The Environmental Protection Agency is set to repeal a key finding that greenhouse gas emissions threaten public health, a move that would amount to a major rollback of government regulation of vehicle pollution.

The EPA proposed a rule last year to repeal the 2009 Endangerment Finding, which concluded that six greenhouse gases, including carbon dioxide and methane, pose a threat to public health and welfare. The finding was supported by a 2007 Supreme Court ruling in Massachusetts v. EPA, affirming that greenhouse gases are pollutants under the Clean Air Act.