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In Partnership:
Water Resources Center
University of Minnesota Extension
College of Food, Agricultural and Natural Resource Sciences

Water Resources Center
173 McNeal Hall
1985 Buford Avenue
St. Paul, MN 55108
612-624-9282
umwrc@umn.edu

Nitrate in Drinking Water

Barbara Liukkonen, Water Resources Education Coordinator, author and contact 
Fred Bergsrud,  Extension agricultural engineer

Nitrate occurs naturally in soil, or may be derived from nitrogen fertilizers, crop residues, human and animal wastes, and some other industrial wastes. All are possible sources of nitrate, which is soluble and moves with surface and ground water. In Minnesota, the biggest cause of nitrate-contaminated drinking water is improper waste water treatment. This often results from feedlot runoff and septic systems that are not built to code or are not maintained properly.

Nitrate itself is not harmful. However, certain bacteria in infants' digestive systems transform nitrate into nitrite. It is the nitrite that is harmful. Nitrite is absorbed into the bloodstream, where it reacts with hemoglobin (the red, oxygen-carrying blood pigment) to form methemoglobin. Methemoglobin does not carry oxygen. As the level of methemoglobin in the blood increases and the level of oxygen decreases, mild symptoms of asphyxiation occur. This is indicated by a bluish tinge around the lips, eyes, fingertips, and toes.

This condition is called methemoglobinemia, or blue-baby syndrome. It can occur in infants under six months of age because of their weak stomach acids. Lack of acids allows the growth of bacteria that transform nitrate into nitrite. Starting at about three months of age, there is an increase in the amount of hydrochloric acid in a baby's stomach, which kills the nitrate-reducing bacteria. By the time a baby is six months old, its digestive system is fully developed and none of the nitrate-reducing bacteria remain.

In older children and adults, nitrate is absorbed and excreted and has not been shown to be a health risk. The Minnesota Department of Health has reported no illnesses resulting from adult consumption of water with nitrate levels over 100 parts per million (ppm, the same as mg/L). However, little is known about the long-term risks or chronic health effects of drinking water high in nitrate.

The U.S. Environmental Protection Agency (USEPA) primary drinking water standard and Minnesota Department of Health Recommended Allowable Limit (RAL) for nitrate have both been set at 10 ppm. Nitrate levels are most commonly reported as nitrate-nitrogen (N03 - N). If nitrate levels in your water supply are near or above 10 ppm, you should use an alternate source of water for making infant formula and food. More importantly, you should identify and eliminate the source of nitrate contamination to your well and if possible, take measures to correct the contamination.

The presence of high nitrate levels may indicate that other, more serious contaminants may also be entering your water supply. Nitrate and coliform bacteria concentrations are commonly used to indicate well water contamination by surface waters. The Minnesota Department of Health feels that nitrate levels of 1 ppm or above serve as a warning of possible contamination. However, naturally elevated nitrate concentrations may occur in some areas.

Private water supplies should be tested for nitrate. The Minnesota Department of Public Health recommends periodic testing of your private water supply if previous tests showed nitrate levels of 1 ppm or above; if water is used from a shallow, dug well; if you or your neighbors have problems with septic system drainage; or if you have or are expecting a baby.

If water testing indicates high nitrate levels in your well, you have several treatment options. Distillation, reverse osmosis, and anion exchange systems will reduce nitrate-nitrogen concentrations. Disinfection of water through boiling or chlorination is not effective against nitrate, because it is not a living organism. In fact, boiling actually concentrates nitrate to higher levels and increases health risks. Do not boil water high in nitrate for infant formula in an attempt to purify it.

For information on water testing services, water treatment devices, and nitrate in your drinking water, contact your community health service or your University of Minnesota Extension county office.

For additional information on nitrate in drinking water, contact:

Barbara Liukkonen
Water Resources Education Coordinator
Water Resources Center
173 McNeal Hall
1985 Buford Ave.
Saint Paul, MN 55108
Phone: (612) 625-9256

Minnesota Department of Health
Building:
Well Management Section
Environmental Health Division
Minnesota Department of Health
625 North Robert Street
St. Paul, MN 55155-2538

Mailing:
Well Management Section
Environmental Health Division
Minnesota Department of Health
P.O. Box 64975
St. Paul, MN 55164-0975

Phone: (651) 201-4600

The Extension Water Quality Program in Minnesota is a part of the Great Lakes Regional Water Program and the CSREES National Water Program of the United States Department of Agriculture. Extension Water Quality programming in Minnesota is coordinated by the University of Minnesota Water Resources Center and delivered by University of Minnesota Extension. The University of Minnesota is an equal opportunity educator and employer. These materials available in other formats upon request. Privacy Policy
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