28 February 2001

In its decision of February 27, the US Supreme Court unanimously upheld the 1997 EPA National Ambient Air Quality Standards (NAAQS) for ozone and fine particulate matter (PM2.5). The court rejected arguments by the industry, led by the American Trucking Association, that EPA acted unconstitutionally in issuing the standards.

The industry groups also charged the EPA with failure to consider industry’s costs for compliance when issuing health standards, but the court said no such cost-benefit requirement exists under the Clean Air Act.

The debated standards were adopted by the EPA in July 1997. The most important and controversial changes, relative to the previous standards, were:

  • Introduction of a new annual PM2.5 (particulate matter below 2.5 micron) standard of 15 micrograms per cubic meter (µg/m3) and a new 24-hour PM2.5 standard of 65 µg/m3.
  • Tightening the existing 8-hour ozone standard to 0.08 parts per million (ppm), down from the previous 0.12 ppm.

An alliance of industry groups challenged the new standards arguing that they would cause excessive compliance costs. In May, 1999, the standards were remanded by the US Court of Appeals. The EPA had to withdraw the standards, but continued the court battle. After another defeat in the Court of Appeals, the EPA took the case to the Supreme Court.

The new EPA Administrator Whitman hailed the Supreme Court ruling as an “endorsement of EPA’s efforts to protect the health of millions of Americans”. Now, the EPA will be working towards re-imposing the standards, but no details on the exact schedule were given.

Environmentalists and the American Lung Association praised the Supreme Court ruling as a victory for public health. The American Trucking Association and other industry groups were clearly disappointed with the court decision.

The National Ambient Air Quality Standards establish the ambient air quality targets in the USA and are the basis for all other federal and state emission regulations, including those pertaining to engine emissions.

Supreme Court ruling
ATA on the ruling