Water Quality Standards

Fluorine accounts for about 0.3 g/kg of the earth's crust. Inorganic fluorine compounds are used in the production of aluminium, and fluoride is released during the manufacture and use of phosphate fertilizers, which contain up to 4% fluorine.

Levels of daily exposure to fluoride depend on the geographical area. If diets contain fish and tea, exposure via food may be particularly high. In specific areas, other foods and indoor air pollution may contribute considerably to total exposure. Additional intake may result from the use of fluoride toothpastes.

Exposure to fluoride from drinking-water depends greatly on natural circumstances. Levels in raw water are normally below 1.5 mg/litre, but ground water may contain about 10 mg/litre in areas rich in fluoride-containing minerals. Fluoride is sometimes added to drinking-water to prevent dental caries.

Soluble fluorides are rapidly absorbed in the gastrointestinal tract after intake in drinking-water.

In 1987, IARC classified inorganic fluorides in Group 3. Although there was equivocal evidence of carcinogenicity in one study in male rats, extensive epidemiological studies have shown no evidence of carcinogenicity in humans.

There is no evidence to suggest that the guideline value of 1.5 mg/litre set in 1984 needs to be revised. Concentrations above this value carry an increasing risk of dental fluorosis, and much higher concentrations lead to skeletal fluorosis. The value is higher than that recommended for artificial fluoridation of water supplies. In setting national standards for fluoride, it is particularly important to consider climatic conditions, volumes of water intake, and intake of fluoride from other sources (e.g., food, air). In areas with high natural fluoride levels, it is recognized that the guideline value may be difficult to achieve in some circumstances with the treatment technology available.