27 May 2000

The US Supreme Court recently announced that it has agreed to the EPA's request to review the Court of Appeals ruling of 14 May 1999, which said that the agency exceeded its authority in issuing new National Ambient Air Quality Standards (NAAQS) for ozone and particulate matter in 1997.

The EPA standards remanded by Court include an ozone standard of 0.8 ppm (down from the previous 0.12 ppm) and a new standard for ambient particulate matter below 2.5 microns (PM2.5). The Appeals Court cited the doctrine of “nondelegation”, which limits the ability of Congress to delegate powers to executive agencies, and found that EPA had assumed an “unconstitutional delegation of legislative power”. The Court upheld its decision in a second ruling in October 1999.

The 1997 NAAQS were challenged by a coalition of industry groups led by the American Trucking Association, along with the states of Michigan, Ohio and West Virginia.

The Supreme Court will hear this appeal in the fall and is expected to issue a decision some time next year.

The NAAQS set the ambient air quality targets, which influence all other federal and state emission regulations, including those pertaining to diesel and gasoline engine emissions.