ELR Citation: 43 ELR 20158
No(s). 08-1200 (D.C. Cir. Jul 23, 2013)

The D.C. Circuit remanded for reconsideration EPA's revisions to the secondary, welfare-based NAAQS for ozone, but denied petitions challenging revisions to the primary, health-based ozone NAAQS. Primary standards set limits to protect public health, including the health of "sensitive" populations such as asthmatics, children, and the elderly. Secondary standards set limits to protect public welfare, including protection against visibility impairment, damage to animals, crops, vegetation, and buildings. In its review of the ozone NAAQS, EPA concluded that the existing 0.08 ppm primary standard was not requisite to protect the public health with an adequate margin of safety. Although the Clean Air Scientific Advisory Committee had recommended a level as low as 0.060 to 0.070 ppm, the Agency opted for a level of 0.075 ppm. EPA also determined that the secondary standard should be revised to be identical to the new primary standard. One set of petitioners—comprising several states, the District of Columbia, New York City, and a number of environmental and public health groups—argued that the primary and secondary NAAQS are not protective enough, while the other set—comprising the state of Mississippi and several industry groups—claimed they are too protective. The court denied petitions challenging the primary NAAQS. EPA's conclusion that a level of 0.075 ppm is "requisite" to protect public health can be rationally drawn from the entire body of scientific evidence that was before it. But the court remanded the secondary NAAQS. It was insufficient for EPA merely to compare the level of protection afforded by the primary standard to possible secondary standards and find the two roughly equivalent. EPA must expressly “determine what level of . . . protection is requisite to protect the public welfare,” and explain why this is so. Accordingly, because EPA failed to determine what level of protection was “requisite to protect the public welfare,” its explanation for the secondary standard violated the CAA. [Editors note: On December 11, 2013, the court amended the opinion to clarify the deference EPA is due when determining the margin of safety of air quality standards. The order can be found at the end of the decision.]