WASHINGTON — A federal appeals court has set aside the U.S. Environmental Protection Agency (EPA)’s significantly tightened air quality standards for ozone and particulate matter, issued in 1997. The National Paint & Coatings Association (NPCA) and other industry groups had challenged the standards in court. The three-judge panel said the EPA’s interpretation of the section of the 1990 Clean Air Act on which the agency relied in issuing the air quality standards amounted to “an unconstitutional delegation of legislative power,” an argument the NPCA had concentrated on in challenging the standards.

The EPA’s regulation dramatically tightened federal air-quality requirements for ozone pollution, or smog, by changing the existing standard of 0.12 parts per million (ppm) over a one-hour average to 0.08 ppm over an eight-hour average. The regulation also, for the first time, required states to regulate microscopic particles, or soot, down to 2.5 microns, or 28 times smaller than the width of a human hair.

While the court did not vacate the ozone rule, simply stating that the standard “cannot be enforced,” the judges did nullify the particulate-matter standard and direct EPA to develop a new one.

“This is a very significant decision,” said NPCA General Counsel Tom Graves, because the court agreed with the NPCA’s argument that Congress did not give the EPA “unfettered discretion to fundamentally rewrite the legislation.”

The EPA may appeal the decision by seeking a review by the full panel of the U.S. Court of Appeals (D.C. Circuit) and/or petition for review by the U.S. Supreme Court.