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Updated 05 October 2015

Q&A on fluoridated water

Virtually all water contains some amount of fluoride. But these compounds have sparked controversy. Here's what you need to know.

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What is fluoride?

Fluoride is the name given to a group of compounds that are composed of the naturally occurring element fluorine and one or more other elements. Fluorides are present naturally in water and soil.

What is fluoridated water?

Virtually all water contains some amount of fluoride. Water fluoridation is the process of adding fluoride to the water supply so that the level reaches approximately 1 part fluoride per million parts water (ppm) or 1 milligram fluoride per liter of water (mg/L); this is the optimal level for preventing tooth decay.

Why fluoridate water?

In the early 1940s, scientists discovered that people who lived where drinking water supplies had naturally occurring fluoride levels of approximately 1.0 ppm had fewer dental caries (cavities). Many more recent studies have supported this finding.

Fluoride can prevent and even reverse tooth decay by enhancing remineralisation, the process by which fluoride “rebuilds” tooth enamel that is beginning to decay.

Can fluoridated water cause cancer?

The possible relationship between fluoridated water and cancer has been debated at length. The debate resurfaced in 1990 when a study by the American National Toxicology Program, part of the American National Institute of Environmental Health Sciences, showed an increased number of osteosarcomas (bone tumours) in male rats given water high in fluoride for 2 years. However, other studies in humans and in animals have not shown an association between fluoridated water and cancer.

In a February 1991 Public Health Service (PHS) report, the agency said it found no evidence of an association between fluoride and cancer in humans. The report, based on a review of more than 50 human epidemiological (population) studies produced over the past 40 years, concluded that optimal fluoridation of drinking water “does not pose a detectable cancer risk to humans” as evidenced by extensive human epidemiological data reported to date.

In one of the studies reviewed for the PHS report, scientists at the American National Cancer Institute evaluated the relationship between the fluoridation of drinking water and the number of deaths due to cancer in the United States during a 36-year period, and the relationship between water fluoridation and number of new cases of cancer during a 15-year period. After examining more than 2.2 million cancer death records and 125 000 cancer case records in counties using fluoridated water, the researchers found no indication of increased cancer risk associated with fluoridated drinking water.

In 1993, the Subcommittee on Health Effects of Ingested Fluoride of the American National Research Council, part of the American National Academy of Sciences, conducted an extensive literature review concerning the association between fluoridated drinking water and increased cancer risk. The review included data from more than 50 human epidemiological studies and six animal studies. The Subcommittee concluded that none of the data demonstrated an association between fluoridated drinking water and cancer.

A 1999 report by the CDC supported these findings. The report concluded that studies to date have produced “no credible evidence” of an association between fluoridated drinking water and an increased risk for cancer.

Source: US National Cancer Institute


 
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