An endangerment finding is an administrative agency's scientific and legal determination that a substance threatens public health or the environment. When the EPA issues an endangerment finding, it establishes the factual basis for that agency to issue regulations controlling the substance.
In December 2009, the EPA issued its greenhouse gas endangerment finding, concluding that six greenhouse gases (carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride) threaten the public health and welfare of current and future generations. This finding, required by the Supreme Court's 2007 ruling in Massachusetts v. EPA, unlocked EPA's authority to regulate greenhouse gas emissions from vehicles, power plants, oil and gas operations, and other sources under the Clean Air Act.
In February 2026, the Trump administration's EPA repealed the endangerment finding, rolling back 16 years of greenhouse gas regulations. The repeal attempts to eliminate EPA's authority to regulate climate emissions by eliminating the scientific finding that triggered it—though it directly contradicts the Supreme Court's precedent that greenhouse gases are air pollutants requiring regulation. The repeal's legality remains uncertain and faces court challenges.
The endangerment finding repeal cuts the legal ground out from under climate regulation. All EPA greenhouse gas rules—vehicle standards, power plant limits, methane controls—rested on the 2009 finding. Repealing the finding is the fastest path to eliminating those rules, but it contradicts a Supreme Court precedent that endangered finding repeals.
People often think the EPA decided on its own to regulate greenhouse gases. In fact, the Supreme Court forced the EPA's hand in Massachusetts v. EPA, ruling that the agency had to make the endangerment determination if it found greenhouse gases threatened health. The 2009 finding was legally required, not a policy choice.
The endangerment finding repeal cuts the legal ground out from under climate regulation. All EPA greenhouse gas rules—vehicle standards, power plant limits, methane controls—rested on the 2009 finding. Repealing the finding is the fastest path to eliminating those rules, but it contradicts a Supreme Court precedent that endangered finding repeals.
People often think the EPA decided on its own to regulate greenhouse gases. In fact, the Supreme Court forced the EPA's hand in Massachusetts v. EPA, ruling that the agency had to make the endangerment determination if it found greenhouse gases threatened health. The 2009 finding was legally required, not a policy choice.