New York Private Well Water Risk: Arsenic & Nitrate
These figures are USGS statistical estimates for private (domestic) wells in New York. They describe the area's modeled risk — not any single well.
This is a modeled probability for the area, not a measurement of your well. USGS statistical models estimate how many private wells in this area are likely to exceed the federal limit — they cannot tell you what is in your water. Two neighbors can have very different results. The only way to know your well is to test it.
Nitrate
0%
of the private-well population is modeled above the 10 mg/L nitrate limit
~0
people on wells estimated above the limit
~1,850,000
total residents on private wells statewide
Source: USGS machine-learning nitrate model, Ransom et al. (2022), domestic-well depth zone.
Arsenic
Across New York, an estimated ~66,265 people rely on private wells with modeled arsenic above the 10 µg/L EPA limit. The highest modeled exposure is in Suffolk County (~6,834 people).
Counties with the highest modeled arsenic exposure
| County | Est. well residents over arsenic limit | 90% range |
|---|---|---|
| Suffolk County | ~6,834 | 4,337–10,721 |
| Steuben County | ~4,077 | 2,800–5,849 |
| St. Lawrence County | ~2,885 | 2,290–3,622 |
| Erie County | ~2,800 | 1,906–4,090 |
| Wyoming County | ~2,661 | 1,832–3,798 |
| Tioga County | ~2,484 | 1,704–3,573 |
| Broome County | ~2,482 | 1,705–3,563 |
| Yates County | ~2,426 | 1,685–3,391 |
| Washington County | ~2,130 | 1,552–2,894 |
| Cattaraugus County | ~1,965 | 1,325–2,878 |
| Onondaga County | ~1,733 | 1,385–2,251 |
| Genesee County | ~1,728 | 1,383–2,358 |
| Columbia County | ~1,688 | 1,225–2,290 |
| Orange County | ~1,660 | 1,232–2,318 |
| Chenango County | ~1,632 | 1,151–2,307 |
| Otsego County | ~1,409 | 1,049–1,891 |
| Allegany County | ~1,371 | 939–1,985 |
| Ontario County | ~1,300 | 938–1,855 |
| Clinton County | ~1,237 | 950–1,624 |
| Chautauqua County | ~1,188 | 787–1,771 |
| Dutchess County | ~1,177 | 941–1,476 |
| Orleans County | ~1,163 | 976–1,402 |
| Schuyler County | ~1,159 | 787–1,680 |
| Cortland County | ~1,114 | 766–1,621 |
| Saratoga County | ~1,101 | 876–1,402 |
| Putnam County | ~1,064 | 820–1,398 |
| Ulster County | ~950 | 743–1,228 |
| Livingston County | ~931 | 663–1,288 |
| Rensselaer County | ~827 | 632–1,087 |
| Seneca County | ~816 | 587–1,156 |
| Cayuga County | ~758 | 557–1,082 |
| Oneida County | ~660 | 513–870 |
| Monroe County | ~654 | 545–844 |
| Montgomery County | ~626 | 511–774 |
| Westchester County | ~600 | 446–820 |
| Schoharie County | ~539 | 435–673 |
| Franklin County | ~529 | 422–666 |
| Fulton County | ~506 | 380–691 |
| Herkimer County | ~499 | 397–634 |
| Sullivan County | ~482 | 392–599 |
| Greene County | ~470 | 371–595 |
| Wayne County | ~423 | 333–645 |
| Delaware County | ~421 | 325–546 |
| Oswego County | ~402 | 317–516 |
| Madison County | ~400 | 326–493 |
| Schenectady County | ~386 | 317–474 |
| Niagara County | ~356 | 285–474 |
| Lewis County | ~286 | 221–370 |
| Tompkins County | ~280 | 190–407 |
| Warren County | ~267 | 208–353 |
| Chemung County | ~243 | 165–347 |
| Jefferson County | ~243 | 188–318 |
10 additional New York counties have lower modeled arsenic exposure (fewer than 100 estimated well residents over the limit).
Source: USGS domestic-well arsenic model, Lombard et al. (2021); county population product (2017).
Treating arsenic in New York
Arsenic is not removed by carbon pitchers or faucet filters. Reverse osmosis is the treatment that brings it below the federal limit at your tap.
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