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Area Designations for 1997 Ground-level Ozone Standards

Fact Sheet

Final Rule Identifying Areas for Which the 1-Hour Ozone Standard Has Been Revoked

  • On July 26, 2005, the Environmental Protection Agency (EPA) issued a final rule identifying the designation and classification status of areas throughout the country covered by the national air quality standards for 1-hour ozone as of June 15, 2004. On that day the designations of attainment/nonattainment status under the more health protective 8-hour ozone standard became effective for most areas of the country.
  • This rule also codifies the revocation of the national air quality standards for 1-hour ozone. Phase I of EPA's rule implementing the 8-hour ozone standard established that the existing 1-hour standards would be revoked on June 15, 2005 - one year after the designations of attainment/nonattainment under the 8-hour standard became effective for most areas of the country.
  • In order to avoid losing clean air progress achieved under the 1-hour standard, EPA requires that certain emissions control requirements for areas designated as nonattainment or maintenance for the revoked 1-hour standard must remain in place. (e.g., application of reasonable available control technology to limit volatile organic compound emissions, and adherence to requirements to make reasonable further progress towards reducing ozone forming emissions)
  • The national air quality standards for 1-hour ozone continue to apply in Early Action Compact Areas. However, in exchange for a deferred effective date of their 8-hour ozone designation, these areas have agreed to take action to achieve clean air earlier than required under the 8-hour standard - no later than December 31, 2007.
  • Today's rule also makes several technical corrections to the Phase 1 Ozone Implementation Rule. Specifically, changes to the Code of Federal Regulations to accommodate the areas that must continue to meet the 1-hour ozone standard.

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  • 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 was 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.
  • 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 (PDF) (97 pp., 263KB))
  • Also on April 30, 2004, EPA took final action on key elements of the program to implement the 8-hour ozone NAAQS. [Final Rule to Implement the 8-Hour Ozone National Ambient Air Quality Standard - Phase I, (69 FR 23951 (PDF) (2 pp, 131KB)).
For Further Information
  • Contact Annie Nikbakht of Office of Air Quality Planning and Standards (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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