One of the goals of the EPA was to set national air quality standards for six common air pollutants—carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter, and sulfur dioxide. Since passage of the Clean Air Act in 1970, the amount of these six pollutants in the air has decreased by more than 50 percent. Other accomplishments are:

• The reduction by nearly 70 percent of air toxics from large industrial sources (chemical plants, petroleum refineries, and paper mills)
• New cars are more than 90 percent cleaner
• Production of most ozone-depleting chemicals has ceased.