EPA’s Endangerment Finding in Danger?

On his first day in office, President Trump signed Executive Order (EO) 14154, Unleashing American Energy. Halfway through the lengthy Order, one paragraph requires the Administrator of the Environmental Protection Agency (EPA) to submit recommendations within 30 days “on the legality and continuing applicability of” EPA’s findings, “Endangerment and Cause or Contribute Finding for Greenhouse Gases Under Section 202(a) of the Clean Air Act.”¹  While this paragraph initially went unnoticed, the revocation of the endangerment finding could foreshadow severe repercussions for greenhouse gas (GHG) regulation in the United States.

What is the Endangerment Finding?

Section 202(a) of the Clean Air Act (CAA) requires EPA to regulate air pollutants if it finds that they “cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare.”²  In 1999, EPA received a rulemaking petition to regulate GHG emissions from new motor vehicles under the CAA. Four years later, the agency denied the petition, refusing to issue an endangerment finding based on the premise that GHGs were not “air pollutants” under the CAA. States and private entities sued, and in the monumental case Massachusetts v. EPA (2007), the Supreme Court held that GHGs are air pollutants within EPA’s authority under the CAA, and that EPA was required by the rulemaking petition to either determine endangerment or provide a reasonable explanation for not doing so.³  As a result, in 2009, President Obama’s EPA published the two findings at issue in this EO 14154: (1) the endangerment finding, which concluded that each GHG threatens public health and welfare, and (2) the cause or contribute finding, which concluded that the combined GHGs from new motor vehicles contribute to pollution that threatens public health and welfare.⁴  The findings were subsequently upheld in numerous legal challenges⁵  and served as the basis for many subsequent EPA GHG regulations.

In 2022, Congress passed the Inflation Reduction Act (IRA) adding seven new sections to the CAA.⁶  In the new sections, Congress made attempts to enhance the durability of the endangerment finding by including language in specific provisions that expressly deemed GHGs—such as carbon dioxide, methane and hydrofluorocarbons—to be pollutants for purposes of the amended sections of the CAA. These sections included, but were not limited to, Sec. 60101 on establishing a program for clean heavy-duty vehicles, Section 60103 on establishing the GHG Reduction Fund, and Section 60105 on providing grants to states to adopt GHG emissions standards for mobile sources among other appropriations for multi-pollutant monitoring stations and grants. These statutory determinations of GHGs as pollutants may factor into and or complicate EPA’s determination revisiting the endangerment finding, especially as Congress contemplates reconsidering those provisions during the budget reconciliation process.

Before the CAA amendments of 2022, under the IRA, and even still, the endangerment finding serves as the basis for regulating GHGs under the CAA, allowing EPA to establish emissions standards for vehicles, power plants, aircraft and other sources shown to reasonably affect health and welfare.

Approach, Arguments, and Implications

The first Trump administration did not seek to revisit the findings, in part due to pushback from industry groups, as well as from then-EPA Acting General Counsel David Fotouhi, who recently rejoined the agency as Deputy Administrator.⁷  However, EO 14154 signals that the new administration has taken it under stronger consideration. Given EPA Administrator Zeldin’s voting record against an appropriations rider that targeted the findings,⁸  he could report to the President that the original findings are well supported. However, Zeldin could instead recommend that one or both findings are not adequately supported by scientific evidence, or that the findings lack legal and/or practical applicability. For example, the Administrator might claim that after being codified into the IRA in 2022, the findings no longer serve a legal purpose. The Administrator could also claim that emissions from the United States do not “meaningfully contribute” to global emissions.

Such a recommendation could lead to a formal EPA challenge and eventual finding that U.S. GHG emissions do not meaningfully contribute to climate change or endanger public health or welfare. Paired with a repeal of the IRA, this would allow EPA to efficiently remove significant GHG regulations that were enacted based on the original endangerment finding. While Zeldin has not commented on what he may do regarding the findings, when challenged in his confirmation hearing in January on the topic, he refused to acknowledge that Massachusetts v. EPA “mandated” EPA to regulate GHGs, instead stating that the decision “authorized” the agency to regulate GHGs.

Obstacles to Repeal & Opportunities for Engagement

EPA faces scientific and legal barriers to challenging the endangerment finding. First, scientific data on the impacts of GHGs on climate change has only increased since the original 2009 finding. Scientists can more readily link impacts attributable to anthropogenic climate change and the relative contributions of different sources for those impacts, undermining arguments that emissions reductions in one jurisdiction will not meaningfully “contribute” to addressing global climate change.⁹  Second, any decision against the findings would be immediately challenged in court. The findings have been upheld against various legal challenges over the years, with the Supreme Court declining to hear challenges to it as recently as December 11, 2023.¹⁰  Nevertheless, recent landmark decisions in the Supreme Court have demonstrated a willingness to deviate from precedent in matters of environmental regulations and otherwise. If challenged, these potential legal proceedings will present opportunities for engagement for environmental and industry groups to file amicus briefs or join likely challenges from Democratic states.

Administrator Zeldin’s recommendations on the legality and ongoing relevance of the findings are due today, February 19, 2025.

^{1 Exec. Order No. 14,154 Sec. 6(f), 90 Fed. Reg. 8353, 8357 (Jan. 29, 2025).}

^{2 42 U.S.C. § 7521(a).}

^{3 Massachusetts v. EPA, 549 U.S. 497 (2007).}

^{4 74 Fed. Reg. 66496 (Dec. 15, 2009).}

^{5 E.g., Coal. for Responsible Regul., Inc. v. EPA, 684 F.3d 102 (D.C. Cir. 2012); see Karen Zraick & Lisa Friedman, Inside Trump’s Renewed Effort to Undo a Major Climate Rule, N.Y. Times (Jan. 28, 2025), https://www.nytimes.com/2025/01/28/climate/trump-endangerment-finding-epa.html (“[The endangerment finding] was challenged in more than 100 lawsuits and was previously upheld by a federal appellate court. And as recently as 2023, the Supreme Court . . . declined to review the case.”).}

^{6 Inflation Reduction Act. P.L. 117-169, Title VI.}

^{7 Kevin Bogardus, Trump’s EPA Deputy Pick Is a Familiar Face in HQ, E&E News (Jan. 13, 2025), https://www.eenews.net/articles/trumps-epa-deputy-pick-is-a-familiar-face-in-hq/.}

^{8 Jean Chemnick, Trump Set a Deadline on the Endangerment Finding. Here’s What Might Happen., POLITICOPRO (Feb. 12, 2025), https://subscriber.politicopro.com/article/eenews/2025/02/12/trump-set-a-deadline-on-the-endangerment-finding-heres-how-it-could-play-out-00203693.}

^{9 Attribution Science and Climate Law Conference 2025, COLUM. L. SCH., SABIN CTR. FOR CLIMATE CHANGE L., https://climate.law.columbia.edu/content/attribution-science-and-climate-law-conference-2025 (last visited Feb. 17, 2025).}

^{10 Supreme Court Order List, 601 U.S. (Dec. 11, 2023), https://www.supremecourt.gov/orders/courtorders/121123zor_e29g.pdf.}