FLUORINE IN BIOAPATITE: FLUORIDATION AND FOSSILIZATION

Fluorine is considered an essential element and is usually ingested in waters whose composition range is variable although usually less than the WHO guideline amount of 1 mgL-1. Analysis in various natural surface waters show values up to 1600 mg L-1 where volcanic ash and gases contaminate the surface waters as in Lake Magardi, Africa. Geogenic sources, F-containing micas and amphiboles, and including marine aerosols, mean that local soils and groundwaters may accumulate fluorine and transfer the element great distances altering in the process the reactions in the subsurface rock layers and lead to hazardous situations when humans tap these aquifers.

The bone mineral, bioapatite, because of its crystal chemistry and size, is a natural sponge for many anions and cations. Fluorine can take the place of OH in the crystal structure. Normal active human metabolism means that the mineral formed in the dynamic bone processes is never totally fluorapatite but with chronic intake of elevated amounts of fluorine, and a less than adequate diet, fluorosis, a debilitating disease may occur.

Diagenesis, part of the usual fossilization process, often means incorporation of fluorine in dead bone materials with the amount reflecting the level of the F-containing solutions. The formation of fluorapatite stabilizes the mineral fraction in bone tissues and their morphology. By lowering the dissolution even in acidic environments, fluorine aids preservation of the bones, a distinct advantage to paleontological investigators.

The changing mineral crystallinity and stability through incorporation of fluorine has led medical investigators to consider its use in treating osteoporosis. On the other hand there is a question on whether the general availability of fluorine-containing products (tea, toothpaste) obviates the necessity for widespread fluoridation of community waters. On the other hand fluorine–containing fossil material has allowed the diets and ecology of many different species from diverse geologic ages and localities to be investigated provided the geological and geochemical controls in the environments that relate to the mobilization and behavior of the many elements, including fluoride, can be evaluated in the analyses.