COMMENTARY — Deforestation and mercury

Deforestation, rather than mining activity, is responsible for mercury exposure among villagers living downstream from an artisanal gold mining area along the Tapaj-s River in the Amazon Basin, according to researchers from the Universit du Qubec Montral (UQAM) and Brazil’s Federal University of Par.

“To our surprise, the contamination does not seem to be caused by the mercury used in gold mining but, rather, by mercury in the soil,” says a UQAM researcher. There was no clear difference in the level of mercury exposure between villagers living 100 km downstream and those residing 300 km away from the gold mining area. Instead, mercury that appears naturally in the soil is being washed into streams and waterways through soil erosion caused by deforestation.

Mercury, as it relates to artisanal mining in the Amazon, is used to extract gold. An estimated 1 million miners use this primitive separation technique, and, in doing so, contribute to the release of 130 tonnes of mercury waste into the environment each year. Project researchers wanted to find out whether mercury contamination was affecting people living outside the immediate area of the mines and, with the support of Ottawa-based International Development Research Centre, conducted environmental health studies in villages on the Tapaj-s River.

The scientists focused their research on several villages, several hundreds of kilometers downstream from major gold mining activity. They found that the villagers regularly absorb mercury through a diet of contaminated fish.

Although the levels of exposure were below the World Health Organization threshold of 50 parts per million, villagers showed signs of diminished visual and motor control.

The team of scientists also found widespread contamination of the environment — mercury concentrations in river sediments were ubiquitous and every fish caught by researchers carried the toxin.

The research team advised villagers to eat fewer predatory fish, which have higher levels of mercury than other fish. But more long-term solutions, including slowing the rate of deforestation in the Amazon, are needed to reduce mercury levels there.

— The preceding is an excerpt from a publication of Ottawa-based International Development Research Centre.