Air pollution in the United States poses a public health threat affecting potentially millions of people throughout the country. It is associated with health problems that include increased emergency department visits and hospitals stays for breathing and heart problems, asthma, and increases in illnesses such as pneumonia and bronchitis.

Tracking air pollution can help people understand how often they are exposed to unhealthy levels of air pollution. Having these data can also help public health professionals or policymakers understand which areas may be most in need of prevention and control activities.

The Tracking Network includes data about ozone and particulate matter (PM_2.5).