Nitrate in Missouri well water
In Missouri, 2% of 11,532 private wells tested between 2010 and 2023 had nitrate above the EPA limit (10 mg/L), according to Missouri DHSS.
Nitrate reaches wells from fertilizer, septic systems and manure. Above the limit it can cause methemoglobinemia (blue baby syndrome) in infants under six months, and long-term exposure is associated with some cancers. Shallow and dug wells near farmland or dense septic systems are most at risk.
Check your nitrate 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 nitrate
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 nitrate
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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 nitrate
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
For nitrate
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 nitrate in Missouri: certified labs, state programs and prices.
By county, from homeowner tests
Share of private wells above the state guidance level (10 mg/L) in tests homeowners sent to the state lab, 2010 to 2023.
By county, from individual samples
Public monitoring samples against the EPA limit (10 mg/L); counties with at least 30 samples.
| County | Above EPA limit | Samples | Detected | Median | Highest |
|---|---|---|---|---|---|
| Gentry | 52 | 90% | 3.7 | 200 mg/L | |
| Cass | 102 | 88% | 1.5 | 110 mg/L | |
| Bates | 81 | 77% | 1.5 | 53 mg/L | |
| Nodaway | 95 | 95% | 5.5 | 63 mg/L | |
| Daviess | 47 | 85% | 3.5 | 350 mg/L | |
| Clark | 71 | 77% | 0.28 | 110 mg/L | |
| Christian | 50 | 68% | 0.09 | 140 mg/L | |
| Greene | 125 | 80% | 0.37 | 130 mg/L | |
| Clinton | 36 | 97% | 2 | 32 mg/L | |
| Carroll | 82 | 77% | 0.14 | 990 mg/L | |
| Vernon | 172 | 76% | 0 | 115 mg/L | |
| St. Charles | 625 | 59% | 0.2 | 4,380 mg/L | |
| Scott | 57 | 72% | 0.4 | 24 mg/L | |
| Butler | 33 | 64% | 0.049 | 17 mg/L | |
| Audrain | 46 | 74% | 0.01 | 60 mg/L |
- Centralia township, Boone County90% of 321
- Springfield township, Greene County23% of 35
- Fishing River township, Clay County16% of 31
- Boone township, St. Charles County15% of 481
- Weldon Spring township, St. Charles County13% of 31
- O'Fallon township, St. Charles County3% of 31
- Rock Bridge township, Boone County2% of 2,519
- New Haven township, Franklin County1% of 73
- Carroll township, Reynolds County<1% of 112
- Katy township, Boone County<1% of 418
- Blue township, Jackson County<1% of 1,570
- Piney township, Pulaski County<1% of 482
- Eminence township, Shannon County0% of 37
- Cullen township, Pulaski County0% of 165
- Winona township, Shannon County0% of 36
- Roubidoux township, Pulaski County0% of 309
- Rivers township, St. Charles County0% of 30
- Berwick township, Newton County0% of 30
- Randolph township, St. Francois County0% of 91
- St. Francois township, St. Francois County0% of 126
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. nitrate counts and shares are listed on each county and town page with their sources.
Analysis: Nitrate in private wells, decade by decade, from the same public records.