<P> The issue came to international attention in 1995 . The study conducted in Bangladesh involved the analysis of thousands of water samples as well as hair, nail, and urine samples . They found 900 villages with arsenic above the government limit . </P> <P> Criticism has been leveled at the aid agencies, who denied the problem during the 1990s while millions of tube wells were sunk . The aid agencies later hired foreign experts who recommended treatment plants that were inappropriate to the conditions, were regularly breaking down, or were not removing the arsenic . </P> <P> In West Bengal, India, water is mostly supplied from rivers . Groundwater comes from deep tubewells, which are few in number . Because of the low quantity of deep tubewells, the risk of arsenic poisoning in West Bengal is comparatively less . According to the World Health Organisation, "In Bangladesh, West Bengal (India), and some other areas most drinking - water used to be collected from open dug wells and ponds with little or no arsenic, but with contaminated water transmitting diseases such as diarrhoea, dysentery, typhoid, cholera, and hepatitis . Programmes to provide' safe' drinking - water over the past 30 years have helped to control these diseases, but in some areas they have had the unexpected side - effect of exposing the population to another health problem--arsenic ." The acceptable level as defined by WHO for maximum concentrations of arsenic in safe drinking water is 0.01 mg / L. The Bangladesh government's standard is a fivefold greater rate, with 0.05 mg / L being considered safe . WHO has defined the areas under threat: Seven of the twenty districts of West Bengal have been reported to have ground water arsenic concentrations above 0.05 mg / L. The total population in these seven districts is over 34 million while the number using arsenic - rich water is more than 1 million (above 0.05 mg / L). That number increases to 1.3 million when the concentration is above 0.01 mg / L. According to a British Geological Survey study in 1998 on shallow tube - wells in 61 of the 64 districts in Bangladesh, 46 percent of the samples were above 0.01 mg / L and 27 percent were above 0.050 mg / L. When combined with the estimated 1999 population, it was estimated that the number of people exposed to arsenic concentrations above 0.05 mg / L is 28 - 35 million and the number of those exposed to more than 0.01 mg / L is 46 - 57 million (BGS, 2000). </P> <P> Throughout Bangladesh, as tube wells get tested for concentrations of arsenic, ones which are found to have arsenic concentrations over the amount considered safe are painted red to warn residents that the water is not safe to drink . </P>

Problem of water pollution with arsenic is maximum in which state of india