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?
Where can I get more information or help?
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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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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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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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.
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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 affects. In fact, the average adult in
the U.S. 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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The state Health Risk Limit 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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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 Web site 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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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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- 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.
- 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.
- 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."
- 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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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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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 flouride that exceed the health standard.
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If you have any questions about wells or well water quality in Minnesota, contact your local Minnesota Department of Health office and ask to talk with a well specialist or contact the Well Management Section Central Office at health.wells@state.mn.us or at 651-201-4600 or 800-383-9808. Deaf and hard-of-hearing: TTY 651-201-5797.
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