The Clean Air Act directs EPA to establish air quality standards to protect public health and the environment. EPA sets national air quality standards for six principal air pollutants (also called the criteria pollutants): nitrogen dioxide (NO2), ozone (O3), sulfur dioxide (SO2), particulate matter (PM), carbon monoxide (CO), and lead (Pb).
Looking at Growth and Emissions
Each year EPA looks at emissions that impact the ambient concentrations of these pollutants. These annual emissions estimates are used as one indicator of the effectiveness of our programs. The graph below shows that between 1970 and 2005, gross domestic product increased 195 percent, vehicle miles traveled increased 178 percent, energy consumption increased 48 percent, and U.S. population grew by 42 percent. During the same time period, total emissions of the six principal air pollutants dropped by 53 percent.
From 1990 to 2002, air toxics emissions declined by 42%. These reductions are the result of implementing stationary and mobile source regulations. Seventy-five percent of air toxics emitted in 2002 are included below as volatile organic compound and particulate matter emissions.
