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The fine particle pollution that blasts into the air from diesel vehicles and power plants is a health threat well-understood by scientists — causing an estimated 20,000 deaths a year and hospitalizing many more in the United States. But faced with this issue, the Environmental Protection Agency (EPA) for the first time in three decades ignored the advice of its Clean Air Scientific Advisory Committee (CASAC) on air quality standards. Agency administrator Stephen L. Johnson said his 2006 ruling on National Ambient Air Quality Standards for fine particulate matter was “based on the best available science,” as required by the Clean Air Act. But it wasn’t clear what science he was referring to. The CASAC’s disagreements with the parent agency were echoed by the American Medical Association, American Thoracic Society, American Lung Association, American Academy of Pediatrics, American Heart Association, American Cancer Society, and American Public Health Association. EPA did issue a rule requiring that daily exposure levels to fine particulate matter be cut nearly in half by single or multi-county “areas,” to fit just within the revised window recommended by CASAC. But when the committee also recommended toughening the annual air standard for fine particulate matter, EPA disregarded the request. CASAC said that maintaining the current annual standard “does not provide an ‘adequate margin of safety’” The Union of Concerned Scientists cites more than 2,000 peer-reviewed studies published since particulate matter standards were last set in 1997 linking fine particle solution to “strokes, heart disease, respiratory ailments, and premature death.” The EPA press office did not respond to a request for comment, but its fact sheet said the agency “selected levels for the final standards after completing an extensive review of thousands of scientific studies,” and also “carefully reviewed and considered public comment.”

Two members of the House Committee on Energy and Commerce sent a letter to EPA’s Johnson in March 2007 asking why the agency had not yet finalized states’ implementation of new particle standards and other environmental standards issued as far back as 1997. The EPA responded at the end of March, saying it was giving states several years to implement rulings; the Natural Resources Defense Council and the Sierra Club then sued EPA in an effort to speed up the process. The litigation is still pending. In its presidential transition report, the Government Accountability Office suggested re-visiting and strengthening the particulate matter program.

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