15. Fluoride Contamination in Groundwater—A Review

Fluoride contamination in groundwater is a major environmental issue, mostly in the developing world, due to the extensive negative impact that it has on human health. Excessive consumption of fluoride-contaminated water causes dental fluorosis and, in extreme cases, skeletal fluorosis. An estimated 200 million people all over the world, 62 million from India in almost 17 out of 29 states, which includes 6 million children, suffer from fluorosis due to consumption of water with high fluoride concentration. Natural sources such as weathering of rocks bearing fluoride rich minerals, volcanic eruptions are the major sources of fluoride, although anthropogenic sources are also present. Major chemical controlling factors responsible for fluoride contamination of groundwater are dissolution, hydrolysis, precipitation, adsorption, ion exchange and biochemical reactions. Five major fluoride affected belts have been delineated globally. In India, many districts of states such as Rajasthan, Tamil Nadu, Andhra Pradesh, Telengana and West Bengal show high fluoride in groundwater. Determining factors causing fluoride contamination in groundwater are Rock type, Tectonics, Physico-Chemical properties of water, Soil type and weathering.