Source: EPA Documerica "Then and Now Challenge"
The Problem—Increasing Air Pollution in Cities in the mid-1900's
After World War II, economic growth, population growth, rapid suburbanization, and the closing of some public transit systems led to more reliance on personal vehicles for transportation. The number of cars and trucks in the United States increased dramatically, as did the number of highways. One result of the rapid increase of motor vehicles was air pollution, especially in cities, that had serious impacts on public health and the environment.
Historic Success of the Clean Air Act
Congress passed the landmark Clean Air Act in 1970 and gave the newly-formed EPA the legal authority to regulate pollution from cars and other forms of transportation. EPA and the State of California have led the national effort to reduce vehicle pollution by adopting increasingly stringent standards.
The U.S. vehicle pollution control under the Clean Air Act is a major success story by many measures:
New passenger vehicles are 98-99% cleaner for most tailpipe pollutants compared to the 1960s.
Fuels are much cleaner—lead has been eliminated, and sulfur levels are more than 90% lower than they were prior to regulation.
U.S. cities have much improved air quality, despite ever increasing population and increasing vehicle miles traveled.
Standards have sparked technology innovation from industry.