Critical health issues of criteria air pollutants

This chapter summarizes the key health information on ubiquitous outdoor air pollutants that can cause adverse health effects at current or historical ambient levels in the United States. The Clean Air Act (CAA) of the United States requires that the US Environmental Protection Agency (EPA) identify such pollutants (called criteria pollutants) and set standards (National Ambient Air Quality Standards (NAAQS)) to protect sensitive subpopulations from the adverse effects of these compounds. The criteria pollutants are ozone, nitrogen dioxide, sulfur dioxide, particulate matter (PM), carbon monoxide (CO), and lead. The subsequent sections of this chapter focus on the individual criteria pollutants.