Endangerment and Cause or Contribute Findings under the Clean Air Act

GHG Emissions from Motor Vehicles

Before regulating a new pollutant under certain Clean Air Act programs, EPA must make a finding that the pollutant endangers public health or welfare, and that emissions targeted by the regulations cause or contribute to such pollution. In Massachusetts v. EPA, 549 U.S. 497 (2007), the Supreme Court concluded that greenhouse gases (GHGs) are air pollutants under the Clean Air Act, and that EPA must determine under section 202(a) of the Clean Air Act whether or not GHG emissions from new motor vehicles cause or contribute to air pollution that would endanger public health or welfare.

In April 2022, EPA denied four petitions for reconsideration of the 2009 endangerment finding and cause and contribute finding for GHG emissions from new motor vehicles. 87 Fed. Reg. 25,412 (Apr. 29, 2022).

Biden Administration (2021-2024)

In April 2022, EPA denied four petitions for reconsideration of the 2009 endangerment finding and cause and contribute finding for GHG emissions from new motor vehicles. 87 Fed. Reg. 25,412 (Apr. 29, 2022).

First Trump Administration (2017-2020)

N/A

Obama Administration (2009-2016)

On December 7, 2009, EPA promulgated an “endangerment finding” for six GHGs, finding them to threaten public health and welfare: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). 74 Fed. Reg. 66,496 (Dec. 15, 2009). At the same time, EPA promulgated a “cause or contribute finding” for new motor vehicles, concluding that vehicular emissions of greenhouse gases contribute to the endangerment created by greenhouse gas pollution.

EPA used the December 2009 endangerment and contribution findings as a basis for subsequent motor vehicle emission standards. EPA also extensively referenced the endangerment finding in proposing and finalizing subsequent emission standards for new and existing power plants and the oil and gas sector.

Litigation

Utility Air Regulatory Group v. EPA

Twenty-seven cases challenging the Endangerment Finding were consolidated in Utility Air Regulatory Group v. Environmental Protection Agency (D.C. Cir. 2012). In June 2012 the Court of Appeals for the DC Circuit Court upheld the Endangerment Finding, in addition to the Tailpipe Rule (discussed below), holding that EPA’s interpretation of the governing Clean Air Act provisions is unambiguously correct.