Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act

Action

On December 7, 2009, the Administrator signed two distinct findings regarding greenhouse gases under section 202(a) of the Clean Air Act:

Endangerment Finding: The Administrator finds that the current and projected concentrations of the six key well-mixed greenhouse gases—carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF₆)—in the atmosphere threaten the public health and welfare of current and future generations.
Cause or Contribute Finding: The Administrator finds that the combined emissions of these well-mixed greenhouse gases from new motor vehicles and new motor vehicle engines contribute to the greenhouse gas pollution that threatens public health and welfare.

These findings do not themselves impose any requirements on industry or other entities. However, this action was a prerequisite for implementing greenhouse gas emissions standards for vehicles and other sectors.

Findings

These findings were signed by the Administrator on December 7, 2009. On December 15, 2009, the final findings were published in the Federal Register (www.regulations.gov) under Docket ID No. EPA-HQ-OAR-2009-0171. The final rule was effective January 14, 2010.

Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act

Scientific and technical information summarized to support the Endangerment and Cause or Contribute Findings for Greenhouse Gases under the Clean Air Act can be found here:

Technical Support Document for the Findings

Response to Comments

See EPA's response to public comments received on the Proposed Findings here.

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. In making these decisions, the Administrator is required to follow the language of section 202(a) of the Clean Air Act. The Supreme Court decision resulted from a petition for rulemaking under Section 202(a) filed by more than a dozen environmental, renewable energy, and other organizations.

On April 17, 2009, the Administrator signed proposed endangerment and cause or contribute findings for greenhouse gases under Section 202(a) of the Clean Air Act. EPA held a 60-day public comment period, which ended June 23, 2009, and received over 380,000 public comments. These included both written comments as well as testimony at two public hearings in Arlington, Virginia, and Seattle, Washington. EPA carefully reviewed, considered, and incorporated public comments when issuing the final Findings on December 7, 2009.

See the Endangerment Findings timeline from October 20, 1999, to December 7, 2009.

Denials of Petitions for Reconsideration

EPA denied ten Petitions Received in 2009-2010 for Reconsideration of the Endangerment and Cause or Contribute Findings on July 29, 2010.

EPA denied four Petitions Received in 2017-2019 for Reconsideration, Rulemaking, or Reopening of the Endangerment and Cause or Contribute Findings on April 21, 2022.

2012 U.S. Court of Appeals–D.C. Circuit Decision on Endangerment

On June 26, 2012, the U.S. Court of Appeals–D.C. Circuit decided to uphold EPA's GHG Endangerment and Cause or Contribute Findings and greenhouse gas regulations issued under the Clean Air Act for passenger vehicles and Clean Air Act permitting for stationary sources.