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Area Designations for 1997 Ground-level Ozone Standards

Reclassification Fact Sheet

EPA Reclassifies Nine 8-hour Ozone Nonattainment Areas

  • On September 15, 2004, the U.S. Environmental Protection Agency (EPA) reclassified nine of the recently identified  8-hour ozone nonattainment areas from moderate to the next lower classification - marginal. EPA received nine requests for reclassification to a lower category. No areas requested reclassification to a higher category.

  • The nine areas are: Cass County, Michigan; Muskegon County, Michigan; Detroit, Michigan; Greensboro, North  Carolina; Kent/Queen Anne Counties, Maryland; Lancaster, Pennsylvania; LaPorte, Indiana; Memphis, Tennessee/Arkansas; and Richmond, Virginia.

  • Reclassifying a nonattainment area to a lower classification means that the area is expected to achieve clean air sooner. While moderate areas must attain national air quality standards for 8-hour ozone no later than June 2010, marginal areas must attain no later than June 2007.

  • Reclassifying an area to a lower classification also means that the area is subject to fewer mandatory emissions control requirements such as tighter requirements to offset emissions of ozone forming compounds from new and modified industrial facilities. 


  • On April 30, 2004, EPA published a final rule designating and classifying all areas in the United States, including Indian country, for the more protective national air quality standard for 8-hour ozone. (69 FR 23858)

  • The Clean Air Act authorizes EPA to reclassify an ozone nonattainment area to the next higher or lower classification under certain conditions. The Act requires reclassifications to occur within 90 days of the area's initial classification.

  • Only areas with a design value within 5% of the cutoff for the next highest or lowest category were eligible for reclassification under the 8-hour ozone standard. Reclassification requests were due to EPA by July 15, 2004.

  • A design value is based on the monitored air quality reading used by EPA to determine an area's air quality status.  Design values inidcate whether an area is violating the national ambient air quality standards.

  • Using the rounding convention EPA established in its 1998 guidance "Guideline on Data Handling Conventions For the  8-Hour Ozone NAAQS," up to 5.4% rounds down to 5% while anything higher than that rounds up to 6%. A moderate area  with a design value up to 97 part per billion (ppb) was eligible for a reclassification down to a marginal area (design values for marginal areas range from 85 ppb up to but not including 92 ppb).

  • In making a decision on reclassification, the Clean Air Act authorizes EPA to consider the number of exceedances of  the primary national ambient air quality standard for ozone in the area; the level of pollution transport between the area and other affected areas, including both intrastate and interstate transport; and the mix of sources and air pollutants in the area.

  • The April 30 notice invited states to submit requests to reclassify areas. This notice also listed the specific criteria EPA would use to evaluate a reclassification request. The criteria include:

    • Discontinuity:  A five percent reclassification down should not create an area where one classification is surrounded by areas of higher classification.
    • Attainment:  Evidence should be available that the proposed area would be able to attain by the earlier date  specified by the lower classification.
    • Emissions reductions:  Evidence should be available that the area would achieve the emission reductions necessary to attain in the shorter time period.
    • Trends:  Historical air quality data should indicate substantial air quality improvement.
    • Years of data:  For the 8-hour ozone standard, the 2001-2003 period is central to determining classification. 

    EPA could approve reclassification requests provided an area meets at least some of these criteria and does not violate any of them.
For Further Information: 
Contact Doug Grano of Office of Air Quality Planning and Standards (OAQPS), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711 , phone number (919) 541-3292 or by e-mail at: grano.doug@epa.gov or Annie  Nikbakht of OAQPS, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, phone number (919) 541-5246 or by e-mail at: nikbakht.annie@epa.gov.

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