This document discusses air pollution and the Clean Air Act. It notes that the Clean Air Act was established in 1963 to study and clean up air pollution, with the EPA taking the lead role in 1970. The 1990 revisions expanded EPA authority and emphasized more cost-effective regulation. As a result of these laws, the six main air pollutants have decreased over 50% since 1970. The document urges readers to help reduce pollution through energy conservation and efficient transportation. It also explains thermal inversions, how they trap pollutants near the ground, and demonstrates this phenomenon with an experiment.