The lower court's decision last year effectively blocked the implementation of the EPA's air quality standards for ozone and fine particulates. EPA must set these standards to protect the public health with an adequate margin of safety. EPA determined in 1997 that its longstanding air quality standard for ozone was inadequate to protect the public health. EPA then revised its ozone standard and issued new standards for fine particulates. Ozone, commonly known as smog, is formed when air pollutants combine in the heat of the summer sun.
Fine particulates are tiny particles of soot and dust that lodge deeply in the lungs.
Various parties sued to challenge the new standards, including owners of coal-fired power plants in the Midwest and South, oil companies and automakers. With costs of complying with the new standards expected to be greatest in the Midwest and South, Ohio, Michigan and West Virginia joined the opponents. Massachusetts and New Jersey intervened in support of the air quality standards and other Northeast states filed supporting briefs with the Court of Appeals. The lower court did not challenge EPA's conclusions that the old standards inadequately protected the public's health. Massachusetts and New Jersey also argued that the ruling effectively prevents EPA from enforcing the new standard, a result that Congress could not have intended.