The simple act of enjoying a banana could pose a hidden health risk for young children in Brazil, years after one of the country’s worst environmental disasters. New research reveals that bananas grown in areas near the Doce River, contaminated by toxic metals released from a collapsed mining dam, contain levels of lead and cadmium that exceed safe limits for children under six. The findings underscore the long-lasting and complex consequences of the 2015 Mariana disaster, and raise concerns about food safety in affected communities.
On November 5, 2015, the Fundão tailings dam, operated by Samarco Mineração S.A., failed in Mariana, Minas Gerais state, releasing between 55 and 62 million cubic meters of iron mining tailings into the Doce River watershed. The resulting environmental catastrophe impacted hundreds of kilometers of river and coastline, and continues to affect the health and livelihoods of communities downstream. Researchers are now uncovering the extent to which the disaster has infiltrated the food supply, specifically focusing on crops grown in contaminated soil.
Linking Mine Waste to Childhood Exposure
A team of scientists from the University of São Paulo (USP), the Federal University of Espírito Santo (UFES), and the University of Santiago de Compostela investigated the presence of potentially toxic elements (PTEs) – cadmium, chromium, copper, nickel, and lead – in bananas, cassava, and cocoa pulp cultivated in the Linhares region of Espírito Santo state. This area was directly impacted by the mudslide following the dam collapse. Their work, published in Environmental Geochemistry and Health, demonstrates a clear pathway for these metals to move from the mining waste into edible plants.
“The iron oxide content in the soil, which is the main constituent of the tailings, correlates with its content in the plant,” explains Amanda Duim, the study’s lead author and a doctoral candidate at USP’s Luiz de Queiroz College of Agriculture (ESALQ-USP). “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.” Researchers found that although most PTEs accumulated in the roots and tubers of bananas and cassava, cocoa pulp showed elevated levels of copper and lead, exceeding limits set by the Food and Agriculture Organization of the United Nations (FAO).
Health Risks and Risk Assessments
To assess the potential health impacts, the researchers calculated risk quotients (RQ), risk indices (RI), and total risk indices (TRI) for both children and adults consuming these crops. A TRI below 1 indicates a low risk of non-carcinogenic health effects. While the TRI values were generally below 1 for adults, the analysis revealed a concerning trend: the TRI for bananas exceeded 1 for children under six. Elevated lead levels were identified as the primary driver of this increased risk, with cadmium also contributing to the concern.
“These elements exist naturally in the environment, and we’re exposed to them in lower concentrations,” says Tamires Cherubin, a health sciences Ph.D. And co-author of the study. “But in the case of a disaster like the one in Mariana, when exposure is expected to increase, we need to exercise extra caution.” Long-term exposure to even low levels of lead can have lasting consequences for brain development, potentially lowering IQ and contributing to attention and behavioral problems, researchers note.
Beyond Bananas: Long-Term Concerns and Ongoing Research
The study also highlights the potential for cumulative effects over time. Researchers caution that continued consumption of food grown in contaminated soil over decades could increase the risk of cancer due to potential DNA damage. “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,” Cherubin explains. The body’s ability to absorb and metabolize these elements will play a crucial role in determining the long-term health outcomes.
The research builds on years of investigation into the impacts of the dam collapse. Tiago Osório, an agronomist and professor at ESALQ-USP, recalls that his team recognized the potential for widespread contamination immediately after the disaster. “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?”
Amanda Duim’s doctoral work, which forms the basis of this study, has already garnered significant recognition, including the USP Thesis Award in Sustainability and the Capes Thesis Award from the Brazilian Ministry of Education. Her research also explored the potential of native plant species to support restore contaminated environments, identifying several that could aid in the cleanup process.
Brazilian authorities have not yet issued specific guidance regarding the consumption of locally grown produce in the affected areas. The researchers emphasize the need for further studies to fully evaluate the potential health effects of metal exposure and to implement effective remediation strategies. The Brazilian Institute of Geography and Statistics (IBGE) data on local food consumption patterns were used to inform the risk assessments, but ongoing monitoring and public health interventions will be critical to protecting vulnerable populations.
The findings serve as a stark reminder of the enduring consequences of industrial disasters and the importance of proactive environmental monitoring and food safety measures. The next step, researchers say, is to expand the scope of the study to include a wider range of crops and to assess the effectiveness of potential mitigation strategies.
Have you been affected by the Doce River disaster? Share your thoughts and experiences in the comments below.
