RESEARCH COMMUNICATIONS High fluoride in groundwater and with hot and humid climate exhibit higher incidence of fluorosis owing to excessive intake of fluoride rich fluorosis related health hazard in Rarh water6. According to Central Ground Water Board Bengal, India: a socio-environmental (CGWB)7, more than 95 million people including 6.5 mil- study lion children are suffering from dental, skeletal and non- skeletal fluorosis in India. The CGWB report also high- 1, 2 lights that 223 districts in 23 states are under the impact Biswajit Bera *, Sumana Bhattacharjee , of high to severe fluoride contamination in groundwater. 1 1 Meelan Chamling , Arijit Ghosh , Figure 1 a shows district map of West Bengal. In 3 1 Nairita Sengutpa and Supriya Ghosh 2017–2018, fluoride contamination in groundwater was 1Department of Geography, Sidho-Kanho-Birsha University, noticed (ranging from 1 to 10 mg/l) in 43 blocks of 7 dis- Purulia 723 104, India tricts in West Bengal, India. The district includes Purulia, 2 Department of Geography, Jogesh Chandra Chaudhuri College Bankura, Birbhum, Malda, North Dinajpur, South Dinaj- (Calcutta University), Kolkata 700 033, India 3Department of Geography, Diamond Harbour Women’s University, pur, and 24 Parganas (S). In three districts, namely Puru- Sarisha 743 368, India lia (17 Blocks), Bankura (10 Blocks) and Birbhum (7 Blocks) of Rarh Bengal, the groundwater is moderately to More than 600,000 people in the three districts in highly contaminated by fluoride ion. But fluorosis related Rarh Bengal, namely Purulia, Bankura and Birbhum health hazard like dental and skeletal fluorosis are mostly live in fluoride endemic area where dental, skeletal found in the districts of Purulia and Birbhum8. In 2017– and non-skeletal fluorosis is wide spread. Rarh Bengal 2018, worst affected blocks under Purulia district were is in an extended part of Chotanagpur Plateau in Purulia I (10.75 mg/l and 11,400 mg/kg), Purulia II Eastern India. Fluoride content in 727 water samples (6.25 mg/l and 9,000 mg/kg) and Hura (6.25 mg/l and of drinking water and petrography of 34 rock chip 10,200 mg/kg). Similarly, the present study (in the year samples from these districts have been studied to 2017–2018) revealed that 4 blocks (Bankura-II, Indpur, understand fluoride in the drinking water. About 1753 households (in 410 villages) were surveyed using stra- Khatra and Simlapal) of Bankura district and 1 block tified random and quota sampling techniques to assess (Khoyrasole) of Birbhum district of Rarh Bengal were the number of people affected by fluorosis. Fluoride also highly affected. In recent years, groundwater conta- risk analysis was performed by applying the standard mination by fluoride and fluorosis related health hazard fluoride hazard index and fluoride vulnerability has become a serious health cum societal issue in the index. Results showed that granite gneiss and pegma- Rarh Bengal9,10. People suffer from yellow cracked teeth, tite are responsible for release of fluoride ions into the joint pains, crippled limbs and quick ageing11. The spec- soils and groundwater. About 118 villages in 14 blocks trum of fluorosis related health hazard that leads to cur- of Purulia, 15 villages in 7 blocks in Bankura and 9 rent status, health challenges and mitigation measures villages in 5 blocks in Birbhum are found to be have been studied by many scientists12. Young boys and affected by severe fluorosis. girls are mostly affected by dental fluorosis, whereas adults are affected more by skeletal and non-skeletal fluo- Keywords: Fluoride, hazard, host rocks, Rarh Bengal, rosis13. risk, vulnerability. Rarh Bengal (Figure 1 a) is located on an extended part of the Singbhum Craton and lies between Chota Nagpur FOR strong teeth and bones in human beings, fluoride is a plateau and the Ganges Delta. It is characterized by undu- requisite micronutrient. In 1984, World Health Organiza- lating terrain in the west and alluvial tract in the east. tion (WHO) prescribed the desirable fluoride limit bet- Purulia, Bankura, Birbhum, Murshidabad, Jhargram, Pur- ween 0.6 and 1.5 mg/l in drinking water. Bureau of India ba Barddhaman, Paschim Barddhaman, Purba Medinipur, Standard (BIS) has fixed the range between 0.6 and Paschim Medinipur, Hooghly and Howrah districts com- 1.2 mg/l whereas Indian Council of Medical Research prise Rarh Bengal. Groundwater of three districts, viz. (ICMR) has standardized the limit as 0.5–1.5 mg/l. Purulia, Bankura and Birbhum are found to be highly Beyond the given standard range, fluoride concentration contaminated by fluoride. The main objective of this in drinking water is detrimental to human health1,2. work is to find out: (i) the reasons for fluoride contamina- Fluoride contamination in groundwater is a socio- tion in groundwater through petrological and hydro- environmental jeopardy. Nearly 261 million people in the geomorphological studies of Rarh Bengal and (ii) identify world are found to be consuming groundwater with high the high-risk blocks with magnitude of fluorosis. fluoride content. More than 29 nations are suffering from To understand the geology and structure of Rarh Ben- severe dental and skeletal fluorosis resulting in health gal, lineament map has been prepared using module edge hazard and societal vulnerability3–5. Tropical countries filtering technique (performed using PCI Geomatica V 9.1.0 software) using ETM and ASTER imageries. ETM *For correspondence. (e-mail: [email protected]) imagery is composed of six VNIR bands and has 30 m CURRENT SCIENCE, VOL. 120, NO. 7, 10 APRIL 2021 1225 RESEARCH COMMUNICATIONS Figure 1. a, District map of West Bengal; b, Simplified geological map of Rarh Bengal. resolution and 8 SWIR band having 15 m resolution. On related health issues, fluoride hazard and vulnerability the other hand, ASTER imagery consists of 3 VNIR have been calculated as6 bands of 30 m resolution and SWIR band of 15 m resolu- tion14. A lineament density index (LDI) is computed by FHI = (% of geographical areas affected by fluoride taking into consideration total length of lineament per + tfhev)/100, (2) unit area (km/km2) and expressed as where FHI is the fluoride hazard index and tfhev is the N total fluoride hazard evaluation value. LDI = ∑ xi km/km2, (1) i=1 FVI = ratings of mtf + ef + adwa + sa, (3) where LDI is the lineament density index (total length of where FVI means fluoride vulnerability index, mtf, medi- lineament), N denotes number of lineament and xi is the cal treatment facilities within 5 km radius, ef, education length of lineament number i. facilities, adwa, alternate drinking water availability and Total of 727 water samples were collected from Puru- sa is the social awareness. Thus on the basis of FHI and lia, Bankura and Birbhum districts of Rarh Bengal and FVI, fluoride risk is computed as important parameters, viz. fluoride (F–), pH, iron (Fe), potassium (Na), calcium (Ca), magnesium (mg), bicarbo- R = H + V, (4) nate (HCO3), etc. were determined. LKB UV-visible spectrophotometer model 4054 attached with an automatic where R, Risk, H, Hazard and V, Vulnerability. cell driver, 1 cm quartz cell and spectrum recorder has Figure 1 b shows simplified geological map of Rarh been used for the measurement of fluoride (mg/l) concen- Bengal. The rock formations principally belong to the tration in the water samples. Thin sections of 34 rock Precambrian Chotanagpur gneissic complex (CGC) expo- chip samples have been collected from the three districts sed to the north of Singbhum Craton15,16. The study and these were examined under the petrological micro- shows that the predominant Precambrian metamorphic scope and the mineralogy was determined by X-ray rocks constituting Chotanagpur granitic gneiss complex powder diffractometry in the laboratory of the Geological are granite gneiss, cal-granulites and meta-basic rocks. Survey of India. In order to analyse the magnitude of The banded gneisses of this region are similar to other fluorosis, a total of 1753 households (410 villages) were basement rocks of the Indian Shield. Amphibolites, surveyed applying stratified random and quota sampling hornblende gneiss and diorite gneisses are exposed as technique. To determine the degree of risk due to fluoride bands occasionally amidst the gneisses17. Gneissic rocks 1226 CURRENT SCIENCE, VOL. 120, NO. 7, 10 APRIL 2021 RESEARCH COMMUNICATIONS Table 1. Affected villages with high fluoride content in different blocks under the three districts of Rarh Bengal (2019) Total no. of Average Villages with Highest Highest fluoride Fluoride affected fluoride highest fluoride fluoride value (rock chip) bearing Districts Blocks villages (mg/l) concentration (mg/l) (mg/kg) minerals Purulia Arsha 17 0.71 Kishanpur 1.59 5,110 Apatite Baghmundi 43 0.25 Burda 0.65 4,507 Fluorite Balarampur 25 0.77 Biramdih 1.63 5,202 Apatite Bandwan 8 0.33 Gurur 0.85 4,700 Biotite mica Barabazar 21 0.68 Ladiha 1.87 5,330 Fluorite Hura 17 0.89 Palgan 1.85 5,324 Biotite mica Jhalda I 18 0.68 Ichag 2.58 5,500 Apatite Jhalda II 21 0.75 Sarjumatu 1.88 5,338 Hornblende Joypur 19 0.53 Karkara 1.96 5,400 Hornblende Kashipur 19 0.38 Rambani 8.01 12,400 Fluorite Manbazar I 45 1.40 Daha 6.77 9,900 Fluorite Manbazar II 21 0.55 Sankura 1.52 4,995 Biotite mica Neturia 44 0.58 Gunyara 3.65 6,300 Apatite Para 20 0.64 Kaluhar 1.83 5,315 Hornblende Puncha 48 1.10 Kenda 2.92 5,822 Biotite mica Purulia I 43 0.72 Dimdiha & Bhul 1.96 5,337 Fluorite Purulia II 78 1.43 Bhangra 5.56 8,500 Apatite Raghunathpur I 20 0.70 Shanka 2.18 5,445 Hornblende