Nitrates in Well Water

HealthLinkBC File Number: 
Last Updated: 
April 2015

What are nitrates?

Nitrates occur naturally and are widespread in the environment, at low levels. They are produced by the oxidation of nitrogen by microorganisms. Nitrates are essential for plant growth and are present in all vegetables and grains. Nitrates are colourless, tasteless and odorless.

Nitrates should not be confused with nitrites. Nitrites are mainly used as a food preservative, especially in cured meats. Both nitrates and nitrites can be a health hazard when consumed in food and water. High nitrate concentrations in drinking water are a health concern for infants because they reduce the ability of blood to transport oxygen.

How do nitrates get into well water?

Nitrates enter the ground water and make their way into well water through many sources such as:

  • agricultural activities (including over-application of chemical fertilizers and animal manure);
  • wastewater treatment through septic systems or leaking sewage lines;
  • industrial processes;
  • improperly functioning septic systems;
  • motor vehicles; and
  • some de-icing agents used at airports.

How do I know if there are nitrates in my well water?

Since nitrates are colourless, tasteless, and odorless, you cannot tell if you have nitrates in your well water unless you test for it.

Nitrate levels in ground water may change over time, especially after a heavy rainfall. High levels (more than 10 milligrams per litre (mg/L)) of nitrates have been found in well water samples throughout B.C., especially near heavily farmed areas. In some cases, wells located near each other may have different levels of nitrates, so you cannot rely on test results from a neighbour’s well.

What are the health risks of high nitrate levels?

Some evidence suggests that consuming high levels of nitrates may be a health risk to pregnant women, a developing baby, babies under 6 months of age, the elderly, and individuals with weakened immune systems, or chronic heart, lung and blood conditions.

In recent years, new studies have suggested there can also be certain health risks for adults and children who have had exposure to high levels of nitrates.

Exposure to high levels of nitrates reduces the amount of oxygen in the blood. This condition is called methemoglobinemia. Babies under 6 months are particularly at risk from drinking well water high in nitrates. In severe cases, this can cause an infant to turn a grey-blue colour, mainly around the eyes and mouth due to the lack of oxygen in their blood. Immediate medical attention is necessary, as this serious condition can be fatal. Babies who have diarrhea or a bacterial infection are at greater risk of the harmful effects from high nitrates levels.

What should I do if there is a pregnant woman or baby in the household?

Research continues on the effects of nitrates during pregnancy. The safest choice for pregnant women is to drink water that does not have high levels of nitrates. To help keep your family safe you should:

  • Have your well water tested for both nitrates and coliform bacteria if there is an infant, a pregnant woman, or a woman planning on becoming pregnant in your household.
  • Breastfeed your child if possible.
  • Never feed your baby well water, or infant formula mixed with well water, unless the well water has first been tested safe for nitrates levels. Ready-to-feed formula is recommended if you are not breastfeeding and you do not have a safe water source.

For more information on preparing infant formula, see HealthLinkBC File #69b Feeding Your Baby Formula: Safely Making and Storing Formula.

For more information on feeding infants, see HealthLinkBC File #69c Baby's First Foods.

How can I get my well water tested?

Testing of your well water for nitrates and coliform bacteria can be done by a private laboratory. Laboratories which provide this service can be found on the internet under Laboratories – Analytical. Your local environmental health officer may also be able to give you a list of labs in B.C. that test drinking water.

Most laboratory tests for nitrates give their results in milligrams of nitrates, where the Guidelines for Canadian Drinking Water Quality’s maximum acceptable concentration for nitrates is 10 mg/L. If laboratory test results give the level of actual nitrate, rather than the level of nitrate(s) (i.e. nitratenitrogen), then the Guidelines recommends a maximum acceptable concentration of 45 mg/L of nitrate.

If you get your water tested and are unsure how to read the results, please call the environmental health officer at your local health authority.

All wells should be tested for nitrates. For more information on well water testing, see HealthLinkBC File #05b Should I Get My Well Water Tested?

What if my water is high in nitrates?

Homeowners that have nitrates test results consistently above the acceptable concentrations should consider the following:

  • install a drinking water treatment device;
  • use an alternative drinking water source; or
  • relocate or drill a deeper well that has been tested or verified and deemed to be a safe supply.

It is especially important to consider the above options if you are pregnant, have a baby under 6 months of age or have a health condition that puts you at risk.

You should use 1 or more of the following water sources for your drinking water:

  • water from a municipal distribution system;
  • water from a nearby well that has been tested safe for nitrates;
  • commercially bottled water; or
  • use an ion exchange or reverse osmosis treatment system specifically designed to remove nitrates, and where possible, should be certified by NSF international or an accredited agency.

It is important to note that boiling water will not reduce or remove nitrates. Also, most counter-top filtration units will not remove nitrates. There is no substitute for having your water tested.

You should continually monitor your well water for nitrates to make sure that your water is safe. This should be done in addition to other parameters such as free ammonia or total chlorine.

Shallow wells that are located in agricultural areas are more likely to be contaminated with nitrates. It is recommended that homeowners with these types of wells test their water at least once a year, either in the spring or fall, when concentrations are often highest.

For More Information

For more information on wells and quality well water, see:

Is it an emergency?

If you or someone in your care has chest pains, difficulty breathing, or severe bleeding, it could be a life-threatening emergency. Call 9-1-1 or the local emergency number immediately.
If you are concerned about a possible poisoning or exposure to a toxic substance, call Poison Control now at 1-800-567-8911.

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