PFAS in Rural U.S. Well Water: Using Participatory Science to Identify and Communicate Results to Address Risks.

Drinking water contributes 1.2-61% of perfluoroalkyl and polyfluoroalkyl substances (PFAS) exposure, but little information is available on PFAS in private wells serving 17% of the U.S. population. Well users ( = 271) from four U.S. states collected tap water samples for analysis of 25 PFAS. Participants received results report comparing their water to PFAS health guidelines and recommending water filters when guidelines were exceeded. Follow-up surveys asked respondents what actions they took in response. To identify potential PFAS sources, we computed distances from households to PFAS sources recorded in EPA's PFAS Analytic Tools and other public databases and used spatial regression models to analyze relationships between these sources and water quality. PFAS were found in 15% of wells in the area with no known sources, some above a health guideline, and 53-88% of wells at sites with known sources. Total PFAS concentrations were significantly higher in wells closer to PFAS production facilities, Superfund sites, spill sites, and federal facilities. When recommended, 49% installed filters, while none did where water met the guidelines. Our study sheds insight into geographic variation in PFAS in private wells, the influence of potential PFAS sources on well water quality, and private well user decision-making in response to PFAS water quality information.