Arsenic in Maine well water
In Maine, 17% of 27,616 private wells tested had arsenic above the Maine guideline (10 ug/L), according to Maine CDC.
Arsenic occurs naturally in New England bedrock and dissolves into well water. Long-term exposure raises the risk of bladder, lung and skin cancers, and is linked to heart disease and lower IQ in children. It has no taste or smell, so testing is the only way to know.
By county, from homeowner tests
Share of private wells above the state guidance level (10 ug/L) in tests homeowners sent to the state lab, to .
| County | Wells tested | Above state level | Highest | |
|---|---|---|---|---|
| Kennebec | 4,743 | 28% | ||
| York | 2,174 | 23% | ||
| Hancock | 2,622 | 22% | ||
| Somerset | 952 | 18% | ||
| Cumberland | 4,050 | 17% | ||
| Washington | 1,210 | 17% | ||
| Knox | 798 | 17% | ||
| Androscoggin | 1,293 | 15% | ||
| Piscataquis | 320 | 12% | ||
| Franklin | 778 | 10% | ||
| Waldo | 1,434 | 9% | ||
| Penobscot | 2,501 | 8% | ||
| Sagadahoc | 1,019 | 5% | ||
| Oxford | 1,108 | 5% | ||
| Lincoln | 1,770 | 4% |
Towns with the highest share above the state level
- Manchester, Kennebec County57% of 207 wells
- Sedgwick, Hancock County52% of 81 wells
- Gorham, Cumberland County49% of 508 wells
- Otis, Hancock County49% of 37 wells
- Monmouth, Kennebec County48% of 257 wells
- Eliot, York County46% of 89 wells
- Surry, Hancock County46% of 176 wells
- Winthrop, Kennebec County44% of 371 wells
- Hollis, York County43% of 133 wells
- Buxton, York County42% of 317 wells
- Trenton, Hancock County42% of 112 wells
- Readfield, Kennebec County42% of 334 wells
- Litchfield, Kennebec County41% of 249 wells
- Blue Hill, Hancock County41% of 175 wells
- Orland, Hancock County40% of 99 wells
- Charlotte, Washington County39% of 31 wells
- Hallowell, Kennebec County39% of 57 wells
- Minot, Androscoggin County38% of 76 wells
- Wales, Androscoggin County37% of 49 wells
- Dayton, York County36% of 64 wells
- Saco, York County35% of 230 wells
- Danforth, Washington County34% of 38 wells
- Camden, Knox County34% of 47 wells
- Owls Head, Knox County34% of 80 wells
- Mount Vernon, Kennebec County34% of 175 wells
By county, from individual samples
Public monitoring samples against the EPA limit (10 ug/L); counties with at least 30 samples.
| County | Samples | Detected | Above EPA limit | Median | Highest |
|---|---|---|---|---|---|
| Kennebec | 114 | 99% | 90% | 49.4 | 410 ug/L |
| York | 48 | 98% | 69% | 55.5 | 710 ug/L |
| Cumberland | 73 | 71% | 52% | 24 | 450 ug/L |
| Hancock | 64 | 84% | 50% | 10.1 | 720 ug/L |
| Androscoggin | 33 | 91% | 36% | 2.7 | 190 ug/L |
| Somerset | 31 | 94% | 35% | 1.9 | 120 ug/L |
| Washington | 61 | 98% | 28% | 1 | 3,000 ug/L |
| Oxford | 31 | 74% | 16% | 0.1 | 330 ug/L |
Sources
- Maine Tracking Network private well summaries: Town summaries of private well tests run by the Maine Health and Environmental Testing Laboratory, published by Maine CDC through the Maine Tracking Network. Shares are against Maine's guideline for each analyte (arsenic 10 ug/L, uranium 30 ug/L, fluoride 2 mg/L, manganese 0.3 mg/L, nitrate 10 mg/L, nitrite 1 mg/L). Towns with too few tests are suppressed (NR). Only the share above the guideline and wells tested are published; no medians. Retrieved September 3, 2026.
- Individual samples from the USGS Water Quality Portal and state monitoring, summarized per geography. arsenic counts and shares are listed on each county and town page with their sources.