Nitrate in Public Water and Health

nitrate in public water

Nitrate and nitrite are nitrogen-oxygen molecules that can combine with many organic and inorganic compounds. Nitrate is the form commonly found in water, often in areas where nitrogen-based fertilizers are used. The greatest use of nitrate is as a fertilizer. Infants are at greatest risk for illness from exposure to high levels of nitrate. The maximum contaminant level (MCL) for nitrate is 10 mg/L.

Exposure and Risk

Infants under the age of 6 months who drink water containing more than 1 mg/L nitrite, or 10 mg/L nitrate, could become seriously ill and, if untreated, may die. In the body, nitrate changes to nitrite. Nitrite interferes with the oxygen-carrying capacity of blood, so the oxygen you breathe in doesn't get distributed throughout the body. Symptoms, such as shortness of breath and blueness of the skin, can occur rapidly over a period of days. Read more about Nitrate from the CDC.

Infants are at greatest risk for illness from exposure to high levels of nitrate.

  • Short-term: Excessive levels of nitrate in drinking water have caused serious illness and sometimes death. The serious illness in infants is due to the conversion of nitrate to nitrite by the body, which can interfere with the oxygen-carrying capacity of the child's blood. This can be an acute condition in which health gets worse rapidly over a period of days. Symptoms include shortness of breath and blueness of the skin.
  • Long-term: Researchers continue to explore if there are associations with long-term exposures to nitrate, including adverse reproductive effects and some cancers. The studies are not conclusive at this time, and health standards are focused on protecting infants.


Nitrate is monitored at least once a year in every public water supply. If the test result is above half of the MCL the system is sampled quarterly; if the result is at 10.0 mg/L, the system is sampled monthly for at least one year. If the system has a potential to form nitrite, in Iowa, the system is required to conduct additional monitoring at the entry point to the distribution system as well as in the distribution system to ensure that the nitrite levels remain below the MCL of 1.0 mg/L at all times.

The following treatment methods have been approved by the EPA for removing nitrate/nitrite:

  • ion exchange
  • reverse osmosis
  • electro dialysis

Both nitrate and nitrite are acute contaminants. If the levels of nitrate or nitrite exceed their Maximum Contaminant Levels, the system must notify the public within 24 hours via newspapers, radio, TV, and other means. Additional actions, such as providing alternative drinking water supplies, may be required to prevent serious risks to public health.