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July 26, 2012
SO2 standard not arbitrary and capricious

A double-pronged attack on EPA’s June 2010 revisions to the primary National Ambient Air Quality Standards (NAAQS) for sulfur dioxide (SO2) met with a double defeat at the hands of the U.S. Appeals Court for the District of Columbia. In National Environmental Development Association’s Clean Air Project v. EPA, challenges jointly organized by industry organizations and a handful of states alleged that the EPA’s hybrid approach to monitoring SO2 (to identify attainment/nonattainment areas) described in the final rule was not adequately described in the proposed rule. The petitioners also alleged that EPA’s final numeric primary NAAQS for SO2 were arbitrary and capricious because the Agency cherry-picked the health studies upon which the standard was based.

Short-term exposure

The 2010 SO2 primary NAAQS were a significant departure from the preexisting standards, which had been in effect for almost 40 years. The EPA decided to revoke both the annual and daily standards and replace them with a single 1-hour standard of 75 parts per billion (ppb). According to the EPA, the standard would protect people with compromised or still-developing lung function (e.g., asthmatics and children) from 5-or 10-minute bursts of SO2, which the Agency came to believe pose higher risks than those addressed in the annual and 24-hour NAAQS.

Choice of studies

According to the petitioners, the EPA ignored heath studies that would support a standard in the neighborhood of 400 ppb. The Court replied that those studies did not investigate effects on the most vulnerable subgroups for which the Agency’s revised standard provides a “not unreasonable” margin of safety.

The petitioners also criticized the EPA for not following one set of guidelines issued by the American Thoracic Society. Those guidelines emphasized the importance of considering the adverse effects of SO2 on lung function in conjunction with effects caused by other air pollutants. The DC Circuit disagreed, stating that the Clean Air Act (CAA) does not compel the EPA to rely on any one study in setting the NAAQS and that the Agency looked at other relevant studies.

The court also found no basis in the allegation that the EPA did not consider the effects of other pollutants and noted that the EPA made use of three multipollutant studies conducted in the United States, which made them particularly relevant for the NAAQS.

Not a final action

The hybrid monitoring approach involves a combination of direct air sampling and computer modeling. The EPA indicated that such an approach provides more flexibility than an approach that uses only monitors. For example, the inclusion of modeling allows monitors to be stationed for measurement of cross-boundary impacts rather than only near major sources of SO2 emissions.

The Court found that the EPA had introduced hybrid monitoring as guidance and not as a final Agency action. In fact, the Court said, the EPA indicated that it is possible that its approaches to monitoring may continue to evolve as experience with actual implementation is acquired. In any event, since the Agency did not impose specific legal requirements pertaining to the hybrid monitoring approach, the DC Circuit found that it did not have the jurisdiction to rule on its legality under the Administrative Procedures Act.

“Petitioners will be free to challenge any final action EPA takes that imposes an obligation Petitioners must meet,” stated the court. “The challenged provisions here do not meet that standard.”

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