EPA's  Endangerment Finding
Legal Background
Today's Action
On December 7, 2009, EPA finalized its finding under Clean Air Act section 202(a) that greenhouse
gases in the atmosphere endanger both the public health and the environment for current and future
generations. The agency also found that the combined emissions of greenhouse gases from new motor
vehicles and new motor vehicle engines are contributing to the buildup of greenhouse gases in the
atmosphere, and thus to the climate change problem. The specific findings are:

    EPA finds that the elevated concentrations of the six greenhouse gases in the atmosphere  carbon
     dioxide (CO2), methane (CFLO, nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons
     (PFCs), and sulfur hexafluoride (SF6)  endanger both the public health and the public welfare of
     current and future generations.
    EPA finds that the combined emissions of greenhouse gases from new motor vehicles and new
     motor vehicle engines contribute to the greenhouse gas air pollution which endangers both public
     health and welfare.

Key Milestones
    On October 20, 1999, the International Center for Technology Assessment and 18 other
     environmental and renewable  energy industry organizations filed a petition seeking the regulation
     of greenhouse gas emissions from on-road vehicles under the Clean Air Act.
    On April 2, 2007, after years of litigation related to the petition, the Supreme Court ruled in
     Massachusetts v. EPA, that greenhouse gases are air pollutants covered by the Clean Air Act and
     that EPA 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.
    On December 5, 2007, EPA sent a draft proposal to the White House Office of Management and
     Budget, finding that concentrations of six key greenhouse gases in the atmosphere endanger the
     public welfare and that emissions from new motor vehicles contribute to this problem. After the
     Bush Administration refused to consider the proposal, EPA later withdrew the rulemaking.
    On July 1 1, 2008, EPA issued a broad Advance Notice of Proposed Rulemaking (ANPR) regarding
     regulating greenhouse gases under the Clean Air Act. The ANPR, among other things, summarized
     the key issues from the 2007 endangerment and contribution proposal, and included a "technical
     support document" that summarized the findings of the major science assessment reports on climate
     science and impacts.
    On April 17, 2009, EPA issued the proposed findings for greenhouse gases under Section 202(a) of
     the Clean Air Act and released a revised technical support document, updated to reflect more recent
     science and input received through public comment on the ANPR.
    During the 60-day public comment period on the Proposed Findings, which ended June 23, 2009,
     EPA received more than 380,000 public comments, including both written comments and oral
     testimony  at two public hearings in Arlington, Virginia and Seattle, Washington.
    EPA carefully reviewed and considered the public comments, as indicated in EPA's Final Findings,
     the final technical support document, the 1 1 -volume Response to Comments document, and other
     supporting materials released along with the Findings.

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