Mississippi v. EPA: Support of the Clean Air Science Advisory Committee is Not Necessary to Affirm EPA’s NAAQS

On Tuesday, in Mississippi v. EPA, the Court of Appeals for the D.C. Circuit affirmed EPA’s 2008 NAAQS for ozone of 0.075 ppm.  However, it remanded EPA’s decision to set the secondary NAAQS, for public welfare, at the same 0.075 ppm level.  With respect to the primary standard, the Court gave short shrift to industry and red-state challenges that the standard was too stringent.  This is not surprising, since the Clean Air Science Advisory Committee had recommended a range of between 0.060 and 0.070 ppm.

The interesting part of the decision is the Court’s explanation of why it rejected environmental group and blue-state challenges which argued that the standard was not sufficiently protective, given the CASAC recommendation.  As this space has addressed in connection with judicial review of the PM, SO₂, and NO_x NAAQS, the Court’s decisions in recent years have severely circumscribed EPA’s discretion to ignore CASAC.

I think it clear from this decision that CASAC support remains sufficient to justify the NAAQS set by EPA, but the Court has now carved out a narrow window where CASAC support is not necessary; EPA has some discretion to set an NAAQS outside of CASAC’s recommendation, so long as EPA clearly explains why it has rejected CASAC’s recommendation.  It may also be necessary that the basis for CASAC’s recommendation to be at least arguably ambiguous.

As the Court noted:

CASAC concluded that “the current primary 8-hr standard of 0.08 ppm needs to be substantially reduced to be protective of human health, particularly in sensitive subpopulations” and that the standard should be set within the range of 0.060 to 0.070 ppm. Id. at 4–5. CASAC reiterated this recommendation in a March 2007 letter to EPA, underscoring that “overwhelming scientific evidence” supported its recommendation “that the level of the current primary ozone standard should be lowered from 0.08 ppm to no greater than 0.070 ppm.”

Believe it or not, to the Court, this was not a sufficiently clear statement that CASAC believed that adverse health effects were in fact likely above 0.070 ppm.

Had CASAC reached a scientific conclusion that adverse health effects were likely to occur at the 0.070 ppm level, EPA’s failure to justify its uncertainty regarding the existence of adverse health effects at this level would be unacceptable.  …

But we are unable to determine whether CASAC reached any such scientific conclusion.  Although CASAC stated that “overwhelming scientific evidence” supported its recommendation that the standard be set no higher than 0.070 ppm, Mar. 2007 CASAC Letter, at 2, it never explained whether this proposal was based on its scientific judgment that adverse health effects would occur at that level or instead based on its more qualitative judgment that the range it proposed would be appropriately protective of human health with an adequate margin of safety.

I’m sorry, but does anyone doubt that, if CASAC were asked the precise question framed by the Court, its answer would have been that it indeed believed that adverse impacts are likely above 0.070 ppm?  It is difficult to see this decision other than as the Court trying really hard to preserve final decision-making authority for the EPA administrator.  I’m sympathetic to that view.  The Administrator is appointed by the President; CASAC members are not.  Nonetheless, I have a hard time buying the Court’s rationale here.

It may not matter much in the long run, because the evidence for a standard at or below 0.070 ppm has only gotten stronger.  So long as EPA does not propose a standard below natural background, the new standard, due late in 2014, is certainly not going to be above 0.070 ppm, and is likely to be affirmed – because it will be consistent with the CASAC recommendation.