The endangerment finding was a scientific determination adopted by America's Environmental Protection Agency in 2009, concluding that emissions of six greenhouse gases—including carbon dioxide, methane and HFCs—posed a threat to human health and well-being. Backed by years of scientific evidence, it became the keystone on which many of America's federal climate regulations rested, because the Clean Air Act requires the EPA to regulate pollutants that threaten human health. It compelled the agency to introduce vehicle-emissions standards and limits on greenhouse-gas emissions from oil and gas infrastructure.
The finding was set in motion by the Supreme Court's 2007 ruling in Massachusetts v EPA, which held that greenhouse gases are pollutants falling under the EPA's regulatory mandate. Having been told that greenhouse gases fell within its purview, the agency then had to determine whether they posed a threat to human health.
In 2022, in West Virginia v EPA, the Supreme Court struck down President Barack Obama's Clean Power Plan, reasoning that a federal agency cannot claim sweeping powers without clear authorisation from Congress. This principle, the "major questions doctrine", is often cited by those who argue the EPA exceeded its legal powers in its efforts to fight climate change.
On February 12th 2026 President Donald Trump announced the termination of the endangerment finding. Lee Zeldin, the EPA administrator, called it "the single largest deregulatory action in US history". The EPA says the repeal will save Americans more than $1.3trn by easing the burden on fossil-fuel-burning industries. Critics counter that the EPA fails to take proper account of costs, such as the $1.7trn more Americans may spend on petrol by 2035. The Environmental Defence Fund estimates the repeal will result in tens of thousands of extra premature deaths by mid-century, as greenhouse gases raise air pollution by fostering more frequent and intense wildfires and accelerating the formation of ground-level ozone.
A Yale poll found that three-quarters of registered American voters think the government should regulate carbon dioxide as a pollutant.
Nostalgia is living life in the past lane.