More than 120 million people in the Indian state of West Bengal and neighbouring Bangladesh pay a high price for living there.
Reliant on water laced with arsenic — which occurs naturally in the groundwater — they are victims of what some call the biggest mass poisoning in history.
In West Bengal alone 14,000 people have succumbed to arsenic poisoning, which can cause skin lesions, skin cancer and death. But it didn't have to be this way, reports Yudhijit Bhattacherjee.
Critics say West Bengali officials have been slow to act and made a catalogue of errors, despite having 25 years to tackle the problem.
Despite compelling evidence, the government failed to provide alternative water sources and poured money into filtration and drilling projects without success. It also resisted educating villagers about the risks, to avoid social unrest.
There are now plans to spend US$500 million on 360 tube wells equipped with facilities to remove arsenic, as well as five surface water treatment plants.
But, say critics, charges for the piped water could mean people continue to use the free public wells. The scant efforts to educate the public means millions are still at risk.