Illegal gold mining exposing Peru's indigenous tribes to mercury poisoning

The mercury dumped by miners settles in the sediments at the bottom of the rivers and gets converted into an organic form, Methylmercury, which is absorbed by biological organisms and concentrated up the food chain.
Through the methylmercury in the fish which local people eat they are "exposed to levels which are tens of thousands, up to millions of times more concentrated than the mercury levels in the water in which the fish are swimming," Fernandez told The Guardian.
He added it was a "very serious public health crisis … with very few sources of information for the people to understand what they're being exposed to."
The miners have also deforested around 70sqkm of rainforest, according to official figures. Madre de Dios, known as the "capital of biodiversity," is renowned for its eco-tourism.
http://www.theguardian.com/environment/2013/sep/09/peru-amazon-indigenous-tribe-gold-mining