Long-Term Emissions Trends

Before the Clean Air Act was signed into law in 1963, the 20th century had witnessed a significant and continued increase in air pollution levels. Although efforts made during the 1960's by State and local air pollution agencies in certain polluted cities in the Northeast helped reduce pollution in some local areas, emissions continued to increase on a national level.

Between 1900 and 1970, emissions of nitrogen oxides increased 690 percent, volatile organic compounds increased 260 percent, and sulfur dioxide increased 210 percent. Emissions of these pollutants have decreased significantly since the passage of the 1970 Clean Air Act Amendments. Without pollution controls resulting from these Amendments, emissions would have continued to increase as illustrated in these charts.