Fluoride is a naturally occurring mineral salt in soil. It can dissolve in groundwater. Water is not the only source of fluoride. It can also be found in:

  • Food and beverages such as tea
  • Some dental hygiene products such as toothpastes and mouthwashes

A small amount of fluoride in drinking water has beneficial effects. By helping with the mineralization of teeth, fluoride protects against dental cavities. To learn more, read Fluoridation of drinking water.

By Québec standards, the concentration of fluoride in drinking water must not exceed 1.5 mg/L.

Health risks

Prolonged consumption of water containing fluoride concentrations that exceed 1.5 mg/L can cause dental fluorosis in children under nine years old. Dental fluorosis is characterized by the appearance of white or brown stains on the teeth.

Consumption of water containing fluoride concentrations exceeding 4 mg/L can cause skeletal fluorosis in people that consume it over many years. Skeletal fluorosis makes bones more fragile and can cause pain and stiffness in the joints.

Protection and prevention

Your water should be tested for fluoride at least once during the period of usage of the well, ideally in the spring or fall.

If the concentration of fluoride in your well water exceeds 1.5 mg/L, take steps to reduce the risk of dental fluorosis. Check with your public health department for the best measures to take. The general advice is to use a source of water other than your well to:

  • Give children under nine years old a drink
  • Make beverages, including baby formula

If the concentration of fluoride in your well exceeds 4 mg/L, use another source of water for drinking and preparing beverages.

You can still use well water to:

  • Wash food
  • Steam food
  • Wash dishes and clothes
  • Take a shower or bath

If your water has a high concentration of fluoride, tell your doctor and your dentist.

Boiling water to eliminate fluoride is pointless because it does not evaporate. Doing so can even increase the concentration of fluoride in the water.

You can install a residential water treatment system to reduce the concentration of fluoride in water to an acceptable level. Be sure to install a certified system conforming to NSF/ANSI standards and follow the manufacturer's maintenance recommendations.