Canadian Cancer Society logo
You are here: 

Fluoride in water

Fluorides are chemical compounds that help prevent tooth decay. They are found in nature – in rocks and soil, in fresh water and in ocean water. They are also found in some types of food.

Decades of research have shown that adding fluoride to water (fluoridation) helps prevent tooth decay. In some communities, natural levels of fluoride in the water supply match the optimal level to prevent tooth decay. In many others, the level of fluoride is too low and has to be added to the water supply. In Canada, the optimal range for fluoride in drinking water suggested by Health Canada is 0.7 milligrams per litre (mg/L).

  • Water fluoridation and cancer

    Many studies done by government agencies (such as Health Canada and the U.S. Food and Drug Administration) and independent academic investigators haven’t shown a link between water fluoridation and cancer. But a small and very weak body of scientific evidence suggests there is a relationship between exposure to high levels of fluoride in drinking water and osteosarcoma (a rare type of bone cancer) in boys younger than 19.

    There are also a small number of studies showing that rats and mice exposed to very high levels of fluoride (100–200 times the recommended level in Canada) may have a higher risk of developing osteosarcoma. The evidence in these studies is uncertain and has not been confirmed in further studies.

  • Our perspective

    On the basis of current evidence, we believe it is unlikely that water fluoridation increases the risk of cancer, including osteosarcoma, in humans. At the same time, we know that there are many benefits to water fluoridation, especially for people who have less access to dental care. We will continue to watch this area of research and update our information as it becomes available.

    We urge the governments of Canada to make sure people are aware of the fluoride levels in their drinking water. We also ask government agencies to work together to make sure that fluoride in drinking water is reduced to the lowest level needed to have a maximum health benefit.

  • For more information

    Health Canada – Fluoride and human health
    Center for Disease Control and Prevention (US) – Community water fluoridation
    Canadian Dental Association – Fluoride FAQs



Dr Lillian Sung Improving supportive care for children with cancer

Read more

Funding lifesaving clinical trials

Illustration of science instruments

The Canadian Cancer Society is funding lifesaving clinical trials that give people with cancer access to the newest types of treatment.

Learn more