Well Management
Nitrate in Well Water

On this page:
Introduction
What is nitrate?
How does nitrate get in well water?
What are the health risks of nitrate in well water?
Why are young infants more susceptible?
How much nitrate is too much?
How do I know if my well water has nitrate?
How often should I have my well tested for nitrate?
What if nitrate is found in my water?
What about a water treatment unit?
Should I test my well water for anything other than nitrate?

Introduction

Nitrate is a common contaminant found in many wells in Minnesota. Too much nitrate in drinking water can cause serious health problems for young infants. This page provides a basic explanation of nitrate in wells and gives steps that you as a well owner can take to protect your family and visitors from illness.

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What is nitrate?

Nitrate (NO3) is a naturally occurring chemical made of nitrogen and oxygen. Nitrate is found in air, soil, water, and plants. Much of the nitrate in our environment comes from decomposition of plants and animal wastes. People also add nitrate to the environment in the form of fertilizers.

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How does nitrate get into well water?

Natural levels of nitrate in Minnesota groundwater are usually quite low (less than 1 milligram per liter [mg/L] of nitrate-nitrogen). 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. Elevated nitrate levels in groundwater are often caused by run-off from barnyards or feedlots, excessive use of fertilizers, or septic systems.

Wells most vulnerable to nitrate contamination include shallow wells, dug wells with casing which is not watertight, and wells with damaged, leaking casing or fittings.

Nitrate contamination of a well is often regarded as a first sign of deteriorating groundwater quality.

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What are the health risks of nitrate in well water?

Too much nitrate in drinking water poses a risk to infants under six months of age. If an infant is fed water or formula made with water that is high in nitrate, a condition called "blue baby syndrome" (or "methemoglobinemia") can develop. Bacteria which are present in an infant's stomach can convert nitrate to nitrite (NO2), a chemical which can interfere with the ability of the infant's blood to carry oxygen. As the condition worsens, the baby's skin turns a bluish color, particularly around the eyes and mouth. If nitrate levels in the water are high enough and prompt medical attention is not received, death can result. See also: Safe Drinking Water For Your Baby.

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Why are young infants more susceptible?

As an infant ages, its stomach acidity increases, reducing the numbers of nitrite-producing bacteria. After six months, the conversion of nitrate to nitrite in the stomach no longer occurs. Most adults can consume large amounts of nitrate with no ill effects. In fact, the average adult in the United States consumes about 20-25 milligrams of nitrate-nitrogen every day in food, largely from vegetables.

Pregnant women, people with reduced stomach acidity, and people with certain blood disorders may also be susceptible to nitrate-induced methemoglobinemia. Some research has suggested that nitrate may also play a role in the development of some cancers. However, at this time there is no clear evidence that nitrate ingestion results in an increased cancer risk.

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How much nitrate is too much?

The federal drinking water standard for nitrate is 10 mg/L of nitrate-nitrogen, which provides newborns with reasonable protection against blue baby syndrome. This level is mandatory for all public water systems, and recommended for private wells.

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How do I know if my well water has nitrate?

Nitrate is tasteless, odorless, and colorless. To find out if there is nitrate in your water, have it tested by a laboratory that is certified for nitrate testing by the Minnesota Department of Health. Laboratories will provide sampling bottles and instructions. The price for the test typically ranges from $7 to $25. Visit the MDH - Certified Environmental Contract Laboratories website for all your water testing needs. Regardless of which tests you want done, always make sure to use a laboratory that has been certified to perform each of those particular tests. Testing for nitrate look for “SDWP Inorg.”

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How often should I have my well tested for nitrate?

It's a good idea to have a routine nitrate test every two or three years, more frequently if nitrate has been detected in previous sampling. State regulations require well contractors to have a water sample tested for bacteria and nitrate when they construct a new well. After that, owners of private wells must arrange for their own water testing.

You should also have your water tested for nitrate if you are a woman planning on becoming pregnant or if infants will be using the water.

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What if nitrate is found in my water?

  1. If the nitrate-nitrogen concentration exceeds the health limit of 10 mg/L, do not give the water to any infant under six months of age, either directly or in formula. Infants should be provided with water from a source which has been tested and shown to be low in nitrate and bacterially safe. Commercially bottled water is required to meet the nitrate standard.
  2. Do not boil to "treat" high nitrate water. Nitrate is not removed from the water by boiling. Boiling actually concentrates the nitrate, due to evaporation of the water.
  3. Have your well inspected. It's a good idea to have your well inspected by a licensed well contractor if the well is old, or you do not know if it is structurally sound. Nitrate and bacteria problems are sometimes caused by structural flaws which allow contaminated surface water to enter the well. Repairing the well or constructing a new, deeper well often results in a results in a significant reduction in the nitrate level. To find licensed well drillers in your area, look in the Yellow Pages under "Well Drilling and Service."
  4. Identify and remove sources of nitrate near the well. Fertilizers, animal wastes, and sewage systems should be located and managed so that they do not contaminate the well. If a nitrate source is too close to the well and cannot be moved, then you may need to consider having the well permanently sealed and replaced by a licensed well contractor.

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What about a water treatment unit?

Home water treatment units are not recommended for treating high nitrate water which will be given to infants. There is no foolproof way of knowing when the treatment system may fail, and blue baby syndrome has been known to occur after just one day of exposure to high nitrate water.

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Should I test my well for anything other than nitrate?

Yes. Private wells should be tested at least once a year for bacterial safety. It is also wise to test well water for bacteria any time the water changes in taste, odor, or appearance. See also: Bacterial Safety of Well Water.

In addition, water can absorb lead from old lead pipes, lead-soldered copper pipes, or brass plumbing components, when the water stands idle in the pipes for more than a few hours. It is recommended to either flush standing water until you feel the water get colder (usually 30-60 seconds), or have your water tested for lead after it has been standing in the pipes at least six hours. Also, never use water from hot water faucets for drinking or cooking. See also: Lead in Well Water Systems.

Arsenic occurs naturally in about half the wells in Minnesota, and about 10 percent of wells produce water which exceeds 10 micrograms per liter (parts per billion), the federal drinking water standard. Arsenic is more prevalent in western Minnesota, but can occur almost anywhere in the state (see map on arsenic occurrence ). Long-term consumption of arsenic above the drinking water standard may increase the risk of health problems of the skin, circulatory system, nervous system, lungs, and bladder, including some forms of cancer. Every private well should be tested at least once or twice to determine if arsenic is present in the water. See also: Arsenic in Minnesota's Well Water.

Other contaminants sometimes occur in private water systems, but much less frequently than bacteria, nitrate, arsenic, or lead. If the well is located close to fuel tanks or to a commercial or industrial area, a test for "volatile organic chemicals" (VOCs) is a good idea. A brochure, VOCs, is available from the MDH. Agricultural chemicals are sometimes found in wells located near cropped fields or handling areas for agricultural chemicals. Shallow wells are more vulnerable to pesticide contamination than are deep wells. If your well is located in an agricultural area, and especially if it is a shallow well, testing for several of the pesticides most commonly used in the area may be warranted.

If children or adolescents are drinking the water, a test for natural levels of fluoride will give your dentist useful information when considering fluoride supplements. A small number of wells in Minnesota (primarily northeastern Minnesota) do have naturally-occurring levels of fluoride that exceed the health standard.

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Questions?
Contact the MDH Well Management Section
651-201-4600 or 800-383-9808
health.wells@state.mn.us

Minnesota Department of Health
Updated Tuesday, April 01, 2014 at 03:30PM