ABSTRACT
The new PM2.5 and PM10 NAAQS were challenged by the American Truckers Associations, who filed a lawsuit against the EPA Administrator claiming that EPA had exceeded its authority to regulate, that the basis of the standards was not sufficiently well defined, and that the regulations were arbitrary and capricious. With the exception of one part of the suit concerning PM10, which EPA did not contest, the U.S. Supreme Court upheld EPA’s position and thus, at the present time, PM2.5 is in effect. The argument with respect to the PM10 standard was that it includes PM2.5 and therefore is not the appropriate indicator for coarse particles. If EPA has a basis for the regulation of coarse particles, an appropriate standard, including a well-defined indicator, should be defined. As discussed below, a coarse particle standard is expected to be proposed in 2005. The existing 1987 PM10 standard remains in effect.
