US EPA

EPA has released the Integrated Science Assessment for Ozone and Related Photochemical Oxidants (Second External Review Draft) for independent peer review and public review. This draft document represents a concise synthesis and evaluation of the most policy-relevant science and will ultimately provide the scientific bases for EPA’s decision regarding the adequacy of the current national ambient air quality standards for ozone to protect human health, public welfare, and the environment.

EPA released the Second External Review Draft of the Integrated Science Assessment for Ozone and Related Photochemical Oxidants for peer review and public comment. Ozone (O₃) is one of six principal (or criteria) pollutants for which EPA has established national ambient air quality standards (NAAQS). The Clean Air Act requires EPA to periodically review the scientific basis for these standards by preparing an Integrated Science Assessment (ISA), formerly called an Air Quality Criteria Document (AQCD). These reviews play a significant role in EPA’s commitment to ensuring a clean and healthy environment for the public. The second draft ISA is part of the Agency’s periodic review of the primary and secondary NAAQS for O₃. New material has been included in this draft, but many of the overall conclusions remain generally the same as the last NAAQS review which was completed in 2008. For example, in relation to short-term exposures, new evidence for O₃-induced health effects strengthens the body of evidence for associations with respiratory morbidity and mortality. Also, the current ambient O₃ concentrations in many areas of the US are sufficient to impair growth of numerous plant species. Within an ecosystem, O₃ can alter timber production, water availability in watersheds and carbon sequestration; and, it can affect ecosystem biodiversity. In addition, as was concluded in the last NAAQS review, O₃ can affect the climate by acting as a climate-forcing greenhouse gas. In contrast to the last review, there is now evidence suggesting that respiratory morbidity and mortality are associated with O₃ long-term exposure.

Critical evaluation and integration of the evidence on health and environmental effects of ozone to provide scientific support for the review of the NAAQS for ozone.

This draft document addresses CASAC and public comments received on the first draft ISA. Once final, the complete ISA will be posted on the EPA Web site to provide the scientific bases for EPA’s periodic review and possible revision of the primary NAAQS for ozone and Related Photochemical Oxidants.

U.S. EPA. Integrated Science Assessment (ISA) for Ozone and Related Photochemical Oxidants (Second External Review Draft, Sep 2011). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-10/076B, 2011.

Comments on this draft report may be submitted and reviewed using the e-Government Regulations.gov Web site. From the site, select “Environmental Protection Agency” and the keyword “EPA-HQ-ORD-2011-0050" (for the docket ID) to comment on this report.