The District of Columbia Circuit Court of Appeals has dismissed an industry challenge to the U.S. Environmental Protection Agency’s (EPA’s) national ambient air quality standard (NAAQS) for sulfur dioxide (SO 2). Nat’l Envtl. Dev. Ass’n Clean Air Project v. EPA, No. 10-1252 (D.C. Cir. 7/20/12). Petitioners challenged, in part, EPA’s statements in its final rule that the agency would implement the standard through a combination of air quality modeling and monitoring, a change from the past practice of using monitoring data only.

According to the court, those statements did not constitute final agency action under the Administrative Procedure Act (APA) and therefore the challenge to the agency’s rulemaking procedure was not within the court’s jurisdiction. In denying the petitioners’ second argument that EPA acted arbitrarily when it set the maximum SO 2 concentration at a lower level than statutorily authorized by the Clean Air Act, the court said it owed deference to EPA regarding the reliability of scientific evidence.  

In its rulemaking, EPA set the one-hour SO 2 standard at 75 parts per billion, based on studies that the agency believed indicated would allow for a “reasonable margin of safety” for severe asthmatics. Petitioners disagreed and argued that the agency “cherry picked” the studies on which it relied. The court deferred to EPA’s “significant discretion” to revise the NAAQS for SO 2.