Researchers have found elevated levels of toxic metals like lead and cadmium in bananas grown in soil contaminated by Brazil's 2015 Fundão dam collapse. The study highlights potential health risks for children under six who consume these bananas. While adults face lower immediate threats, long-term exposure could pose cumulative dangers.
In November 2015, the Fundão tailings dam collapsed in Mariana, Minas Gerais, Brazil, releasing iron mining waste that reached the Doce River estuary in Linhares, Espírito Santo. 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 in Spain examined crops in this affected area, focusing on bananas, cassava, and cocoa.
The researchers analyzed levels of cadmium, chromium, copper, nickel, and lead in soil and plant tissues. Their work, published in Environmental Geochemistry and Health in 2025, revealed that these potentially toxic elements (PTEs) from the mining tailings are absorbed by plants. In bananas and cassava, most PTEs accumulated more in roots and tubers than in edible parts, except for chromium. Cocoa showed higher concentrations in stems, leaves, and fruits, with copper and lead in pulp exceeding limits set by the Food and Agriculture Organization of the United Nations (FAO).
Lead author Amanda Duim, whose doctoral research at USP's Luiz de Queiroz College of Agriculture began in 2019, explained the transfer process: "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."
Health risk assessments used metrics like the total risk index (TRI), factoring in consumption data from the Brazilian Institute of Geography and Statistics (IBGE), body weights, and exposure durations. For adults over 18, TRI values were below 1 for most metals, indicating low non-carcinogenic risk. However, for children under six, the TRI for bananas exceeded 1, driven by lead levels above 0.8-2.3 mg/kg and cadmium surpassing 0.05 mg/kg in fruits.
Tiago Osório, a professor at USP, noted the ongoing study: "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."
Tamires Cherubin, a co-author, cautioned: "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."
The team warns of potential long-term effects, including kidney, heart, and neurological issues from lead, and possible carcinogenic risks over a 75-year lifespan due to DNA damage. Short-term concerns involve gastrointestinal, lung, skin, and eye problems.
