"Air quality has improved substantially in the United States in the 40 years of EPA's [Environmental Protection Agency] Clean Air Act regulation, but more needs to be done, according to the agency's science advisers, to protect public health and the environment from the effects of air pollution. Thus, the agency continues to promulgate regulations addressing air pollution using authority given it by Congress more than 20 years ago. In the 112th Congress, Members from both parties have raised questions about the cost-effectiveness of some of these regulations and/or whether the agency has exceeded its regulatory authority in promulgating them. Others in Congress have supported EPA, noting that the Clean Air Act, often affirmed in court decisions, has authorized or required the agency's actions. EPA's regulatory actions on greenhouse gas (GHG) emissions have been one focus of congressional interest. Although the Obama Administration has consistently said that it would prefer that Congress pass new legislation to address climate change, such legislation now appears unlikely. Instead, over the last three years, EPA has developed GHG regulations using its existing Clean Air Act authority. EPA finalized GHG emission standards for cars and light trucks on April 1, 2010, and for larger trucks, August 9, 2011. The implementation of these standards, in turn, triggered permitting and Best Available Control Technology requirements for new major stationary sources of GHGs."
CRS Report for Congress, R41563