Unintended Consequences of Cholera Relief Effort

Science Fair wrote an article about how an international relief effort to fight cholera and other water borne illnesses led to massive, mysterious arsenic poisoning.

when organic carbon settles at the bottom of these [manmade] ponds, it seeps underground where microbes consume it. This creates a chain of biochemical events that causes naturally occurring arsenic to dissolve out of the sediment and into the ground water.