1. Clean Air Act The Clean Air Act was first passed in 1963
This was when air pollution first began to be regulated
Then the act was updated in 1970, 1977, 1990
This is just a national act

2. Purpose and enforcement
The first federal legislation regarding air pollution control. The first Clean Air Act (CAA) permitted the development of a program to clean up air pollution and research methods to reduce air pollution.
Key milestones were 1967: enforcement procedures for air pollution problems
1970: establishment of National Ambient Air Quality Standards. establishment of New Source Performance Standards for new and modified stationary sources Authorized the establishment of National Emission Standards for Hazardous Air Pollutants
1990: Authorized programs for Acid Deposition Control. Authorized a program to control 189 toxic pollutants. Established permit program requirements
All the years the acts were updated also just increased enforcement authority.
Environmental issue affected was the air quality
The states regulate these acts