A three-judge panel of the D.C. Circuit Court of Appeals on Friday rejected a challenge from the Midwest Ozone Group to EPA’s Cross-State Air Pollution Rule for the National Ambient Air Quality Standards (NAAQS).

The Midwest Ozone Group (MOG) is made up of numerous large industrial firms from the region, including utilities such as Ameren, American Electric Power, Associated Electric Cooperative Inc., Buckeye Power, Duke Energy and FirstEnergy.

The rule that the group challenged was updated by EPA after the court remanded it to the agency in a 2019 decision. In the revised rule, the agency addressed its failure to balance emissions obligations in accordance with the 2008 NAAQS and its date of attainment.

MOG argued that the revised rule is arbitrary and capricious and that the agency failed to conduct a legally and technically appropriate assessment of it.

The Clean Air Act authorizes EPA to adopt NAAQS to regulate air pollutants including ozone, which can be blown from facilities in one state into another. The law includes the “good neighbor provision” that requires every upwind state to prevent its pollutant emissions from contributing significantly to nonattainment in downwind states.

For 2021, EPA set specified, enforceable measures in federal implementation plans for Illinois, Indiana, Kentucky, Louisiana, Maryland, Michigan, New Jersey, New York, Ohio, Pennsylvania, Virginia and West Virginia.

MOG argued that EPA took mathematical and analytical shortcuts in its analysis of upwind states’ ozone contributions under the good-neighbor rule. Eleven of the 12 states identified were considered significant pollution contributors based on that flawed data, it said. EPA also failed to consider programs in downwind states to control pollution and exceptional events that could impact air quality monitors, MOG said.

EPA said it used the method to figure out how much improvement should have been expected by 2021, but even if it used MOG’s preferred method, the same states would have obligations to clean up their ozone pollution.

The court said its review of the case was simple: As long as the action was not against the law, all EPA had to do was act reasonably and reasonably explain its actions. The court had to give deference to the agency’s interpretation of “highly complex and technical matters.”

The kind of statistical analysis EPA used has been described as “perhaps the prime example of an area of technical wilderness into which judicial expeditions are best limited to ascertaining the lay of the land,” the court said.

The D.C. Circuit has never required EPA to use a particular method to generate its data, or to adhere to past practice; it just has to show a reasonable connection between the facts on the record and its decision, the judges said.

“MOG fails to demonstrate that EPA’s promulgation of the revised rule was arbitrary, capricious or promulgated in violation of its statutory authority under the good-neighbor provision,” the court said. “Accordingly, we deny MOG’s petition.”