In consolidated petitions, several states, cities, counties and industry groups challenged EPA’s promulgation of area designations for the annual national ambient air quality standard applicable to fine particulate matter, a category of air pollutants consisting of miniscule airborne particles known to cause adverse health risks. These groups claimed that EPA’s methodology for designating areas as “nonattainment” for the fine particulate matter standard violates the Clean Air Act, which governs such designations, and that the methodology and the individual designations it produced are “arbitrary and capricious.”
The petitioners asked the court to vacate the nonattainment designations and to send EPA back to the drawing board.
“With one minor exception, we deny the petitions for review,” the court ruled. “Faced with the complex task of identifying those geographic areas that contribute to fine particulate matter pollution, EPA both complied with the statute and, for all but one of the 225 counties or partial counties it designated as nonattainment, satisfied – indeed, quite often surpassed – its basic obligation of reasoned decision-making.”
