The fluorine content of surface waters essentially depends on the leaching of rocks and soils. Abnormal values may appear in the presence of fluorite concentrations (ore deposits), particular volcanic products originally anomalous in fluorine content, and thermal spring waters related to volcanic activity. From a structural point of view the strong link between rift systems and fluorspar districts is well known, and Sardinian fluorine geochemistry is an interesting example of the possible consequences of the development of rifting at different times of the geological history. The East African Rift is another important example of such a link, because of the highly anomalous fluorine content of its surface waters. The present geochemistry of fluorine in a given area is thus a result of the local geological history, whose structural fabric evolution may be strongly affected by rift structures. Fluorspar deposits must be considered only a possible end effect of the hydrothermal systems that always form along the rift faults and fractures and involve huge volumes of F-rich solutions directly or indirectly responsible for the origin and geochemical balance of fluorine in the surface waters.
On the other hand, this study enables to suggest the control of areas where the anomalies in fluoride can be expected to be harmful to health. Indeed, links between high grade fluorine and some diseases are well known. The fluorosis, which is particularly widespread in some developing countries (e.g. China, Ethiopia) grows where excessive F (as fluoride) occurs in the waters used for civilian purposes.
The interest of the scientific international community is increasingly oriented towards multidisciplinary studies involving the themes "Health and Environment" and "Geomedicine". Recently international agencies were established: "The European Centre of Environment & Health" - WHO; "Environment and Health Committee" of the European Union, dealing with the theme "Environment and Health". If knowledge about pollution caused by human activities and their health effects is detailed, too short time has been devoted to study of the health effects induced by local and natural geochemical characteristics. All the information obtained about the distribution, the mechanisms of migration of chemical elements, the background in different lithologies and their bioavailability are essential for epidemiological and geomedical investigations.
Therefore, the results of this study could be used for the environmental epidemiological surveying in natural fluorine high grade areas.