Two recent D.C. Circuit Court of Appeals decisions affect the U.S. Environmental Protection Agency’s (EPA’s) air toxics regulatory program. In the first, the court upheld EPA’s determination of how to regulate hazardous air pollutants (HAPs) from gold mines under the Clean Air Act (CAA). Desert Citizens Against Pollution v. EPA, No. 11-1113 (D.C. Cir. 11/9/12).

The case involved differences in statutory treatment of pollutants identified in the CAA and those identified by EPA under the CAA. The CAA itself identifies seven specific HAPs and instructs EPA to identify others. EPA has accordingly identified hundreds of substances as HAPs by regulation. Mercury is a HAP listed within the CAA, and one source of HAP mercury emissions is gold mining operations. In February 2011, EPA identified gold mines as a HAP source and established emission standards for mercury emissions from such operations.

Environmental advocacy organization plaintiffs challenged the rule, asserting that gold mines emit other HAPs not named in the CAA but identified by EPA regulations. They asserted that the CAA required EPA to establish emission standards for gold mines’ emissions of those other HAPs and not just for mercury. Plaintiffs also challenged EPA’s determination that the regulation’s emission standard for mercury does not apply to fugitive emissions from mine operational features such as tailings ponds, leach fields and waste rock piles.

The court found that the statute is ambiguous as to whether emission standards for identified HAP sources must include HAPs other than those listed in the CAA. While the court found the plaintiffs’ construction of the statutory language “linguistically possible,” it deferred to EPA’s interpretation because the statute is ambiguous and thus upheld the agency’s decision to regulate only mercury emissions from gold mines.

With respect to coverage of fugitive emissions, the court noted that in the process of responding to comments on the regulation, EPA had clarified arguably ambiguous applicability provisions, limiting applicability of the emission standards to specifically defined “affected sources.” The court concluded that it must review EPA’s interpretation of its own regulations even more deferentially than its interpretation of the CAA and could overturn such an interpretation only if it is plainly erroneous. Applying this standard, the court held that EPA’s more limited applicability determination is entitled to deference and was not plainly erroneous. The court therefore rejected the plaintiffs’ challenge relating to fugitive emissions.

In the second decision, the court held that EPA was required to follow notice-and-comment procedures when issuing its determination that it had completed certain specific responsibilities under the CAA. Sierra Club v. EPA, No. 11-1184 (D.C. Cir. 11/9/12). The CAA required EPA to identify sources and issue standards to cover 90 percent of HAP emissions by November 15, 2000. EPA did not meet that deadline, but continued to identify sources and set standards in subsequent years, often under court-ordered deadlines. The last of the court ordered deadlines was February 21, 2011. On March 21, 2011, EPA published a “determination” concluding that it “has completed sufficient standards to meet the [CAA’s] 90 percent requirement.”

The Sierra Club sought review of that determination, arguing that it was incorrect—that EPA has not issued standards covering at least 90 percent of toxic air emissions—and that EPA failed to follow notice-and-comment procedures in publishing the determination. The D.C. Circuit concluded that EPA should have followed notice-and-comment procedures and that, by developing the record needed for the notice-and-comment process, EPA would provide the court a better record on which to analyze the merits of the determination itself. Accordingly, the court remanded the determination to EPA for notice-andcomment action consistent with the Administrative Procedure Act.

In a separate concurring opinion, Circuit Judge Karen LeCraft Henderson suggests that the Sierra Club’s standing to challenge the determination is “far from certain” and that the court’s decision will not redress Sierra Club’s concern. According to the concurrence, “EPA is under no obligation, statutory or otherwise, to inform anyone that it has satisfied the requirements of [the CAA HAP provisions]. The issuance of the Determination was purely voluntary, amounting to little more than a public service message.” Judge Henderson speculates that EPA will simply abandon the determination, rather than go through full noticeand- comment processes to re-issue it.