ELR Citation: ELR 20143
No(s). 05-1064 (D.C. Cir. Jul 7, 2009)

The D.C. Circuit upheld EPA's area designations for the annual NAAQS for fine particulate matter. Several states, counties, and industrial entities argued that by applying the consolidated metropolitan statistical areas presumption and a nine-factor test to identify areas that contribute to nearby PM2.5 violations, EPA's methodology for designating areas as nonattainment for the fine particulate matter standard violates CAA §107(d). But §107(d) does not unambiguously preclude EPA from adopting this method, and EPA reasonably interpreted the statute as permitting it to do so. Section 107(d) requires only that EPA designate, based on air quality monitoring data, nonattainment areas that either violate or contribute to violations of the PM2.5 NAAQS. Acting on evidence that urban PM2.5 violations usually stem from metropolitan-wide activities, EPA reasonably adopted a presumption that designates all of a metropolitan area as nonattainment when at least one part of that area registers a PM2.5 violation, and a specifically defined multi-factor analysis to assess when that presumption fails to reflect the realities of a given metropolitan area. Petitioners also argued that the rule itself was arbitrary and capricious, but the Agency was entitled to deference. In basing its designation decisions on a rigorous analysis of each county’s particular attributes, EPA satisfied the requirements of reasoned decisionmaking. Last, petitioners argued that even if the PM2.5 nonattainment designations are reasonable as a general matter, certain individual county designations are independently arbitrary and capricious. But for all but one of the 225 counties or partial counties it designated as nonattainment, the Agency satisfied its basic obligation of reasoned decisionmaking. In light of the Agency's scientific expertise and the complexity of the designation process, the court remanded the case to give EPA another opportunity to provide a coherent explanation for its designation of that county.