Parts 1 and 2 of this series were published in CEP in May 2025 and December 2025, respectively, and shared on ChEnected. Part 3 of this series focuses on how recent agency actions regarding the U.S. Environmental Protection Agency (EPA) Endangerment Finding may impact chemical engineers.
The Endangerment Finding
In 2009, the U.S. EPA determined that greenhouse gases (GHGs) threaten public health and welfare, thereby establishing the basis for regulating emissions under the U.S. Clean Air Act. The EPA did so by adopting its Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act, 74 Fed. Reg. 66,496 (Dec. 15, 2009), following the U.S. Supreme Court’s decision in Massachusetts v. EPA, 549 U.S. 497 (2007). The EPA’s 2009 action identified carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6) as GHGs subject to potential regulation.
This year, despite mounting evidence of global climate change, the EPA promulgated a final rule seeking to reverse course with its Recission of the Greenhouse Gas Endangerment Finding and Motor Vehicle Greenhouse Gas Emission Standards Under the Clean Air Act. With this final rule, the EPA abandons its arguments against the consensus science of climate change and relies solely on legal arguments.
The EPA’s final rule is consistent with the current administration’s regulatory rollback strategy. As a result, multiple petitioners filed timely appeals in the U.S. Court of Appeals for the District of Columbia Circuit. As of this writing, the challengers include: a coalition of 17 health and environmental organizations, environmental non-governmental organizations (NGOs), public health organizations, and scientific organizations, as well as 24 states, 10 municipalities, and others, with additional challenges expected before the rule’s effective date of Apr. 20, 2026.
After exhausting applicable administrative prerequisites, petitioners are expected to file a unified motion for a stay of the final rule, pending full judicial review. Such a stay would preserve the status quo during the appeal. In order to support their motion, petitioners are likely to argue that a stay will prevent irreparable harm, and that they have a substantial likelihood of success.
Practical impacts
Chemical engineers are directly affected by the 2009 Endangerment Finding because it provides the legal foundation for Clean Air Act regulation of GHG emissions from both mobile and stationary sources. If the rescission is upheld, the EPA anticipates that regulations promulgated since 2009 that rely on the finding would lose their legal basis.
If the EPA’s positions are upheld in court, this would have sweeping consequences. Affected regulations could include the light-duty vehicle and heavy-duty engine and vehicle emission standards at 40 CFR Parts 85, 86, 600, 1036, and 1037; the mandatory GHG reporting rule at 40 CFR Part 98; and the Oil and Natural Gas Sector NSPS standards at 40 CFR Part 60, Subparts OOOO and OOOOa.
It could also affect the non-sector-specific New Source Review (NSR) program under the Clean Air Act’s Prevention of Significant Deterioration (PSD) provisions, including 40 CFR 52.21(b)(49) and 52.21(j), which govern Best Available Control Technology (BACT), federal GHG-related preconstruction permitting requirements, as well as Title V operating permit programs and annual reporting obligations.
In the absence of federal regulation, states may adopt or expand their own GHG regulations. At the same time, climate litigation is likely to continue — and potentially accelerate. Columbia Law School’s Sabin Center for Climate Change Law tracks thousands of climate-related cases in the U.S. and hundreds more internationally. If past trends continue, the absence of a clear federal regulatory framework may increase litigation risk and regulatory uncertainty for GHG emitters.
Chemical engineers and climate change
Whether the Endangerment Finding is ultimately preserved or rescinded, chemical engineers remain uniquely positioned to develop technologies that reduce GHG emissions. The existing AIChE policy statement, adopted by the Board of Directors in October 2024, states: “Climate change solutions require chemical engineers as leaders in developing processes and alternative strategies that reduce greenhouse gas emissions from all contributing sources; offering new carbon neutral approaches to energy production; creating technologies for the removal of carbon from the atmosphere; and providing society with the means to adjust to a changing world.” Material and energy balances remain among the fundamental tools for understanding the sources and impacts of GHG emissions and for designing systems that reduce releases from both mobile and stationary sources, thereby advancing the present and future safety, health, and welfare of the public.
PAIC’s continued support
The Public Affairs and Information Committee (PAIC) remains committed to updating AIChE members on policy developments, supporting them during this period of uncertainty, and providing tools for implementing the 2024 AIChE Climate Change Policy Statement.
To that end, PAIC is developing public engagement toolkits, fact sheets, and educational modules to support members in their individual and collective efforts to mitigate climate change. Members should expect to see these resources posted on the PAIC website as they are completed this summer.
This article originally appeared in the ChE in Context column in the May 2026 issue of CEP. Members have access online to complete issues, including a vast, searchable archive of back issues found at www.aiche.org/cep.
