Nitrates and nitrites

Nitrates and nitrites in water may result from:

  • Chemical fertilizers and manure
  • Failing septic systems
  • Decomposition of plant and animal matter

In addition to drinking water, some foods such as vegetables and cold meats can contain low concentrations of nitrates and nitrites.

By Québec standards, the concentration of nitrates and nitrites in drinking water should not exceed 10 mg/L.

Health risks

Babies under six months who are exposed to nitrates and nitrites can experience breathing problems due to a slowdown in oxygen reaching their lungs and tissues. Heavy contamination of nitrates and nitrites causes a bluish discolouration of the skin and lips in infants.

Current studies show that regular consumption of drinking water contaminated with nitrates and nitrites over several decades can lead to a risk of cancer.

Protection and prevention

You should test for nitrates and nitrites in your well water twice a year, in the spring and fall. This recommendation particularly applies if you live in an agricultural area or in a residential area where septic systems are private. Testing for nitrates and nitrites is even more important if the concentration exceeds 5 mg/L.

You must also test your well water for nitrates and nitrites if:

  • A pregnant woman is drinking water from the well
  • You are using water from the well to prepare a feeding bottle for a baby under six months old

If the concentration of nitrates and nitrites in your well exceeds 10 mg/L, for pregnant women and babies under six months, use another source of water to:

  • Drink
  • Prepare beverages for a pregnant woman
  • Prepare feeding bottles and baby food

Avoid drinking water with over 10 mg/L of nitrates and nitrites regularly. If the concentration exceeds 20 mg/L, you should stop drinking the water.

Boiling water is pointless because nitrates and nitrites do not evaporate. In fact, doing so can increase the concentration of nitrates and nitrites in the water.

To fix the problem, determine the cause of contamination, such as a septic system or fertilizer application, and then apply the proper corrective measures. You can install a residential water treatment system to reduce the concentration of nitrates and nitrites in water to an acceptable level. Be sure to install a certified system that conforms to NSF/ANSI standards and follow the manufacturer’s maintenance recommendations.

Last update: August 22, 2016


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