Foreword
Clean air first became a national issue in the 1950s, when the Federal Government began helping States research and measure pollution. When it became obvious that air quality was an interstate concern, Congress passed the landmark Clean Air Act of 1970, setting national requirements but letting States decide how to meet them. Under the Clean Air Act, the Environmental Protection Agency (EPA) regulates six common "criteria" air pollutants — ozone, particulate matter (such as dust, dirt, smoke, and soot), carbon monoxide, nitrogen oxides, sulfur dioxide, and lead — using two standards. The primary standard protects health; the secondary standard prevents…
