As PFAS regulations, litigation, and site investigations continue to expand, environmental professionals need better data on how these compounds move through air, water, soil, and ecosystems. One important piece of that picture is now coming into focus: PFAS monitoring in precipitation.
The National Atmospheric Deposition Program (NADP), a long-term atmospheric deposition monitoring program, began developing a PFAS monitoring network in the late 2010s to help researchers and practitioners better understand how per- and polyfluoroalkyl substances move through the atmosphere and return to the environment through wet deposition.
After several years of planning, NADP established a provisional PFAS-NTN Subnetwork, known as PFN, on January 1, 2024. The network transitioned to an official NADP subnetwork in April 2026 after NADP finalized quality assurance documentation and standard operating procedures. The official network is designed to provide weekly concentrations and deposition fluxes for more than 40 PFAS compounds in precipitation.
Why does this matter?
According to NADP, PFAS in wet deposition can contribute to contamination of surface water, drinking water sources, soil, and vegetation. In some environments, atmospheric deposition may represent the largest source of PFAS to affected ecosystems. That makes atmospheric data increasingly relevant for evaluating background conditions, identifying potential transport pathways, and interpreting PFAS detections at regulated or investigated sites.
The network currently collects precipitation samples from monitoring sites across the United States. Those samples are analyzed for more than 40 PFAS constituents using isotope-dilution liquid chromatography tandem mass spectrometry. NADP plans to post final PFAS concentration and deposition data publicly after laboratory quality assurance and quality control checks are complete.
For consultants, site owners, municipalities, utilities, and regulators, these data could become a valuable reference point. PFAS monitoring through NADP may help project teams distinguish local source impacts from broader atmospheric contributions, support conceptual site models, and provide additional lines of evidence when evaluating compliance monitoring data.
Action Items for Environmental Compliance in Industry and Municipalities
Additional Information about the PFAS monitoring program, including NADP standard operating procedures, is available here:
