Arsenic in Well Water
Arsenic is a naturally occurring element that dissolves from rock and soil into groundwater. It has no color, taste or smell, so the only way to detect it is a test. Long-term exposure is linked to skin, bladder and lung cancers, and to cardiovascular and developmental effects.
The EPA limit
The federal maximum contaminant level (MCL) for arsenic is 10 µg/L (micrograms per liter, equal to 10 parts per billion). Public water systems must meet it; private wells are not regulated, so it's up to the owner to test and treat.
Where arsenic concentrates
Arsenic in groundwater is highest across parts of the Southwest, the Upper Midwest, New England and the Rockies, where local geology favors it. Using the USGS model, the counties with the most people on high-arsenic private wells include:
- Wayne County, OH ~22,522
- Rockingham County, NH ~21,388
- Mecklenburg County, NC ~19,183
- Penobscot County, ME ~18,708
- Los Angeles County, CA ~17,244
- Hillsborough County, NH ~17,240
How to remove arsenic
Activated-carbon pitchers and faucet filters do not remove arsenic. The reliable point-of-use treatment is reverse osmosis (look for NSF/ANSI 58 certification). Anion exchange and adsorptive media also work but need proper sizing. Whichever you choose, re-test after installing to confirm it's working.
Match the filter to your test result
Carbon pitchers and faucet filters do not remove arsenic or nitrate. Reverse osmosis is the point-of-use fix; a whole-house system handles the rest of the home.
APEC ROES-50 5-Stage Reverse Osmosis System
5-stage RO, ★ 4.7 — removes arsenic, nitrate, lead, fluoride and PFAS.
Check price on Amazon →Whole-house well water system
Treats every tap, shower and appliance — the right scale for sediment, iron, sulfur and bacteria on a private well.
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Under-sink units tested for arsenic reduction — the point-of-use fix for a well over the limit.
Shop on Waterdrop direct →Affiliate links — we may earn a commission at no extra cost to you. Re-test after installing to confirm the system is working.