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Environmental Assessment

Research Needed to Improve Health and Ecological Risk Assessments for Ozone (Second External Review Draft)

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Report Information

Ozone is one of six criteria air pollutants whose ambient concentrations are regulated under the National Ambient Air Quality Standards (NAAQS) established by the U.S. Clean Air Act (U.S. Code, 1991). The NAAQS apply to both human health (primary standard) and public welfare (secondary standard). Primary standards protect sensitive members of the human population from adverse health effects of criteria air pollutants, with an adequate margin of safety. Secondary standards protect the public welfare from any known or anticipated adverse effects associated with the presence of a pollutant in the ambient air. Welfare effects include but are not limited to effects on soils, water, crops, vegetation, manmade materials, animals, wildlife, weather, visibility, and climate, damage to and deterioration of property, and hazards to transportation, as well as effects on economic values and personal comfort and well-being.

The U.S. Environmental Protection Agency (EPA) document Air Quality Criteria for Ozone and Related Photochemical Oxidants (Ozone AQCD) published in July 1996, assembled, summarized, and interpreted available scientific evidence on exposure to, and health and ecological effects of, ambient ozone. Subsequent studies have provided important additional observations. There is clear agreement that short-term ozone exposure produces or promotes significant health effects, not merely temporary physiologic changes. Also, current experimental and epidemiologic evidence provides ample reason for suspicion that long-term ambient ozone exposure induces deleterious human health effects. At the same time, important uncertainties remain in the available health effects database for ambient ozone. This combination of legitimate concern and scientific uncertainty creates a strong case for continued health-related research on ozone, both alone and in combination with other environmental substances.

An ecological risk assessment process has been developed by EPA to assist in evaluating the likelihood that adverse ecological effects may occur or are occurring as a result of exposure to one or more stressors. These assessments are conducted to bring scientific information to bear on risk management decisions. Research conducted to address needs identified in this document will serve as inputs to future risk assessments being developed to characterize ozone effects on ecosystems.

The research needs presented in this document do not constitute a specific research program or research plan. Rather, these needs are intended to provide a broad conceptual context, within which specific research programs and plans can be developed. In this regard, the research approaches mentioned under some specific research needs should not be taken to constitute predictions of specific future requests for proposals issued by U.S. EPA or any other sponsoring organization. Rather, consistent with the broader scope and spirit of this document, the research needs are presented as springboards for further thought and discussion.

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