PFOS in Massachusetts well water
In Massachusetts, 10% of 1,793 private wells tested between 2020 and 2023 had PFOS above the EPA limit (4 ng/L), according to MassDEP.
PFOS is a forever chemical with the same sources as PFOA. It is linked to immune suppression, thyroid disease, liver effects and cancer. Wells near airports, fire training areas, landfills and plating plants are most at risk.
Check your PFOS number
Type the value from your lab report. It is compared to the EPA limit and the EPA limit, the same way the full interpretation does it.
Test your Massachusetts well for PFOS
Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.
Order the Tap Score well water test kit, from $209Already tested? Upload the report
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Systems that remove PFOS
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Some links below are affiliate links. If you buy through one, the merchant pays us a commission at no extra cost to you. It does not change which products we list or what the data says.
For PFOS
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
For PFOS
Whole-house PFAS carbon system
whole-house, at the point of entry, about $3,000
Granular activated carbon certified to NSF/ANSI 53 for PFOA and PFOS; replace media on schedule.
For PFOS
Aquasana SmartFlow reverse osmosis
under-sink or countertop, about $225
Certified to NSF/ANSI 58 and 53 to reduce arsenic (96%, pentavalent), fluoride (90%), lead (99%), nitrate, nitrite and PFOA/PFOS at the kitchen tap, with a remineralizer.
Rather have it installed and sized for your well? Book a free in-home water test with a licensed local company.
Where to get a well tested for PFOS in Massachusetts: certified labs, state programs and prices.
By county, from homeowner tests
Share of private wells above the state guidance level (4 ng/L) in tests homeowners sent to the state lab, 2020 to 2023.
Towns with the highest share above the state level
- Newbury, Essex County41% of 32 wells
- Carlisle, Middlesex County35% of 55 wells
- Sherborn, Middlesex County33% of 43 wells
- Tyngsborough, Middlesex County29% of 51 wells
- Carver, Plymouth County28% of 36 wells
- Stow, Middlesex County26% of 50 wells
- Granby, Hampshire County24% of 33 wells
- Boxborough, Middlesex County20% of 49 wells
- Westport, Bristol County19% of 43 wells
- Nantucket, Nantucket County17% of 48 wells
- Wellfleet, Barnstable County13% of 48 wells
- Harvard, Worcester County13% of 32 wells
- Lakeville, Plymouth County11% of 45 wells
- Rehoboth, Bristol County9% of 44 wells
- West Tisbury, Dukes County7% of 46 wells
- Shutesbury, Franklin County7% of 46 wells
- Westhampton, Hampshire County6% of 34 wells
- Hampden, Hampden County3% of 35 wells
- Pelham, Hampshire County3% of 39 wells
- Leverett, Franklin County0% of 43 wells
- Wendell, Franklin County0% of 41 wells
- New Salem, Franklin County0% of 39 wells
- Truro, Barnstable County0% of 35 wells
- Boxford, Essex County0% of 35 wells
- Richmond, Berkshire County0% of 34 wells
By county, from individual samples
Public monitoring samples against the EPA limit (4 ng/L); counties with at least 30 samples.
| County | Above EPA limit | Samples | Detected | Median | Highest |
|---|---|---|---|---|---|
| Barnstable | 113 | 83% | 120 | 20,800 ng/L |
Sources
- MassDEP Private Well PFAS Sampling Program: Private well PFAS results from the Massachusetts Department of Environmental Protection free sampling program, 2020 to 2023, one anonymized row per well. Shares are against the EPA limit for each compound (4 ng/L for PFOA and PFOS, 10 ng/L for PFHxS and PFNA). Massachusetts applies its own PFAS6 standard of 20 ng/L to the sum of six compounds; that sum is not a contaminant page here. Zero means not detected. Retrieved September 16, 2026.
- Individual samples from the USGS Water Quality Portal and state monitoring, summarized per geography. PFOS counts and shares are listed on each county and town page with their sources.
Analysis: PFAS in private wells: known sources versus routine testing, from the same public records.