Low-cost state testing
Missouri's state lab tests well water for bacteria for a $10 fee. Check which tests it includes before you count on it for arsenic.
Missouri's private well pageArsenic in Missouri well water, by county
Arsenic is widespread, over the limit in 15% or more of tested wells, in 1 of the 7 Missouri counties with 10 or more tested wells. 3 more look high, but those results likely overstate it. A county's share tells you how likely a problem is nearby. Only a test of your own well tells you what's in it.
How Missouri compares with the rest of the country
Across Missouri, about 2 in 10 tested wells had arsenic over the EPA limit of 10 µg/L (51 of 314). Across all tested wells in the US it's about 1 in 9. So arsenic turns up somewhat more often in Missouri than in the country as a whole. Check your county below.
Why it matters: Drinking it for years raises the risk of skin, bladder and lung cancer.
Arsenic dissolves out of certain rocks and old sediments, so it can be high even where nobody has polluted anything.
Arsenic in tested wells, county by county
Share of each county's tested wells with at least one result over the EPA limit of 10 µg/L. Counties need 10 or more tested wells to be listed. Widespread means 15% or more, worth checking 5 to 15%, rare under 5%.
| County | Wells tested | Wells over the limit | Level |
|---|---|---|---|
| Reynolds County | 26 | Widespread | |
| St. Francois County | 27 | Widespread | |
| St. Charles County | 15 | Widespread | |
| Jackson County | 55 | Widespread | |
| Clay County | 11 | Worth checking | |
| Pulaski County | 75 | Rare | |
| Franklin County | 16 | Rare |
* Likely overstated. These shares come from a narrow set of wells, so they probably run high for the county as a whole:
- Reynolds County: All of these tests come from the US Geological Survey between 2004 and 2006 in one small part of the county, so this likely overstates it.
- St. Francois County: All of these tests come from the US Geological Survey between 2004 and 2007 in one small part of the county, so this likely overstates it.
- Jackson County: All of these tests come from the US Geological Survey in one small part of the county, so it may not match the rest of the county.
49 more Missouri counties have 1 to 9 tested wells for arsenic, too few to rate.
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Where to get your well tested for arsenic in Missouri
A lab Missouri certifies
Ask for arsenic by name. Results from a certified lab count for a home sale or a loan.
Labs certified by MissouriA mail-in kit
Fill the bottles at your kitchen tap and mail them back. We mark the kits that include arsenic.
Compare kitsKeep reading about wells in Missouri
- Well water testing in Missouri: how to get tested and what turns up statewide
- Arsenic in well water: where it comes from, what it does and how to remove it
- Nitrate in Missouri wells, by county
- Manganese in Missouri wells, by county
- Lead in Missouri wells, by county
Questions people ask about arsenic in Missouri
Is there arsenic in Missouri well water?
Arsenic is widespread, over the limit in 15% or more of tested wells, in 1 of the 7 Missouri counties with 10 or more tested wells. 3 more look high, but those results likely overstate it. Across Missouri, about 2 in 10 tested wells had arsenic over the EPA limit of 10 µg/L (51 of 314). Across all tested wells in the US it's about 1 in 9. So arsenic turns up somewhat more often in Missouri than in the country as a whole. Check your county below.
Where can I get my well tested for arsenic in Missouri?
Missouri's state lab tests well water for bacteria for a $10 fee. If that doesn't cover you, use a lab certified by Missouri for drinking water, or a mail-in kit that includes arsenic from a certified lab.
See Missouri's list of certified labs, or compare mail-in kits.
Where these numbers come from
- Lab tests: Water Quality Portal (USGS and EPA), well samples since 2000. A well counts as over if any of its tests was over the EPA limit of 10 µg/L. Wells tested for studies and monitoring, not a random sample of homes.
- Likely overstated: our own check of who tested the wells, when and where. How we check.
- State programs and links: Missouri Department of Health and Senior Services.