On Friday, a unanimous three-judge panel of the U.S. Court of Appeals for the D.C. Circuit invalidated the Environmental Protection Agency's rules implementing the new 8-hour National Ambient Air Quality Standard (NAAQS) for ozone (aka "smog"). The EPA adopted the 8-hour ozone NAAQS under the Clinton Administration. The controversial standard, upheld by the Supreme Court in Whitman v. American Trucking Associations, tightened the ozone standard from 0.12 parts per million (ppm) to 0.08 ppm, while lengthening the time period over which ozone measurements are averaged from one to eight hours.
In South Coast Air Quality Management District (SCAQMD) v. EPA, various organizations challenged the EPA's "Phase One" regulations implementing the new NAAQS as being either too lenient or too stringent. In the end, the D.C. circuit agreed with environmentalist organizations that portions of the EPA's plan were too lenient and constituted impermissible "backsliding" under the CAA. Specifically, the Court found the EPA lacked the discretion to adopt a more permissive timetable for compliance with a revised NAAQs than thatspecifically outlined for the ozone NAAQS in force when the CAA was last amended in 1990 and found that the EPA's decision to allow states to withdraw provisions of their state air pollution control plans.
The Washington Post covered the decision here.