A Clean Air Act describes one of many pieces of legislation connected with the reduction of smog and air pollution. The use of governments to enforce clean air standards has contributed to an improvement in human health and longer life spans. Critics argue it has also exhausted corporate profits and contributed to outsourcing, while defenders argue that improved environmental air quality has generated more jobs than it has eliminated.

The United States Congress passed the Clean Air Act in 1963, the Air Quality Act in 1967, the Clean Air Act Extension of 1970, and Clean Air Act Amendments in 1977 and 1990. Numerous state and local governments have enacted similar legislation, either implementing federal programs or filling in locally important gaps in federal programs. The Clean Air Act of 1990 proposed emissions trading, added provisions for addressing acid rain, ozone depletion and toxic air pollution, and established a national permits program.

President Bush issued an executive order to cut greenhouse gas emissions from motor vehicles. This order incited a Supreme Court ruling that the Environmental Protection Agency must take action under the Clean Air Act to regulate GHG emissions from cars. President Bush proposed the "20-in-10" bill, a goal of reducing gasoline by 20 percent over the next 10 years.

The proposal would have the following steps:
- First, set a mandatory fuel standard that requires 35 billion gallons of renewable and other alternative fuels by 2017. That's nearly five times the 2012 current target. In 2017, this will displace 15 percent of projected annual gasoline use.

- Second, the proposal of continuing the efforts to increase fuel efficiency: reforming and modernizing Corporate Average Fuel Economy (CAFE) Standards for cars and extending the current Light Truck Rule. In 2017, this will reduce projected annual gasoline use by up to 8.5 billion gallons, a further 5 percent reduction that, in combination with increasing the supply of renewable and other alternative fuels, will bring the total reduction in projected annual gasoline use to 20 percent.