07/27/2020 - Legal Analysis - Student Work

Immediate Executive Action: Unexplored Options for Addressing Climate Change Under the Existing Clean Air Act

by Grace Weatherall

Below is a summary, see the full paper here.


As November approaches, climate lawyers, advocates, and policy experts are contemplating a future in which President Biden inherits an executive branch and a looming climate disaster. It is imperative that a Biden administration act immediately on climate, and this likely will mean applying its existing executive powers, including regulation under the Clean Air Act (CAA).

While President Obama’s EPA rolled out a series of rules addressing greenhouse gas (GHG) emissions under various CAA programs, two significant unexplored avenues for GHG regulation under the CAA remain: (1) regulating GHGs as a criteria pollutant under the NAAQS program; and (2) regulating GHGs under the § 115 provision on international air pollution. Various climate advocates have long promoted EPA exploration of these approaches, because each offers a vast regulatory potential. Each, if successfully implemented, could not only address greenhouse gas emissions from almost all sectors of the economy, but also curtail pollution from existing sources—dual objectives that no other GHG regulation program under the CAA could achieve in tandem.

In my white paper, I analyze the legal and practical challenges associated with regulating GHGs under the NAAQS program and § 115, and I suggest EPA’s best response to each challenge. Having weighed both options, I conclude that an incoming Biden administration would find an easier legal path in listing GHGs as a criteria pollutant and working to design a GHG NAAQS program. Thus, while I would encourage Biden’s EPA to attempt GHG NAAQS regulation, I argue that EPA should eschew attempting to implement § 115 for GHG emissions—at least until after completing an attempt at a GHG NAAQS.


The NAAQS program, established in §§ 108–110 of the CAA, sets the foundation of EPA regulatory authority by empowering the Administrator to set “primary” and “secondary” federal national ambient air quality standards (“NAAQS”) for each air pollutant “emissions of which, in [her] judgment, cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare”,[1] and “the presence of which in the ambient air results from numerous or diverse mobile or stationary sources”,[2] and then implement those standards through a powerful system of cooperative federalism. Pollutants subject to NAAQS standards are known as “criteria pollutants”, and per § 110 of the CAA, states must develop and maintain State Implementation Plans (SIPs) to meet the NAAQS for each criteria pollutant.[3] There are currently six criteria pollutants;[4] GHGs would be the seventh.[5]

Listing GHGs as a criteria pollutant would usher in a vast regulatory potential for EPA, but it would also present significant legal and practical challenges. In developing a NAAQS program for GHGs, EPA would need to both (1) develop a NAAQS implementation rule, or series of rules, capable of surviving judicial review; and (2) respond to the various problematic practical implications of regulating GHGs under the NAAQS program.

Specifically, in order to survive judicial review, EPA would need to (a) demonstrate that GHGs fit the criteria for listing under the NAAQS program; (b) demonstrate that its approach to regulating GHGs as criteria pollutants is reasonable as a matter of law; and (c) address the “timeline problem” associated with primary standards.[6] And in order to successfully implement a GHG NAAQS program, EPA would need to both (a) avoid regulating millions of new “major” sources under the Title V permitting program; and (b) ensure that an adequate number of states produced acceptable SIPs, so as to avoid being overwhelmed by the responsibility to design too many of its own Federal Implementation Plans (FIPs).

Despite these challenges, I conclude that, with the correct legal approach, a GHG NAAQS program is likely to survive judicial review. First, I argue that GHGs fit the criteria for listing because GHG emissions cause or contribute to air pollution which endangers public health and welfare, and GHGs can be considered “ambient” air pollutants. Second, I argue that EPA, armed with the significant discretion afforded to the Administrator under §§ 108–110, can successfully argue that a NAAQS program for GHGs is reasonable as a matter of law. Third, I argue that EPA can avoid the timeline problem either by setting primary standards at a level clearly attainable over a ten-year period, or by setting secondary standards only.

Further, I conclude that EPA can also address the practical implications of a GHG NAAQS. First, EPA can avoid the responsibility of regulating millions of new major sources of GHGs, likely by designing broadly applicable regulations to cover extraneous sources. Second, current political trends suggest that an adequate number of states will produce acceptable SIPs.

Having concluded that EPA is likely to survive the legal and practical challenges of regulating GHGs under the NAAQS program, and considering the enormous regulatory benefit of so doing, I recommend that a Biden EPA set to work immediately in developing a NAAQS program for GHGs.

Section 115

Section 115 is an interesting case. The only provision of the CAA concerning international air pollution, this section boasts broad language granting the Administrator the power to address pollution endangering health and welfare in foreign countries through implementation of the domestic SIP framework. This means that in theory, § 115 has the potential to provide the same greenhouse-gas emissions reduction benefit to EPA that listing greenhouse gases as criteria pollutants under the NAAQS program would. This makes § 115 a tantalizing option for GHG regulation, and indeed, several scholars and advocacy groups are in vocal support of using § 115 to regulate GHG emissions.[7] In practice, however, § 115 has never been used to regulate any pollutant, let alone GHGs, and I conclude in my white paper that an attempt to use this section for GHG regulation is unlikely to survive judicial review.

Section 115 operates as follows. Once the Administrator determines, based on international studies or reports, that “any air pollutant or pollutants emitted in the United States cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare in a foreign country”[8]—or the Secretary of State requests that the Administrator make such a finding[9]—the Administrator is empowered to direct the state responsible for that pollution to revise their SIP to address the issue.[10] Importantly, however, subsection 115(c) establishes a reciprocity requirement, specifying that the protections given under § 115 shall apply only to those foreign countries which “the Administrator determines ha[ve] given the United States essentially the same rights with respect to the prevention or control of air pollution occurring in that country as is given that country by this section.”[11]

In order to successfully implement a § 115 program for GHG regulation and survive judicial review, EPA would need to (1) establish endangerment; (2) demonstrate reciprocity; (3) develop a legal grounding for the allocation of responsibility among the states; and (4) demonstrate that § 115 can be applied to GHGs in the first place. I conclude that while EPA can likely prevail on the first three points above, the Supreme Court is unlikely to hold that § 115 applies to GHGs. Specifically, I suspect that the Court will hold that § 115 applies only to criteria pollutants. More problematically, the Court could also declare that GHGs are broadly unsuitable for SIPs regulation, thus torpedoing any hopes for GHG NAAQS regulation, as well. In either case, it behooves EPA to attempt a NAAQS program for GHGs before taking any action under § 115.


Both the NAAQS program and § 115 present tantalizing options for GHG regulation under the Clean Air Act. Indeed, both programs essentially represent different paths to the same outcome: successful implementation of either program would allow EPA to implement a system of SIPs to reduce GHG emissions from every sector of the economy, and from both new and existing sources. I argue, however, that it would be unwise to pursue GHG regulation under § 115 before at least attempting to regulate GHGs as a criteria pollutant. While I believe that regulation of GHGs under § 115 is unlikely to survive judicial review, I feel strongly that EPA has a good chance of success in implementing a NAAQS program for GHGs. An incoming Biden administration, then, should immediately focus its efforts on establishing a GHG NAAQS program. If successful, the payoff of such a program would be astronomical.

See the full paper here.



[1] 42 U.S.C. § 7408(a)(1)(A).

[2] Id. at § 7408(a)(1)(B).

[3] See id. at § 7410(a). If any state fails to produce an adequate SIP, EPA will develop a Federal Implementation Plan (FIP).

[4] The original six criteria pollutants are lead, carbon monoxide, sulfur dioxide, nitrogen dioxide, particulate matter, and ground-level ozone. For information, see the EPA’s website here.

[5] EPA’s 2009 endangerment finding for GHGs identified the six primary “well-mixed” greenhouse gases as a single pollutant for purposes of regulation. This approach is consistent with EPA’s regulation of particulate matter (PM)—a mixture of different materials with common properties and effects on human health and welfare, classified together as a sole criteria pollutant, see Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act, 74 Fed. Reg. 66496, 66519 (Dec. 15, 2009), and EPA would presumably follow the same approach for a GHG NAAQS program.

[6] While secondary standards require only that the Administrator set a date by which she expects attainment can be achieved “as expeditiously as practicable,” 42 U.S.C. § 7502(a)(2)(B), primary standards require the Administrator to set an attainment date no later than ten years after the nonattainment finding—a problem for GHGs, which are long-lived and remain in the atmosphere for many years. See id. at § 7502(a)(2)(A).

[7] See, e.g., Michael Burger et al., Summary: Combating Climate Change with Section 115 of the Clean Air Act, Columbia University Sabin Center for Climate Law, New York University School of Law Institute for Policy Integrity, UCLA School of Law Emmett Institute (June 2020), https://perma.cc/62BW-V3N3; Michael Burger et al., Legal Pathways To Reducing Greenhouse Gas Emissions Under Section 115 Of The Clean Air Act, Columbia University Sabin Center for Climate Law, New York University School of Law Institute for Policy Integrity, UCLA School of Law Emmett Institute (Jan. 2016), https://perma.cc/7J7M-7JD6; Hannah Chang, Cap and Trade Under the Clean Air Act?: Rethinking Section 115, 40 Envtl. L. Rep. News & Analysis 10894 (2010).

[8] 42 U.S.C. § 7415(a).

[9] Id. at § 7415(a).

[10] Id. at § 7415(b).

[11] Id. at § 7415(c).