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BACKGROUND ON THE STANDARDS REVIEW <br />The Clean Air Act directs EPA to set National Ambient Air Quality Standards for pollutants <br />that the Agency has listed as "criteria pollutants," based on their likelihood of harming public <br />health and welfare. EPA sets national air quality standards for six common air pollutants: <br />ground -level ozone (smog), carbon monoxide, lead, nitrogen dioxide, sulfur dioxide, and <br />particulate matter. <br />• For each of these pollutants, EPA has set health -based or "primary" standards to protect <br />public health, and "secondary" standards to protect the public welfare from harm to crops, <br />vegetation, wildlife, buildings and national monuments, and visibility. <br />• The Clean Air Act requires EPA to review the standards once every five years to determine <br />whether revisions to the standards are appropriate. <br />• EPA has regulated particulate matter since 1971. The Agency added specific standards for <br />fine particles following its last review, in 1997. <br />• Under terms of a consent decree, EPA agreed to issue a proposal on the particulate matter <br />standards by December 20, 2005; and committed to finalizing any revisions to the standards <br />by September 27, 2006. <br />• The review of a standard begins with an assessment of science about the particular pollutant <br />and its effects on public health and welfare. EPA's National Center for Environmental <br />Assessment undertakes an extensive scientific and technical assessment process during the <br />standard review for any pollutant. The first step in the process is the preparation of an "Air <br />Quality Criteria Document," an extensive assessment of scientific data pertaining to the <br />health and environmental effects associated with the pollutant under review. <br />EPA's Office of Air Quality Planning and Standards then prepares a document (known as a <br />"staff paper") that interprets the most relevant information in the "criteria document" and <br />identifies: 1) factors EPA staff believes should be considered in the standard review; 2) <br />uncertainties in the scientific data; and 3) ranges of alternative standards the staff believes <br />should be considered. Technical staff then compiles a paper that outlines the policy <br />implications of the science. This paper represents the views of the staff and, in final form, is <br />ultimately used as the basis for staff recommendations to the EPA Administrator. <br />• Drafts of both the "criteria document" and the "staff paper," which are based on thousands of <br />peer-reviewed scientific studies, receive extensive review by representatives of the scientific <br />community, industry, public interest groups and the public, as well as the Clean Air <br />Scientific Advisory Committee (CASAC) -- a group of independent scientific and technical <br />experts established by Congress. <br />• As part of its mandate, CASAC makes recommendations to EPA on the adequacy of the <br />existing standards and revisions it believes would be appropriate. Based on the scientific <br />7 <br />