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The BBC, reporting on a meeting at the Royal Geographical Society, says that 140 million people in developing countries are drinking water with such high concentrations of arsenic as to constitute poisoning. Experts estimate that one out of ten people living in these areas will die of aresenic-induced ailments, particularly cancer.

The problem resulted from the well-intentioned efforts of aid agencies to steer communities in poor areas away from using surface water, which is often badly contaminated by bacteria, towards well-digging, not realizing the well water could have high levels of arsenic.