Arsenic in Missouri well water
In Missouri, 1% of 6,973 private wells tested between 2010 and 2023 had arsenic above the EPA limit (10 ug/L), according to Missouri DHSS.
Arsenic occurs naturally in New England bedrock and dissolves into well water. Long-term exposure raises the risk of bladder, lung and skin cancers, and is linked to heart disease and lower IQ in children. It has no taste or smell, so testing is the only way to know.
Check your arsenic number
Type the value from your lab report. It is compared to the EPA limit and the EPA limit, the same way the full interpretation does it.
Test your Missouri well for arsenic
Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.
Order the Tap Score well water test kit, from $209Already tested? Upload the report
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Systems that remove arsenic
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Some links below are affiliate links. If you buy through one, the merchant pays us a commission at no extra cost to you. It does not change which products we list or what the data says.
For arsenic
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
For arsenic
Whole-house arsenic and uranium filter
whole-house, at the point of entry, about $2,500
Adsorptive iron-based media; sized to your well yield.
For arsenic
Aquasana SmartFlow reverse osmosis
under-sink or countertop, about $225
Certified to NSF/ANSI 58 and 53 to reduce arsenic (96%, pentavalent), fluoride (90%), lead (99%), nitrate, nitrite and PFOA/PFOS at the kitchen tap, with a remineralizer.
Rather have it installed and sized for your well? Book a free in-home water test with a licensed local company.
Where to get a well tested for arsenic in Missouri: certified labs, state programs and prices.
By county, from homeowner tests
Share of private wells above the state guidance level (10 ug/L) in tests homeowners sent to the state lab, 2010 to 2023.
| County | Above state level | Wells tested | Highest |
|---|---|---|---|
| Iron | 35 | ||
| St. Louis | 44 | ||
| Platte | 68 | ||
| Lewis | 52 | ||
| Cape Girardeau | 124 | ||
| Franklin | 38 | ||
| Shannon | 39 | ||
| Madison | 395 | ||
| St. Francois | 224 | ||
| McDonald | 169 | ||
| Marion | 43 | ||
| Ralls | 50 | ||
| St. Charles | 73 | ||
| Christian | 235 | ||
| St. Clair | 121 |
By county, from individual samples
Public monitoring samples against the EPA limit (10 ug/L); counties with at least 30 samples.
| County | Above EPA limit | Samples | Detected | Median | Highest |
|---|---|---|---|---|---|
| Reynolds | 54 | 96% | 118 | 405 ug/L | |
| St. Francois | 98 | 89% | 12.6 | 133 ug/L | |
| Clay | 108 | 76% | 0.3 | 33 ug/L | |
| Boone | 861 | 55% | 1 | 72 ug/L | |
| Jackson | 421 | 89% | 1.4 | 110 ug/L | |
| Cape Girardeau | 35 | 34% | 0 | 28 ug/L | |
| Mississippi | 30 | 17% | 0 | 17 ug/L | |
| St. Charles | 133 | 50% | 0.14 | 18.5 ug/L | |
| New Madrid | 31 | 35% | 0 | 27 ug/L | |
| Pulaski | 476 | 6% | 0 | 31 ug/L | |
| Franklin | 39 | 49% | 0 | 10 ug/L | |
| Vernon | 45 | 16% | 0 | 10 ug/L | |
| Shannon | 34 | 9% | 0 | 1 ug/L | |
| Bates | 34 | 3% | 0 | 7 ug/L | |
| Nodaway | 44 | 2% | 0 | 7 ug/L |
- Carroll township, Reynolds County83% of 53
- St. Francois township, St. Francois County57% of 61
- Katy township, Boone County22% of 153
- Chouteau township, Clay County20% of 105
- Blue township, Jackson County18% of 421
- Rock Bridge township, Boone County18% of 698
- Cullen township, Pulaski County3% of 73
- Roubidoux township, Pulaski County<1% of 155
- New Haven township, Franklin County0% of 35
- Boone township, St. Charles County0% of 102
- Piney township, Pulaski County0% of 247
Sources
- Missouri DHSS private well sampling summaries: County summaries of private well samples analyzed by the Missouri State Public Health Laboratory, 2010 to 2023, published by the Missouri Department of Health and Senior Services. Counts are samples, not distinct wells. Shares are against the EPA maximum contaminant level, or the EPA secondary standard for chloride and iron. Counties with fewer than 20 samples are flagged unreliable by DHSS and are kept here with their counts so the threshold rule can judge them. Barium, sulfate and zinc layers exist but have no contaminant page yet. Retrieved September 15, 2026.
- Individual samples from the USGS Water Quality Portal and state monitoring, summarized per geography. arsenic counts and shares are listed on each county and town page with their sources.
Analysis: Arsenic in private wells, state by state, from the same public records.