US Environmental Protection Agency
Epa: Criteria Air Pollutants
Find out about the six major air pollutants. In-depth descriptions of ozone, nitrogen dioxide, particulates, sulfur dioxide, carbon monoxide, and lead are provided.
Other
California Air Resources Board: Air Pollution Particulate Matter Brochure
This online brochure focuses on particulate matter in the atmosphere and its health effects.
CK-12 Foundation
Ck 12: Earth Science: Types of Air Pollution
[Free Registration/Login may be required to access all resource tools.] Distinguishes between primary and secondary pollutants and identifies examples of each.