Groundwater arsenic contamination in one of the 107 arsenic-affected blocks in West Bengal, India: Status, distribution, health effects and factors responsible for arsenic poisoning.

A somewhat detailed study was carried out in Gaighata, one of the 107 arsenic-affected blocks in West Bengal, India, to determine the degree of groundwater contamination with arsenic, its depth wise distribution, correlation with iron, arsenical health effects to the inhabitants and the factors responsible for arsenic poisoning. Groundwater in all the 107 mouzas over 13 gram-panchayets in Gaighata block contains arsenic above 0.01mgl(-1) and in 91 mouzas, arsenic concentration has been found above 0.05mgl(-1). About 59.2 and 40.3% of the tubewell water samples contain arsenic above 0.01 and 0.05mgl(-1), respectively. The approximate population drinking arsenic-contaminated water above 0.01 and 0.05mgl(-1) are 106,560 and 72,540, respectively. The tubewells that were installed within the depth range of 15.4-30.3m are mostly arsenic-contaminated. Even the shallow groundwater level (7.87-15.1m) is arsenic-contaminated. Both arsenic and iron concentrations in groundwater gradually increase from lower depth to higher depth up to 39.4m, and then decrease with increasing depth. About 58% of the deep tubewell water samples (depth range 122-182m, n=31) contain arsenic ≥0.05mgl(-1). About 72% of the arsenic-contaminated deep tubewells (n=18) were safe when surveyed first time. But within a span of 2-5 years, they became contaminated with arsenic. The linear regression shows direct correlation between arsenic and iron concentrations in groundwater (r(2)=0.8114, p<0.0001, n=912). Intakes of inorganic arsenic from water by an adult male and female in the surveyed areas are 11.7 and 13.1μg/kg body wt./day, respectively and these values are higher than the WHO recommended PTDI value of inorganic arsenic (2.1μg/kg body wt./day). Mean arsenic concentrations in urine, hair and nail samples, collected from the inhabitants of Gutri mouza are higher than their normal level and the values are 292μgl(-1) (range: 8.35-1024μg l(-1), n=193), 2.50mgkg(-1) (range: 0.17-5.99mgkg(-1), n=132), and 6.05mgkg(-1) (range: 0.55-16.7mgkg(-1), n=116), respectively. About 83% and 68% of the urine samples (n=250) contain arsenic above 100 and 200μgl(-1), respectively. Linear regressions show very good correlations between arsenic concentrations in water vs. urine, hair and nail samples from the inhabitants (n=103) of Gutri mouza. About 18.3% of the population (n=930) were registered with arsenical skin lesions.