Nitrate in Drinking Water

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.

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.

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).

The U.S. Environmental Protection Agency (EPA) standard for nitrate in drinking water is 10 milligrams of nitrate (measured as nitrogen) per liter of drinking water (mg/L).* Drinking water with levels of nitrate at or below 10 mg/L is considered safe for everyone.

*One milligram per liter (mg/L) is roughly the same as 1 part per million.

If you have a private well

The following types of wells are the most vulnerable to nitrate contamination, especially if they are near septic tanks or areas with agricultural activities:

Below are recommendations on how to prevent and address nitrate contamination. You can access a PDF version at Nitrate in Well Water (PDF).

• Shallow wells
• Wells in sand aquifers
• Dug wells with casings that are not watertight
• Wells with damaged or leaking casings or fittings

Prevent Contamination

• Construct your well in a safe spot (see Protect Your Well for guidance).
• Keep nitrate sources away from your well. Sources may include fertilizer,septic systems, and animal waste.
• Regularly inspect your well for damage (see Protect Your Well for guidance). Contact a licensed Well Contractor if you find any damage.
• Test for nitrate every other year. You are responsible for keeping your private well water safe and testing it as needed. Minnesota Department of Health (MDH) recommends using an accredited laboratory to test your well water (see Accredited Labs in Minnesota Accepting Samples from Private Well Owners [PDF]). Contact an accredited laboratory to get a sample container and instructions, or ask your county environmental or public health services if they provide well water testing services.

Address Contamination

If nitrate is detected in your well water, there may be other contaminants in the water as well. Drinking water with levels of nitrate above 10 mg/L can lead to immediate health problems for infants below the age of six months and people with certain health problems. If nitrate is detected in your water at levels above 10 mg/L, follow these steps:

• Get your drinking water from a safe alternative source, such as bottled water. This is especially important if there are any babies under six months old drinking the water or formula made with water. Boiled water is not a safe alternative if there is nitrate in your water; boiling water will make nitrate more concentrated.
• Have a Licensed Well Contractor inspect your well for damage.
• Find and remove potential sources of nitrate contamination on your property. Protecting Your Well can help you identify sources to check.
• Home Water Treatment may be an option if you meet these three criteria:

1. You have taken steps to reduce or eliminate potential sources of nitrate on your property;
2. A licensed well contractor inspected your well and determined it is working properly; and
3. No babies under six months old drink the water (this is a safety precaution in the event the water treatment fails).

If you are on a public water system

Your public water system regularly tests for nitrate and ensures levels meet the EPA standard. Your public water system will let you know if they detect nitrate at a level above the EPA standard. You can find the level of nitrate detected in the system serving where you live by reading the system’s Water Quality Report (also known as a Consumer Confidence Report [CCR]). Search for your Consumer Confidence Report (CCR) online or contact your public water system to get a paper copy. If you want to find the level of nitrate for a place besides your home, contact the water system serving that location.

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 processes can cause low levels of nitrate in drinking water—usually less than 3 mg/L. The health concern is with levels of nitrate over 10 mg/L. 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 has been detected in surface water and groundwater in many places in Minnesota. Both land use and hydrogeology affect the levels of nitrate in water. MDH data show that about 4 percent of all private wells constructed in Minnesota since 1991 have nitrate levels above 3 mg/L. While 3 mg/L is less than the EPA standard, it is 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.

The Minnesota Pollution Control Agency (MPCA) found that 27 percent of surface water samples had nitrate levels above 10 mg/L. Southern Minnesota had the highest levels of nitrate.

Community public water systems with elevated nitrate levels tend to be in southwestern, southeastern, central, and north-central areas of the state. Over the past 20 years, a few public water systems in Minnesota have detected nitrate levels above 10 mg/L in treated water; they have worked to address the issue. You can learn more at Nitrate in community water systems: facts and figures.

MDH regularly publishes a report which summarizes nitrate monitoring data for community water systems and describes the steps being taken to lower the levels of nitrate in Minnesota’s drinking water. You can find the most recent nitrate report at MDH Drinking Water Protection Annual Reports.

MDH assists and regulates public water systems by:

• Approving public water systems’ construction and treatment plans
• Enforcing the Safe Drinking Water Act (Public Drinking Water Program)
• Testing public water systems
• Helping public water systems prevent and respond to nitrate issues
• Requiring public water systems to protect water sources from contamination and providing technical assistance and grants to help do so (Source Water Protection)

MDH regulates private and public wells by:

• Establishing and enforcing Laws and Rules for proper Construction of Wells and Borings and Sealing of Wells and Borings
• Providing guidance for private well owners on Water Quality/Well Testing/Well Disinfection

MDH helps monitor nitrate in Minnesota public and private drinking water wells. Learn more at Reports and Geospatial Data.

MDA monitors and helps reduce nitrate from agricultural sources. Major efforts include private well Water Testing for Nitrate, Township Testing Program, Characterizing Nitrate in Private Drinking Water Wells, Groundwater Protection Rule, and the Minnesota Nitrogen Fertilizer Management Plan.

Local government, including counties and Soil and Water Conservation Districts, help people manage nitrate from lawns, agriculture, and other sources.

The University of Minnesota Extension Services conducts research, provides education, and makes recommendations for Lawn Care and Nutrient Management for agriculture.

MPCA released the Groundwater Protection Recommendations Report (PDF) in 2016 that outlines ways to reduce nitrate and other contaminants in our water.