www.cgwskolkata.com 40 VOL V, July 2015 : INDIAN GROUNDWATER Occurrence and Impacts of Fluoride in Drinking Water —A Review 1 Council of Scientific and Industrial Research-National Environmental Engineering Research Institute (CSIR-NEERI), Kolkata Zonal Laboratory, Kolkata 700107, West Bengal, India 2 CSIR-NEERI, Nehru Marg, Nagpur 440070, Maharashtra, India 3 School of Environmental Studies, Jadavpur University, Kolkata 700032, West Bengal, India * Corresponding Author: Dr. Sunil Kumar, Tel: + 91 712 2249752, Email: s_kumar@neeri.res.in OCCURRENCE AND IMPACTS OF FLUORIDE IN DRINKING WATER —A REVIEW S. Satheesh Babu 1 , Sunil Kumar 1,2* , Tarit Roychowdhury 3 , Vijay Vidyadharan 2 , Nilanjana Roychowdhury 3 , Juin Samanta 3 , Subhojit Bhowmick 3 ABSTRACT Exposure of fluoride (F - ) through drinking water and its adverse health effects have been reported in many parts of the world. Higher level of F - in groundw ater has been reported from many parts of the developing countries and F - is endemic in at least 25 countries across the globe. In India, a large number of population are facing acute fluorosis problem due to intake of F - through drinking water. Presently, it has been estimated that fluorosis is prevalent in 56.2 millions of people in various parts of India. An estimated 62 million people from 19 out of the 32 states in India are affected with dental, skeletal and/or non-skeletal fluorosis. The extent of F - contamination of water varies from 1.0 to 48.0 mg L -1 . The various geochemical factors that influence the leaching of F - from source to aquifer have been critically reviewed and presented in this paper. Moreover, the adverse health effects of F - on human and other living organisms have been critically emphasized with recent literature. The present review work will further help to design an appropriate F - removal technology in relation with environment friendly conditions. Keyw ords: Fluoride; Source; Leaching mechanism; Groundw ater; pH; Adverse health effects; Treatment 1. Introduction Water is essential for life. No living being on planet earth can survive without it. Unfortunately in many countries around the w orld, including India, some drinking w ater supplies have become contaminated, w hich has impacted on the human health. Contaminants, such as harmful microorganisms; heavy metals like cadmium, mercury, lead; metalloid like arsenic, other inorganic pollutants like fluoride and nitrate and salinity due to seawater intrusion into coastal areas have been found their w ay into w ater supplies as a result of inadequate treatment and disposal of w aste (human and livestock), industrial discharges, and over-use of limited water resources [1]. Fluoride (F - ) is a common element that does not occur in the elemental state in the nature due to its high reactivity. It accounts for about 0.3 g/kg of the Earth’s crust. The oxidation state of fluoride is -1 [2]. F - in natural waters may originate from the solution of fluorite or apatite and more commonly from the solution of fluoride-bearing micas and amphiboles. A common sink for F - is adsorption by clay minerals. F - content in groundw ater usually depends on the rock-type, water interaction period with host rock, as well as the dissolution kinetics for fluorite, apatite or silicate minerals [3]. F - contamination in drinking water is beneficial at lower concentrations but hazardous to health at higher levels. Several kinds of health related problems, such as crippling fluorosis, etc., have been observed due to higher concentration of F - in drinking water [4]. According to the World Health Organization (WHO), the maximum allowed concentration (MAC) of F - in drinking water is 1.5 mg L -1 but it is not universally accepted. WHO suggested that in warm climate, the MAC of fluoride should be < 1.0 mg L -1 while in cooler climate; it can go up to 1.2 mg L -1 [5].