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Middlesex-London Health Unit

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Water Fluoridation

Water fluoridation is the process of monitoring and adjusting the fluoride level in drinking water to achieve the optimal level of 0.7mg/L or 0.7ppm for dental health.1 Some communities have naturally-occurring fluoride in their water supplies at levels that help prevent cavities. Other communities adjust their fluoride levels to achieve the optimal level for dental health.


What about London?

The City of London draws its water supply from Lakes Huron and Erie, which have relatively low natural fluoride levels. Fluoride is added to drinking water to help people have the best possible dental health.2

Reduces Cavities

Drinking fluoridated water reduces cavities by about 25% in children and adults.3 The small amount of fluoride in saliva bathes the teeth, stopping or even reversing the damaging effects that acids found in the food and beverages we consume can have on tooth enamel.

Health Effects

Drinking water that has been fluoridated to the optimal level for dental health is not associated with adverse health effects. Research into the health effects of water fluoridation has been going on for more than 70 years. There are more than 90 well-respected national and international organizations that support water fluoridation, including:

  • World Health Organization
  • Centers for Disease Control and Prevention, USA
  • Health Canada
  • Canadian Medical Association
  • Canadian Paediatric Society
  • Canadian Dental Association
  • American Dental Association



Read Frequently Asked Questions about Water Fluoridation from the City of London’s website


The US Centres for Disease Control and Prevention have also listed fluoridation of drinking water as one of the 10 greatest public health achievements of the 20th century.


If you have questions about the drinking water in London and Middlesex County, please call the Environmental Health Team to speak with a Public Health Inspector at 519-663-5317.

Date of creation: November 12, 2012
Last modified on: May 18, 2021


1Health Canada (2011) Guidelines for Canadian drinking water quality: Guideline technical document - Fluoride. Retrieved from
2City of London. (2018, April 30). Water Fluoridation. Retrieved from
3Centers for Disease Control and Prevention. (2016, October 4). Community Water Fluoridation. Retrieved from