Vol. 15 No. 1
Arsenic contamination through food-chain in Gangetic delta of West Bengal – looking beyond drinking water pollution menace
Author(s): B. SINHA, K. BHATTACHARYYAAND P. K. GIRI
Abstract: The widespread arsenic contamination in groundwater in different parts of West Bengal has been detected to be distributed over 111 blocks, with dietary exposure of arsenic to nearly 35 million people. Rice (Oryza sativa L.) is the major food crop of the endemic area which accounts for withdrawal of more than 50 per cent of the total contaminated groundwater drifted for irrigation. An effort has been made, through the present study, to take an account of arsenic accumulation in rice over seasons along with possibilities of mitigating the toxicity hazard, in the arsenic affected villages of Chakdaha block, Nadia district, West Bengal, India having an arsenic concentration of irrigation water drifted from the shallow tube wells in the range of 0.03-0.32 mg l-l. The unique waterlogged rice rhizosphere was also contaminated by arsenic to the tune of 10.24-19.17 mg kg-1. Accumulation of the toxin in rice grain were observed to the tune of 0.42-1.33 (pre-kharif rice), 0.32-0.62(kharif rice) and 0.46-1.69 (summer rice). Consumption of rice straw containing considerable amount of arsenic (4.56-17.18 mg kg-1) by cattle could potentially lead to increased arsenic levels in livestock and products. A risk assessment of dietary arsenic intake of arsenic through rice revealed that maximum tolerable daily intake (MTDI) of arsenic for an adult of 60 kg body weight being 0.12 mg, a daily consumption of rice of 300 g day-1 would indulge a risk of daily arsenic intake of 0.507 mg which is > 400 % of MTDI. Use of relatively uncontaminated surface water (below detection level-0.03 mg l-l) or soil amendment through organic manures like vermicompost, phosphocompost, FYM, municipal sludge etc. were observed to offload arsenic accumulation in rice grain.
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