privatewelldata / States / New York / Arsenic
Arsenic in well water in New York
2% of 3,544 sampled wells in New York had arsenic above the EPA limit of 10 µg/L (latest result per well, 57 counties, samples 1919–2023). The highest county share was Allegany County: 19% of 32 wells. Data updated 2026-10-18.
of sampled wells above 10 µg/L
wells with a result
counties with data
counties where 1 in 4+ wells were above
Arsenic in wells usually comes from the rock and sediment the water passes through, so it can vary a lot between neighbouring wells. You cannot see, smell or taste it; only a lab test shows it. Federal limits apply to public water systems; a private well is the owner's responsibility to test (EPA).
% of sampled wells above the EPA limit (latest result per well; counties with 10+ wells). Source: USGS/EPA Water Quality Portal, 2026-10-18 · privatewelldata.com
Arsenic by county in New York
| County | Above 10 µg/L | Median | 90th pct. | Years |
|---|---|---|---|---|
| Allegany County | 19% of 32 | 1 µg/L | 64 | 1971–2021 |
| Monroe County | 18% of 28 | 0.685 µg/L | 11.2 | 1972–2022 |
| Oswego County | 17% of 42 | 1.05 µg/L | 17.8 | 1971–2022 |
| Tioga County | 15% of 20 | 0.9 µg/L | 14.3 | 1972–2019 |
| Niagara County | 13% of 24 | 2 µg/L | 10 | 1982–2011 |
| Greene County | 9% of 11 | 3 µg/L | 6.5 | 1972–2021 |
| Oneida County | 8% of 38 | 0.08 µg/L | 4 | 1973–2022 |
| Rensselaer County | 7% of 15 | 0.65 µg/L | 3.2 | 1973–2022 |
| Westchester County | 6% of 66 | 1 µg/L | 8 | 1971–2018 |
| Ulster County | 6% of 68 | 0.265 µg/L | 6.4 | 1972–2021 |
| Wayne County | 6% of 17 | 2.2 µg/L | 10 | 1972–2022 |
| Saratoga County | 6% of 69 | 0.07 µg/L | 4 | 1971–2023 |
| Broome County | 5% of 41 | 0.43 µg/L | 4 | 1971–2023 |
| Chenango County | 5% of 21 | 0.45 µg/L | 3.1 | 1972–2019 |
| Livingston County | 5% of 21 | 0.27 µg/L | 3 | 1971–2020 |
| Steuben County | 5% of 21 | 0.16 µg/L | 6.5 | 1970–2020 |
| Tompkins County | 4% of 72 | 0.455 µg/L | 5.5 | 1973–2023 |
| Onondaga County | 4% of 27 | 0 µg/L | 2 | 1970–2022 |
| Chautauqua County | 3% of 29 | 0.3 µg/L | 2 | 1971–2021 |
| Sullivan County | 3% of 30 | 0.485 µg/L | 7 | 1971–2020 |
| Erie County | 3% of 79 | 0 µg/L | 1 | 1971–2021 |
| Suffolk County | 2% of 866 | 0 µg/L | 1 | 1919–2022 |
| Nassau County | 0% of 888 | 0 µg/L | 0 | 1971–2022 |
| Queens County | 0% of 153 | 0 µg/L | 1.5 | 1971–2013 |
| Kings County | 0% of 73 | 0 µg/L | 1 | 1970–2013 |
| Orange County | 0% of 48 | 0 µg/L | 1 | 1970–2020 |
| St. Lawrence County | 0% of 48 | 0.31 µg/L | 1.8 | 1970–2020 |
| Essex County | 0% of 39 | 0.1 µg/L | 1.5 | 1971–2022 |
| Delaware County | 0% of 37 | 0.3 µg/L | 2.6 | 1971–2020 |
| Dutchess County | 0% of 36 | 0 µg/L | 1 | 1971–2018 |
| Jefferson County | 0% of 34 | 0.09 µg/L | 1 | 1971–2020 |
| Cattaraugus County | 0% of 33 | 0.2 µg/L | 1 | 1971–2021 |
| Schenectady County | 0% of 32 | 0.8 µg/L | 2.6 | 1970–2021 |
| Warren County | 0% of 30 | 0 µg/L | 1.7 | 1971–2022 |
| Albany County | 0% of 27 | 0.5 µg/L | 3 | 1970–2021 |
| Cortland County | 0% of 27 | 0 µg/L | 0.61 | 1971–2019 |
| Clinton County | 0% of 26 | 0.15 µg/L | 1.3 | 1972–2019 |
| New York County | 0% of 26 | 0.54 µg/L | 1.7 | 1973–2011 |
| Herkimer County | 0% of 25 | 0.15 µg/L | 0.5 | 1971–2023 |
| Lewis County | 0% of 24 | 0.03 µg/L | 1 | 1972–2020 |
| Putnam County | 0% of 23 | 0 µg/L | 2 | 1972–2018 |
| Richmond County | 0% of 23 | 1 µg/L | 2.1 | 2005–2012 |
| Washington County | 0% of 23 | 0.31 µg/L | 3 | 1971–2023 |
| Madison County | 0% of 22 | 0.225 µg/L | 1.5 | 1972–2022 |
| Ontario County | 0% of 20 | 0 µg/L | 1.1 | 1972–2022 |
| Genesee County | 0% of 19 | 0.24 µg/L | 4 | 1970–2021 |
| Schoharie County | 0% of 19 | 0.6 µg/L | 4.9 | 1973–2021 |
| Franklin County | 0% of 18 | 0.09 µg/L | 1.3 | 1972–2020 |
| Otsego County | 0% of 18 | 0.22 µg/L | 2.5 | 1973–2019 |
| Wyoming County | 0% of 18 | 0.17 µg/L | 1.2 | 1972–2021 |
| Cayuga County | 0% of 17 | 0.17 µg/L | 6 | 1972–2022 |
| Hamilton County | 0% of 17 | 0 µg/L | 0.19 | 2005–2022 |
| Fulton County | 0% of 15 | 0.1 µg/L | 0.6 | 1971–2022 |
| Montgomery County | 0% of 15 | 0.1 µg/L | 1.5 | 1970–2021 |
| Columbia County | 0% of 14 | 0.38 µg/L | 2.4 | 1971–2018 |
| Chemung County | 0% of 10 | 0.39 µg/L | 1 | 1972–2018 |
| Seneca County | 0% of 10 | 0 µg/L | 1 | 1973–2022 |
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Download this table (CSV) · public-domain source data: Water Quality Portal (USGS, EPA, NWQMC). How we calculate these numbers.
How New York compares
Share of sampled wells above the EPA arsenic limit in each state we cover (states with 100+ wells).
| # | State | Above 10 µg/L |
|---|---|---|
| 1 | Maine | 59% of 261 |
| 2 | Minnesota | 19% of 5,914 |
| 3 | Michigan | 15% of 1,077 |
| 4 | Ohio | 15% of 620 |
| 5 | New Hampshire | 14% of 863 |
| 6 | California | 14% of 8,314 |
| 7 | Massachusetts | 8% of 474 |
| 8 | Pennsylvania | 4% of 3,072 |
| 9 | North Carolina | 4% of 340 |
| 10 | Wisconsin | 3% of 610 |
| 11 | New Jersey | 2% of 2,227 |
| 12 | New York | 2% of 3,544 |
| 13 | Virginia | 1% of 298 |
Where to test: official lab list for New York
About this data
- Each well counts once, using its latest arsenic result in the Water Quality Portal (siteType = Well), downloaded 2026-10-18.
- Results reported as "not detected" count as below the limit. Results far outside the plausible range are withheld for review, not shown.
- Sampled wells include monitoring and research wells, not only household wells, and are not a random sample, so the share is a guide to local risk, not a rate for all homes.
- The limit is the EPA maximum contaminant level for public water systems (EPA).
Questions
Is arsenic common in New York well water?
In our data, 75 of 3,544 sampled wells in New York (2%) had a latest arsenic result above the EPA limit of 10 µg/L, across 57 counties. That ranks New York 12 of 13 states we cover for this share.
Which New York counties have the most wells above the arsenic limit?
Among counties with at least 10 sampled wells: Allegany County (19%, 6 of 32 wells); Monroe County (18%, 5 of 28 wells); Oswego County (17%, 7 of 42 wells).
Does this tell me whether my well is safe?
No. These are past results from wells sampled by USGS, EPA and state programs, including monitoring wells, and levels differ from well to well. The only way to know your water is to test your own well at a certified lab.
How do I test my well for arsenic in New York?
Order a arsenic test from a lab on New York's official certified-lab list (linked on this page) and ask for its bottles and sampling instructions. Our test helper suggests what else to test for at the same time.
What should I do if my arsenic result is above 10 µg/L?
Retest to confirm, use another water source for drinking and cooking while you sort it out, and look at certified treatment options. Our guide walks through each step with sources.