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FLUORIDE

Fluorinea is present in small but widely varying concentrations in practically all soils, water supplies, plants, and animals, and is a constituent of all diets. The major tissues known to incorporate fluoride are bones and tooth enamel, the incorporation being proportional to the total intake (Hodge and Smith, 1970). The primary route of fluoride excretion is the kidney, and urine generally accounts for approximately 90% of the total fluoride excreted (Maheshwari et al., 1981; Spencer et al., 1981). There is a direct linear relationship between plasma fluoride level and the concentration of fluoride in the community water supply up to 6 mg/liter (Taves and Guy, 1979), but there can be substantial diurnal variations of these levels (Ekstrand, 1978).

The status of fluorine as an essential nutrient has been debated. Several studies in rodents have provided conflicting results. Addition of 2.5 mg of fluoride per kilogram of basal diet, the content of which varied but occasionally dropped below 0.04 mg/kg, stimulated the growth of rats housed in a trace element-controlled environment (Milne and Schwarz, 1974; Schwarz and Milne, 1972). In contrast, no effect of fluoride was seen in mice fed another low-fluorine diet (0.2 mg/kg) containing ingredients grown hydroponically, even when the diet was fed over six generations (Weber and Reid, 1974). An earlier report that fluoride added to the drinking water at 50 mg/ liter protected pregnant mice against impaired reproduction and severe anemia (Messer et al., 1973) was not confirmed (Tao and Suttie, 1976). These contradictory results do not justify a classification of fluorine as an essential element, according to accepted standards. Nonetheless, because of its valuable effects on dental health, fluorine is a beneficial element for humans.

a Fluoride is the term for the ionized form of the element flourine, as it occurs in drinking water. The two terms are used interchangeably.