4. Fluoride in Drinking Water: Health Effects and Remediation

Fluoride at low concentration is an essential element for dental health. However groundwater in many countries has exceeding concentrations of fluoride, which poses a health threat to millions of people around the world. It has been estimated that more than 200 million people from among 25 nations are suffering from fluorosis due to the consumption of fluoride-rich drinking water. Fluoride contamination is mostly geogenic however, in some cases anthropogenic industrial inputs may cause a threat. Many techniques have been developed for defluoridation. However a solution is still to be found especially for the household and community supply. This article presents a global overview of the distribution of fluoride rich groundwaters and defluoridation techniques. Focus is given on efficient and cost-effective defluoridation for rural communities for both household filtration units and community water supplies. Rocks containing fluoride-rich minerals are the main sources of high fluoride in groundwater especially in the developing world. Other sources are volcanic and industrial. Gneisses and granites sometimes contain very high concentrations of fluoride reaching more than 5000 mg/kg. Weathering and release of fluorides in rocks, secondary minerals and soils are ruled by alkalinity, specific conductivity and evaporation. Exposure to high fluoride levels in drinking water cause endemic dental and skeletal fluorosis, and crippling. Those diseases are common in India, Sri Lanka, Pakistan, Ethiopia, Ghana, Kenya and China. The most common defluoridation techniques are coagulation and adsorption, although those methods are not the best for fluoride removal. Membrane processes are quite efficient but not economical for the developing communities. Eletrocoagulation may be a solution but requires high energy and, as a consequence, is less available to poor communities. To conclude, most defluoridation techniques are not achieving social acceptance and sucessful implementation. Therefore, a better technology is lacking for fluoride removal.