“Many women end up losing their children,” says Alessandra Korap, a community leader of the Munduruku people from the Brazilian Amazon.
“Either they can’t get pregnant, or they lose their [foetus] over time.
“So, women are afraid of getting pregnant.”
For centuries, the indigenous Munduruku have lived in an area across what is now the states of Amazonas and Para in northern Brazil, especially around the Tapajos River.
But in recent decades, villagers had been plagued by curious symptoms that they didn’t realise could be related: children unable to lift their heads, adults unable to walk any more, muscle tremors, memory loss, fading hearing and vision, miscarriages.
Now they are finally closing in on the cause.
The Tapajos river, their lifeblood, is laced with highly toxic mercury.
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Mercury poisoning is hard to diagnose because symptoms resemble other degenerative illnesses like Parkinson’s or Alzheimer’s, says Gabriela Arrifano, professor of mercury toxicology at the Federal University of Para.
“But there is now enough evidence to relate the signs and symptoms found in people exposed to mercury.”
And they have no doubts about where it’s coming from.
“We have robust evidence that mercury emissions to the environment comes from illegal gold mining activity,” says Prof Arrifano in her university lab, where she analyses hair and blood samples.
When researchers began studying the symptoms, Alessandra “didn’t know what mercury was”, she says.
Hand in hand with drugs
In Brazil, gold mining is outlawed in indigenous territory.
Yet swathes of it are pockmarked with red and orange craters from illicit gold projects – a trend fuelled by record-high prices around the world.
The underground trade works hand in hand with organised crime groups, sharing the same makeshift runways and roads through the Amazon rainforest, and using the gold to launder drug money.
The gold, once locked in the mountainside of the Andes, was gradually washed away by ancient rain into the Amazon basin.
To extract it, illegal miners churn up the riverbed and combine it with mercury because it binds to gold.
The process releases mercury into the air, water and soil.
Over time, the mercury coursing through the waterways accumulates in river fish, which indigenous communities eat for breakfast, lunch, dinner.
One study found one in five fish in markets in northern Brazil had dangerous levels of mercury (0.5 micrograms per gram).
Once in the guts, it enters the bloodstream and makes its way to the brain, where it can cause lesions.
Even low levels of exposure can disrupt most of the body’s systems, whether reproductive, skin, or nervous systems.
Prof Arrifano says people’s visual field shrinks so they lose their peripheral vision. “And then you can imagine this is very hard for people who live in the forest that need their complete senses.”
The Munduruku have been fending off mining on their land since 1960s, Alessandra tells Sky News in Para’s state capital Belem, as the city hosted international climate talks.
Her symptoms aren’t so bad. “I feel tingling in my hands, brain fog, forgetfulness, that is because of the mercury.”
But her niece can’t walk or talk.
Alessandra suspects it’s got something to do with the girl’s grandfather being a fisherman.
“So maybe because of this, the mother ended up ingesting a lot of mercury in her body that went to the child.”
The toxic metal also accumulates in placentas, breast milk and children, often two or three times the safe threshold for pregnant women.
One study across all of Brazil identified 668 cases of mercury poisoning, but that’s thought to be a vast underestimate due to poor data collection and lack of access to healthcare.
How global gold prices fuel the problem
The current administration under President Luiz Inacio Lula da Silva has been attempting a widespread crackdown on illegal mining.
Its environmental protection agency, IBAMA, swoops in by helicopter, blows up equipment, torches makeshift buildings and flies out again.
It has also frozen assets and ended the presumption of “good faith” – that gold for sale was extracted from lawful sights.
In the Yanomami Indigenous Territory in the far north, federal government figures show a 94% reduction in active illegal mining areas between 2023 and 2025.
But some of these miners have set up camp elsewhere, and the ever-soaring price of gold is making it “harder” to combat, one of Brazil’s top officials admits.
“We thought that the amount would be reduced, and initially it did,” Adalberto Maluf, national secretary for water resources in the environment ministry, overseeing the crackdown, tells Sky News in Belem.
“But I think it’s not going as fast as we wanted, or we thought it could happen, mainly because the price of gold continues rising.”
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The problem is not unique to Brazil, but common across South America and parts of Africa.
Prices are surging as investors seek security from market turbulence and geopolitical tensions – upping the incentive for miners despite the risks, says Julia Yansara from the Financial Accountability and Corporate Transparency Coalition.
“It is driving illegal gold miners into new areas. And it’s driving new criminal groups to get involved in this for the first time.”
‘If we don’t fight, we are crushed’
The Munduruku were formerly known as an aggressive group, feared by neighbouring peoples, before being fought down by colonisers who annexed their territory.
This year, they capitalised on the global attention on Brazil as it hosted the UN climate talks (COP30) to fight for their land once again.
Halfway through the conference they peacefully blocked the entrance, forcing a meeting with officials that then won them the legal rights to two further portions of territory.
When the land is demarcated, it’s easier to pressure the government to protect the land, says Alessandra.
“If we don’t fight, we are crushed, we are taken over.”
But she too knows they are fighting a rising tide.
“When the price increases, everyone wants to invade our land, to pollute the water, to destroy the forest, because they need to take the gold to sell to other countries.”
But those buyers don’t know “what is happening to our bodies, to our lives”, she adds.
