EPA: airing on the side of caution or pulling standards out of thin Air?

In May 1999, a federal appeals court ruled that the U.S. Environmental Protection Agency (EPA) had violated the Constitution when it strengthened regulations for ground-level ozone and particulate matter (PM). Although the court did not question the validity of the EPA's scientific basis for establishing the PM and ozone standards, it did challenge how the EPA selected the particular levels since the scientific record in both rules did not indicate unequivocally where the standards should be set. The agency failed to identify an "intelligible principle" that would guide such choices, the court said, and thereby exceeded the power it was granted by Congress. Because scientific uncertainty attends so much rule making, the ruling leaves open the question of when the EPA may make what is essentially a policy determination versus when those determinations must be made by Congress. For this reason, observers consider the ruling to have potentially significant implications beyond just the ozone and PM standards that may affect other EPA regulations and regulations by other agencies.