Yes, at low levels. 2 PFAS were detected, all below EPA's 2024 limits.
Also detected, no federal limit: PFHxA, PFPeA.
Dennis Water District is a public water system drawing on groundwater, based in South Dennis, Massachusetts, serving about 65,000 people, including Brewster, Dennis Port, East Dennis, South Dennis, West Dennis. Under EPA's Fifth Unregulated Contaminant Monitoring Rule it was tested for 29 PFAS and lithium 18 times across 9 sampling points between Oct 2023 and Apr 2024.
| PFAS | Detected | Highest | Worst point avg | EPA limit |
|---|---|---|---|---|
| PFHxA Perfluorohexanoic acid |
1 of 18 | 5.6 ppt | 2.8 ppt | none |
| PFPeA Perfluoropentanoic acid |
1 of 18 | 5.1 ppt | 2.6 ppt | none |
Not detected: PFMBA, NEtFOSAA, PFTrDA, PFTA, PFHpS, PFPeS, HFPO-DA, PFEESA, NMeFOSAA, PFMPA, 8:2 FTS, 4:2 FTS, PFDA, PFBA, NFDHA, 9Cl-PF3ONS, PFNA, PFHxS, PFHpA, PFBS, 6:2 FTS, ADONA, PFOS, 11Cl-PF3OUdS, PFUnA, PFDoA, PFOA.
Lithium, tested in the same program: not detected.
In April 2024 EPA set enforceable limits of 4 ppt for PFOA and PFOS, 10 ppt each for PFHxS, PFNA and GenX, and a hazard index of 1 for mixtures. Utilities were given until 2029 to comply. In May 2026 EPA proposed keeping only the PFOA and PFOS limits and moving that deadline to 2031. Until that proposal is final, the 2024 limits stand.
Compliance is judged on a running annual average at each entry point, so we show the average at this system's worst sampling point next to its single highest result. UCMR 5 results do not by themselves put a utility in or out of compliance.
Levels here are under EPA's limits, so no treatment is required. If you want them lower anyway, a certified reverse osmosis system under the sink handles drinking water, and a whole-house carbon filter also takes out the chlorine or chloramine your utility adds.
All 263 tested systems in Massachusetts
02631 02639 02641 02660 02670
As reported by the utility to EPA. Neighbouring ZIPs are often split between systems; your water bill names yours.
Well & Tap. "PFAS in Dennis Water District water: EPA UCMR 5 results." Data: U.S. EPA Fifth Unregulated Contaminant Monitoring Rule, final release August 2026, PWSID MA4075000. https://wellandtap.com/pfas/massachusetts/dennis-water-district/
Source: U.S. EPA, UCMR 5 occurrence data, final release August 2026 (PWSID MA4075000). Population: EPA SDWIS. Averages count results below the reporting level as zero, the same convention EPA uses for running annual averages. Full method.
