For the past two decades, water from a million or more wells sunk into the alluvum of the Ganga delta by agencies such as UNICEF, the World Bank and Britain's Overseas Development Administration has been slowly poisoning Bangladeshi villagers with a naturally occuring arsenic. Now thousands of villagers are being diagnosed with the debilitating marks of arsenic poisoning on their skins. Doctors believe that hundreds of thousands more victims remain undetected.