Nitrates and Nitrites

Nitrates and nitrites are a major constituent of fertilizers and have been used for many years in lawn treatments. Without the addition of these, crops would deplete nitrogen from soil. Unfortunately, when nitrogen fertilizers are used, they can get into wells and contaminate them. Nitrates and nitrites from these fertilizers also seep into groundwater, especially shallow wells (1,2).

The Environmental Protection Agency has set a maximum contaminant level (MCL) of 10 mg/L for nitrate and nitrite in public water supplies(3). Users of private water supplies should have their water tested annually, especially in areas where fertilizers are commonly used. It is estimated that 1.5 million people are potentially exposed to nitrates from rural domestic wells (3).

Nitrites are cause for concern in infants under 6 months of age and farm animals. They affect the blood's ability to carry oxygen. Nitrites get into the body when nitrates are ingested, both from food and water, and nitrate reducing bacteria in an infant's digestive tract converts the nitrate to nitrite. Once the nitrite enters the blood stream and binds to the hemoglobin, oxygen cannot be carried, and "blue-baby" syndrome (bluish tint to skin due to lack of oxygen) occurs, as well as shortness of breath, increased sensitivity to illness, heart attacks, and possibly death by asphyxiation. However, as the infant ages, stomach acid becomes stronger, and bacteria that cause the conversion of nitrate to nitrite are reduced. Older children and adults generally do not have a problem with nitrates  (1,2).

If nitrates are a concern in your area, it is best to use bottled water for the infant's formula. Boiling the water will not make the nitrates go away, it will instead cause an increase in the amount of nitrates present (2).

The best way to tell if your water has nitrates is to have it tested by a reputable lab. If your water is found to be contaminated, it can be treated in a variety of ways, including filtration, distillation, or a system similar to a water softener. However, to choose a treatment, a professional should be consulted.

For additional information about nitrates/nitrites, the website at North Carolina State University's Cooperative Extension Service provides more specific information regarding the toxicity and more treatment options for nitrite/nitrate problems (see links below).

Some external links that have information about nitrates:

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  1. Water Quality Basics, Nitrates and Nitrites. Water Quality Association. 1996. URL:
  2. SiouxLan, Serving Iowa, Nebraska, and South Dakota. URL:
  3. Water Environmental Indicators #11, EPA Office of the Water, June 1996. URL:

URL Reference:

  1. North Carolina State University Cooperative Extension Service: URL:

This page was prepared by S.L. Keyser, June 1997, UCD EXTOXNET FAQ Team.
Revised by B.T. Johnson, October 1997.