Nitrogen is essential for all living things as it is an essential component of protein. Nitrogen exists in the
environment in many forms and changes forms as it moves through the nitrogen cycle. However, excessive
concentrations of nitrate-nitrogen in drinking water can be hazardous to health, especially for infants and
Sources of Nitrate in Drinking Water
Nitrogen is the nutrient applied in the largest quantities for lawn and garden care and crop production.
Feedlots, animal yards, septic systems, and other waste treatment systems are additional sources of
nitrogen. Nitrogen occurs naturally in the soil in organic forms from decaying plant and animal residues.
Bacteria in the soil convert various forms of nitrogen to nitrate, a nitrogen/oxygen ion (NO3-). This is
desirable as the majority of the nitrogen used by plants is absorbed in the nitrate form. However, nitrate is
highly leachable and readily moves with water through the soil profile. If there is excessive rainfall or
over-irrigation, nitrate will be leached below the plant's root zone and may eventually reach groundwater.
Nitrate-nitrogen (NO3-N) in groundwater may result from point sources such as sewage disposal systems
and livestock facilities, from nonpoint sources such as fertilized cropland, parks, golf courses, lawns, and
gardens, or from naturally occurring sources of nitrogen. Proper site selection for the location of domestic
water wells, upslope and with adequate separation distances between wells and possible contamination
sources, can reduce potential nitrate contamination of drinking water. Proper well construction and
maintenance also reduces potential drinking water contamination.
Indications of Nitrate
Nitrate in water is undetectable without testing because it is colorless, odorless, and tasteless. A water test
for nitrate is highly recommended for households with infants, pregnant women, nursing mothers, or
elderly people. These groups are the most susceptible to nitrate.
Nitrate-nitrogen occurs naturally in groundwater, usually at concentrations far below a level of concern for
drinking water safety. An initial test of a new water supply is needed to determine the baseline nitrate
concentration. In addition, if the water supply has never been tested for nitrate, it should be tested.
Activities near the well potentially can contaminate the water supply, changing the nitrate concentration.
Domestic wells near potential point sources of contamination, such as livestock facilities or sewage
disposal areas, should be tested at least once a year to monitor changes in nitrate concentration.
Depending on the location of the well relative to areas where nitrogen fertilizer is applied, follow-up testing
to monitor changes from nonpoint sources may be conducted less often. All drinking water supplies should
be checked at least every two or three years to assure that significant increases in nitrate concentrations
are not occurring.
If a fertilizer or manure spill occurs, the spill should be cleaned up immediately and any wells near the spill
should be tested. Unfortunately, any nitrate from the spill may not move through the soil profile quickly and
annual testing is recommended to monitor the effects of the spill.
Potential Health Effects
The primary health hazard from drinking water with nitrate-nitrogen occurs when bacteria in the digestive
system transforms nitrate to nitrite. The nitrite oxidizes iron in the hemoglobin of red blood cells to form
methemoglobin, which lacks the oxygen-carrying ability of hemoglobin. This creates the condition known as
methemoglobinemia (sometimes referred to as "blue baby syndrome"), in which blood lacks the ability to
carry sufficient oxygen to the individual body cells.
Most humans over one year of age have the ability to rapidly convert methemoglobin back to
oxyhemoglobin; hence, the total amount of methemoglobin within red blood cells remains low in spite of
relatively high levels of nitrate/nitrite uptake. However, in infants under six months of age, the digestive
system has an underdeveloped capability to secrete gastric acid, thus the pH level in the digestive system
may rise. At a higher pH, bacteria levels may rise, increasing the transformation of nitrate to nitrites. In
addition, the enzyme systems for reducing methemoglobin to oxyhemoglobin are incompletely developed in
infants under six months of age. Thus, methemoglobinemia can occur. Older persons who have a
gastrointestinal system disorder producing a pH level which allows for increased bacteria growth may be at
greater risk than the general population. In addition, individuals who have a genetically impaired enzyme
system for metabolizing methemoglobin are at greater risk.
In 1962, the U.S. Public Health Service adopted drinking water standards and set the recommended limit
for nitrate-nitrogen at 10 mg/L. This drinking water standard was established to protect the health of
infants and was based on the best knowledge available.
The Environmental Protection Agency (EPA) has since adopted the 10 mg/L standard as the maximum
contaminant level (MCL) for nitrate-nitrogen in public water systems. Subsequent reviews of this standard
have not resulted in any changes. However, it is difficult to establish an exact level at which nitrogen
concentrations in water are safe or unsafe. The intake of nitrogen from food and other sources also is
important and must be considered.
Even though the MCL for nitrate-nitrogen in drinking water is 10 mg/L, there have been cases where
infants have been exposed to water with nitrate-nitrogen concentrations greater than 10 mg/L without
developing methemoglobinemia. Definitive guidelines for determining susceptibility to hethemoglobinemia
have not been developed. Therefore, if your water contains more than 10 mg/L nitrate-nitrogen, it is
advisable to use an alternate source of water for infant formula and food.
In addition, because of some reports of potential birth defects when pregnant women drank high nitrate
water, pregnant women should not drink water containing more than 10 mg/L NO3-N. It also is
recommended that nursing mothers use water that has an NO3-N concentration below 10 mg/L since
nitrate may be passed to infants in breast milk.
Older youth and adults can tolerate higher levels of nitrate-nitrogen with little or no documented adverse
health effects, and may be able to drink water with nitrate-nitrogen concentrations considerably greater
than the 10 mg/L level with no acute toxicity effects. However, the potential health hazard for older youth
and adults depends on the individual's reaction to nitrate-nitrogen and the total ingestion of
nitrate-nitrogen and nitrates from all sources. In addition, little is known about possible long-term chronic
effects of drinking high nitrate water. If your water test indicates a level of nitrate-nitrogen above 10 mg/L
and only adults or older children will be drinking it, consult your family physician for a medical
A potential cancer risk from nitrate (and nitrite) in water and food has been reported. A possibility exists
that nitrate can react with amines or amides in the body to form nitrosamine which is known to cause
cancer. Nitrate must be converted to nitrite before nitrosamine can be formed. The magnitude of the
cancer risk from nitrate in drinking water is not known.
Bacteriological contamination in water may contribute to an individual's susceptibility to the presence of
nitrate. All drinking water sources also should be tested for bacteriological contamination, particularly if the
nitrate-nitrogen level exceeds the 10 mg/L standard. The presence of both nitrate and bacteriological
contamination may indicate poor well location or construction, and possible contamination from surface
drainage, feedlots, sewage systems, or some other source.
Select a laboratory and obtain a drinking water nitrate test kit from them. The kit will contain a sterilized
sample bottle, an information form, sampling instructions, and a return mailing box.
The sample bottle for nitrate-nitrogen testing may contain a preservative to prevent any loss of
nitrate-nitrogen in the sample. This sample bottle should not be rinsed before filling and should only be
used for samples intended for nitrate-nitrogen analysis.
The sampling instructions provide information on how to collect the sample. Follow these instructions
carefully to avoid contamination and to obtain a representative sample. Promptly mail the sample with the
completed information form to the laboratory.
Although field test kits are available for measuring nitrate-nitrogen concentration, they are not as accurate
as laboratory procedures. Results from field test kits can be affected by the presence of certain chemicals
and by temperature variation. Laboratory testing should be used to assure the most accurate and reliable
Interpreting Test Results
The laboratory will report the nitrate concentration as milligrams per liter (mg/L) or as parts per million
(ppm), which are equivalent for the concentrations occurring in water (1 mg/L = 1 ppm).
Most laboratories report nitrate as nitrate-nitrogen (NO3-N), which is the amount of nitrogen in the nitrate
form. Some labs may report total nitrate (NO3-). Be sure to check your test report for which quantity,
NO3-N or NO3-, is reported. Use the following to compare the two reporting systems:
10 mg/L nitrate-nitrogen (NO3-N) = 44.3 mg/L nitrate (NO3-)
The U.S. Public Health Service recommended limit of 10 mg/L NO3-N in drinking water is used by the EPA
as the maximum contaminant level for public water systems. Public water systems are legally defined as
those that have 15 or more connections or regularly serve more than 25 persons. These systems must
comply with the 10 mg/L NO3-N standard in order to be an approved water supply.
EPA requires regular testing of public water systems for nitrate-nitrogen and these test results are
available from the supplier. If a test indicates that the nitrate-nitrogen concentration of the delivered water
exceeds the standard, the public must be notified and treatment must be performed. Often, the treatment
may be as simple as blending the water that exceeds the standard with water that has a nitrate-nitrogen
concentration less than 10 mg/L such that the average concentration of the delivered water is below the
If excessive nitrate-nitrogen is present in your water supply, you have two basic choices: obtain an
alternate water supply or use some type of treatment to remove the nitrate-nitrogen.
The need for an alternate water supply or nitrate-nitrogen removal should be established before making
an investment in treatment equipment or an alternate supply. Base the decision on a nitrate analysis by a
reputable laboratory, and after consulting with your physician to help you evaluate the level of risk.
Alternate Water Supply
It may be possible to obtain a satisfactory alternate water supply by drilling a new well in a different location
or a deeper well in a different aquifer, especially if the nitrate contamination is from a point source such as
livestock or human wastes. If the water supply with high nitrate is coming from a shallow aquifer, there may
be an uncontaminated, deeper aquifer protected by a clay layer that prevents the downward movement of
the nitrate-contaminated water. A new well should be constructed so surface contamination cannot enter
the well. It should be located away from any potential sources of contamination, such as septic systems,
feedlots, or underground fuel tanks.
The Nebraska Health and Human Services System Department of Regulation and Licensure may be able
to assist you in determining the cause of water contamination and make recommendations to correct the
problem. In addition, the Conservation and Survey Division of the University of Nebraska-Lincoln can
provide general information on the possible location of a water supply with satisfactory quality. Both are
based in Lincoln but have offices at several locations across the state.
Another alternate source of water is bottled water that can be purchased in stores or direct from bottling
companies. This alternative especially might be considered when the primary concern is water for infant
food and drinking.
The Nebraska Department of Agriculture licenses and inspects bottling companies, but does not routinely
sample bottled water. You should assure yourself of the nitrate content, general quality, and bacterial
quality of any water purchased. In all cases, the purchased water must be handled and stored in a manner
to prevent contamination.
Nitrate can be removed from drinking water by three methods: distillation, reverse osmosis, and ion
exchange. Home treatment equipment using these processes is available from several manufacturers.
Carbon adsorption filters, mechanical filters of various types, and standard water softeners do not remove
The distillation process involves heating the water to boiling and collecting and condensing the steam by
means of a metal coil. Nearly 100 percent of the nitrate-nitrogen can be removed by this process. Merely
boiling water will increase rather than decrease the nitrate concentration. Water without nitrate is obtained
by collecting and condensing the steam generated as the water boils.
In the reverse osmosis process, pressure is applied to water to force it through a semipermeable
membrane. As the water passes through, the membrane filters out most of the impurities. According to
manufacturers' literature, from 85 to 95 percent of the nitrate can be removed with reverse osmosis. Actual
removal rates may vary, depending on the initial quality of the water, the system pressure, and water
Ion exchange for nitrate-nitrogen removal operates on the same principle as a household water softener.
In a standard water softener, calcium and magnesium ions are exchanged for sodium ions. However, for
the nitrate removal process, special anion exchange resins are used that exchange chloride ions for
nitrate and sulfate ions in the water as it passes through the resin. Since most anion exchange resins have
a higher selectivity for sulfate than nitrate, the level of sulfate in the water is an important factor in the
efficiency of an ion exchange system for removing nitrates.
All of the methods described here for the removal of nitrate are relatively expensive. Consider both the
initial cost and the operating costs. Operating costs include the energy needed to operate the system,
additional water that may be needed for flushing the system, consumable supplies and filters, repairs, and
Regardless of the quality of the equipment purchased, it will not perform satisfactorily unless it is
maintained in accordance with the manufacturer's recommendations. Maintenance of the equipment may
include periodic cleaning and replacement of some components. Also consider any special installation
requirements that may add to the equipment cost.
Reputable water conditioning equipment dealers can assist you in evaluating available equipment.
Equipment should be purchased only through reputable dealers and manufacturers. This helps assure
that the equipment will perform the necessary task, and maintenance and repair parts will be available
when needed. Check to see if the equipment has been tested or evaluated by an independent agency.
The Water Quality Association (WQA) and the National Sanitation Foundation (NSF) both operate
voluntary programs to test water treatment equipment for manufacturers. Equipment listed by WQA and
NSF has been evaluated, meets the test standards requirements, and normally has a label identifying the
WQA or NSF testing. This independent testing provides some assurance that the manufacturers' claims
have been verified.
Nitrate in drinking water can be a problem, especially for infants. A water test is the only way to determine
whether the nitrate-nitrogen concentration is under the acceptable standard of 10 mg/L. Proper well
location and construction are key practices to avoiding nitrate contamination of drinking water.
Management practices to reduce the risk of contamination from applied fertilizers and manure help keep
the water supply safe.
If drinking water exceeds the acceptable nitrate-nitrogen standard, the choices are to use an alternate
water supply or treat the water. An alternate supply may be bottled water for drinking, especially for infant
formula, or a new well in a different location or aquifer. Water treatment options are distillation, reverse
osmosis, or ion exchange.
NITRATE-NITROGEN IN DRINKING WATER