Brazil tackles illegal miners, but finds their mercury legacy harder to erase

Brazil tackles illegal miners, but finds their mercury legacy harder to erase

  • As the details of the humanitarian crisis in the Yanomami Indigenous Territory unfold amid action to remove illegal miners, mercury left by the rampant gold mining in the area will remain a lingering toxic legacy.
  • A range of solutions is needed to support communities at risk, monitor the situation, assist in the remediation of forests, and prevent continued pollution, experts say.
  • New technologies that can filter mercury are under development and testing, but are still far from being viable solutions at the scale that the problem inside the Amazon calls for.

In 2015, researchers in Brazil started a project to address a tricky challenge: Reducing exposure to mercury contamination in the region of the Tapajós River, a major tributary of the Amazon. Artisanal miners use the heavy metal to separate gold from ore, then burn it off. The waste mercury then ends up in the air, vegetation and water. In bodies of water like the Tapajós, it undergoes a transformation into methylmercury, a toxic substance that can move up the food chain, concentrating in carnivorous fish. For residents of this northern area of Brazil’s Pará state, fishing is an important source of food.

The Tapajós Basin has been plagued by illegal mining and mercury pollution for decades. That’s why the researchers at Pará Federal University (UFPA) started working with villagers to raise awareness of the dangers of mercury and help manage their exposure, principally by reducing their consumption of potentially contaminated fish. The researchers used learning sessions and local radio to share information about the health risks associated with mercury. Participants in the project also helped to spread the word among other community members. Similar interventions have also proved successful in the past as a short-term solution to address mercury exposure.

Of 34 participants whose hair samples were tested in consecutive years during the project, more than half showed reduced exposure to mercury. Though a small sample, the researchers say it indicates that such knowledge-sharing initiatives can be effective to reduce exposure.

“We need to provide knowledge to local communities about the mercury problem,” Gabriella Arrifano, a visiting professor at UFPA who worked on the project, told Mongabay by phone. The accumulation of mercury in organisms higher up the food chain, known as biomagnification, means carnivorous fish have much higher concentrations of mercury than other species. So “by eating those with less mercury, we can try to make an equilibrium with the amount of exposure,” Arrifano said.

Communities living alongside rivers can be at particular risk of mercury exposure, studies show, due to bioaccumulation and biomagnification of methylmercury in the fish species they eat. Support to change diets, using consultative and culturally sensitive approaches, are needed, say experts. Image courtesy of Gabriela Arrifano.

Indigenous and riverine communities are struggling with mercury contamination in parts of the Brazilian Amazon. Exposure can have harmful and toxic effects on the nervous, digestive and immune systems, lungs, kidneys, skin and eyes. The metal is in the top 10 list of chemicals of major public health concern, according to the World Health Organization. The substance also plays a major role in the recent health crisis in the Yanomami Indigenous Territory.

Established in 1992 and covering an area larger than Portugal, the Yanomami territory is home to some 30,000 Indigenous people, who in recent years have suffered waves of violence, disease and malnutrition linked to illegal mining. Under the presidency of Jair Bolsonaro, from 2019 to 2022, more than 20,000 illegal miners are thought to have invaded the territory. Mining in Indigenous lands is forbidden in Brazil under any circumstances, yet Bolsonaro was vocal in his support for opening up these lands to mining and other extractive activities. As a member of Congress, he’d tried repeatedly to overturn the demarcation of the Yanomami territory.

Past studies in Indigenous villages have established a connection between gold mining activities and mercury exposure, a scenario that has played out across the Amazon for decades. The highest incidences of mercury exposure among Indigenous peoples are found in areas where gold mining occurs.

After Luiz Inácio Lula da Silva became president at the start of 2023, his administration acted to expel the illegal miners from the Yanomami land. Many already fled, but the mercury they used will remain in the soil, rivers, fish and animals.

Experts say it’s no easy task to clean an area contaminated by mercury. But Luis Fernandez, executive director of the Center for Amazonian Scientific Innovation (CINCIA), said he agrees that the kind of approach taken by the UFPA researchers in their Tapajós project is necessary to support Amazonian communities who are highly dependent on fish and thus at elevated risk for mercury exposure. “That requires education, awareness raising, and finding culturally appropriate ways to suggest changing diets to basically decouple people from the pollution in the environment,” Fernandez told Mongabay by phone.

It’s just one of a suite of possible solutions to manage mercury pollution left from gold mining activities, experts say. In the absence of a quick fix, surveillance of the problem, management, and support for communities most at risk are all urgently needed.

Maria Elena Crespo-López and her colleagues with school children.
As part of a project to support Indigenous Amazonian communities, Maria Elena Crespo-López and her colleagues carried out educational activities in communities. Image courtesy of Maria Elena Crespo-López/UFPA Laboratory of Molecular Pharmacology.

A ‘tricky’ problem

Often used in small-scale or “artisanal” mining activities to separate gold from other materials, mercury’s release into remote areas reverberates throughout the forest ecosystem, with impacts potentially greater than often assumed. Globally, a report by the U.N. estimates more than 2,000 metric tons of mercury are used in gold mining. The metal pollutes rivers, contaminates fish, harms the health of Indigenous people, and threatens wildlife to an extent that’s not yet fully understood.

According to Brazil’s Ministry of Environment, gold mining releases between 11 and 161 metric tons of mercury annually, but these figures date from 2016 and haven’t been updated to reflect the surge in illegal mining during the Bolsonaro years.

The proliferation of mercury comes despite Brazil being a signatory to the Minamata Convention, an international treaty designed to protect human health and the environment from mercury pollution. The convention states that countries must “take steps to reduce, and where feasible eliminate, the use of mercury and mercury compounds in, and the emissions and releases to the environment of mercury” from artisanal mining.

It also provides guidance on managing sites contaminated by mercury due to small-scale illegal gold mining, underlining that the issue is “challenging to manage and remediate.” Management efforts include assessing the site, removing mercury pools, developing engagement programs with local communities, and taking steps to decontaminate soil and sediment, where feasible due to costs.

In remote and difficult-to-access areas, technology used to address industrial-scale pollution “may therefore need to be adapted to permit smaller, modular, transportable and environmentally sound technologies to be brought to the contaminated site to treat the contaminated materials,” it says.

Biomonitoring as a first step allows for an assessment of the scale of the contamination and identification of key hotspots of risk, according to Arrifano and Maria Elena Crespo-López, head of the molecular pharmacology lab at UFPA. They add there also needs to be professional medical assistance for people living in high-risk areas.

“The problem of mercury [in the Amazon] is really tricky, so things that have been done previously in other countries are difficult to apply here,” Arrifano said. “We need to find tailored solutions for the Amazon and first of all we need to know how big the problem is.”

Rivers in the state of Roraima, inside the Yanomami Indigenous Territory, can become contaminated.
Illegal gold mining in the Amazon is thought to use hundreds of tons of mercury. Rivers in the state of Roraima, inside the Yanomami Indigenous Territory, can become contaminated, putting people and wildlife at risk. Image courtesy of Fernando Frazão/Agência Brasil.

Fixing mercury with nature?

Research from a protected area in Peru and published last year shows that mercury released from gold mining becomes fixed in forests, with substantial “accumulation in soils, biomass, and resident songbirds.”

“Mercury is a legacy contaminant, which means that once it’s entered into any ecosystem, it’s going to take centuries to go away,” said Jacqueline Gerson, a watershed biogeochemist at Michigan State University and first author of the paper. She said that in the United States, historical gold mining has left a mercury problem that lingers to this day. Importantly, however, the amount of methylation — the conversion of elemental mercury into the highly toxic methylmercury — is “much lower” in forests than in aquatic systems, Gerson said.

“One of the important lessons from this paper was that we need to be protecting these forests to prevent that mercury from entering the aquatic ecosystem,” she said. “In an ideal world, you protect those forests, but also move mining further away from these conservation areas — that have a huge amount of biodiversity, or Indigenous communities living in them — to begin with.”

Researchers say conserving tropical forests is potentially both a way to help tackle the mercury problem — due to their capacity to act as a sink — and avoid remobilizing fixed mercury, which can contribute to the existing burden.

“What our work is sort of pointing to is that there’s also links between forest and ecosystem conservation and the mercury problem,” Aryeh Feinberg, a postdoctoral fellow in the Institute for Data, Systems, and Society at the Massachusetts Institute of Technology, told Mongabay by phone.

Feinberg has carried out research on the capacity of the Amazon to act as a sink of atmospheric mercury; more studies are needed to better understand these connections, he said. “At least from the information that we have, there’s quite substantial pollution which is released during deforestation that has been overlooked by policy so far,” he said.

Illegal mining areas inside Yanomami land near the Mucajaí River.
Illegal mining areas inside Yanomami land near the Mucajaí River, photographed in February this year. Image courtesy of Fernando Frazão / Agência Brasil.

Mercury in the Amazon is thus part of a “complicated system,” Fernandez said, as it also occurs naturally in some parts of the Amazon forest and soils. Deforestation for agriculture, the construction of hydroelectric dams, and soil erosion can also act as additional drivers of heightened mercury pollution, by potentially mobilizing mercury that can then end up in waterways, where it then transforms into methylmercury.

This complex picture doesn’t diminish the massive impact of gold mining, Fernandez said, but it can influence potential solutions. Experts note that reforestation, though complicated in remote areas, is a potential solution to help manage mercury pollution.

It can be done to remediate mining areas, but is intensive and “extremely expensive to do it at scale,” Fernandez said. Alongside a careful selection of the appropriate tree species, his organization, CINCIA, uses biochar — a “highly stable form of charcoal” — soaked in fertilizers and with added microorganisms to help recovery in highly disturbed areas where the soil has been degraded.

“We see the recovery rate [of trees] using a ring of biochar that has these nutrients and these microorganisms really gives them the chance,” Fernandez said. “Otherwise, you’re going to have very low survivorship in some cases.”

Reforestation is important to recover the health of forests and local people, according to Jailson Bittencourt de Andrade, vice president of the Brazilian Academy of Sciences and coordinator of a working group on mercury contamination. But the mercury contamination will remain in the soil, sediment and rivers for a “very long time”, he told Mongabay by phone. “So, it’s a complex problem, it’s a multitask problem that should be attacked in a concerted way … it’s a policy problem, a health problem, and a nutrition problem.”

A machine by Scottish company SEM World.
Scottish company SEM World has developed technology that can be used either to prevent some mercury pollution during processing or remediate potentially contaminated mining waste. Image courtesy of Leigh Cassidy/SEM World.

Ending mercury use in gold mining

Stopping the pollution at the source is one of the best approaches, experts say. Expanding mercury-free mining and increasing the use of tools such as retorts, which enable miners to capture some of the mercury used and allow it to be reused rather than dispersed into the environment, are needed. Innovative capture technologies that could reduce mercury pollution are also under development.

Earlier this year, a natural filtration system developed by Scottish company SEM World won an award from Conservation X Labs, which runs a competition seeking solutions to mercury use in mining. The winning solution helps treat contaminated effluent created during the mining process using local products, thereby reducing mercury pollution and recovering leftover metals, thus providing an economic incentive for its use.

“What we do is treat the water in the tailing ponds,” Leigh Cassidy, lead scientist at SEM World, told Mongabay by phone. In testing in the Madre de Dios region of Peru, the system effectively removed 90% of the mercury in ponds, she said. “We’re focused on remediation rather than prevention. The only way to prevent it is for miners to use something other than mercury.”

For Fernandez, whose organization partnered with the Conservation X Labs for the competition, it highlights the role such technology can play in finding solutions. “It shows that there needs to be a lot of innovation, a lot of creativity in this space to solve these really intractable problems,” he said.

Amid calls for bans on the use of mercury in mining, experts say tackling illegal gold mining in protected lands is also fundamental to managing the problem.

“The main solution is to control the entry of illegal mercury into the country and stop illegal gold mining in the Amazon,” Andrade said. “The Brazilian Constitution is clear on prohibiting mining on Indigenous lands. The first step is the action of the federal government to stop and mitigate the quantity of mercury that comes into the environment.”

That, however, requires enforcement, formalization of Indigenous lands, and support for miners themselves, researchers say. Simply removing miners from these areas without addressing the factors driving the practice is likely to be ineffective in the long-term,according to UFPA’s Crespo-López. “We need to provide economic alternatives for people living in the Amazon,” she said. “There is huge potential for ecotourism or sustainable industry.”


Banner image: Illegal mining areas inside Yanomami land near the Mucajaí River, photographed in February this year. Image courtesy of Fernando Frazão / Agência Brasil.


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