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

The 2023 Annual Report was published. The report is a snapshot of the activities in 2023, including air quality trends and quality assurance results.
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).
The draft 2025 CASTNET Annual Network Plan (pdf) (3 MB, 5/21/2025) is now available for public comment.
EPA developed a three-year plan to modernize the Clean Air Status and Trends Network. The CASTNET Modernization Plan is now available.
CASTNET established a new site at Haskell Indian Nations University (HAS012) in November 2024.

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