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Private Ground Water Supplies and Nitrate Testing

SIMCOE, January 16, 2015 – The Haldimand-Norfolk Health Unit (HNHU) encourages members of the public using private ground water drinking supplies to test their water supply for nitrates. Nitrates are an odourless and colourless compound naturally present throughout the environment. Nitrates are not harmful when found at levels below 10 mg/L. Drinking water is considered to be contaminated with nitrates when found at levels greater than 10 mg/L. Significant sources of nitrate contamination include:

  • Fertilizers (agricultural, lawn, garden)
  • Animal manure
  • Compromised septic tanks
  • Acid rain

Infants under the age of 6 months should not consume this water as it may put them at risk for methaeglobinemia (‘blue baby syndrome’) which can be fatal.  In addition, this water to should not be used to prepare baby formula.

Infants less than 6 months old do not produce enough of the enzyme needed to break down nitrates. The nitrates remain in the infant’s system and convert to nitrites. Nitrites reduce the blood’s ability to carry oxygen, causing the infant’s skin to have a bluish tint characteristic of “blue baby syndrome “.

Pregnant women are to avoid drinking water high in nitrates because their red blood cells carry oxygen less efficiently once nitrates are converted to nitrites in the body. This is a concern because the developing baby depends on oxygen carried by the red blood cells across the placenta from the mother.

Those with long-term illnesses and the elderly may also experience unwanted health effects from consuming water with elevated nitrates due to the reduction of oxygen being carried throughout the body as a result of nitrites binding more easily with the red blood cells.

If there are members of your household who are under the age of 6 months, are pregnant or are hoping to conceive a baby, have a compromised immune system or are elderly, the HNHU advises to test your private water supply at least once a year for nitrates. Nitrates are usually found in the greatest amount between April and July. Although the HNHU does not provide nitrate testing, it can refer those on private water supplies to approved laboratories providing this service. There is a cost associated with nitrate testing which varies between each laboratory.

Keep in mind that one nitrate test may not indicate periodic increases or decreases in nitrate concentration over time so if your nitrate result is close to 10 mg/L, it may be advisable for infants and pregnant women not to drink that water. Also be aware that different laboratories report nitrates in different ways. Sometimes the results may be expressed as nitrites, which should not exceed 1 mg/L or as nitrates and nitrites combined, which should not exceed 10 mg/L. Please contact the laboratory if you have difficulty understanding your results.

If your private drinking water is found to have elevated levels of nitrates, the following are actions you can take to protect the members of your household:

  • Use bottled water for drinking and cooking. Limit well water use for bathing.
  • Consider changing the source of your water and installing a cistern filled with water from the municipal water system (please note this is a more costly alternative).
  • Obtain a water treatment unit that will remove nitrates from your water supply such as a reverse osmosis water purifier, an ion-exchange unit or a distillation unit (these units can be more on the expensive side and may require the water to be pre-treated for maximum effectiveness)
  • DO NOT BOIL WATER TO REMOVE NITRATES as this will concentrate the amount of nitrate in the water. Boiling water does not remove nitrates.

To prevent nitrate contamination of your water supply, the following measures can be taken:

  • Ensure your well has a secure cover that prevents the entrance of surface water which can contain nitrates.
  • Check your well for cracks in the casing or grout and make sure that the seal is intact.
  • Regularly maintain the area around the well and ensure the ground around the well is sloped downwards.
  • Septic systems should be at least 15 metres or 50 feet away from wells and at a lower elevation.
  • Avoid mixing or storing chemicals near your well to prevent contamination from spills.
  • Be aware that shallow, older or dug wells are at higher risk for contamination.

For more information, please contact the Haldimand-Norfolk Health Unit at 519-426-6170 or visit

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Media contact:

Adrienne Andrew
Program Manager, Environmental Health Team
Haldimand-Norfolk Health Unit
Ext. 3216 at either 519-426-6170 or 905-318-6623
[email protected]