Last Friday, the U.S. Court of Appeals for the District of Columbia Circuit published two decisions in cases involving environmental groups’ challenges to EPA’s efforts to regulate certain classes of hazardous air pollutants (“HAPs”).  Both cases concerned Section 112(c)(6) of the Clean Air Act, a provision enacted by Congress in 1990 that requires EPA to (1) complete a list of sources of seven specified HAPs that accounts for at least ninety percent of the total emissions of each of the seven HAPs and (2) subject these listed sources to emissions standards.  42 U.S.C. § 7412(c)(6).  Section 112(c)(6) gives EPA a choice among two emission standards:  (1) a stringent standard known as “maximum achievable control technology” (“MACT”) or (2) a standard based on health thresholds.  See § 112(c)(6), (d)(2) and (d)(4).  The cases decided last Friday highlight both procedural and substantive aspects of regulating air pollution. Read More »

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