A Clean Air Act may be one of a number of pieces of legislation relating to reduction of smog and atmospheric pollution in general. The United States Congress passed the Clean Air Act in 1963, the Clean Air Act Amendment in 1966, the Clean Air Act Extension in 1970, Clean Air Act Amendments in 1977, and Clean Air Act Amendments in 1990. Numerous state governments and local governments have enacted similar legislation, either implementing federal programs or filling in locally important gaps in federal programs.

The use of the federal government and state and local governments to enforce clean air standards has contributed to an improvement of the health of Americans and a longer life span for Americans. Critics argue it has also sapped corporate profits, and contributed to outsourcing abroad, while defenders counter that improved environmental air quality has increased more jobs than it has decreased. A Pennsylvania legislative supporter of clean air standards, Rep. Mark B. Cohen of Philadelphia, said "Vast progress has been made toward the development of clean air, but sufferers of asthma and other diseases need us to make much more progress in the future."

United Kingdom

• The Clean Air Act 1956 responded to London's Great Smog of 1952.

United States

• The Clean Air Act (USA) (1970) introduced regulation
• The Clean Air Act (USA) (1990) proposed emissions trading