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Environmental Assessment

Air Quality Criteria for Ozone and Related Photochemical Oxidants (2006 Final)


On a February 28, 2006 Federal Register Notice, EPA announced the release of EPA's final document, Air Quality Criteria for Ozone and Other Photochemical Oxidants.

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Tropospheric or surface-level ozone (O3) is one of six major air pollutants regulated by National Ambient Air Quality Standards (NAAQS) under the U.S. Clean Air Act. As mandated by the Clean Air Act, the U.S. Environmental Protection Agency (EPA) must periodically review the scientific bases (or criteria) for the various NAAQS by assessing newly available scientific information on a given criteria air pollutant. This document, Air Quality Criteria for Ozone and Other Photochemical Oxidants, is an updated revision of the 1996 Ozone Air Quality Criteria Document (O3 AQCD) that provided scientific bases for the current O3 NAAQS set in 1997.

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The Clean Air Act mandates periodic review of the National Ambient Air Quality Standards (NAAQS) for six common air pollutants, also referred to as criteria pollutants, including ozone. Under the review process, EPA's Office of Research and Development develops a criteria document - a compilation and evaluation by U.S. EPA scientific staff and other expert authors of the latest scientific knowledge relevant to assessing the health and welfare effects of the air pollutant. In this case, the Ozone Criteria Document presents the latest available pertinent information on atmospheric science, air quality, exposure, dosimetry, health effects, and environmental effects of ozone and other related photochemical oxidants.

Development of the Ozone Criteria Document has included extensive review by the Clean Air Scientific Advisory Committee (CASAC) and the public. The document is divided into three volumes:
  • Volume I (Executive Summary and Chapters 1 through 11);
  • Volume II (annexes to Chapters 2 through 7), and
  • Volume III (annex to Chapter 9).


Jul 1996EPA Released an external Review Draft as Volume I, Volume II and Volume III.
1996EPA Releases the Air Quality Criteria for Ozone and Related Photochemical Oxidants
2000EPA begins the mandated periodic revision of the 1993 Final Ozone Criteria Document.
2002CASAC and the public review and comment on the Project Work Plan for the Ozone Criteria Document.
2003-2004EPA prepares initial draft chapters of the Ozone Criteria Document, which are discussed at peer consultation workshops and meetings. In 2004, EPA revised the chapters, taking into account comments from these discussions.
Jan 2005EPA releases the first external review draft of the Ozone Criteria document for public review and comment. [Federal Register Jan 31, 2005]
Aug 2005EPA releases the second external review draft of the Ozone Criteria Document for public review and comment. [Federal Register Aug 31, 2005]
Feb 2006EPA released the final report of the Air Quality Criteria Document for Ozone. This is the most current version of the report. [Federal Register Feb 28, 2006]
Mar 2008The NAAQS review for ozone was completed with a final rule signed in March 2008.
Sep 2009On September 16, 2009, the EPA Administrator announced a decision to reconsider the primary and secondary NAAQS for ozone based on the record from the last review.
Nov 2009EPA released a provisional assessment on new ozone research.

Next Steps

As a follow-up, EPA's Office of Air Quality Planning and Standards (OAQPS) prepares a staff paper that bridges the gap between scientific assessments in the criteria document and judgments required of the EPA Administrator in evaluating whether to retain or revise the Ozone NAAQS.

Further information on this process is available at http://www.epa.gov/ttn/naaqs/standards/ozone/s_03_index.html.

Additional Information


U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (2006 Final). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006.


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