This Staff Paper, prepared by staff in the U.S. Environmental Protection Agencys (EPA) Office of Air Quality Planning and Standards (OAQPS), evaluates the policy implications of the key studies and scientific information contained in the document, Air Quality Criteria for Ozone and Related Photochemical Oxidants (USEPA, 2006; henceforth referred to as the CD), prepared by EPAs National Center for Environmental Assessment (NCEA). This document also presents and interprets results from several quantitative analyses (e.g., air quality analyses, human exposure analyses, human health risk assessments, and an environmental assessment of vegetation-related impacts) that we believe should also be considered in EPA's current review of the national ambient air quality standards (NAAQS) for ozone (O(sub 3)), and presents factors relevant to the evaluation of current primary and secondary 0(sub 3) standards. Finally, this document presents staff conclusions and recommendations on a range of policy options that we believe are appropriate for the Administrator to consider concerning whether, and if so how, to revise the primary (health-based) and secondary (welfare-based) O(sub 3) NAAQS. The policy assessment presented in this Staff Paper is intended to help 'bridge the gap' between the scientific assessment contained in the CD and the judgments required of the EPA Administrator in determining whether it is appropriate to retain or revise the NAAQS for O(sub 3). This policy assessment considers the available scientific evidence and quantitative risk-based analyses, together with related limitations and uncertainties, and focuses on the basic elements of air quality standards: indicator, averaging times, forms, and levels. These elements, which serve to define each standard, must be considered collectively in evaluating the health and welfare protection afforded by the O(sub 3) standards. Our conclusions and policy recommendations on whether, and if so how, to revise these
standard elements are based on the assessment and integrative synthesis of information presented in the CD and on staff analyses and evaluations presented in this document, and are further informed by comments and advice received from an independent scientific review committee, the Clean Air Scientific Advisory Committee (CASAC), in their review of earlier drafts of this document, as well as comments on earlier drafts submitted by public commenters.