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EPA Completes Second Step in Ongoing Ground-Level Ozone Air Quality Standards Review

Release Date: 01/30/2007
Contact Information: John Millett, (202) 564-4355 /

(1/30/07) A key document in EPA's review of national air quality standards for ozone will recommend the administrator consider strengthening the current ozone standards to better protect public health. The document, known as the "final staff paper," contains staff recommendations for the administrator to consider in upcoming decisions about revising the agency's ozone standards.

The Clean Air Act requires EPA to periodically review its air quality standards to ensure they continue to protect health and the environment, and to update the standards if necessary. EPA last updated the standards for ozone in 1997.

The final ozone staff paper addresses a primary standard, designed to protect public health; and a secondary standard, set to protect the public welfare, including crop health.

  • Primary standard: The final staff paper concludes that the current primary standard is not adequate to protect public health. Staff made this conclusion based on an expanded body of scientific evidence that shows significant ozone health effects occur even in areas with ozone levels below the current standard.
    Staff recommends a range of levels for the administrator to consider in setting the ozone standard. That range extends from below 0.080 ppm down to 0.060 ppm. The previous draft of the staff paper identified options that included retaining the current standard of 0.084 ppm, along with a range of alternative levels down to 0.064 (the lowest level analyzed), with a focus on a level of 0.07 ppm.
    The final staff paper also recommends specifying the level of the standard to three decimal places. Ozone air quality measurements have advanced sufficiently to now reflect that level of precision.
  • Secondary Standard: The final staff paper recommends the administrator set a secondary standard to protect against ozone damage to welfare, including damage to plants. This includes damage to natural vegetation, forests and commercial crops. Staff recommended a standard that is a cumulative, weighted total of daily 12-hour exposures over a three-month period within the growing season. It would give greater weight to exposures at higher ozone concentrations.
    Staff also recommended a range for this standard, from 21 parts per million-hours to 7 parts per million-hours.

EPA will make the final ozone staff paper available on the web on Wednesday, Jan. 31, 2007. Also this week, the agency will release technical documents used in developing the staff paper. These documents include a health risk assessment for meeting the current ozone standards along with potential alternative standards, and an assessment of the effects of ozone on vegetation.

The assessments, conclusions and recommendations included in the staff paper are staff judgments. They do not represent agency decisions on the ozone standards. EPA will propose action on the ozone standards by June 20, 2007 and take final action by March 12, 2008.

EPA recently changed the process for reviewing the National Ambient Air Quality Standards to streamline future such reviews to ensure the agency meets its five-year deadlines for reviewing the standards.

Emissions of the pollutants that contribute to ground-level ozone have decreased by nearly 50 percent since 1970, and EPA, and state and local agencies have a number of programs in place to continue this progress.

Final Ozone Staff Paper (to be posted 01/31/07) and Fact Sheet:

Technical Support Documents (to be posted later this week):