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In eastern Peru, wildcat gold miners are seeking their fortune in the headwaters of the Amazon, but in the process they're polluting the river with mercury. And a research paper from scientists at Duke University finds toxic residue from the mines hundreds of miles downstream. NPR's global health correspondent Jason Beaubien reports.
JASON BEAUBIEN, BYLINE: Over the last decade, thousands of people have moved to a remote part of the Amazon jungle in eastern Peru. They're hoping to strike it rich, or at least find work from the gold-mining boom. Unfortunately, the process of extracting tiny specks of gold from the riverbed of the Madre de Dios River involves mercury, and it's poisoning the waterway. Researchers say mercury is showing up downstream at levels that pose a significant public health threat.
BILL PAN: Bill Pan, I'm an assistant professor at the Global Health Institute at Duke, and I've been working in Peru for about 10 years.
BEAUBIEN: Pan started out looking at environmental issues related to the recently completed Interoceanic Highway that links Brazil to the Pacific Ocean. And while doing that, he noticed that wildcat miners were having a huge impact on the region. In addition to infusing cash into this remote part of the jungle, they were cutting down trees and tearing up the river banks. Many of the miners operate on floating makeshift barges in the river. Pan says the barges are about the size of two compact cars strapped together.
PAN: You get these little tiny boats where there are two Hondas hooked together with this enormous tube that someone will dive down into the bottom of the river with a scuba suit or some kind of - connected to some tube so they can breathe underwater, and they're just on the bottom of the river sucking up the dirt.
BEAUBIEN: The miners then use mercury to extract the flecks of gold from the sludge. The mercury binds to the gold and the rest of the sediment is dumped overboard. Some of the mercury, however, clings to the slurry and ends up in the river. The team from Duke found dangerously high mercury levels, not just near the mining operations, but far downstream.
PAN: There's definitely strong correlations between where the mining is occurring and where people are at risk for mercury toxicity. And that risk actually stays elevated, you know, for hundreds of miles.
BEAUBIEN: This current report just looks at the levels of mercury in fish and river sediment. An earlier study in 2013 from the Carnegie Institute looked at the impact on people. It found mercury levels far above what the World Health Organization views as acceptable. Mercury exposure can lead to neurological damage and it's particularly dangerous for pregnant women and young children.
Heileen Hsu-Kim, who worked on the Duke study, says it's clear that mercury levels in fish and people have been going up as mining has expanded.
HEILEEN HSU-KIM: There's been an increase, certainly, in the last 10 years and the increase tracks - it's like, almost one-to-one with the global price of gold. And with that increase in the price of gold, there's been an increase in mining in this area.
BEAUBIEN: The government of Peru has attempted to crack down on illegal miners operating on the Madre de Dios River. The Peruvian navy has even blown up some of the barges. But with gold prices remaining well above a $1,000 an ounce, laborers are flocking to the boats, where they can earn far more than in most other jobs in the area.
Jason Beaubien, NPR News.