The Clean Air Act of 1970 is a United States federal law that was enacted to regulate air pollution on a national level. It is one of the most comprehensive air quality laws in the world and has been amended several times since its original passage. The Act sets national air quality standards, sets limits
From Wikipedia
The Clean Air Act (CAA) is the United States' primary federal air quality law, intended to reduce and control air pollution nationwide. Initially enacted in 1963 and amended many times since, it is one of the United States' first and most influential modern environmental laws.