The federal government's Environmental Protection Agency (EPA) oversees the Nation's regulation of air pollution sources. The Clean Air Act, initially enacted in 1963 and significantly amended in 1970 and 1990, is the primary federal law under which the EPA operates. The Clean Air Act was the first comprehensive environmental law. Unfortunately, air pollution remains a significant threat to human health. Statistics show that each year at least fifty million people in the United States live in areas that fail to meet air quality standards. While our motor vehicles and factories are more environmentally friendly than thirty years ago, our air continues to deteriorate because we simply build more motor vehicles and factories.

Poor air quality is rarely the primary cause of illness or death, however, in combination with other environmental hazards, air pollution increases the occurrence of lung cancer, emphysema, tuberculosis, pneumonia, bronchitis, and asthma. The difficulty in regulating air pollution is the mobile nature of the pollutants themselves. The common sources of air pollution, such as cars, trucks, factories (electric and other utilities), mining sites, and construction sites must obtain permits from the EPA prior to emitting certain pollutants. Some common pollutants include ozone, particulate matter, vinyl chloride, arsenic, radionuclides, benzene, mercury, beryllium, lead, asbestos, nitrogen dioxide, sulfur dioxide, and carbon monoxide. Exposure to these substances may cause or aggravate respiratory problems (asthma, congestion, bronchitis, lung cancer), irritate the ears, nose, and throat, cause brain damage, heart / cardiovascular damage, leukemia, and other cancers.