Mercury Poisoning: Hazards of the Amazonian Gold Boom

May 21, 2011

As illegal gold miners flock to the southeastern Peruvian region of Madre de Dios, an Amazon Conservation Association (ACA)-sponsored study reveals alarming rates of mercury contamination in some of the region’s most commonly consumed fish. Researchers Luis Fernandez of the Carnegie Institution for Science and Victor Hugo Gonzalez of the Universidad Técnica de Machala tested locally-caught freshwater fish purchased in markets in Puerto Maldonado, Peru. They found that three very popular fish had mercury levels well above—in one case double—the maximum recommended concentration set by the World Health Organization. Because the human body completely absorbs most fish-borne mercury, researchers concluded that it is easily possible to consume more than the safe limit in a single meal. These results are alarming, and the threats to the local environment and human health are growing.

An estimated 300 people now arrive in Madre de Dios each day, most of them impoverished and looking for work in informal, small-scale gold mining. These miners use mercury to amalgamate gold. By discarding polluted tailings and burning mercury off the gold amalgam, miners release an estimated 30 to 40 tons of mercury annually into the environment in Madre de Dios alone. Miners work without safety measures or even rudimentary equipment to prevent or reduce mercury pollution. Their negligence threatens the health and livelihoods of their families and friends and contaminates the fragile ecosystems through burning of mercury and improper disposal of the toxic chemical.

Mercury consumption is extremely hazardous to human health, with effects ranging from brain damage, memory loss, personality change, and tremors, to permanent developmental damage to growing fetuses. While the local population is largely aware of the potential hazards associated with mercury consumption, many residents incorrectly assume that, as mercury sinks to the bottom of rivers, only bottom-dwelling fish are contaminated. To improve local awareness, ACA has used the results of the Fernandez-Gonzalez study to create an informational video on mercury poisoning, and the researchers themselves have been featured on Peruvian television broadcasts. Residents have indicated their surprise upon learning that larger, carnivorous fish have higher concentrations of mercury.        

In response to these mounting threats, ACA is working to encourage greener mining practices and technologies that reduce the need for mercury. ACA is also promoting open dialogue between the Ministry of Environment and local stakeholders regarding mining regulations and the promotion of alternative sustainable livelihoods. One such alternative is aquaculture of native fish: in uncontaminated water, aquaculture can improve human health by providing fish with low levels of mercury, while simultaneously stimulating the local economy.