Sierra Club v. U.S. Environmental Protection Agency

Record contained sufficient evidence to support E.P.A. finding that requisite ozone drops in three Midwest areas were reasonably attributable to “permanent and enforceable” reductions in ozone pollutants so as to support E.P.A. finding that said areas had attained 1997 National Ambient Air Quality Standards for ozone. While plaintiff had sufficient standing to bring instant lawsuit, where plaintiff showed likelihood that ozone levels would rise under relaxed regulations applicable to E.P.A.’s finding of attainment, plaintiff still failed to show that E.P.A.’s decision was arbitrary or capricious, where E.P.A. identified eight factors/measures that it deemed “permanent and enforceable” and estimated impact that each factor/measure would have on emissions that caused ozone pollution. Ct. further noted that E.P.A could base its findings on estimated calculations, and that Clean Air Act did not require E.P.A. to prove causation of instant reductions to absolute certainty.