Esteban Felix/AP
In this photo taken May 21, 2011 miners work at a legal mining concession in Huaypetue, Madre de Dios, Peru. Government efforts to halt illegal mining have mostly been futile. The state of Madre de Dios prides itself on its biodiversity and attracts eco-tourists for its monkeys, macaws and anacondas. But an estimated 35 metric tons of mercury is released annually by miners in this state alone, slowly poisoning people, plants, animals and fish, scientific studies show.

Poisoning the Indigenous: Peru’s Mercury Levels 5x Higher Than Normal

Barbara Fraser
September 17, 2013


Indigenous people, especially children, in Peru’s southeastern Madre de Dios region have high levels of mercury in their bodies, a new study has found.

Analysis of hair samples from urban and rural residents of the Amazonian region showed that three-quarters of the participants in the study had mercury levels above 1 part per million, the “reference dose” or maximum limit established by the U.S. Environmental Protection Agency (EPA).

The average level in indigenous communities was 5.3 parts per million, five times above the EPA’s reference dose and more than twice the level found in non-indigenous communities, according to Luis Fernández of the Carnegie Institution for Science at Stanford University, who led the study.

Mercury levels in the hair of indigenous children were three times those of children in non-indigenous communities.

Mercury is linked to problems with children’s neurological and cognitive development, as well as cancer, kidney damage, and digestive and vision problems. Children exposed to mercury in the womb may suffer brain damage, mental retardation, seizures and inability to speak, according to the U.S. Centers for Disease Control and Prevention.

Klaus Quicque, president of the Native Federation of the Madre de Dios River and its Tributaries (FENAMAD, for its Spanish initials), an umbrella organization of indigenous groups in the region, declined to comment on the report, saying representatives of the organization had been unable to attend a presentation on September 11 in Puerto Maldonado, the regional capital.

The Madre de Dios region is the epicenter of Peru’s boom in unregulated gold mining. Miners use mercury to separate gold from sediment, and wastewater containing the metallic element contaminates streams and rivers.

Mercury accumulates in fish, and the effect is magnified farther up the food chain, as larger fish eat smaller fish, Fernandez said. Humans, who are at the top of the food chain, receive the largest dose if they eat contaminated fish.

While residents of urban areas in Madre de Dios may eat chicken or other meats, fish are the main source of protein in indigenous communities, so residents suffer the greatest exposure, he said.

Some fish contain extremely high levels of mercury, while others are safe to eat, according to Fernández, whose team measured mercury levels in the tissue of 15 fish species that are commonly eaten in that region of the country.

They found that nine species had levels higher than the maximum allowed under EPA. People can minimize their risk of mercury exposure by eating the other species or by eating farmed fish, Fernández said.

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