Research report Fluoride 43(2)160–164 April-June 2010 Fluoride concentration in groundwater in the North 24-Paraganas district of West Bengal, India Kundu, Mandal 160 160 FLUORIDE CONCENTRATION IN GROUNDWATER IN THE NORTH 24-PARAGANAS DISTRICT OF WEST BENGAL, INDIA MC Kundu, Biswapati Mandal a Kalyani, India SUMMARY: One hundred and sixty samples of ground source drinking water were collected at different depths in the 24-Paraganas District of West Bengal and analysed for pH, electrical conductivity (EC), and fluoride (F). Nearly all the samples had pH ~ 7.0, low salinity (EC < 1.0 ds/m), and low F (0.01–1.18 mg/L). While exhibiting little dependence on location or depth of sampling, only 2.5% of the samples contained more than 1.0 mg F/L that might pose a potential threat of endemic fluorosis. On the other hand, the F content in the water had a significant positive correlation (r = 0.16, p<0.05) with the amount of phosphate fertilizer use, thereby indicating its possible role in F enrichment of the groundwater. The threat of F toxicity exists for a few villages in the district. Keywords: Agricultural activities; Fluoride in groundwater; 24-Paraganas district; Phosphate fertilizer usage; West Bengal. INTRODUCTION It is well known that chronic fluoride intoxication (fluorosis) is a worldwide health problem and is caused by the consumption of drinking water containing high fluoride. 1 Fluorosis is endemic in 20 states of India, affecting more than 65 million people including 6 million children. 2 The amount of F occurring naturally in groundwater is governed principally by climate, composition of the host rock, and hydrogeology. Some anthropogenic activities such as use of phosphatic fertilizers, pesticides, sewage and sludges for agriculture, depletion of groundwater, etc., are also implicated as causes of increased F concentration in groundwater. 3,4 An inventory of F concentration in drinking groundwater is thus important toward curbing the spread of fluorosis. The North 24-Paraganas district of West Bengal is one of the most intensively cultivated, highly fertilized, and highest pesticide usage districts of India, and has an alarming groundwater depletion rate. 5 This study was undertaken to investigate the quality of ground source drinking water of this district in regard to F concentration and relate this to geology of the area and certain agricultural practices. This district lies between 88º19' E, 23º20' N to 89º10' E, 22º01' N comprising 5 subdivisions and 22 blocks, with an area of 4094 sq km and population of 9.0 million (as per 2001 census) (Figure 1). The hydrogeology of the district is characterised by predominance of shallow aquifers (12–15 m below ground level) mostly of unconfined nature, with two more aquifers at depths ranging from 35 to 46 m and 70 to 150 m. Normal average rainfall of the district is 1,579 mm, air temperature ranges from 10°C (in January) to 41ºC (in May), relative humidity ranges between 50% in March and 90% in July. Soil type varies from sandy to clay loam. a For correspondence: Professor Biswapati Mandal, Directorate of Research, Bidhan Chandra Krishi Viswavidyalaya, Kalyani - 741 235, West Bengal, India; Email: mandalbiswapati@rediffmail.com.