ELR Citation: ELR 20042
No(s). 06-1410 (D.C. Cir. Feb 24, 2009)

The D.C. Circuit remanded the U.S. Environmental Protection Agency's (EPA's) national ambient air quality standards (NAAQS) for fine particulate matter (PM). EPA failed adequately to explain why, in view of the risks posed by short-term exposures and the evidence of morbidity resulting from long-term exposures, its primary annual fine PM standard is sufficient "to protect the public health [with] an adequate margin of safety" as required by Clean Air Act §7409(b)(1). As for the secondary NAAQS for fine PM, EPA unreasonably concluded that the NAAQS are adequate to protect the public welfare from adverse effects on visibility. EPA's decision to set secondary fine PM NAAQS identical to the primary NAAQS was unreasonable and contrary to the requirements of §7409(b)(2). The court, however, denied petitions for review of the Agency's standards for coarse particulate matter because those standards are not arbitrary, capricious, or otherwise contrary to law.