Breast milk is no longer safe, said Alessandra Korap, a leader of the Munduruku people. In Sai Cinza, a small Munduruku community surrounded by illicit mining pits, the family of three-year-old Rany Ketlen struggles for answers. Rany cannot lift her head, suffers constant muscle spasms, and has never walked. Scientists now believe she may hold a key to unraveling one of the Amazon’s most silent and devastating crises.

Rany is one of at least 36 people in the region, most of them children, suffering unexplained neurological disorders. Preliminary findings from a landmark study led by Brazil’s public health institute Fiocruz suggest mercury contamination may be to blame — a connection that, if confirmed, would mark the first scientific proof linking illegal mining to disabilities among Indigenous communities.

Rany’s father, Rosielton Saw, has long mined for gold near the village, as his father Rosenildo did before him. Sitting outside their modest wooden home, the elder miner admits he knows the dangers of mercury — the silvery liquid used to bind tiny flecks of gold in river sediment.
But mining gives us just enough to survive, he said quietly.

The family’s meals depend on the river. They eat surubim, a carnivorous fish known to accumulate mercury, and even Rany drinks broth made from it because she cannot swallow solid food.

Across the wider Munduruku territory, health workers have documented dozens of similar cases. Yet, limited medical access and almost no neurological testing mean the full scope of the crisis remains invisible.

Now, a multi-year study — to conclude in 2026 — is tracking pregnant women and newborns to document the long-term neurological impacts of mercury exposure. Early data are alarming: in Sai Cinza, mothers’ mercury levels were five times higher than the Brazilian Health Ministry’s safety threshold, and their babies’ levels were three times higher.


Still, health guidance offers little solace. If we stop eating fish, we will starve, said Chief Zildomar Munduruku, who also works as a nurse. If we keep eating it, we get poisoned.

As world leaders prepare for COP30, the UN climate summit to be held in the Amazon next month, the crisis in Munduruku lands underscores the collision between global demand for gold and the survival of forest peoples.

President Luiz Inácio Lula da Silva has expelled thousands of miners from Indigenous territories since 2023. But experts warn that the damage is enduring — mercury does not degrade. Once released, it circulates through air, soil, and water, poisoning ecosystems and people for decades.

Even if every gold mine were shut down today, the mercury already released would linger for generations, said Paulo Basta, a Fiocruz researcher who has studied mercury contamination for more than 30 years.

Brazil’s Health Ministry says it has expanded water monitoring, trained local medics to detect mercury poisoning, and invested in clean water projects. But many scientists fear these are only stopgap measures. The humanitarian crisis unleashed by illegal mining will leave permanent scars, Basta warned.

Past studies paint a grim picture. A 2021 Fiocruz report found that two-thirds of Munduruku mothers tested carried unsafe mercury levels. Among the Yanomami people, nearly every villager examined showed toxic concentrations in their blood. As of March 2025, 546 confirmed cases of mercury contamination had been officially recorded — almost all identified by Basta’s team. That’s only the tip of the iceberg, he said.

Yet proving that mercury directly causes developmental disabilities is scientifically difficult. The Fiocruz researchers must rule out other factors such as genetic disorders, infections, and malnutrition — all prevalent in isolated Indigenous communities.


The evidence points to mercury, said Fernando Kok, a geneticist at the University of São Paulo involved in the study. But in medicine, correlation is not causation — and mercury leaves no fingerprints.

Indeed, tests showing mercury in a person’s body reflect only recent exposure; they cannot capture contamination during pregnancy or early development. It’s a perfect crime, Kok said, because it leaves no signature.

In Sai Cinza, nurse Cleidiane Carvalho has spent years connecting families like Rany’s with researchers, fearing their suffering would otherwise remain invisible. This disease — if you don’t look for it, you won’t find it, she said. Without these studies, the crisis will stay silent, neglected forever.

For the Munduruku, the poison has already seeped into their rivers, their food, and their blood. Now, it threatens their future — a tragedy that, like the mercury itself, will not fade with time.