D.C. Circuit Grants Rehearing In Clean Air Act Case

On December 11, a D.C. Circuit panel (Tatel, Brown, Griffith) granted in part environmental and state petitions for rehearing in Mississippi v. EPA (Nos. 08-1200 et al.), revising key language describing the court's review of certain agency actions.  In July, the panel affirmed EPA's 2008 revisions to the primary ozone National Ambient Air Quality Standards ("NAAQS"), while remanding the revised secondary ozone NAAQS for reconsideration.  EPA set both the primary and secondary standards at the same level: 0.075 ppm (parts per million), revised downward from the 1997 level of 0.08 ppm.

Under Clean Air Act Section 109(b)(1), primary NAAQS set pollution levels that "allow[] an adequate margin of safety . . . requisite to protect the public health"; secondary NAAQS under Section 109(b)(2) set levels "requisite to protect the public welfare."  The court's July opinion rejected arguments that EPA had improperly disregarded a recommendation from the Clean Air Science