Clean Air Status and Trends Network (CASTNET)

Monitoring Sites

Learn about the deposition data and site characteristics of over 90 CASTNET sites.
Monitoring Surface Water Chemistry

Learn about EPA's Long-Term Monitoring (LTM) program, which tracks changes in surface water chemistry in response to changing air emissions and acid deposition.
Beltsville CASTNET Site Video

Hear from University of Maryland researchers who manage the Beltsville CASTNET site.

CASTNET is a national monitoring network established to assess trends in pollutant concentrations, atmospheric deposition, and ecological effects due to changes in air pollutant emissions. See the CASTNET Overview Fact Sheet (pdf) (2.93 MB, May 2025) and the CASTNET Ozone Monitoring page for more information.

Monitoring

Download Data

Publications

Bibliography
CASTNET Reports
CASTNET QA Documents
Tribal Program (pdf) (542.23 KB, Jan, 2024)

What's New

In October 2025, CASTNET added a new site in Martin County, FL (MAR013) with support from the Indian River Lagoon Council.
Weekly filterpack concentration data (1990-2024) are now available in AQS. A list of CASTNET parameter codes can be found in the lookup table: CASTNET AQS Parameter Codes (xlsx) (24.77 KB, 8/7/2025)
The Bureau of Land Management (BLM) issued a stop work order (SWO) on the WARMS contract in April 2025. The SWO terminated support for data collection at five CASTNET sites across WY: Basin (BAS601), Buffalo (BUF603), Fortification Creek (FOR605), Newcastle (NEC602), and Sheridan (SHE604).
EPA developed a three-year plan to modernize the Clean Air Status and Trends Network. The CASTNET Modernization Plan is now available.

Clean Air Status and Trends Network (CASTNET)

Monitoring Sites

Monitoring Surface Water Chemistry

Beltsville CASTNET Site Video

Monitoring

Download Data

Publications

What's New

Additional Resources