Bananas and Cassava May Carry Heavy Metals in Areas Affected by Brazilian Mining Disaster
Researchers have discovered potentially toxic metals accumulating in bananas, cassava and cocoa grown in soil contaminated by the Fundão tailings dam collapse in Brazil. While the risk to adults appears low, the study highlights a potential health hazard for young children consuming bananas grown in the affected region.
The research, conducted by teams from the University of São Paulo (USP), the Federal University of Espírito Santo (UFES), and the University of Santiago de Compostela, focused on the Doce River estuary in Linhares, Espírito Santo, an area heavily impacted by iron mining waste following the dam disaster. The soil in this region contains elevated levels of cadmium, chromium, copper, nickel, and lead – all elements associated with iron oxides, the primary component of the mining tailings.
How Metals Move From Soil to Food
The study, published in Environmental Geochemistry and Health, details how plants absorb these potentially toxic elements (PTEs) from the contaminated soil and store them in edible tissues. Researchers examined the levels of these metals in various parts of the plants – roots, stems, leaves, and fruits – to understand how they move through the plant and ultimately into the human food supply.
“First, we need to know which elements are there and in what quantities in order to understand the biochemical dynamics of their release,” explained Tiago Osório, an agronomist and professor at the University of São Paulo.
The team found that in bananas and cassava, most PTEs accumulated in the roots and tubers. Cocoa, however, showed elevated levels in stems, leaves, and the pulp of the fruit. Notably, copper and lead concentrations in cocoa pulp exceeded limits set by the Food and Agriculture Organization of the United Nations (FAO).
Risk Assessment: Children More Vulnerable
To assess the potential health risks, the researchers calculated risk quotients (RQ), risk indices (RI), and total risk indices (TRI) for both children under six years of age and adults over 18. The TRI helps determine the potential for non-carcinogenic health effects from exposure to PTEs, with a value below 1 indicating low risk.
For most metals, the TRI values were below 1, suggesting minimal risk for adults consuming these foods. However, the TRI for bananas exceeded 1 for children, raising concerns about potential health impacts. Elevated lead levels were identified as the primary driver of this increased risk, with cadmium concentrations in bananas also surpassing FAO recommendations.
“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,” said Tamires Cherubin, a health sciences Ph.D. And co-author of the study.
Researchers emphasize that even low levels of lead exposure can have lasting effects on brain development in children, potentially lowering IQ and contributing to attention and behavioral problems.
Long-Term Exposure and Potential Cancer Risk
The study also cautions that long-term consumption of food grown in contaminated soil could lead to cumulative health 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,” Cherubin explained. This genetic damage could potentially increase the risk of cancers affecting the central nervous system, gastrointestinal tract, and blood-forming tissues.
The researchers acknowledge that the bioavailability of these elements – how readily the body can absorb and utilize them – plays a crucial role in determining the extent of health risks. Short-term effects of exposure can include skin irritation, eye problems, kidney and heart issues, gastrointestinal discomfort, and lung damage if inhaled.
Ongoing Research and Monitoring
The research builds on years of investigation into the impacts of the dam collapse. Researchers began collecting samples just seven days after the accident, recognizing the immediate risk of contamination to the surrounding environment. The current study represents a critical step in understanding the long-term consequences of the disaster and protecting public health.
Amanda Duim, the lead author of the study and a doctoral candidate at USP, received recognition for her work in , earning both the USP Thesis Award in Sustainability and the Capes Thesis Award from the Brazilian Ministry of Education. Her research has resulted in seven international publications.
While the findings highlight a potential risk, researchers stress the importance of continued monitoring and further investigation to fully understand the extent of contamination and develop strategies to mitigate its impact on the health of local communities.
