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

The artisanal gold miners, who use mercury to extract the precious metal from river silt, dump more than 30 tons of the toxic metal in rivers and lakes in the Amazon region every year.
Native communities had levels of mercury roughly five times that considered safe by the World Health Organisation (WHO), whereas people in urban areas had double the safe limit.
http://www.theguardian.com/environment/2013/sep/09/peru-amazon-indigenous-tribe-gold-mining