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Endangerment and Cause or Contribute Findings for Greenhouse Gases under the Clean Air Act

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

These findings do not themselves impose any requirements on industry or other entities.  However, this action is a prerequisite to finalizing the EPA’s proposed greenhouse gas emission standards for light-duty vehicles, which were jointly proposed by EPA and the Department of Transportation’s National Highway Safety Administration on September 15, 2009. 


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 which 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 and has now issued these final Findings. 

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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 will be effective January 14, 2010.

Technical analyses developed in support of the Endangerment and Cause or Contribute Findings for Greenhouse Gases under the Clean Air Act may be found here:

Response to Comments

EPA’s response to public comments received on the Proposed Findings and accompanying Technical Support Document may be found here:

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To access materials related to the proposed finding, please visit the Proposed Endangerment and Cause or Contribute Findings for Greenhouse Gases under the Clean Air Act archive.

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Contact Us

Contact us at ghgendangerment@epa.gov with questions about this action.

Disclaimer: The comment period for this action has ended; comments made during this time will not be entered into the docket.

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