little data for
light-duty diesels. For 75[deg] F FTP standards, the same set of
standards apply, but in the 20[deg] F context we know very little about
diesel emissions due to a lack of data. Currently, diesel vehicles are
not subject to the cold CO standard, so there are no requirements to
test diesel vehicles at cold temperatures. There are sound engineering
reasons, however, to expect cold NMHC emissions for diesel vehicles to
be as low as or even lower than the proposed standards. This is because
diesel engines operate under leaner air-fuel mixtures compared to
gasoline engines, and therefore have fewer engine-out NMHC emissions
due to the abundance of oxygen and more complete combustion. A very
limited amount of confidential manufacturer-furnished information is
consistent with this engineering hypothesis. A comprehensive assessment
of appropriate standards for diesel vehicles would require a
significant amount of investigation and analysis of issues such as
feasibility and costs. This effort would be better suited to a future
rulemaking. Therefore, at this time, we are not proposing to apply the
cold NMHC standards to light-duty diesel vehicles. We will continue to
evaluate

[[Page 15852]]

data for these vehicles as they enter the fleet and will reconsider the
need for standards if data indicate that there may be instances of high
NMHC emissions from diesels at cold temperatures. We have proposed cold
temperature FTP testing for diesels as part of the Fuel Economy
Labeling rulemaking, including NMHC measurement.\194\ This testing data
would allow us to assess NMHC certification type data over time.
However, this wouldn't include development testing manufacturers would
need to do in order to meet a new diesel cold temperature standard.
---------------------------------------------------------------------------

\194\ ``Fuel Economy Labeling of Motor Vehicles; Revisions to
Improve Calculation of Fuel Economy Estimates,'' Proposed Rule, 71,
FR 5426, February 1, 2006.
---------------------------------------------------------------------------

In addition, there currently is no cold CO testing requirement for
alternative fuel vehicles. There are little data upon which to evaluate
NMHC emissions when operating on alternative fuels at cold
temperatures. For fuels such as ethanol, it is difficult to develop a
reasonable proposal due to a lack of fuel specifications, testing
protocols, and current test data. Other fuels such as methanol and
natural gas pose similar uncertainty. Therefore, we are not proposing a
cold NMHC testing requirement for alternative fuel vehicles. We will
continue to investigate these other technologies and request comment on
standards for vehicles operating on fuels other than gasoline.
We are proposing that flex-fuel vehicles would still require
certification to the applicable cold NMHC standard, though only when
operated on gasoline. For multi-fuel vehicles, manufacturers would need
to submit a statement at the time of certification that either confirms
the same control strategies used with gasoline would be used when
operating on ethanol, or that identifies any differences as an
Auxiliary Emission Control Device (AECD). Again, dedicated alternative-
fueled vehicles, including E-85 vehicles, would not be covered.
For heavy-duty gasoline-fueled vehicles, we have no data, but we
would expect a range of emissions performance similar to that of
lighter gasoline-fueled trucks. Due to the lack of test data on which
to base feasibility and cost analyses, we are not proposing cold
temperature NMHC standards for these vehicles at this time. We request
comments and data on these vehicles and plan to revisit this issue when
sufficient data is available.
b. Useful Life
The ``useful life'' of a vehicle means the period of use or time
during which an emission standard applies to light-duty vehicles and
light-duty trucks.\195\ Consistent with the current definition of
useful life in the Tier 2 regulations, for all LDVs/LDTs and HLDTs/
MDPVs, we are proposing new full useful life standards for cold
temperature NMHC standards. Given that we expect that manufacturers
will make calibration or software changes to existing Tier 2
technologies, it is reasonable for there to be the same useful life as
for the Tier 2 standards themselves. For LDV/LLDT, the full useful life
values would be 120,000 miles or 10 years, whichever comes first, and
for HLDT/MDPV, full useful life is 120,000 miles or 11 years, whichever
comes first.\196\
---------------------------------------------------------------------------

\195\ 40 CFR 86.1803-01.
\196\ 40 CFR 86.1805-04.
---------------------------------------------------------------------------

c. High Altitude
We do not expect emissions to be significantly different at high
altitude due to the use of common emissions control calibrations.
Limited data submitted by a manufacturer suggest that FTP emissions
performance at high altitude generally follows sea level performance.
Furthermore, there are very limited cold temperature testing facilities
at high altitudes. Therefore, under normal circumstances, manufacturers
would not be required to submit vehicle test data for high altitude.
Instead, manufacturers would be required to submit an engineering
evaluation indicating that common calibration approaches are utilized
at high altitude. Any deviation from sea level in emissions control
practices would be required to be included in the auxiliary emission
control device (AECD) descriptions submitted by manufacturers at
certification. Additionally, any AECD specific to high altitude would
require engineering emission data for EPA evaluation to quantify any
emission impact and validity of the AECD.
d. In-Use Standards for Vehicles Produced During Phase-In
As we have indicated, the standards we are proposing would be more
challenging for some vehicles than for others. With any new technology,
or even with new calibrations of existing technology, there are risks
of in-use compliance problems that may not appear in the certification
process. In-use compliance concerns may discourage manufacturers from
applying new calibrations or technologies. Thus, it may be appropriate
for the first few years, for those vehicles most likely to require the
greatest applications of effort, to provide assurance to the
manufacturers that they will not face recall if they exceed standards
in use by a specified amount. Therefore, similar to the approach used
in Tier 2, we are proposing an in-use standard that is 0.1 g/mile
higher than the certification FEL for any given test group for a
limited number of model years.\197\ For example, a test group with a
0.2 g/mile FEL would have an in-use standard of 0.3 g/mile. This would
not change the FEL or averaging approaches and would only apply in
cases where EPA tests vehicles in-use to ensure emissions compliance.
---------------------------------------------------------------------------

\197\ ``Control of Air Pollution from New Motor Vehicles: Tier 2
Motor Vehicle Emissions Standards and Gasoline Sulfur Control
Requirements'', Final Rule, 65 FR 6796, February 10, 2000.
---------------------------------------------------------------------------

We propose that the in-use standards be available for the first few
model years of sales after a test group meeting the new standards is
introduced, according to a schedule that provides more years for test
groups introduced earlier in the phase-in. This schedule provides
manufacturers with time to determine the in-use performance of vehicles
and learn from the earliest years of the program to help ensure that
vehicles introduced after the phase-in period meet the final standards
in-use. It also assumes that once a test group is certified to the new
standards, it will be carried over to future model years. The tables
below provide the proposed schedule for the availability of the in-use
standards.

Table VI.B-3.--Schedule for In-Use Standards for LDVs/LLDTs
----------------------------------------------------------------------------------------------------------------
Model year of introduction 2008 2009 2010 2011 2012 2013
----------------------------------------------------------------------------------------------------------------
Models years that the in-use standard is 2008 2009 2010 2011 2012 2013
available for carry-over test groups......... 2009 2010 2011 2012 2013 2014
2010 2011 2012 2013 2014
2011 2012 2013
----------------------------------------------------------------------------------------------------------------

[[Continued on page 15853]]

Notices For
2009
2008
2007
2006
2005
2004
2003
2002
2001
2000
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1998
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1996
1995
1994

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