EPA’s Office of Air Quality Planning and Standards (OAQPS) has set primary (health-based) National Ambient Air Quality Standards (NAAQS) for six common air pollutants, often referred to as criteria air pollutants (or simply criteria pollutants). Each NAAQS has an averaging period (e.g., one-hour, eight-hour, 24-hour, three-month, annual) and a level.

• Environments and Contaminants: Criteria Air Pollutants (PDF)(21 pp, 274 K)