The team focused on bananas, cassava, and cocoa pulp cultivated in soil affected by the disaster. They examined levels of cadmium, chromium, copper, nickel, and lead, metals linked to iron oxides, which are the primary component of the tailings. Their findings suggest that eating bananas grown in contaminated soil may present a potential health risk for children six years old and younger.

“Our group has been studying the impacts of the dam collapse for years. We obtained the first samples seven days after the accident and immediately understood that there was an imminent risk of contamination of plants, soil, water, and fish. But the question remained: Does this contamination pose a risk to human health?” recalls Tiago Osório, an agronomist and professor in the Department of Soil Science at the Luiz de Queiroz College of Agriculture at the University of São Paulo (ESALQ-USP).

The study, published in Environmental Geochemistry and Health, explains how plants absorb potentially toxic elements (PTEs) from mining waste and store them in edible tissues. It also outlines how these substances can move into the human food supply. The research forms part of Amanda Duim’s doctoral work at ESALQ. Her thesis has produced seven international publications and earned two major awards in 2025: the USP Thesis Award in Sustainability and the Capes Thesis Award, granted by the Brazilian Ministry of Education’s Coordination for the Improvement of Higher Education Personnel (CAPES). Duim received support from FAPESP through a doctoral scholarship.

How Contaminated Soil Transfers Metals Into Plants

Duim, the study’s lead author, says the research stands out because it directly links human health risk to the movement of PTEs from soil into crops. “The iron oxide content in the soil, which is the main constituent of the tailings, correlates with its content in the plant. We studied the passage of constituents from the tailings in the soil to the water, and then from the water to the plant, including its leaves and fruits.”

“First, we need to know which elements are there and in what quantities in order to understand the biochemical dynamics of their release,” Osório explains.

Duim began her doctoral research in 2019 by exploring whether plants from flood-prone areas could help restore contaminated environments. She evaluated both cultivated crops and native species. “We evaluated cultivated and native species. In the case of the latter, we wanted to know how they affect the dissolution of iron oxide and, in this process, understand if and how the PTEs associated with this waste enter the plant, since different species accumulate PTEs differently,” she says. “The idea was to find the best native species for cleaning up contaminated environments, and we found more than one species that can fulfill this function, with results already published. In the case of cultivated species, we wanted to know if PTEs would be transferred to the fruits and edible parts of the plants.”

To measure contamination, the researchers carefully collected soil and plant samples. They washed and weighed the fresh plants, then dried them and weighed them again. Roots, stems, leaves, and peeled fruits were ground separately for analysis. “We dissolved the ‘plant powder,’ transforming it into a solution using various acids, and determined the concentration in the solution. We converted the calculation of the concentration of material in the solution and compared it with the weight of the diluted material, thus obtaining the PTE concentration in milligrams per kilogram of dry biomass,” Duim describes.

In bananas and cassava, nearly all PTEs except chromium were found in higher amounts below ground, in roots and tubers. Cocoa behaved differently, with elevated levels in stems, leaves, and fruits. In cocoa pulp, copper and lead concentrations exceeded limits set by the Food and Agriculture Organization of the United Nations (FAO).

When the team discovered that some edible portions contained PTE levels above recommended standards, they conducted a formal health risk assessment.

Health Risk Assessment for Children and Adults

The scientists calculated the risk quotient (RQ), risk index (RI), and total risk index (TRI) for people consuming bananas, cassava rhizomes, and cocoa pulp. They evaluated children (under six years of age) and adults (over 18 years of age) separately. The RQ compares a person’s estimated daily intake of a substance to a reference dose considered safe. The TRI helps determine potential non-carcinogenic health risk from exposure to PTEs. A TRI below 1 indicates low risk.

“These elements exist naturally in the environment. We’re exposed to them in lower concentrations. But in the case of a disaster like the one in Mariana, when exposure is expected to increase, we need to exercise extra caution,” says Tamires Cherubin, a health sciences Ph.D. and co-author of the study. Standard methods evaluate how bioavailable these elements are, since certain concentrations can lead to kidney and heart problems, gastrointestinal discomfort, and lung damage if inhaled. Short-term effects may also include skin irritation and eye problems.

The researchers factored in how much locally grown food residents consume, using data from the Brazilian Institute of Geography and Statistics (IBGE). They also considered how long individuals might be exposed, differences in body weight between children and adults, and the time required for harmful effects to develop.

“According to the reference daily intake doses for contaminants covered by the literature, we consider the limits of 0.05 mg/kg^-1 for the presence of cadmium in fruits and 0.1 mg/kg^-1 in tubers, 0.5-1.0 mg/kg^-1 for the presence of chromium, 20.0 mg/kg^-1 for copper, 0.5-1.0 mg/kg^-1 for nickel, 0.8-2.3 mg/kg^-1 for lead, and 50.0 mg/kg-¹ for zinc,” Cherubin explains.

For most metals, TRI values were below 1, indicating no significant non-carcinogenic risk for adults consuming these foods from the Doce River estuary. However, the TRI for bananas exceeded 1 for children, signaling possible health concerns. Elevated lead levels were the primary driver, and cadmium concentrations in bananas also surpassed FAO recommendations. The researchers note that long-term exposure to lead, even at low levels, can permanently affect brain development, potentially lowering IQ and contributing to attention and behavioral problems.

Long-Term Cancer Concerns and Ongoing Exposure

The team cautions that eating food grown in contaminated soil over many years could lead to cumulative effects. “Over time, considering the life expectancy in Brazil of around 75 years, there may be a carcinogenic risk since there’s a possibility of direct and indirect DNA damage,” says Cherubin. Such genetic damage may increase the likelihood of cancers affecting the central nervous system, digestive tract, and blood-forming tissues. “It all depends on the human body’s ability to absorb and metabolize these elements that are available in the environment,” she adds.

The work builds on a fresh investigation of a famous Upper Paleolithic burial discovered in 1963 at Grotta del Romito in southern Italy. For decades, the site intrigued scientists because of unusual skeletal traits and the way the two individuals were laid to rest. Researchers long questioned how the pair were related and whether a medical condition explained their short stature.

Ice Age Double Burial Raises New Questions

The two individuals were buried in an embrace. “Romito 2,” a young person with notably shortened limbs who was once believed to be male, rested in the arms of “Romito 1,” thought to be an adult female. There were no signs of injury. Romito 2 stood about 110 cm (3’7″) tall, a height consistent with a rare skeletal disorder called acromesomelic dysplasia, although bones alone could not confirm that diagnosis. Romito 1 was also shorter than average for that time period at roughly 145 cm (4’9″). Over the years, experts debated their sex, their relationship, and whether the same condition might explain both of their statures.

To investigate further, scientists extracted ancient DNA from the petrous portion of the temporal bone in both skeletons, an area known for preserving genetic material. The results showed the two were first-degree relatives. The team then examined genes involved in bone growth and compared the detected variants with modern medical data. This collaborative effort brought together paleogenomics, clinical genetics, and physical anthropology, with researchers from the University of Vienna working alongside colleagues in Italy, Portugal, and Belgium.

Earliest Known Genetic Diagnosis in Humans

Genetic testing revealed that both individuals were female and closely related, most likely a mother and daughter. In Romito 2, researchers found a homozygous mutation in the NPR2 gene, which plays a key role in bone development. This provided clear evidence of acromesomelic dysplasia, Maroteaux type — a very rare inherited disorder characterized by severe short stature and significant shortening of the limbs.

Romito 1 carried a single altered copy of the same gene. That genetic pattern is associated with a milder form of short stature, explaining the difference in height between the two women.

Rare Genetic Diseases Deep in Human History

Ron Pinhasi, University of Vienna, who co-led the study says: “By applying ancient DNA analysis, we can now identify specific mutations in prehistoric individuals. This helps establish how far back rare genetic conditions existed and may also uncover previously unknown variants.”

Daniel Fernandes of the University of Coimbra, first author of the study, adds: “Identifying both individuals as female and closely related turns this burial into a familial genetic case. The older woman’s milder short stature likely reflects a heterozygous mutation, showing how the same gene affected members of a prehistoric family differently.”

The findings underscore that rare genetic diseases are not limited to modern populations. Adrian Daly of Liège University Hospital Centre, a co-leader of the study, notes: “Rare genetic diseases are not a modern phenomenon but have been present throughout human history. Understanding their history may help recognising such conditions today.”

Evidence of Social Care in the Ice Age

Despite serious physical challenges, Romito 2 lived into adolescence or adulthood. Her survival suggests she received consistent support from her community. Alfredo Coppa of Sapienza University of Rome, who also co-led the study, says: “We believe her survival would have required sustained support from her group, including help with food and mobility in a challenging environment.”

Key Findings

• Ancient DNA analysis revealed that two individuals buried together in southern Italy were closely related — most likely mother and daughter.
• In the younger individual, two altered copies of the NPR2 gene confirmed acromesomelic dysplasia (Maroteaux type), a condition marked by severe short stature and pronounced limb shortening; the older individual carried one altered copy linked to milder short stature.
• The findings show that rare genetic diseases were already present in prehistoric populations and can now be studied using paleogenomics.
• The younger individual’s survival despite severe physical limitations suggests sustained care and social support within her community.