If you've seen the extremely poor air quality in parts of China, Russia and the Baltic States you have an idea of how bad it would be.
The first Clean Air Act was passed in 1963 and created a regulatory program in the U.S. Public Health Service. The 1967 Air Quality Act mandated enforcement of interstate air pollution standards and authorized ambient monitoring studies and stationary source inspections.
In the Clean Air Act Extension of 1970, Congress greatly expanded the federal mandate by requiring comprehensive federal and state regulations for both industrial and mobile sources. The law established four new regulatory programs:
The 1970 law is sometimes called the "Muskie Act" because of the central role Maine Senator Edmund Muskie played in drafting the bill.
The Clean Air Act Amendments of 1977 required Prevention of Significant Deterioration (PSD) of air quality for areas attaining the NAAQS, and added requirements for non-attainment areas.
The 1990 Clean Air Act added regulatory programs for control of acid deposition (acid rain) and stationary source operating permits. The NESHAPs program was expanded to control additional toxic air pollutants, and the NAAQS program was also expanded. Other new provisions covered stratospheric ozone protection, increased enforcement authority, and expanded research programs.