Approximately 40% of Canadians have access to community-fluoridated water through their municipal water supply systems.

Scientific research has shown that fluoride helps prevent tooth decay, particularly in children. However, fluoride has not been unequivocally established as an essential element for humans, and excessive intake can be harmful. Some countries add fluoride to drinking water in areas with low fluoride levels to prevent tooth decay, while others oppose this practice. Generally, fluoride in the human body comes from drinking water, food, and other sources. Most of the fluoride in an adult’s body is stored in hard tissues such as bones and teeth.

In its natural state, fluoride is present in soil, seawater, surface water, and groundwater. Fluorine primarily occurs in nature in compound form, mainly in minerals such as fluorite, fluoroapatite, and cryolite, which are important raw materials used in aluminum smelting, phosphate fertilizer production, steel manufacturing, and the production of fluorinated chemicals. However, fluoride-containing wastewater, exhaust gases, and solid waste discharged during some industrial processes can cause environmental pollution; the combustion of coal can also release fluoride-containing emissions. Excessive fluoride exposure can harm plants, and leaves can absorb fluoride from the air. The absorbed fluoride can accumulate at leaf tips and margins, where sufficiently high concentrations may cause tissue damage and necrosis.

High concentrations of certain fluoride compounds can cause skin burns, dermatitis, and respiratory tract irritation or injury, depending on the compound and route of exposure. Excessive long-term fluoride intake can cause dental and skeletal fluorosis. Dental fluorosis can cause changes in tooth enamel, while severe skeletal fluorosis can lead to bone pain, joint stiffness, and skeletal deformities. Research has also investigated other possible health effects of fluoride exposure, including effects on metabolism and development. However, the strength of evidence varies by outcome and exposure level, and some findings remain uncertain. It is well established that excessive fluoride intake can be harmful to health.

By Michael Chiu, MWS, CI – Updated and Revised in 2026