Uranium in well water
The county where Uranium is found above the limit most often is Cumberland County, Maine: 20% of 3,441 private wells tested, according to Maine Tracking Network private well summaries.
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.
- EPA limit
- 30 ug/L (EPA MCL (40 CFR 141.66))
- New Hampshire level
- 30 ug/L
- CAS number
- 7440-61-1
Where uranium is worst, by homeowner tests
Counties ranked by the share of private wells above the state guidance level in tests homeowners sent to the state lab. Shares combine town summaries, weighted by wells tested.
| County | Wells tested | Above state level | Highest | |
|---|---|---|---|---|
| Cumberland County, Maine | 3,441 | 20% | ||
| Androscoggin County, Maine | 1,016 | 14% | ||
| Oxford County, Maine | 953 | 9% | ||
| Hancock County, Maine | 2,264 | 8% | ||
| Sullivan County, New Hampshire | 619 | 7% | 1,600 ug/L | |
| Lincoln County, Maine | 1,490 | 7% | ||
| Waldo County, Maine | 1,191 | 6% | ||
| Orleans County, Vermont | 768 | 6% | 893 ug/L | |
| Kennebec County, Maine | 4,005 | 6% | ||
| Merrimack County, New Hampshire | 4,248 | 6% | 3,340 ug/L | |
| Carroll County, New Hampshire | 1,701 | 5% | 420 ug/L | |
| Rockingham County, New Hampshire | 2,790 | 5% | 860 ug/L | |
| Hillsborough County, New Hampshire | 3,323 | 5% | 584 ug/L | |
| Franklin County, Maine | 645 | 4% | ||
| Coos County, New Hampshire | 430 | 3% | 270 ug/L |
By individual samples
Counties with at least 30 individual samples in public monitoring data, against the EPA limit.
| County | Samples | Detected | Above EPA limit | Median |
|---|---|---|---|---|
| Cumberland County, Maine | 32 | 78% | 25% | 2.57 ug/L |
| Kennebec County, Maine | 48 | 81% | 10% | 1.69 ug/L |
| Carroll County, New Hampshire | 31 | 94% | 6% | 0.898 ug/L |
| Hillsborough County, New Hampshire | 185 | 54% | 5% | 0.096 ug/L |
| Rockingham County, New Hampshire | 155 | 86% | 2% | 1.1 ug/L |
| Merrimack County, New Hampshire | 111 | 67% | 2% | 0.044 ug/L |
| Grafton County, New Hampshire | 30 | 73% | 0% | 0.176 ug/L |
How to test
Use a state-certified lab and a proper sampling bottle; hardware-store strips cannot measure uranium at the levels that matter. Collect from the kitchen tap before any treatment, and again after treatment if you install it.
How to treat
- Point-of-use reverse osmosis
- Anion exchange
- Whole-house anion exchange