|The Clean Air Act evolved from a 1955 clean air law initially aimed at dirty air that plagued many cities. The law added provisions about the effects of sources of pollution in 1970 and 1977. The law established quantity limits for the release of common industrial air contaminants. In 1990 amendments required stricter control over 189 air toxins based on 350 different categories. Students leave this course with the most updated information available for the clean air regulations they have to face.