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Area Designations for 1997 Ground-level Ozone Standards

Fact Sheet

Clean Air Ozone Rules Of 2004

Final Rule Designating And Classifying Areas Not Meeting The
National Air Quality Standard For 8-Hour Ozone

ACTION -- April 15, 2004

  • As part of a continuing federal-state effort to make the nation's air healthier to breathe, today the Environmental Protection Agency (EPA) named new areas that will be required to reduce emissions of ozone-causing pollution.
  • These areas, called nonattainment areas, have (or contribute to) ozone levels higher than allowed under EPA's 8-hour ozone national air quality standard. The standard is designed to protect the public from exposure to ground-level ozone. Ozone is unhealthy to breathe B especially for people with respiratory diseases, and for children and adults who are active outdoors.
  • The designation and classification process plays an important role in letting the public know whether air quality in their community is healthy. Once designations and classifications take effect on June 15, 2004, state, tribal and local governments must prepare a plan which describes their efforts to reduce ground-level ozone. By law, nonattainment areas may be subject to certain requirements to reduce ozone-forming pollution.
  • Many areas will be categorized as basic nonattainment areas. They will have to comply with the more general nonattainment requirements of the Clean Air Act. EPA classifies ozone nonattainment areas based on the severity of their ozone problem. Classified areas fall into five categories: marginal, moderate, serious, severe, or extreme.
  • Nonattainment areas with higher classifications must meet additional requirements and have later attainment deadlines. States and tribes seeking a reclassification to the next higher or lower classification should make that request by July 1, 2004.
  • This rule also defers the effective date of nonattainment designations for certain areas of the country that do not meet the national 8-hour ozone air quality standard. These communities, known as Early Action Compact areas, have signed innovative agreements with EPA to reduce ground-level ozone pollution sooner than the Clean Air Act requires.
  • EPA will designate EAC areas as "nonattainment" for the 8-hour standard. However, as long as Early Action Compact areas meet agreed upon milestones, the impact of nonattainment designations for the 8-hour ozone standard will be deferred, which means that certain Clean Air Act requirements, such as controls on new sources, will not apply.
  • In a separate action, EPA is also finalizing the first phase of the rule implementing the 8-hour ozone standard. This action outlines the first steps areas will have to take to maintain or improve their air quality.
  • This phase of the implementation rule explains how EPA is classifying areas not meeting the national air quality standard for 8-hour ozone. It also establishes a process for transitioning from implementing the 1-hour standard for ozone to implementing the more protective 8-hour ozone standard. The rule also establishes attainment dates for the 8-hour standard and the timing of emissions reductions needed for attainment.



  • The Clean Air Act requires state, tribal and local governments to take steps to control ozone pollution in nonattainment areas. Those steps may include stricter controls on industrial facilities, additional planning requirements for transportation sources, and vehicle emissions inspection programs. Not every nonattainment area, however, will have to adopt these controls.
  • State and local governments must detail these control requirements in plans demonstrating how they will meet the 8-hour standard. Those plans are known as state implementation plans, or SIPs. States must submit their plans to EPA within three years after the Agency makes final designations.
  • Nonattainment areas are subject to a measure known as "transportation conformity," which requires local transportation and air quality officials to coordinate planning to ensure that transportation projects, such as road construction, do not affect an area's ability to reach its clean air goals. Transportation conformity requirements become effective one year after an area is designated as nonattainment.
  • Once designated, nonattainment areas also are subject to new source review requirements. New Source Review is a permitting program for industrial facilities to ensure that new and modified sources of pollution do not impede progress toward cleaner air.
  • EPA provided guidelines to states and tribes for recommending nonattainment area boundaries for the 8-hour ozone standard. Those guidelines included directions to first base their boundaries on Consolidated Metropolitan Statistical Area, Metropolitan Statistical Area, or 1-hour ozone nonattainment area boundaries, whichever area was larger.
  • States and tribes also were asked to consider the following factors as they developed their boundary recommendations:
    • emissions and air quality in adjacent areas
    • population density and commercial development in adjacent areas
    • ozone air quality data - does it represent local or larger area
    • location and size of emission sources - traffic and commuting patterns
    • extent, pattern and rate of growth
    • weather and transport patterns
    • mountains or other air basin boundaries
    • jurisdictional boundaries
    • level of control of emission sources
    • enforceable regional emission reductions strategies
  • After states were given the opportunity to recommend the boundaries, EPA made the final decision.

Early Action Compacts

  • Early Action Compact areas must attain the 8-hour ozone standard no later than December 31, 2007. In areas that do not meet the Early Action Compact attainment deadline, a nonattainment designation will become effective April 15, 2008.
  • Only areas that were already meeting the national 1-hour ozone standard were eligible for this innovative program because EPA wants to ensure that the communities participating have a proven record of environmental progress.
  • Early Action Compacts were signed by representatives of the local communities, state air quality officials, and EPA Regional Administrators.
  • In order to qualify for the first deferred effective date (to September 30, 2005), areas must have submitted to EPA a complete compact by December 31, 2002. The area must meet a number of milestones (for submitting implementation plans, implementing local control measures, making progress reports, etc.). EPA would withdraw an area's nonattainment deferral if any milestone set out in the Early Action Compact were missed.
  • On June 16, 2003, areas were required to submit to EPA a preliminary list of control measures the areas were considering adopting and implementing.
  • On March 31, 2004 areas were required to submit to the states early action plans that include final control measures, and modeling showing they could use those measures to meet the ozone standard by December 31, 2007.
  • By December 31, 2004, states with Early Action Plans must submit to EPA revisions to their state implementation plans to incorporate these early action plans.

Implementing the 8-hour Ozone Standard

  • This phase 1 final rule sets forth the classification scheme for nonattainment areas and requirements for States' continued obligations with respect to existing 1-hour ozone requirements.


  • The Clean Air Act contains different sets of control requirements areas are required to include in their plans implementing ozone standards. One set contains general requirements for emission reductions needed for attainment, but the states/tribes have flexibility in which sources to control and by how much. The second set contains specific emission control requirements that must be applied according to the seriousness of the ozone problem in an area.
  • In the final rule EPA will separate areas based generally on their 1-hour ozone design value. A design value is an air quality measurement used to determine an area's air quality status in reference to a national standard. (attainment or nonattainment). This final rule separates eight-hour ozone nonattainment areas into two categories:
    • Areas whose 1-hour ozone design value is less than 0.121 parts per million fall under the more general requirements (attainment deadlines 5-10 years after designation). These areas may be referred to as "Basic Nonattainment Areas" in this fact sheet and other public communication materials.
    • Areas whose 1-hour design value is greater than or equal to 0.121 ppm under the more specific requirements (attainment dates 2007 - 2021). These areas would be further classified as "marginal", "moderate", "serious", "severe", or "extreme" based on the severity of their 8-hour ozone problem.

Revoking the 1-hour standard

  • EPA will revoke the 1-hour standard 1 year after the effective date of designating attainment and nonattainment areas for the 8-hour standard.
  • To avoid "backsliding," or losing clean air progress towards attaining the 1-hour ozone standard, this rule will require the very specific control measures for the 1-hour standard and included in a state's implementation plan to stay in place until an area attains the 8-hour standard.
  • The discretionary emissions reductions in a state's implementation plan would also remain but could be revised or dropped based on modeling demonstrating that it would be appropriate.
  • Phase 2 of the final 8-hour ozone implementation rule will address, among other things, reasonably available control measures, reasonably available control technology, attainment demonstrations and modeling requirements, and will be issued in the next several months.


  • EPA issued the 8-hour ozone standard in July 1997, based on information demonstrating that the 1-hour standard was inadequate for protecting public health. Scientific information shows that ozone can affect human health at lower levels, and over longer exposure times than one hour.
  • Ground-level ozone forms when emissions of nitrogen oxides (NOx) and volatile organic compounds (VOCs) "cook" in the sun. Sources of these pollutants include cars and trucks, power plants, refineries and other large industrial facilities, and some natural sources.
  • Breathing ozone can irritate air passages, reduce lung function, aggravate asthma, and inflame and damage the cells lining the lungs. It also may aggravate chronic lung diseases like emphysema and bronchitis, may reduce the immune system's ability to fight off bacterial infections in the respiratory system and may cause permanent lung damage.
  • The 8-hour ozone standard is 0.08 parts per million (ppm), averaged over eight hours. The 1- hour standard is 0.12 ppm, measured in hourly readings.
  • After a lengthy legal battle, the courts upheld the new ozone standard and a new standard for fine particle pollution. Working with State, Tribal and local environmental agencies, EPA is now in the process of implementing these new standards.
  • Today, EPA is also issuing the first phase of the final implementation rule which addresses key implementation issues such as classifications for the 8-hour standard and transition from the 1-hour to the 8-hour standard, including revocation of the 1-hour standard.


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