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August 07, 2013
Split decision on 2008 ozone NAAQS

In a case that that focused on the legality of EPA’s 2008 National Ambient Air Quality Standards (NAAQS) for ozone, the U.S. Court of Appeals for the D.C. Circuit upheld the primary ozone NAAQS and remanded the secondary ozone NAAQS to the Agency (State of Mississippi v. EPA).  The court ordered that the secondary NAAQS remain in force until the EPA produces a revised standard. 

The actual long-term effect of the decision may be limited because the EPA is scheduled to complete its 5-year review of the ozone NAAQS in 2013.  However, the decision does clarify the D.C. Circuit’s view on how the EPA must justify revisions to the NAAQS.

Too stringent or not enough?

The case consolidates opposing suits against the EPA and the ozone NAAQS.  The state of Mississippi, supported by industry, challenged the Agency’s 2008 ozone NAAQS, which established a 0.075 parts per mission (ppm) 8-hour ozone primary standard and an identical secondary standard.  The primary NAAQS is intended to protect human health while the secondary NAAQS is directed to the protection of public welfare, which includes protection of the environment.  Mississippi argued that in establishing the 0.075 ppm standard, the EPA failed to properly consider the risk assessment conducted for the previous 8-hour NAAQS for ozone (0.08 ppm, established in 1997) and that the 2008 standard was too stringent. 

The 2008 ozone NAAQS was also challenged by a group of northeastern states, supported by environmental organizations, who claimed that the standard was not stringent enough.  The state petitioners asserted that the standard should be in line with a recommendation of between 0.60 and 0.70 ppm, which had been made by the Clean Air Scientific Advisory Committee (CASAC).

Current science critical

Regarding Mississippi’s contention that the EPA could not impose a new standard without placing it in the context of the previous standard, the D.C. Circuit states that the NAAQS must be reviewed in light of “contemporary policy judgments and the existing corpus of scientific knowledge.” 

“It would therefore make no sense to give prior NAAQS the sort of presumptive validity Mississippi insists upon,” the court continues.  “The statutory framework requires us to ask only whether EPA’s proposed NAAQS is ‘requisite’; we need not ask why the prior NAAQS once was ‘requisite’ but is no longer up to the task.” 

The D.C. Circuit says it believes EPA’s rejection of the 1997 NAAQS was “proper” since the Agency relied on a broad array of scientific studies, quantified models, and input from CASAC, EPA staff, and commenters, and it considered not only what was known but also what was not known.  The court adds that because it rejected Mississippi’s challenge to the primary NAAQS, it must also reject the state’s challenge to the secondary NAAQS. 

Margin of safety

The state and environmental petitioners contended that EPA’s 0.075 ppm ozone NAAQS was arbitrary and capricious because the EPA failed to rationally consider scientific evidence demonstrating adverse health effects at ozone levels below 0.075 ppm.  They also argued that the EPA acted contrary to law because it failed to calculate an adequate margin of safety, as required by the CAA.

Finally, they stated that the Agency did not explain and defend its decision to depart from CASAC’s recommendation.
The court agreed that the 0.075 ppm standard was probably protective of human health; but the more important issue was whether the standard provided the requisite margin of safety.  Ultimately, the court sided with the EPA.  “Petitioners have given us no reason to doubt EPA’s characterization of the 0.075 ppm level as ‘appreciably below’ 0.080 ppm,” said the D.C. Circuit.  “EPA complied with Congress’s command in [CAA] Section 109(b)(1) to build in a margin of safety, and its judgment that this margin is adequate was not arbitrary or capricious.”

The D.C. Circuit also found that the CASAC failed to specify whether its 0.070 ppm recommendation derived from a scientific conclusion.  Had the CASAC made a scientific judgment, the EPA would have been required to respond in kind.  But the CASCA did not make such a scientific judgment, said the court; it was more a product of public policy.  “Although both CASAC and EPA must exercise public health policy judgment when confronted with scientific evidence that does not direct it to a specific outcome, it is to EPA’s judgment that we must defer,” stated the court. 

Secondary standard

According to the EPA, the primary ozone NAAQs translated into a seasonal or 3-month standard of 21 ppm-hours.  But the D.C. Circuit found that the EPA never indicated that the 21 ppm-hours was requisite to protect public welfare.  “Perhaps more importantly, EPA never explained why a 21 ppm-hours level would, in fact, be requisite to protect vegetation,” added the court.  Accordingly, the court remanded the secondary standard of the 2008 ozone NAAQS. 
 Click here for The D.C. Court’s opinion in State of Mississippi v. EPA.

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