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A devastating environmental disaster in Brazil continues to yield unforeseen consequences, with recent research revealing potentially toxic metals in bananas grown in areas affected by a 2015 mining dam collapse. The findings, published in Environmental Geochemistry and Health, suggest that children under six years of age may be at particular risk from consuming bananas cultivated in contaminated soil near the Doce River estuary.
The 2015 collapse of the Fundão tailings dam in Minas Gerais released vast quantities of iron mining waste, impacting the surrounding environment and agricultural lands. Researchers from the University of São Paulo (USP), the Federal University of Espírito Santo (UFES), and the University of Santiago de Compostela investigated the extent to which these contaminants were being absorbed by crops, specifically bananas, cassava, and cocoa. Their work focuses on the potential for human exposure to heavy metals like cadmium, chromium, copper, nickel, and lead, all linked to the iron oxides present in the mining waste.
Contamination Pathway: From Mine to Fruit
The study highlights a direct link between the presence of potentially toxic elements (PTEs) in the soil and their accumulation within edible plant tissues. Researchers discovered that plants absorb these metals from the contaminated soil and transfer them to their leaves and fruits. “The iron oxide content in the soil, which is the main constituent of the tailings, correlates with its content in the plant,” explained Amanda Duim, the study’s lead author, detailing how the team traced the movement of contaminants from the soil to the water and ultimately into the plants. The research began in 2019, initially exploring the potential of plants to help restore contaminated environments, but quickly shifted to assessing the risks to human health.
While most PTEs were found concentrated 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). This variation in accumulation patterns underscores the complexity of assessing food safety in the affected region.
Health Risks, Particularly for Young Children
A formal health risk assessment conducted by the research team revealed that, while the risk for adults appeared relatively low, bananas grown in the contaminated soil posed a potential health concern for young children. The assessment, which factored in consumption rates, body weight, and exposure duration, showed that the total risk index (TRI) for bananas exceeded 1 for children, primarily due to elevated lead levels. Cadmium concentrations in bananas also surpassed 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 demand to exercise extra caution,” said Tamires Cherubin, a co-author of the study.
Long-term exposure to even low levels of lead can have lasting effects on brain development, potentially lowering IQ and contributing to attention and behavioral problems. The researchers also cautioned that cumulative exposure over a lifetime – considering Brazil’s life expectancy of around 75 years – could increase the risk of carcinogenic effects due to potential DNA damage.
Ongoing Research and Remediation Efforts
The research team is continuing to investigate potential remediation strategies, including the utilize of native plant species capable of absorbing and removing contaminants from the soil. They found that certain native species show promise in cleaning up contaminated environments, with results already published. The study also builds on years of research following the initial dam collapse, with the team collecting samples just seven days after the disaster and recognizing the immediate risk of widespread contamination.
The findings underscore the long-term consequences of environmental disasters and the importance of ongoing monitoring and assessment of food safety in affected areas. Further research is needed to fully understand the extent of the contamination and to develop effective strategies to protect public health. The Brazilian government has faced criticism for its response to the disaster, and this latest research adds to the urgency of addressing the ongoing environmental and health challenges.
Disclaimer: This article provides informational content about health and environmental concerns and should not be considered medical or environmental advice. Consult with qualified professionals for personalized guidance.
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