air pollution

EPA v. EME Homer City Generation


Consolidated with American Lung Association v. EME Home City Generation (12-1183).

  1. Did the EPA permissibly interpret the phrase “contribute significantly” when it balanced achievable emission reduction levels against the cost of achieving such emission reductions?   
  2. Can states wait for the EPA to adopt a rule quantifying each state’s “good neighbor” obligations before they adopt a state implementation plan prohibiting emissions that “contribute significantly” to other states’ pollution problems?

In 1963, in response to growing concerns of pollution, Congress passed the Clean Air Act (CAA). The CAA requires the Environmental Protection Agency (EPA) to set certain air quality standards for harmful pollutants, and includes a “Good Neighbor” provision requiring states to adopt plans that prohibit pollution that would “contribute significantly” to other states’ nonattainment of these standards.  However, the CAA does not define “significant contribution.”  In 2011, the EPA finalized a rule known as the “Transport Rule.”  Mirroring the language of the “good neighbor” provision, the Transport Rule defines emission reduction obligations for several upwind states that “contribute significantly” to downwind states’ nonattainment of the EPA’s air quality standards.  In determining what constitutes a significant contribution, the EPA balanced achievable emission reductions against the cost of achieving those reductions.  However, in EME Homer City Generations v. EPA, the D.C. Circuit struck down the Transport Rule and rejected the EPA’s analysis for determining what constitutes a significant contribution in this context.  These two cases present the Supreme Court with questions about the EPA’s interpretation of its statutory grant of authority under the CAA as well as questions about the jurisdiction of the D.C. Circuit to hear the challenges presented.  This case also raises concerns about federal intervention in state affairs and public health concerns posed by the EPA’s interpretation of the CAA.  Should the Supreme Court decide this case on the merits, the Court’s decision will significantly affect the EPA’s grant of authority to regulate interstate pollution. 

Questions as Framed for the Court by the Parties: 


The Clean Air Act, 42 U.S.C. 7401 et seq. (Act of CAA), requires the Environmental Protection Agency (EPA) to establish National Ambient Air Quality Standards (NAAQS) for particular pollutants at levels that will protect the public health and welfare. 42 U.S.C. 7408, 7409.  “[W]ithin 3 years” of promulgation of a [NAAQS],” each State must adopt a state implementation plan (SIP) with “adequate provisions” that will, inter alia, “prohibit[]” pollution that will “contribute significantly” to other States’ inability to meet, or maintain compliance with, the NAAQS. 42 U.S.C. 7410(a)(1), (2)(D)(i)(I).  If a State fails to submit a SIP or submits an inadequate one, the EPA must enter an order so finding. 42 U.S.C. 7410(k).  After the EPA does so, it “shall promulgate a [f]ederal implementation plan” for that State within two years. 42 U.S.C. 7410(c)(1).   

The questions presented are as follows: 

  1. Whether the court of appeals lacked jurisdiction to consider the challenges on which it granted relief.
  2. Whether States are excused from adopting SIPs prohibiting emissions that “contribute significantly” to air pollution problems in other States until after the EPA has adopted a rule quantifying each State’s interstate pollution obligations.
  3. Whether the EPA permissibly interpreted the statutory term “contribute significantly” so as to define each upwind State’s “significant” interstate air pollution contributions in light of the cost-effective emission reductions it can make to improve air quality in polluted downwind areas, or whether the Act instead unambiguously requires the EPA to consider only each upwind State’s physically proportionate responsibility for each downwind air quality problem.

American Lung Association v. EME Home City Generation (12-1183)


The Clean Air Act’s “Good Neighbor” provision requires that state implementation plans contain “adequate” provisions prohibiting emissions that will “contribute significantly” to another state’s nonattainment of health-based air quality standards. 42 U.S.C. 7410(a)(2)(D)(i).  A divided D.C. Circuit panel invalidated, as contrary to statute, a major EPA regulation, the Transport Rule, that gives effect to the provision and requires 27 states to reduce emissions that contribute to downwind states’ inability to attain or maintain air quality standards.  The questions presented are:

  1. Whether the statutory challenges to EPA’s methodology for defining upwind states’ “significant contributions” were properly before the court, given the failure of anyone to raise these objections at all, let alone with the requisite “reasonable specificity,” “during the period for public comment,” 42 U.S.C. 7607(d)(7)(B);
  2. Whether the court’s imposition of its own detailed methodology for implementing the Good Neighbor provision violated foundational principles governing judicial review of administrative decision-making; 
  3. Whether an upwind state that is polluting a downwind state is free of any obligations under the Good Neighbor provision unless and until EPA has quantified the upwind state’s contribution to downwind states’ air pollution problems.  



In passing the Clean Air Act, Congress empowered the Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS), the maximum permissible levels of common pollutants released into the air.  See EME Homer City Generation v. EPA, 696 F.3d 7, 12 (D.C. Cir. 2012).

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