Criteria air pollutants

Six common air pollutants for which National Ambient Air Quality Standards (NAAQS) have been established by the U.S. Environmental Protection Agency under Title I of the Clean Air Act (CAA). They are sulfur dioxide, nitrogen oxides, carbon monoxide, ozone, particulate matter (PM_2.5 and PM₁₀), and lead. Standards were developed for these pollutants on the basis of scientific knowledge about their health effects