Minamata Convention aims to reduce global mercury pollution, but may have shifted hazards toward South America’s artisanal mines.
By David J.X. Gonzalez
Highway 120 bisects the Sierra Gorda Biosphere Reserve, snaking through the scrubby terrain of central Mexico’s highlands. Along the way it passes through Peñamiller, a sparse municipality with a few thousand residents. The local economy depends on production from agriculture and mines. A dusty offshoot from the highway leads to one such mine – a cinnabar mine, with tunnels plunging hundreds of meters into the mountainside. Miners process ore in rows of wood-fired brick ovens arranged near the mouths of the tunnels. The homebuilt ovens heat the rocky material, releasing mercury vapors that are captured, condensed, and bottled. Under a cloudless sky, with few trees for shade, the workers wear t-shirts and cover their mouths with bandanas, their only protective equipment. However, the cloth does not protect from mercury vapors, which enter the body through the lungs and cause irreparable damage to the brain and kidneys. Children live in nearby houses and sometimes play in the tailings, breathing in the mercury. This is a toxic site.
Evidence points to an emerging black market for mercury in South America, where most of Mexico’s mercury ends up. Artisanal miners in Peru, Colombia and Bolivia buy mercury and use it to extract gold under similarly hazardous conditions. Artisanal and small-scale gold mining, done by individuals or small groups with limited capital, is the largest human source of mercury pollution, accounting for over one-third of global emissions. It is also a large driver of global mercury demand. The changing landscape of mercury production and trade in Latin America, and the associated hazards, may be an unintended consequence of the global effort to regulate the toxic metal.
The Minamata Convention on Mercury, a UN a treaty that aims to reduce global mercury pollution, was adopted and opened for signatures in 2013. The convention prohibits the opening of new mercury mines, requires existing mines to close within 15 years, and encourages nations to reduce or eliminate mercury use in artisanal gold mining. However, demand persists and millions of miners in low- and middle-income countries in Latin America and elsewhere continue to use mercury.
Peru is the largest gold producer in Latin America, with a highly active artisanal gold mining sector concentrated in the Amazonian region of Madre de Dios. A recent study found that the rate of expansion of gold mines in Madre de Dios increased from 2013 to 2016, following a wave of government action that had reduced mining activity. By 2016, more than 650 square kilometers of rainforest had been cleared for gold mining, an area larger than the city of Chicago and an increase of 40 percent since 2012. There is also evidence of widespread human mercury exposure in Madre de Dios. Last year, Duke University researchers reported high mercury levels in communities throughout the region.
There is a long history of global mercury trade for mining precious metals, with a recent shift to production from high- to middle-income countries. In 2003, the world’s largest mercury mine in Almaden, Spain, shut down after two millennia of service. Over the course of its long life, Almaden produced one-third of all mercury used throughout human history, from the cinnabar that Romans applied as red pigment to liquid mercury used to make century industrial chemicals. Sometime in the 16th century, Spanish colonizers began bringing mercury from Almaden to the Americas, where it was used to enhance yields of the silver and gold that fueled the imperial economy. Eventually, mercury lost its value as safer alternatives were found for its many applications, including mining precious metals. The price of mercury dropped from a high of $80,000 per ton in the 1960s to $5,000 in 2000. By the turn of the 21st century, mercury extraction at Almaden was no longer profitable. Mercury exports from Spain continued for another 10 years. At the start of this decade, Spain and the United States were leading mercury exporters. However, the European Union banned mercury exports in 2011, followed by the United States in 2013. To meet demand, Indonesia and Mexico increased exports and became the leading exporters in 2016.
Recent trends in international mercury trade point to changes on the ground. Peru tightly regulates domestically-produced mercury, prohibiting its use in mining, but imported mercury can be used for mining. Peru imported at least 100 tons of mercury each year from 2010 to 2014. About half of Peru’s mercury imports ended up in Madre de Dios, where artisanal gold miners use an estimated 44 to 50 tons of mercury each year. Peru stopped importing mercury in 2015. However, despite the suspension of mercury imports, there are no indications that artisanal miners have stopped using mercury.
Mercury may be passing from Mexico to Peru by way of Bolivia through an emerging black market. Mexico became the leading mercury supplier to Peru in 2012 as imports from Europe and North America decreased. Mexico remained the leading supplier until Peru stopped importing mercury in 2015. However, as exports from Mexico to Peru decreased, exports from Mexico to Bolivia rose. Between 2014 and 2015, exports from Mexico to Peru dropped from 94 to 9 tons. In the same period, exports from Mexico to Bolivia jumped from 24 to 138 tons. Artisanal gold mining activity in Bolivia has increased during the past decade, but a six-fold increase in one year is unlikely. There is also evidence of transnational mercury smuggling. In August 2015, for example, Peruvian authorities seized an illegal shipment of more than 1 ton of mercury near the Bolivian border.
Continuing demand for mercury and the suspension of exports from high-income countries is driving unsafe mining in Mexico with consequences for human health. Mexican mercury exports increased from 25 to 266 tons between 2010 and 2016. There is little data on the health effects of mercury mining in Mexico, but the studies that exist raise concerns. Researchers found heavy mercury exposure among residents of Plazuela, another mining community in the Sierra Gorda Biosphere Reserve. Children as young as 6 years old had mercury exposure above the national limit. Unfortunately, the results from Plazuela are likely not isolated, and Mexico has numerous artisanal mercury mines.
The apparent rise of a black market for mercury in Peru reveals a challenge for enforcing the Minamata Convention. The Minamata Convention provides a blueprint to reduce mercury pollution in the coming years. In the meantime, the mercury supply chain in Latin America remains toxic, from end to end.
David Gonzalez is pursuing a PhD in the Emmett Interdisciplinary Program in Environment and Resources at Stanford University.
The World Health Organization describes the hazards of mercury pollution and poisoning.
