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PFAS in Onset Fire District drinking water
EPA UCMR 5 results for public water system MA4310003 serving Wareham (Massachusetts). 1 of 29 PFAS detected.
PFOA (highest result)
Not detected (below the 4 ppt reporting level)
PFOS (highest result)
7.1 ppt above 4.0 ppt
PFAS detected
1 of 29 tested
Water system
ONSET FIRE DISTRICT (PWSID MA4310003)
System size
Small (serves 10,000 or fewer people)
Samples
8 sample event(s) at 4 sampling point(s), 2025-06-24 to 2025-12-02
Areas served (SDWIS)
Wareham
Counties
Plymouth
ZIP codes (UCMR 5)
02558
Source
UCMR 5 is a one-time EPA monitoring program, not a compliance determination. The values shown are the highest single sample result at any of the system's sampling points; one result above 4.0 ppt does not mean the system violates the PFAS rule, which is judged on running annual averages under separate compliance monitoring. Results describe the public water system, not an individual home.
Lead service lines
This water system is connected with lead service line inventory data on this site:
All PFAS detected
| PFAS | Highest result (ppt) | Samples with detection | EPA limit (2024 rule) |
|---|
| PFOS (perfluorooctane sulfonic acid) | 7.1 | 2 of 8 | 4.0 ppt (MCL, 2024 rule) |
ppt = parts per trillion (ng/L). EPA reports UCMR 5 results in µg/L; we multiply by 1,000. “Samples with detection” counts results at or above the UCMR 5 minimum reporting level.
What the limits mean
In April 2024 EPA set enforceable limits (MCLs) of 4.0 ppt each for PFOA and PFOS, plus 10 ppt for PFHxS, PFNA and HFPO-DA (GenX) and a Hazard Index for mixtures, with compliance based on a running annual average at each sampling point and due in 2029 (EPA ↗). In May 2026 EPA proposed letting systems request two more years for PFOA/PFOS (to April 2031) and rescinding the PFHxS, PFNA, GenX and Hazard Index limits (EPA: extension proposal ↗ · EPA: rescission proposal ↗). These are proposals, not final rules, as of the date this page was built.
What you can do
- Ask your water utility for its latest PFAS results and plans; its annual water quality report (Consumer Confidence Report) is a good place to start (EPA: Consumer Confidence Reports ↗).
- Read EPA's information on the PFAS drinking water rule (EPA PFAS rule page ↗).
- Home filters: EPA's fact sheet says filters certified to NSF/ANSI 53 or NSF/ANSI 58 (reverse osmosis) for PFAS reduction, such as PFOA and PFOS, are available; check the packaging or the certifier's directory (EPA home filter fact sheet ↗). We do not recommend specific products.
- We do not give medical advice. For health questions, see EPA's resources and talk to a health professional.
Other tested systems in the same area
PFAS disclaimer: PFAS results are copied from EPA's UCMR 5 dataset and describe samples taken at a public water system's entry points between 2023 and 2025, not water at any specific address. Levels may have changed since sampling (for example, after new treatment). “Not detected” means below EPA's UCMR 5 minimum reporting level, not zero. This is not a compliance determination or a water test. Contact your water utility for current information.