The U.S. Environmental Protection Agency compiles air quality monitoring data in the Air Quality System (AQS). Ambient air concentrations are measured at a national network of more than 4,000 monitoring stations and are reported by state, local, and tribal.
You will need Adobe Reader to view some of the files on this page. See EPA’s About PDF page to learn more.- Air Quality System (AQS) Appendix B: Metadata (PDF)(2 pp, 103 K)