In 1977 amendments to the Clean Air Act, the Congress created the Clean Air Scientific Advisory Committee (CASAC), a body of scientists whose job is to advise EPA on the setting of National Ambient Air Quality Standards (NAAQS).
NAAQS is the primary regulatory regime established by the Clean Air Act. The regulation does exactly what its name suggests–it establishes numerical nation-wide ambient air standards for “criteria” pollutants (sulfur dioxide, lead, particulate matter, ozone, nitrogen oxides, and carbon monoxide). There are two types of NAAQS: primary and secondary. Primary NAAQS are set at levels requisite to protect public health, with an adequate margin of safety, while secondary NAAQS are set at levels necessary to protect public welfare.
EPA is required to take CASAC’s advice into account, and, when it publishes any NAAQS, the agency must explain any differences it had with CASAC’s advice. In 2006 and 2008, George W. Bush’s EPA promulgated revised primary NAAQS for particulate matter and ozone, respectively. Both of the regulations were set at levels that were less stringent than the range recommended by CASAC.
In a 2009 ruling, American Farm Bureau Federation v. EPA, the D.C. Circuit Court rejected Bush’s 2006 primary NAAQS for particulate matter. The court reasoned that the agency had inadequately explained its differences with CASAC’s advice.
In a ruling announced last Monday, Mississippi et al. v. EPA, this same court upheld Bush’s 2008 ozone primary NAAQS, despite the fact that it was less stringent than what CASAC had recommended. This time, the court found that EPA had adequately explained the difference.
By the Court’s own admission in the Mississippi et al. v. EPA opinion, there are no clear cut criteria by which EPA’s reasoning is judged. The primary standard seems to be derivative of whether CASAC’s advice is rooted in science versus policy considerations. The former (science considerations) is construed as pertaining to the component of the primary NAAQS that is requisite to protect public health. The latter (policy considerations) is the component of the primary NAAQS that represents an adequate margin of safety. The Court reasoned that EPA’s discretion rises along a decision-making continuum, from “science” to “policy” differences with CASAC. CASAC’s judgment matters more for science–in practice, determining a NAAQS level requisite to protect public health. EPA’s judgement matters more for policy–in practice determining the NAAQS level necessary to achieve an adequate margin of public safety. In this instance, the judges found that CASAC hadn’t explicitly stated which parts of its recommended ozone NAAQS were science-based reasoning, and which parts were policy-based reasoning. In the face of this uncertainty, EPA’s explanation met the low bar by which an agency’s decision is deemed reasonable.
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