August 9, 2014. Missing mercury pollution is enough for mass poisoning. NewScientist.
New data suggests that we still don’t know where our emissions of toxic mercury end up. Somewhere out there are tens of thousands of tons of missing mercury. Mercury is released by several industries and accumulates as methyl mercury in aquatic organisms. It causes brain damage and birth deformities.
Carl Lamborg of the Woods Hole Oceanographic Institution in Massachusetts has found that, since industrialization, mercury levels near the ocean surface have tripled in many places (Nature, DOI: 10.1038/nature13563). The highest rates are in cold waters around Iceland and Antarctica, where they are enough to damage marine life and threaten humans.
But the levels are much lower than expected, Lamborg says, given known emissions from coal burning, cement production, waste incineration and small-scale gold mining. He estimates the oceans contain between 60,000 and 80,000 tons of mercury, less than a quarter of the 350,000 tonnes expected (Environmental Science & Technology, doi.org/ckm949).
Where is the rest? Small-scale gold mining may be a big source, so the lost mercury could be in soils near mines, Lamborg says. Alternatively, the lost mercury could be in sediments of estuaries and coastal waters, particularly in Asia. Last month, Helen Amos of Harvard University estimated that up to 90 per cent of the mercury flowing down rivers from mining areas ends up in these sediments (Environmental Science & Technology, doi.org/t2h). If those sediments get stirred up, local mercury levels could reach those seen at Minamata, which affected thousands of people.
Lizzie Wade. 27 Sep 2013. Mercury Pollution Gold’s Dark Side. Small-scale artisanal gold mining has become the world’s leading source of mercury pollution, poisoning air, rivers, and people. Science: Vol. 341 no. 6153 pp. 1448-9
Endowed with a unique ability to extract gold from low-grade ore, mercury remains the method of choice for artisanal gold miners around the world. Often very poor, these miners work alone or in small groups, using mercury to separate and bind flecks of gold from soupy slurries of water and sediment. They are outlaws in many countries, eking out a living on the margins of the formal economy.
This diffuse industry is now the world’s largest mercury polluter, pumping more mercury into the environment than all the world’s coal-fired power plants combined. The mining operations typically leave a trail of mercury waste, putting as many as 100 million people at risk of poisoning.
The vast quantities of mercury already dumped by artisanal mining will persist in ecosystems for hundreds of years.
With gold prices soaring and as many as 15 million miners were using 1600 metric tons of the mercury in 2012 alone.
It is “an extremely daunting problem,” says Luis Fernandez, an ecologist and expert in artisanal gold mining at the Carnegie Institution for Science in Stanford, California. And the stakes are high: “Once areas are contaminated, they are contaminated for a long time.”
The process creates ample opportunity for pollution—and exposure. Miners simply dump the mercury-infused slurry, which contaminates rivers. Bacteria in the sediments help transform the inorganic mercury to organic methylmercury, which can be absorbed by phytoplankton and accumulate in fish and other creatures higher on the food chain. People who eat contaminated fish are at risk of neurological damage, autoimmune disease, and devastating birth defects. In a new study, Fernandez found that people in the Peruvian state of Madre de Dios, home to much of the country’s artisanal gold mining, have mercury levels in hair averaging 3 parts per million, triple the maximum limit recommended by the U.S. Environmental Protection Agency. “For the most part, these are people who are not miners. These are people who eat fish,” Fernandez says. Levels are even higher—more than 5 ppm—in the state’s indigenous communities, which rely on local fish for protein.
In mining towns like La Rinconada, the threat is more direct: People are exposed every time they take a breath. As gold shops in the center of town burn the mercury-gold amalgams, mercury vapor wafts into crowded neighborhoods. “In effect, some of these little towns have the equivalent of four, five, 10, 20, coal-fired power plants in the center of them,” Fernandez says. Meanwhile, mercury lifted into the upper atmosphere can travel vast distances before falling back to Earth and making its way into the global food web.
Documenting exactly how much mercury miners are using—and exactly how it is affecting people—has been a challenge. Artisanal gold mining often takes place in remote areas, and miners can be wary of scientists, whose findings could threaten their livelihoods. “We’ve been chased out of towns when we’ve tried to do surveys or a give a talk,” Fernandez says. Still, researchers are making progress. The United Nations more than doubled its estimate of mercury emissions from artisanal mining between 2008 and 2013, “mostly due to better reporting,” says Kevin Telmer, executive director of the Artisanal Gold Council in Victoria, Canada, which works to reduce mercury use in small-scale mining.
The United Nations may not have the whole picture, however. “The more you look, the more you find,” says NRDC’s Keane. A 2011 study of the air quality in and around La Rinconada’s some 250 gold shops, for instance, concluded that they could be emitting 20 metric tons of mercury per year. That’s nearly one-third of Peru’s reported annual emissions, suggesting that the official tally is a severe underestimate.
Simply banning artisanal mining—or mercury—isn’t a realistic option, specialists have concluded. “Making [artisanal mining] illegal hasn’t worked,” Keane says. It only demonizes miners and drives their activity further underground, cutting off the very resources they need to improve their practices: education, training, and credit. “You cannot deal with someone who officially doesn’t exist,” says Jacopo Seccatore, a doctoral student in mining engineering at the University of São Paulo in Brazil.