Clean Air Act (CAA)
The Clean Air Act (CAA), codified in U.S.C. Title 42, Chapter 85, is a central piece of legislation in the field of environmental law that promulgates uniform national standards for a wide range of air pollutants and sources. The CAA utilizes a two-prong approach - in addition to regulating the air quality levels, it also regulates sources of pollution.
See EPA Website: http://www.epa.gov/air/caa/