Nitrate in Well Water
Nitrate is a compound that occurs naturally and also has many human-made sources. Nitrate is in some lakes, rivers, and groundwater in Minnesota. When nitrate is found in Minnesota groundwater, it is usually at very low concentrations. However, some groundwater has nitrate concentrations that present a health risk - especially for babies. You cannot taste, see, or smell nitrate in your water.
Drinking water with concentrations of nitrate (measured as nitrate-nitrogen) below 10 milligrams of nitrate per liter of water (mg/L) is considered safe for everyone in your family. 10 mg/L is the U.S. Environmental Protection Agency standard for nitrate in drinking water for public water supplies.
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, left untreated, can result in serious illness or death. Learn more about why babies are at higher risk at Safe Drinking Water for Your Baby.
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 some metabolic problems.
Only recently has scientific evidence emerged to assess the health impacts of drinking water with high nitrate on adults. A growing body of literature indicates potential associations between nitrate/nitrite exposure and other health effects such as increased heart rate, nausea, headaches, and abdominal cramps. Some studies also suggest an increased risk of cancer, especially gastric cancer, associated with dietary nitrate/nitrite exposure, but there is not yet scientific consensus on this question.
To learn more about nitrate and methemoglobinemia, you can view or download our information sheet Nitrate and Methemoglobinemia (PDF).
Test Your Well Water
Test for nitrate every other year. You should also have your water tested for nitrate if you planning on becoming pregnant or if infants will be using the water.
You are responsible for keeping your well water safe and testing it as needed. MDH recommends you use an accredited laboratory to test your water. Contact an accredited laboratory to get sample containers and instructions, or ask your county environmental or public health services if they provide well testing services (Accredited Labs in Minnesota Accepting Samples from Private Well Owners [PDF]).
Go to Well Testing, Results, and Options to learn more about testing well water.
MDH may recommend you test for additional contaminants based on where you live.
- Keep nitrate sources away from your well. Sources may include fertilizer, septic systems, and animal waste.
- Construct your well in a safe spot. See the Protecting Your Well webpage for tips.
- Regularly inspect your well for damage. Contact a licensed well contractor if your well is damaged (Licensed Well and Boring Contractor Directory).
Wells Vulnerable to Nitrate
- Shallow wells.
- Wells in sand aquifers.
- Dug wells with casings that are not watertight.
- Wells with damaged or leaking casing or fittings.
Drinking water with concentrations of nitrate above 10 mg/L can cause immediate health problems. If nitrate is detected in your water at concentrations above 10 mg/L, follow these steps:
- Get your drinking water from a safe alternative source, such as bottled water.
- Make sure babies under six months old do not drink the well water.
- Do not try to boil nitrate out of the water. Boiling will make nitrate more concentrated.
- Have a licensed well contractor inspect your well.
- Find and get rid of any potential sources of nitrate contamination. The Protecting Your Well webpage can help you identify sources to check.
- Home water treatment may be an option if you meet these three criteria:
- You took steps to reduce or eliminate all potential sources of nitrate on your property;
- A licensed well contractor inspected your well and completed any needed repairs; and
- No babies under six months old drink the water (a safety precaution in the event the water treatment fails).
See the Home Water Treatment webpage or contact MDH for guidance.
How Nitrate Gets Into Groundwater
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.
Natural levels of nitrate in Minnesota groundwater are usually quite low (less than 3 milligrams per liter [mg/L]). However, where sources of nitrate such as fertilizers, animal wastes, or human sewage are concentrated near the ground surface, nitrate may seep down and contaminate the groundwater. High levels of nitrate in water can be a result of runoff or leakage from fertilized soil, wastewater, landfills, animal feedlots, septic systems, or urban drainage. It can be difficult to pinpoint where the nitrate in drinking water comes from because there are many possibilities.
Nitrate in Minnesota Water
About 4 percent of new wells have nitrate concentrations above 3 mg/L in Minnesota. While 3 mg/L is less than the EPA standard, it suggests human-made sources of nitrate have contaminated the water and the level could increase over time.
Most concentrations above 3 mg/L are in central and southeastern Minnesota. Concentrations above 10 mg/L are mainly in central and southwestern Minnesota.
The Minnesota Department of Agriculture 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. Learn more at Township Testing Program.
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Should I test my well water for anything besides lead?
Yes. Both natural sources and human activities can contaminate well water and cause short-term or long-term health effects. Testing your well water is the only way to detect most of the common contaminants in Minnesota groundwater; you cannot taste, see, or smell most contaminants. Minnesota Department of Health recommends testing for:
- Coliform bacteria every year and any time the water changes in taste, odor, or appearance. Coliform bacteria can indicate that disease-causing microorganisms may be in your water.
See Bacterial Safety of Well Water.
- Arsenic at least once. About 40 percent of wells in Minnesota have arsenic in the water. Drinking water with arsenic in it for a long time can contribute to reduced intelligence in children and increased risks of cancer, diabetes, heart disease, and skin problems.
See Arsenic in Well Water.
- Lead at least once. The well and water system may have parts that have lead in them, and that lead can get into drinking water. Lead can damage the brain, kidneys, and nervous system. Lead can also slow development or cause learning, behavior, and hearing problems.
See Lead in Well Water Systems.
- Manganese before a baby drinks the water. High levels of manganese can cause problems with memory, attention, and motor skills. It can also cause learning and behavior problems in infants and children.
See Manganese in Drinking Water.
Other contaminants sometimes occur in private water systems, but less often than the contaminants listed above. Consider testing for:
- Volatile organic chemicals if the well is near fuel tanks or a commercial or industrial area.
- Agricultural chemicals commonly used in the area if the well is shallow and is near cropped fields or handling areas for agricultural chemicals or is in an area of geologic sensitivity (such as fractured limestone).
- Fluoride if children or teenagers drink the water.
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