ACS Urges the EPA to Maintain its 2009 GHG Endangerment Finding and Subsequent Environmental Regulations

September 18, 2025

Introduction
The American Chemical Society (ACS) is a congressionally chartered not-for-profit organization and one of the world's largest scientific societies with more than 230,000 individuals in our membership community. ACS advances knowledge and research through scholarly publishing, scientific conferences, information resources for education and business, and professional development efforts. Our commitment is to improve all lives through the transforming power of chemistry. The ACS strives to advance scientific knowledge, empower a global community and champion scientific integrity. We thank the EPA for the opportunity to comment on the reconsideration of the 2009 Endangerment Finding.

Background
On April 2, 2007, in Massachusetts v. EPA, 549 U.S. 497 (2007), the Supreme Court found that greenhouse gases are air pollutants covered by the Clean Air Act. The Court held that the Administrator must determine whether or not emissions of greenhouse gases from new motor vehicles cause or contribute to air pollution that may reasonably be anticipated to endanger public health or welfare, or whether the science is too uncertain to make a reasoned decision. On April 17, 2009, the Administrator signed proposed endangerment and cause or contribute findings for greenhouse gases (GHG) under Section 202(a) of the Clean Air Act.

The 2009 finding was supported by a 210-page technical document that laid out the scientific reasoning to include GHG under the clean air act. This evidence was upheld by the D.C. Circuit Court of Appeals in Coalition for Responsible Regulation v. EPA (2012). The court noted that EPA had reasonably relied on peer-reviewed assessments from the Intergovernmental Panel on Climate Change (IPCC), the U.S. Global Change Research Program (USGCRP), and the National Research Council (NRC).

The sixteen years of rulemaking that EPA has engaged in since the endangerment finding has continued to be built and supported by peer reviewed science. Continued studies, research and reports have strengthened the original findings.

ACS Positions
The ACS supports the critical importance of scientific integrity when policy makers are creating rules and regulations. ACS strongly supports the use of comprehensive, transparent, and unbiased scientific input in the development and evaluation of public policy. Reversing findings that are based on multiple decades of peer reviewed research without sound scientific rationale is counterproductive and removes scientific input from the policy making process. ACS’s position statement on Scientific Integrity clearly states how scientific data and procedures should be used to influence policy decisions.

The ACS also supports the data that influenced the endangerment findings conclusions. Our Global Climate Change statement recognizes that the Earth’s climate is changing in response to increasing concentrations of greenhouse gases (GHGs) and particulate matter in the atmosphere.

Conclusion
The ACS respectfully urges EPA to retain the 2009 Endangerment Finding and continue regulating GHG emissions under the Clean Air Act. Doing so is essential to protect public health, uphold scientific integrity, and support the development of sustainable technologies that address global climate change.