Researchers from the University of São Paulo (USP), the Federal University of Espírito Santo (UFES) in Brazil, and the University of Santiago de Compostela in Spain studied crops grown in soil contaminated by the catastrophic Fundão tailings dam collapse near the Doce River estuary in Brazil in 2015. They examined bananas, cassava, and cocoa pulp cultivated in the affected soil for toxic metals linked to mining waste, including cadmium, chromium, copper, nickel, and lead. The study found evidence that these potentially toxic elements (PTEs) are being absorbed into edible parts of the plants, with bananas showing levels that could pose a potential health risk, especially to children under six years old. Adults were found to face a lower immediate danger, though scientists caution that long-term exposure may carry cumulative health consequences.
The research, published in Environmental Geochemistry and Health, is part of doctoral work by Amanda Duim at USP. Her research linked how iron oxide — the primary component of the mining tailings — facilitates the movement of PTEs from contaminated soil into crops. Samples of soil and plant tissues were analyzed using laboratory dissolution and weighing techniques to quantify metal concentrations in different plant parts. In bananas and cassava, most toxic metals were higher in roots and tubers, while cocoa plants had elevated amounts in stems, leaves, and fruit. Some cocoa pulp samples contained copper and lead levels above standards set by the Food and Agriculture Organization of the United Nations (FAO).
The team conducted formal health risk assessments calculating risk quotients (RQ), risk indices (RI), and total risk indices (TRI) for both children (under six) and adults (over 18). While TRI values for most metals remained below 1 — indicating low non-carcinogenic risk — the TRI for children consuming bananas exceeded 1, driven primarily by elevated levels of lead and cadmium surpassing recommended daily intake limits. Researchers highlighted that chronic lead exposure, even at low concentrations, can impair brain development, lower IQ, and contribute to behavioral issues.
Scientists also warned about possible long-term carcinogenic risks from extended exposure. Although these elements occur naturally in the environment, the disaster likely increased local concentrations. Over many years, DNA damage associated with such exposures could raise the risk of cancers affecting the nervous system, digestive tract, and blood-forming tissues. The researchers urge caution for communities consuming locally grown crops from contaminated soils and emphasize the need for ongoing monitoring and remediation efforts.