In a win for environmentalists, the D.C. Circuit Court has remanded two rules implementing the 1997 PM2.5 National Ambient Air Quality Standard (NAAQS) and ordered the U.S. Environmental Protection Agency (EPA) to re-promulgate the rules in accordance with more stringent statutory requirements. A copy of the Court’s decision is available here. In 2007 and 2008, EPA issued two rules (available here and here) setting out general requirements for implementation of the 1997 PM2.5 NAAQS. With respect to requirements for nonattainment areas, EPA expressly promulgated both rules under the general implementation provision of under Subpart 1, Part D, Title I of the Clean Air Act, and not under the more stringent provisions of Subpart 4, which are specifically applicable to particulate matter (PM). Among other things, Subpart 4 provides less discretion in classifying nonattainment areas and in extending attainment deadlines and includes more stringent requirements for reaching attainment. EPA’s decision to proceed under Subpart 1 was based on the contention that Subpart 4 is specific to PM10, and, therefore, implementation of the PM2.5 standard would fall under the general implementation guidelines of Subpart 1. Environmentalists challenged, arguing that Subpart 4 should have been applied, and the D.C. Circuit Court agreed. The court found that by its plain meaning, Subpart 4 applies to all particulate matter with a diameter of 10 micrometers or less (i.e., PM10 and anything less, including PM2.5) and, given Congress’s intent in Subpart 4 was to limit EPA’s implementation discretion, it would make little sense that Congress would have wanted more relaxed provisions applicable to PM2.5, which EPA has tightened in recognition of its the serious health impacts. The Court remanded both rules to EPA to be re-promulgated, but set no deadline for EPA to act.
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