FOR IMMEDIATE RELEASE
The National Atmospheric Deposition Program Releases First PFAS in Precipitation Data
MADISON, Wis. — October 27, 2026 — The National Atmospheric Deposition Program (NADP) announced the release of its first publicly available dataset of per- and polyfluoroalkyl substance (PFAS) concentrations in precipitation from monitoring sites across the country. PFAS are a very large group of persistent, human-made chemicals of growing environmental and public health concern. The precipitation data are being made available from the PFAS-National Trends Network subnetwork (PFN), NADP’s newest atmospheric monitoring network. The NADP is based at the Wisconsin State Laboratory of Hygiene (WSLH) at the University of Wisconsin-Madison.
This initial data release marks a significant milestone for atmospheric PFAS research, providing environmental scientists, regulatory agencies, and public health researchers with a first look at deposition patterns for these compounds across participating sites. The dataset represents the first and only publicly available record of weekly wet deposition PFAS measurements across the United States, offering a level of sampling frequency, site coverage, and quality assurance not previously available.
The data are free and publicly available at https://nadp.slh.wisc.edu/networks/pfas-ntn-subnetwork/. The weekly data will be posted at regular intervals, typically monthly. Early data shows that 15–20 PFAS compounds are regularly detected in precipitation, with the perfluoroalkyl carboxylic acids (PFCAs) generally the dominant class of PFAS present. PFAS concentrations are typically low (0.1 to 2 ng/L), though concentrations in precipitation can be significantly higher in urban airsheds and near point sources. Legacy compounds such as PFOA and PFOS are frequently detected in precipitation, demonstrating that these and similar PFAS continue to cycle in the environment, despite phase-out of manufacturing. Measured annual deposition fluxes can represent the major source of PFAS to terrestrial and aquatic ecosystems (e.g., large lakes like the upper Great Lakes).
“This dataset is the first and only one of its kind,” said Sarah Benish, Ph.D., NADP Coordinator and Principal Investigator. “That combination of sampling frequency and coverage is critical for estimating and modeling how PFAS move into aquatic and terrestrial ecosystems and for understanding how these compounds cycle across environmental media. Importantly, the network will also facilitate identification of sources of PFAS to the atmosphere, particularly as the network grows. Since the network builds on infrastructure already deployed at more than 200 NADP sites nationwide, we have significant room to grow, expanding PFAS monitoring coverage without having to build from the ground up.”
NADP is looking for additional site sponsors to help expand the PFN’s geographic coverage in areas not currently monitored.
About NADP
Established in 1978, the National Atmospheric Deposition Program is a cooperative monitoring effort supported by scientists, government, state, and tribal agencies, and other organizations that collect, analyze, and interpret data on air quality and atmospheric deposition across North America.
The PFN, after several years as a pilot monitoring program, was established as an official NADP subnetwork in April 2026 to track weekly wet concentrations and deposition fluxes of PFAS. Wet deposition (rain and snow) scrubs PFAS from the atmosphere and deposits these chemicals into aquatic (e.g., lakes, oceans, drinking water sources) and terrestrial (e.g., forest, soils) ecosystems. The PFN comprised of 15 sites when launched in April, and has grown to almost 30 monitoring sites sampling today, measuring 40 individual PFAS compounds. Data from additional sites will be added to the regular data releases as they become available.
Media Contact
Jan Klawitter
Wisconsin State Laboratory of Hygiene, UW–Madison
Jan.klawitter@slh.wisc.edu
(608) 265-2529
NADP Contacts
Sarah Benish
Wisconsin State Laboratory of Hygiene, UW–Madison
sebenish@wisc.edu
(608) 263-9162
Martin Shafer
Wisconsin State Laboratory of Hygiene, UW–Madison
mmshafer@wisc.wisc.edu
(608) 217-7500