ABSTRACT
ABSTRACT: India is one among the 30 countries, where people consume groundwater with more than 1.5 mg/L of fluoride, an upper permissible limit prescribed by WHO. Assam falls in moderately endemic zone with very high fluoride occurring in pockets in certain areas. In the area under investigation fluoride concentration in groundwater varies from0.51 to 14.7mg/L. In contrast to other fluoride affected regions of the world, this area receives high rainfall. Granites, granitic gneisses and phyllitic quartzite are the main hard rock aquifers which contain fluorine bearing minerals such as fluorite, biotite and muscovite. Higher concentration of fluoride in groundwater is found to be associated with granites and controlled by regional shear/fault system.
