U.S. EPA Proposes a Reconsideration of 2009 Endangerment Finding and Greenhouse Gas Vehicle Standards

Posted: August 14th, 2025

Authors: Markie'Sha J.

Introduction

On July 29, 2025, the U.S. Environmental Protection Agency (U.S. EPA) proposed to rescind the 2009 Greenhouse Gas (GHG) Endangerment Finding, which has served as a foundation for regulating GHG emissions from motor vehicles for over a decade. With this rescission, U.S. EPA proposed to eliminate all existing GHG vehicle emission standards for light-, medium-, and heavy-duty on-highway vehicles. If finalized, this proposal would represent a significant shift in Federal climate and transportation policy, affecting automakers, regulatory agencies, and consumers of America.

What is the Endangerment Finding?

The 2009 Endangerment Finding established a formal determination by U.S. EPA, under the Clean Air Act (CAA) Section 202(a), that GHGs – carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF₆) – constitute air pollutants that ultimately pose concern for both public health and welfare. This finding gave U.S. EPA the legal authority to regulate GHGs, laying groundwork for vehicle GHG emissions standards implemented over the past 15 years.

If the 2009 Endangerment Findings were rescinded, U.S. EPA would lose its authority to regulate climate change-related emissions under the CAA. This action would be predicated on the assertion that GHG emissions standards do not advance public health and welfare.

What are the GHG Vehicle Standards?

Following the 2009 finding, U.S. EPA issued multiple rules to limit GHG emissions from vehicles, including:

The 2010 and 2011 rules establish progressively more stringent GHG standards for light-, medium-, and heavy-duty vehicles (see 40 CFR § 86.1818‑12 and 40 CFR Part 1037),
Requirements for technologies like start-stop systems, air conditioning improvements, and hybridization, and
Coordination with the Department of Transportation’s Corporate Average Fuel Economy (CAFE) standards ( see 49 CFR Part 531 and 49 CFR Part 533).

These rules were developed to reduce transportation sector emissions while also improving fuel efficiency and encouraging innovation in vehicle technologies.

Why is U.S. EPA Reconsidering 2009 Endangerment Finding Now?

U.S. EPA’s reconsideration is part of the broader deregulatory agenda aligned with President Trump’s energy policy initiatives. The proposal was delivered by Administrator Lee Zeldin during an event in Indiana, highlighting the agency’s position where the original 2009 Endangerment Finding was based on misinterpreted legal findings and insufficient scientific findings.

Citing recent Supreme Court rulings, including West Virginia v. U.S. EPA and Loper Bright Enterprises v. Riamondo, U.S. EPA argues that major policy decisions, like GHG regulation, should be made by congress, not administrative agencies. The agency also referenced new scientific and economic data that challenge the assumptions behind the 2009 Endangerment Finding. The proposed rule seeks to remove this and the resulting vehicle GHG standards entirely. This includes control, measurement, and reporting obligations for GHG emissions.

What Are the Potential Implications of This Reconsideration?

The proposal seeks to repeal all regulatory provisions relating to GHG emissions of the following rules:

If finalized, U.S. EPA’s proposal would eliminate all Federal GHG emissions standards for new highway vehicles, effectively:

Removing CO₂ and other GHG emissions requirements for cars, trucks, and engines,
Eliminating related compliance obligations for vehicle manufacturers, and
Undoing the Federal basis for current and future electric vehicle (EV) mandates.

However, U.S. EPA’s goal is to retain standards related to criteria pollutants and fuel economy testing. While states such as California, New York, and Oregon currently maintain independent GHG programs, recent federal actions—including challenges to state climate initiatives and efforts to rescind U.S. EPA waivers under the CAA—signal a potential shift toward limiting states’ authority to impose standards stricter than federal requirements. Such conflicts could influence whether a fragmented national vehicle market persists.

The agency claims the proposal will reduce hidden regulatory costs for consumers and restore decision making to elected lawmakers. On the other hand, critics warn it could stall progress on vehicle electrification and climate goals, while triggering legal challenges and prolonging regulatory uncertainty.

What’s Next?

We expect this proposed regulation to be finalized quickly after the public comment period. Nonetheless, it is anticipated that U.S. EPA’s final decision will be subject to litigation, and a court may issue a stay on any action that removes the GHG emissions standards while legal proceedings are ongoing. Automative manufacturers will need to assess both state and Federal regulatory requirements to ensure compliance with the changing regulatory landscape.

U.S. EPA is accepting public comments on the proposed rule through September 15, 2025, under Docket ID No. EPA-HQ-OAR-2025-0194. Comments can be submitted at https://www.regulations.gov/ or via email a-and-r-Docket@epa.gov with the docket number EPA-HQ-OAR-2025-0194 in the subject line. A virtual public hearing is scheduled for August 19 through 21, 2025, depending on demand. Stakeholders- including automakers, environmental groups, and state regulators are expected to actively participate in the process.

Need help understanding how this affects you?

If you are wondering how this proposal will affect your facility or ongoing projects directly, please reach out to your ALL4 project manager or contact Louise Shaffer at lshaffer@all4inc.com