Toxic metals detected in Brazilian banana crops

Researchers examining farmland along the Rio Doce basin, where tailings from the collapse of a Samarco dam spread across hundreds of kilometres, found that toxic elements embedded in contaminated soil are being absorbed by edible plants. Bananas showed levels that could pose a health risk for children under six, while cassava and cocoa also accumulated measurable quantities of heavy metals.

The dam failure in November 2015 at the Fundão tailings facility, operated by Samarco — a joint venture between Vale and BHP — released millions of cubic metres of iron ore waste into the Doce river system. Nineteen people were killed and entire communities were displaced. The sludge travelled through Minas Gerais and Espírito Santo states before reaching the Atlantic Ocean, affecting water supplies, fisheries and agricultural land.

Scientific teams have continued to monitor soil and crop quality in affected regions, focusing on metals commonly associated with mining waste, including lead, cadmium, arsenic and manganese. Laboratory analysis of plant tissue samples indicates that certain crops, particularly bananas, can take up and store these elements in their edible portions. The findings are significant because bananas are widely consumed by children and form part of school feeding programmes in many parts of Brazil.

Health specialists warn that chronic exposure to lead and cadmium, even at relatively low concentrations, can impair neurological development in children and contribute to kidney damage and cardiovascular disease over time. Young children are considered especially vulnerable because their bodies absorb heavy metals more readily and their developing brains are more sensitive to toxic insults.

Researchers assessing dietary intake scenarios concluded that, while adult consumption patterns generally remain below thresholds associated with acute toxicity, children under six who consume bananas grown in the most contaminated plots could exceed recommended intake levels for lead. The risk is described as probabilistic rather than immediate, but the cumulative nature of heavy metal exposure has prompted calls for continued surveillance and targeted remediation.

Local authorities and federal agencies have implemented soil testing and land-use restrictions in some high-impact zones since the disaster. However, agricultural activity resumed in several communities as part of broader economic recovery efforts. Farmers dependent on banana and cassava cultivation argue that blanket bans would undermine livelihoods, underscoring the tension between food safety and income security.

Environmental scientists note that heavy metals bind strongly to soil particles but can become bioavailable depending on pH, organic matter content and plant species. Bananas, with extensive root systems and high water uptake, appear capable of absorbing certain metals from contaminated substrates. Cassava, a dietary staple in rural Brazil, and cocoa, a key export crop, also demonstrated measurable uptake, though levels varied between sampling sites.

The long-term ecological impact of the Fundão collapse remains under scrutiny. Legal proceedings and compensation negotiations involving Vale, BHP and Brazilian authorities have unfolded over several years, with billions of reais earmarked for environmental restoration and community support. Independent studies have repeatedly highlighted the persistence of contamination in river sediments and floodplain soils.

Public health experts emphasise that the presence of metals in crops does not automatically translate into a nationwide food safety crisis. Concentrations differ by location, and produce entering broader commercial markets may originate from unaffected regions. Nonetheless, the findings reinforce the need for traceability, transparent monitoring and community engagement in areas with a legacy of industrial contamination.

Brazil’s National Health Surveillance Agency sets maximum permissible levels for contaminants in food, aligned with international standards. Scientists involved in the crop study argue that regulatory benchmarks should be complemented by localised risk assessments, particularly where children’s exposure could exceed conservative safety margins.

Community leaders in Minas Gerais have called for clearer communication about which plots are safe for cultivation and consumption. Some families rely on home-grown bananas and cassava as primary food sources, increasing the importance of accessible testing and guidance. Researchers recommend soil remediation techniques such as phytoremediation, liming and organic amendments to reduce metal bioavailability over time.