Fluoride occurrence in groundwater systems at global scale and status of defluoridation - State of the art

The occurrence of elevated concentrations of fluoride in the drinking water supply in many regions of the world has caused widespread prevalence of dental and skeletal fluorosis. In this article, the extensive literature on the routes of fluoride exposure, geographic regions with excess fluoride in water sources and various defluoridation techniques has been reviewed. It appears that important economic regions on all continents are affected by unsafe fluoride levels in fresh waters that are current or potential sources for drinking water supply. The widely accepted limit for fluoride in drinking water is 1.5 mg/L, though higher levels are also permitted, especially in low income, water scarce countries. We have discussed fluoride mobilization mechanisms in groundwater and soil environments which could be helpful in assessing the potential (long-term) potability of water from certain wells. Finally it is evident from the literature survey that no single fluoride removal technique fits for diverse technical and socioeconomic situations and there is a pressing need to develop suitable defluoridation techniques for household and community level water supply systems in order to prevent fluorosis.