In 1970, Congress passed the Clean Air Act, the nation's most important air pollutiion law.
It established National Ambient Air Quality Standards for six criteria pollutants known to cause health problems-carbon monoxide, ozone, Lead, Sulfur dixodie, Nirtrogen oxides, and particulates (fine particles).
Todays power plants and motor vehicles use pollution control devices to reduce or elimate certain byproducts of fossil fuel combustion.