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 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.
EPA suspended operations at a number of CASTNET locations throughout the country in May, 2022 due to budget constraints. These sites included: ASH135, UND002, WST109 (sampling resumed in late 2023), HWF187, CDR119, PSU106 (ozone continues), PNF126, ANA115 (ozone continues), and DCP114.

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