Uranium in New Hampshire well water
In New Hampshire, 4% of 17,564 private wells tested between 2006 and 2020 had uranium above the New Hampshire guidance level (30 ug/L), according to NH DHHS.
Uranium in well water comes from granite bedrock. Its main health effect is chemical toxicity to the kidneys rather than radiation. It is common in the same areas where radon and arsenic occur.
By county, from homeowner tests
Share of private wells above the state guidance level (30 ug/L) in tests homeowners sent to the state lab, 2006 to 2020.
| County | Wells tested | Above state level | Highest | |
|---|---|---|---|---|
| Sullivan | 619 | 7% | 1,600 ug/L | |
| Merrimack | 4,248 | 6% | 3,340 ug/L | |
| Carroll | 1,701 | 5% | 420 ug/L | |
| Rockingham | 2,790 | 5% | 860 ug/L | |
| Hillsborough | 3,323 | 5% | 584 ug/L | |
| Coos | 430 | 3% | 270 ug/L | |
| Grafton | 2,141 | 2% | 361 ug/L | |
| Strafford | 405 | 2% | 4,600 ug/L | |
| Cheshire | 434 | 2% | 126 ug/L | |
| Belknap | 1,473 | <1% | 260 ug/L |
Towns with the highest share above the state level
- Conway, Carroll County32% of 38 wells
- New London, Merrimack County31% of 220 wells
- Pelham, Hillsborough County31% of 127 wells
- Bethlehem, Grafton County27% of 48 wells
- Hooksett, Merrimack County27% of 135 wells
- Madison, Carroll County25% of 49 wells
- Milford, Hillsborough County21% of 33 wells
- Hudson, Hillsborough County21% of 140 wells
- Salem, Rockingham County20% of 89 wells
- Randolph, Coos County20% of 30 wells
- Newbury, Merrimack County18% of 237 wells
- Mont Vernon, Hillsborough County18% of 40 wells
- Wakefield, Carroll County17% of 89 wells
- Candia, Rockingham County17% of 66 wells
- Sunapee, Sullivan County16% of 184 wells
- Springfield, Sullivan County16% of 51 wells
- Freedom, Carroll County14% of 50 wells
- Ossipee, Carroll County13% of 124 wells
- Canaan, Grafton County12% of 74 wells
- Londonderry, Rockingham County10% of 337 wells
- Hampstead, Rockingham County10% of 108 wells
- Tamworth, Carroll County10% of 109 wells
- Dunbarton, Merrimack County8% of 121 wells
- Brookline, Hillsborough County8% of 36 wells
- Newport, Sullivan County8% of 49 wells
By county, from individual samples
Public monitoring samples against the EPA limit (30 ug/L); counties with at least 30 samples.
| County | Samples | Detected | Above EPA limit | Median | Highest |
|---|---|---|---|---|---|
| Carroll | 31 | 94% | 6% | 0.898 | 52.7 ug/L |
| Hillsborough | 185 | 54% | 5% | 0.096 | 390 ug/L |
| Rockingham | 155 | 86% | 2% | 1.1 | 210 ug/L |
| Merrimack | 111 | 67% | 2% | 0.044 | 135 ug/L |
| Grafton | 30 | 73% | 0% | 0.176 | 17.3 ug/L |
Sources
- NH DHHS WISDOM private well summaries: Town summaries of private well tests run by the New Hampshire Public Health Laboratories, published by NH DHHS through the WISDOM environmental public health tracking portal. Exceedance shares use New Hampshire guidance levels, which are stricter than EPA for arsenic (5 ug/L), manganese (0.3 mg/L), radon (2,000 pCi/L) and sodium (20 mg/L). Statistics for small counts are suppressed (*). Retrieved September 3, 2026.
- Individual samples from the USGS Water Quality Portal and state monitoring, summarized per geography. uranium counts and shares are listed on each county and town page with their sources.