Carbon monoxide (CO) is a colorless, odorless, and poisonous gas produced by incomplete burning of fuels used in internal combustion engines. Elevated levels of CO generally occur during the winter months because of increased CO emissions from cold vehicles and the occurrence of temperature inversions, which trap pollutants near the ground and inhibit dispersion and dilution. The U.S. Environmental Protection Agency (EPA) has set National Air Ambient Quality Standards (NAAQS) for CO that specify upper limits of 35 ppm for a 1-hour period and 9 ppm for an 8-hour period. Generally, the 8-hour limit is the more restrictive and virtually all exceedances in recent years involve violation of this limit. Monitoring stations are allowed one exceedance of the air quality standard per year. A second exceedance consititutes a violation.
An important program for reducing ambient CO concentrations is the use of cleaner burning oxygenated gasoline. Extra oxygen enhances fuel combustion and helps to offset fuel-rich operating conditions, particularly during vehicle starting in cold weather.(1) Section 211(m) of the Clean Air Act (42 U.S.C. 7401-7671q) requires that gasoline containing at least 2.7 percent oxygen by weight is to be used in the wintertime in those areas of the county that exceed the CO NAAQS. The winter oxygenated gasoline program applies to all gasoline sold in the larger of the Consolidated Metropolitan Statistical Area (CMSA) or Metropolitan Statistical Area (MSA) in which the nonattainment area is located.(2)
| For a current list of oxygenated gasoline program areas, refer to the U.S. Environmental Protection Agency, Office of Mobile Sources, State Winter Oxygenated Fuel Programs. For a current list of ozone nonattainment areas, refer to the EPA Green Book. |
The control period is that portion of the year in which the area is prone to high ambient concentrations of CO, as determined by the EPA ("Guidelines for Oxygenated Gasoline Credit Programs and Guidelines on Establishment of Control Periods Under Section 211(m) of the Clean Air Act as Amended," 57 FR 47853, October 20, 1992).(3)
Beginning on November 1, 1992, 39 areas of the county were required to participate in the oxygenated gasoline program. These 39 original CO nonattainment areas had CO design values of 9.5 ppm or above based on data for the 2-year period of 1988 and 1989 (Table 1).
[Click here for control area populations in Excel .XLS file, 136 KB]
| Table 1. Original Oxygenated Gasoline Control Areas | |||
| Control Area | Estimated Population 7/1/96 (thousands) |
Control Period | |
| Start | End | ||
| Albuquerque, NM * | 527 | Nov. 1 | Feb. 29 |
| Anchorage, AK | 250 | Nov. 1 | Feb. 29 |
| Baltimore, MD * | 2,436 | Nov. 1 | Feb. 29 |
| Boston-Lawrence-Salem, MA * | 3,939 | Nov. 1 | Feb. 29 |
| Chico, CA * | 192 | Oct. 1 | Jan. 31 |
| Cleveland-Akron-Lorain, OH * | 2,811 | Nov. 1 | Feb. 29 |
| Colorado Springs, CO | 473 | Nov. 1 | Feb. 29 ** |
| Denver-Boulder, CO | 2,277 | Nov. 1 | Feb. 29 ** |
| Duluth, MN * | 196 | Oct. 1 | Jan. 31 |
| El Paso, TX | 684 | Nov. 1 ** | Feb. 29 ** |
| Fairbanks, AK | 84 | Nov. 1 | Feb. 29 |
| Fort Collins-Loveland, CO | 222 | Nov. 1 | Feb. 29 ** |
| Fresno, CA * | 751 | Oct. 1 | Jan. 31 |
| Grants Pass, OR | 21 | Nov. 1 | Feb. 29 |
| Greensboro-Winston-Salem-High Point, NC * | 1,025 | Nov. 1 | Feb. 29 |
| Hartford, CT * | 1,062 | Nov. 1 | Feb. 29 |
| Klamath County, OR | 62 | Nov. 1 | Feb. 29 |
| Las Vegas, NV | 1,049 | Oct. 1 | Feb. 29 ** |
| Los Angeles-Anaheim-Riverside, CA | 15,495 | Oct. 1 | Feb. 29 |
| Medford, OR | 169 | Nov. 1 | Feb. 29 |
| Memphis, TN * | 912 | Nov. 1 | Feb. 29 |
| Minneapolis-St. Paul, MN | 2,618 | Oct. 1 ** | Jan. 31 ** |
| Missoula, MT | 88 | Nov. 1 | Feb. 29 |
| Modesto, CA * | 416 | Oct. 1 | Jan. 31 |
| New York City, CT * | 969 | Oct. 1** | Apr. 30 ** |
| New York City, NY-NJ | 17,588 | Oct. 1** | Apr. 30 ** |
| Philadelphia-Wilmington-Trenton, PA-MD-NJ * | 5,832 | Nov. 1 | Feb. 29 |
| Phoenix, AZ | 2,611 | Oct. 1 ** | Feb. 29 ** |
| Portland, OR * (1) | 1,411 | Nov. 1 | Feb. 29 |
| Provo-Orem, UT | 320 | Nov. 1 | Feb. 29 |
| Raleigh-Durham, NC * | 883 | Nov. 1 | Feb. 29 |
| Reno, NV | 299 | Oct. 1 | Jan. 31 |
| Sacramento, CA * | 1,632 | Oct. 1 | Jan. 31 |
| San Diego, CA * | 2,655 | Nov. 1 | Feb. 29 |
| San Francisco, CA * | 6,605 | Oct. 1 | Jan. 31 |
| Seattle-Tacoma, WA * | 2,823 | Nov. 1 | Feb. 29 |
| Spokane, WA | 405 | Sep. 1 | Feb. 29 |
| Stockton, CA * | 533 | Oct. 1 | Jan. 31 |
| Syracuse, NY * | 664 | Nov. 1 | Feb. 29 |
| Vancouver, WA * (1) | 305 | Nov. 1 | Feb. 29 |
| Washington, DC-MD-VA * | 4,216 | Nov. 1 | Feb. 29 |
| Total Population, Mandated Areas | 87,509 | 33.0 % of total U.S. population | |
| Total U.S. Population | 265,284 | ||
Notes:
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Sources:
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Any area that exceeds the CO design value of 9.5 ppm for any 2-year period after 1989, will be designated in nonattainment and must implement an oxygenated gasoline program within 3 years.
| Table 2. Additions to Original Control Areas | |||||
| Control Area | Estimated Population 7/1/96 (thousands) |
Control Period | EPA Federal Register Notice | ||
| Start | End | Citation | Date | ||
| Salt Lake City, UT * | 1,043 | 11/1 | 2/29 | 59 FR 55585 | Nov. 8, 1994 |
| Ogden, UT | 175 | 11/1 | 2/29 | 59 FR 55585 | Nov. 8, 1994 |
Notes:
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| Sources: Population - U.S. Census Bureau, Place and County Subdivision Population Estimates | |||||
An oxygenated gasoline program is no longer required once an area is redesignated in attainment of the CO NAAQS. To be redesignated in attainment, an area must have no more than one exceedance of the CO standard over at least two consecutive years. To provide for the possibility of future NAAQS violations, a maintenance plan must contain contingency measures to assure prompt correction of any air quality problems. A contigency measure for several redesignated areas is reinstatement of the oxygenated gasoline program for the following CO season if there is a violation of the CO standard. An area may also voluntarily continue the oxygenated gasoline programs as part of its maintenance plan (refer to Table 6).
| Table 3. Areas Redesignated in Attainment | ||||
| Control Area | Estimated Population 7/1/96 (thousands) |
EPA Federal Register Notice | ||
| Citation | Date | |||
| Albuquerque, NM * | 527 | 61 FR 29970 | Jun. 13, 1996 | |
| Baltimore, MD | 2,436 | 60 FR 55321 | Oct. 31, 1995 | |
| Boston-Lawrence-Salem, MA | 3,939 | 61 FR 2918 | Jan. 30, 1996 | |
| Chico, CA | 192 | 63 FR 15305 | Mar. 31, 1998 | |
| Cleveland-Akron-Lorain, OH | 2,811 | 59 FR 5332 | Feb. 4, 1994 | |
| Duluth, MN | 196 | 59 FR 17706 | Apr. 14, 1994 | |
| Fesno, CA | 751 | 63 FR 15305 | Mar. 31, 1998 | |
| Greensboro-Winston-Salem-Highpoint, NC | 1,025 | 59 FR 48399 | Sep. 21, 1994 | |
| Hartford, CT | 1,062 | 61 FR 24239 | May 14, 1996 | |
| Memphis, TN | 912 | 59 FR 37939 | Jul. 26, 1994 | |
| Minneapolis-St. Paul, MN * | 2,618 | 64 FR 25855 (proposed rule) | May 13, 1999 | |
| Modesto, CA | 416 | 63 FR 15305 | Mar. 31, 1998 | |
| New York City, CT * | 969 | 64 FR 12005 | Mar. 10, 1999 | |
| Philadelphia-Wilmington-Trenton, PA-MD-NJ | 5,832 | 61 FR 2926 (PA) 61 FR 33678 (NJ) | Jan. 30, 1996 Jun. 28, 1996 | |
| Portland, OR * | 1,411 | 62 FR 46802 | Sep. 2, 1997 | |
| Raleigh-Durham, NC | 883 | 60 FR 39258 | Aug. 2, 1995 | |
| Sacramento, CA | 1,632 | 63 FR 15305 | Mar. 31, 1998 | |
| Salt Lake City, UT | 1,043 | 64 FR 3216 | Jan. 21, 1999 | |
| San Diego, CA | 2,655 | 63 FR 15305 | Mar. 31, 1998 | |
| San Francisco, CA | 6,605 | 63 FR 15305 | Mar. 31, 1998 | |
| Seattle-Tacoma, WA | 2,823 | 61 FR 53323 | Oct. 11, 1996 | |
| Stockton, CA | 533 | 63 FR 15305 | Mar. 31, 1998 | |
| Syracuse, NY | 664 | 58 FR 50851 | Sep. 29, 1993 | |
| Vancouver, WA | 305 | 61 FR 54560 | Oct. 21, 1996 | |
| Washington, DC-MD-VA | 4,216 | 61 FR 2931 | Jan. 30, 1996 | |
| Total Population, Redesignated Areas | 46,456 | 15.2 % of total U.S. population | ||
| Total U.S. Population | 265,284 | |||
Notes:
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| Sources: Population - U.S. Census Bureau, Place and County Subdivision Population Estimates | ||||
The following areas are reported to be preparing or have submitted redesignation requests: (4)
In December 1992, the Governor of Alaska temporarily suspended the oxygenated gasoline program in the cities of Anchorage and Fairbanks because of concerns over the health and driveability of MTBE blended gasoline. Anchorage chose to implement an oxygenated gasoline program using a 10 volume percent ethanol blend rather than MTBE. The Anchorage program resumed on January 1, 1995 and continued through March 31, 1995. In subsequent years, the program will cover the original Nov. 1 through Feb. 29 control period (EPA, 61 FR 24712). The Fairbanks program was scheduled to resume on Nov. 1, 1997 (Alaska Department of Environmental Conservation), however, the program has yet to be reimplemented.
The Salt Lake City-Ogden, UT., metropolitan statistical area was added to the list of nonattainment areas during the winter of 1994-1995. This area has never implemented an oxygenated gasoline program. The Salt lake City area was recently redesignated in attainment and the Ogden area has requested redesignation Utah State Implementation Plan (September 4, 1996).
The Clean Air Act specifies that the length of the control period shall not be less than 4 months unless a state can demonstrate that, because of meteorological conditions, that there will no CO exceedances outside the reduced control period. States may also expand the oxygenated gasoline program beyond the control period designated by the EPA. For example, the state of Minnesota extended the Mineapolis-St. Paul oxygenated gasoline season to a year-round program beginning October 1, 1995.
| Table 4. Revised Oxygenated Gasoline Control Periods | ||||||
| Control Area | Original Period | Revised Period | EPA Federal Register Notice | |||
| Start | End | Start | End | Citation | Date | |
| Colorado Springs, CO | Nov. 1 | Feb. 29 | Nov. 1 | Feb. 7 * | 62 FR 10690 | Mar. 10, 1997 |
| Denver-Boulder, CO | Nov. 1 | Feb. 29 | Nov. 1 | Feb. 7 * | 62 FR 10690 | Mar. 10, 1997 |
| El Paso, TX | Nov. 1 | Feb. 29 | Oct. 1 | Mar. 31 | 59 FR 46766 | Sep. 12, 1994 |
| Fort Collins-Loveland, CO | Nov. 1 | Feb. 29 | Nov. 1 | Feb. 7 * | 62 FR 10690 | Mar. 10, 1997 |
| Las Vegas, NV | Oct. 1 | Feb. 29 | Oct. 1 | Mar. 31 | 63 FR 68415 (proposed rule) | Dec. 11, 1998 |
| Minneapolis-St.Paul, MN | Oct. 1 | Jan. 31 | Jan. 1 | Dec. 31 | 61 FR 6547 | Feb. 21, 1996 |
| New York City, NY-CT-NJ | Oct. 1 | Apr. 30 | Nov. 1 | Feb. 29 | 61 FR 5299 (NJ) 61 FR 38574 (CT) 61 FR 38594 (NY) | Feb. 12, 1996 Jul. 25, 1996 July 25, 1996 |
| Phoenix, AZ | Oct. 1 | Feb. 29 | Nov. 15 | Mar. 31 | ||
| Note: * The control period was first changed to end on Feb. 14. Beginning with the 1998-1999 control period the end date was changed to Feb. 7. | ||||||
EPA may also provide a waiver from the minimum 2.7 weight percent oxygen requirement if the State can demonstrate that using oxygenated gasoline would prevent or interfere with the attainment of a NAAQS or a State or local ambient air quality standard for any air pollutant other than CO. California restricted oxygen content to 1.8 to 2.2 weight percent because of concern over attaining ozone air quality standards. States are also not restricted from requiring a higher oxygen content. Several states have increased the oxygen requirement to be consistent with blending 10 volume percent ethanol (3.5 weight percent oxygen).
| Table 5. Revised Oxygenate Requirements | |||
| Control Area | Description | EPA Federal Register Notice | |
| Citation | Date | ||
| Anchorage, AK | 10 volume % ethanol | 61 FR 24712 | May 16, 1996 |
| California | 1.8 to 2.2 weight % oxygen | ||
| Denver, CO | Average 3.1 weight % oxygen | 62 FR 10690 | Mar. 10, 1997 |
| Fairbanks, AK | 10 volume % ethanol | 61 FR 24712 | May 16, 1996 |
| Las Vegas, NV | 3.5 weight % oxygen | 64 FR 29573 | Jun. 2, 1999 |
| Phoenix, AZ | 3.5 weight % oxygen | ||
| Provo-Orem, UT | average 3.1 weight % oxygen | ||
| Spokane, WA | 3.5 weight % oxygen as ethanol | 62 FR 49442 | Sep. 22, 1997 |
States have also been allowed to implement oxygenated gasoline programs beyond what is required by the Clean Air Act. Areas redesignayted in attainment may continue to require oxygenated gasoline as part of their CO maintenance plan. States may aldso require oxygenated gasoline in areas that have always been in attainement of the CO NAAQS. Forexample, the state of Minnesota has revised is Statutes to require oxygenated gasoline in all parts of the state throughout the year beginning on October 1, 1997.
| Table 6. State Mandated Oxygenated Gasoline Programs | |||||
| Control Area | Estimated Population 7/1/96 (thousands) |
Control Period | State Agency | ||
| Start | End | ||||
| Albuquerque, NM | 527 | 11/1 | 2/29 | Albuquerque/Bernalillo Co. Air Quality Control Board | |
| New York City, CT | 969 | 11/1 | 2/29 | Dept. of Environmental Protection | |
| Minnesota (rest of state) | 2,039 | 1/1 | 12/31 | Pollution Control Agency | |
| Portland, OR | 1,411 | 11/1 | 2/29 | Dept. of Environmental Quality | |
| Tucson, AZ | 767 | 10/1 | 3/31 | Pima Association of Governments | |
Notes:
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The oxygenated gasoline program is administered and enforced by the individual states (in contrast to the reformulated gasoline program, which is administered by the EPA). State requirements may be found in State Implementation Plans filed with the EPA, or in State laws.
| Table 7. State Air Quality Regulations On-Line | ||
| State | Regulation | State Agency |
| Alaska | Title 18 Chap. 53 | Alaska Dept.of Environmental Conservation |
| Arizona | ARS Title 41, Chap. 15, Article 6 | Arizona Dept. of Weights and Measures |
| California | Title 13 CCR | California Air Resources Board |
| Colorado | Regulation No. 13 | Colorado Dept. of Public Health and Environment |
| Minnesota | Mn. Statutes Sect. 239.791 State Implementation Plan | Minnesota Pollution Control Agency |
| Nevada | APC Regs Section 53 | Clark County District Board of Health |
| New Jersey | NJAC, Title 7, Chap. 27, Subchap. 25 | N.J. Dept. of Environmental Protection |
| New York | 6 NYRCC Ch. III, Subpart 225-3 | N.Y. Dept. of Environmental Conservation |
| North Carolina | 15A NCAC 2D.1300 | N.C. Dept. of Environment, Health, and Natural Resources |
| Ohio | OAC 3745 | Ohio Environmental Protection Agency |
| Oregon | OAR Chap. 340 Div. 22 | Oregon Dept. of Environmental Quality |
| Texas | TAC Title 30 Part I Chap. 114 State Implementation Plan | Texas Natural Resource Conservation Commission |
| Utah | UAC R307 State Implementation Plan, Section IX Part C | Utah Dept. of Environmental Quality |
| Washington (Seattle-Tacoma) | PSAPCA Regulation 2.09 | Puget Sound Air Pollution Control Agency |
| Washington (Spokane) | WAC 173-492 | Washington State Dept. of Ecology * |
| Washington (Vancouver) | SWAPCA 492 | Southwest Air Pollution Control Authority |
| Note: * Spokane, WA. program administered by Spokane Country Air Pollution Control Authority | ||
(1) For studies on the effect of oxygenates on vehicle CO emissions and ambient CO concentrations refer to:
(2) For nonattainment areas not in a CMSA or MSA, the control area is the nonattainment area.
(3) The "57 FR 47853" notation is the citation for the Federal Register, volume 57, page 47853.
(4) U.S. Environmental Protection Agency, "State Winter Oxygenated Fuels Program" (June 16, 1999).
File last modified: July 1, 1999
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