Fluoride in the Environment and Its Metabolism in Humans

Fluorine is widely dispersed in nature and is estimated to be the 13th most abundant element on our planet (Mason and Moore 1982). It is the most electronegative of all chemical elements, and as a result, it never exists in elemental form, but rather combines with other elements; fluoride compounds represent about 0.06–0.09% of the content of the earth’s crust (Wedephol 1974). Fluoride is distributed universally throughout soils, plants, and animals, and is assumed to be an essential element in animals, including humans. Fluoride has an important role in bone mineralization and formation of dental enamels. Fluoride, when consumed in inadequate quantities (less than 0.5 ppm), causes health problems such as dental caries, lack of formation of dental enamel, and reduced bone mineralization, especially among children (WHO 1996). In contrast, when fluoride is consumed in excess (more than 1 ppm), health problems may result, which equally affect the young and old (WHO 1996). At higher fluoride concentrations, metabolic processes are affected in humans, and overexposed individuals may suffer from skeletal or dental fluorosis, non-skeletal manifestations, or combinations of these maladies (Susheela et al. 1993). The incidence and severity of fluorosis depends upon the fluoride concentration in air, soil or water, and the degree of exposure to these levels.