The EPA doesn’t have to consider setting new pollutant standards for substances that aren’t already addressed in current standards during regular reviews, the agency said in a brief filed June 25.

The Environmental Protection Agency’s brief in the U.S. Court of Appeals for the District of Columbia Circuit came in response to a lawsuit that several environmental groups filed in September. The groups said the EPA should have determined whether certain combinations of air pollutants associated with pulp mills warranted the creation of new standards during their last review of the policies.

Pulp mills produce the raw material derived...