How one country is grappling with mercury emissions from artisanal gold shops

The central market was bustling in Puerto Maldonado, in the Madre de Dios region of the Peruvian Amazon. On one end of the market, diners sat on plastic stools shaded from the oppressive noon heat as food was prepared at the many open-air stands. Vegetables, fruit, and piles of locally harvested Brazil nuts were displayed nearby. Toddlers played on the ground in front of their parents’ booths.

Across the street, past a row of motorcycle taxis, more children played along the sidewalk, in front of a strip of open-front businesses advertising the purchase and sale of gold.

Such a scene is a common one in many towns in the region, which produces an estimated 15–20% of Peru’s gold exports. Worldwide, artisanal and small-scale gold mining represents about 10% of the world’s gold supply, and some 100 million people depend on such mining for survival, according to the Fairtrade Foundation, which works to promote fairer trading conditions. With gold prices currently at a historical high, miners like those in the Peruvian Amazon, many of whom come from poor Andean communities, are attracted to the sector as a means of improving their lives.

What goes unseen are the toxic emissions from the rudimentary refining taking place within the many gold shops. Shop workers use mercury to separate the gold from other minerals and then burn off the mercury to yield pure gold. Depending on how open the shops are or how equipment is vented, “when they heat the gold up, the pollution travels down the street,” says Adam Kiefer, a chemistry professor at Mercer University.

Kiefer recently headed a team of investigators working with Peru’s Ministry of the Environment to determine the levels of mercury air pollution in Madre de Dios, which is located in southeast Peru and borders Bolivia and Brazil. Peru began the program as part of its efforts to address mercury pollution from artisanal mining operations.

According to the Artisanal Gold Council, a Canadian organization working to promote environmentally sound and socially responsible gold extraction, 180 metric tons of mercury are used annually in illegal gold mining in Madre de Dios. To extract gold, workers flush truckloads of soil with pressurized water, catching heavier material in abrasive mats. They then combine the material with mercury because gold dissolves in mercury, whereas most impurities do not. The subsequent heating step sends mercury into the air; mercury also seeps out of discarded waste and contaminates soil and water.

In August 2017, the Minamata Convention on Mercury entered into force. The global treaty aims to protect human health and the environment from mercury pollution by controlling the metal’s trade and disposal. It was named after a city in Japan where, in the 1970s, children were born with severe disabilities after their mothers ate seafood contaminated with methylmercury released by a nearby factory. Mercury exposure can lead to kidney and lung problems, neurological complications, and even death. Currently, 118 countries are parties to the Minamata Convention. Those countries include China, Colombia, Brazil, and Peru, which are four of the top five artisanal and small-scale gold producers as of 2014, the most recent year for which data are available. The top producer, Sudan, has signed the treaty but not ratified it.

In the Amazon region, a 2013 study by the Carnegie Amazon Mercury Ecosystem Project showed that most people and fish tested in Puerto Maldonado had mercury levels above international health limits, and the researchers concluded that “the scope and intensity of mercury contamination by artisanal gold mining in Madre de Dios is greater than previously thought.”

When Kiefer and his team visited Madre de Dios in 2017, they found that mercury vapor levels in and around gold shops far exceeded international and Peruvian acceptable levels of exposure (Environ. Res. 2019, DOI: 10.1016/j.envres.2019.109042). In Peru’s Delta Uno and Laberinto, two towns where miners bring their gold to trade, mercury vapor topped 2 million ng/m³. Their testing documented multiple cases of gold-burning retorts’ fumes being released directly into the street or into other rooms—including where the shopkeepers lived with their families. Recondensed mercury formed droplets on surfaces in the shops.

“One of the scary things for us was when we crossed the street at one location, one of the gold shops began burning, and the emissions level went up to 1.8 million [ng/m³] on the street, and it broke our instruments”, Kiefer says. Peruvian air-quality regulations limit mercury concentrations to 2,000 ng/m³ averaged over 24 h.

Even in shops that ostensibly had ventilation systems, the setups were questionable. In one shop in Laberinto, where excessively high levels of mercury emissions were recorded even when no gold amalgam was burning, workers used a standard vacuum cleaner as an emission-extraction system—and the vacuum vented directly into the same room as the workers.

In addition to identifying levels of toxic pollution in several mining towns in the region, Kiefer’s team is helping train Peruvian Environment Ministry staff to operate measuring equipment and collect data. The effort is part of Peru’s implementation plan to meet the Minamata Convention requirements. Adopted in Peru in December 2019, the plan delegates emission monitoring to the Environment Ministry.

Camila Alva, director of pollution control and chemical substances at the ministry, tells C&EN that the ministry is developing a detailed environmental and health monitoring program. Peru plans to present it to the Minamata Convention Secretariat in August. One of the key challenges for the ministry is to find financial support to purchase its own measuring devices and hire trained personnel to collect data, Alva says.

But measuring mercury emissions is only part of the challenge. To really address mercury pollution from artisanal gold mining, miners and shopkeepers must change their practices.

In Peru, the government has long dealt with illegal artisanal gold mining through sporadic bombings of mining camps. That changed in February 2019, when the government permanently stationed law enforcement personnel in La Pampa, an area that gold mining has turned from a national rain forest reserve to an environmental wasteland, to monitor gold mining and stop illegal operations.

In parallel, the government has tried to encourage miners to legalize their status. Legalization requires adhering to environmental and social standards, including reforesting mined land and using clean technology such as shaker tables—which vibrate to separate heavier particles of gold from other, lighter minerals. But that requires investing in costly equipment, and only a handful of miners have pursued legal status.

Convincing people to make such investments is difficult. Artisanal gold mining is “not about getting rich,” Kiefer says, noting that the practice of using mercury is passed down through families.

Kiefer does not see an easy way to replace mercury for the average miner in Peru and elsewhere without national legislation and enforcement to limit mercury emissions. “This is a major issue and will continue to be an issue, especially throughout Central and South America,” he says. “It is complex.”

Monika Stankiewicz, the executive secretary of the Minamata Convention Secretariat in Geneva, echoes Kiefer’s view. Eliminating mercury from artisanal and small-scale gold mining is “very challenging,” she says.

Alva, the Peruvian Environment Ministry official, hopes that mercury emission data will help officials push for new laws and enforcement. “Right now, there is a lack of regulatory structures to act upon the collected data,” Alva says.

There are signs that attitudes may be changing. In 2018, Madre de Dios elected a new regional governor, Luis Hidalgo, whose campaign platform included legalization of gold mining. A year into his term, he is also hopeful that mercury pollution can be reduced. “People have to understand that there are alternatives,” he says. “We will continue to work on initiatives, which—to put it in the language of our region—means development.”

Paula Dupraz-Dobias is a freelance writer based in Switzerland.