Environmental non-governmental organisations recently filed a petition for review with the District of Columbia Circuit challenging the Environmental Protection Agency's (EPA's) decision to end its 'once in, always in' interpretation of Section 112 of the Clean Air Act. Under the policy (based on a 1995 guidance document), once an existing source qualified as a major source under Section 112 of the Clean Air Act, it had to continue meeting major source maximum achievable control technology standards for hazardous air pollutants, regardless of whether its emissions subsequently declined below major source thresholds.

The EPA revoked the policy in a January 2018 memorandum, enabling a source to later change from being a major source by taking an enforceable permit limit for hazardous air pollutant emissions at any time (for further details please see "EPA reverses 'once in, always in' policy for maximum achievable control technology standards"). The lawsuit faces a number of threshold issues, including whether the January 2018 memorandum is a final, reviewable agency action. Contemporaneously with its filing of the petition for review, the Environmental Integrity Project – one of the plaintiffs – issued a report alleging that the policy's reversal could lead to a large increase in hazardous air pollutant emissions from major sources.

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For further information on this topic please contact Samuel B Boxerman or Jim Wedeking at Sidley Austin LLP by telephone (+1 202 736 8000) or email (sboxerman@sidley.com or jwedeking@sidley.com). The Sidley Austin LLP website can be accessed at www.sidley.com.