Nitrate in private wells

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Nitrate is a compound that occurs naturally and also has many human-made sources. Nitrate dissolves easily in water and is found in some private drinking water wells in Minnesota. Private wells near septic tanks or agricultural activities are most vulnerable to nitrate contamination. These wells are especially vulnerable if the well is shallow, in a sand aquifer, or is not constructed properly. Levels of nitrate in water above 3 milligrams per liter (mg/L) can be a result of runoff or leakage from fertilized soil, wastewater, landfills, animal feedlots, septic systems, or urban drainage.

Health effects

Consuming too much nitrate can affect how blood carries oxygen and can cause methemoglobinemia (also known as blue baby syndrome). Bottle-fed babies under six months old are at the highest risk of getting methemoglobinemia. Methemoglobinemia can cause skin to turn a bluish color and can result in serious illness or death. Other symptoms connected to methemoglobinemia include decreased blood pressure, increased heart rate, headaches, stomach cramps, and vomiting.[1]

The following conditions may also put people at higher risk of developing nitrate-induced methemoglobinemia: anemia, cardiovascular disease, lung disease, sepsis, glucose-6-phosphate-dehydrogenase deficiency, and other metabolic problems.[2]


Nitrate (NO3) concentration in MN private wells

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Data are from newly-constructed wells (1992-2020)
Data are from newly-constructed wells, 1992 - 2020.

Nitrate in Minnesota well water

MDH data show that about 4 percent of all private wells constructed in Minnesota since 1992 have nitrate levels above 3 mg/L. While 3 mg/L is less than the EPA standard of 10 mg/L, it suggests human-made sources of nitrate have contaminated the water and the level could increase over time. Most newly-constructed wells with nitrate levels above 3 mg/L are in central and southeastern Minnesota. Newly-constructed wells with levels of nitrate above 10 mg/L are concentrated in central and southwestern Minnesota. The Minnesota Department of Agriculture (MDA) Township Testing Program found that over 10 percent of the private wells sampled in some townships in southwestern, southeastern, central and north-central Minnesota have nitrate levels above 10 mg/L.

Sources of nitrate

Nitrate occurs naturally and at safe and healthy levels in some foods (such as spinach and carrots) and comes from natural processes, such as plant decay. Nitrate is in many fertilizers used on yards, golf courses, and crops. Other sources of nitrate include discharge from sewage systems and animal wastes

How to protect yourself and your family

If you get your drinking water from a private well, be sure to prevent nitrate contamination and test your well water every other year for nitrate. MDH has recommendations of what to do if nitrate is detected in your water. You can find all this guidance in the Nitrate in Well Water (PDF) brochure.




[1] Agency for Toxic Substances and Disease Registry (ATSDR). 2015. ToxFAQsTM for Nitrate and Nitrite. Accessed October 2016.