Researchers in soil science, environmental engineering, and public well being from the College of São Paulo (USP), the Federal College of Espírito Santo (UFES) in Brazil, and the College of Santiago de Compostela in Spain investigated whether or not crops grown close to the Doce River estuary are suitable for eating. The realm in Linhares, Espírito Santo, has been uncovered to iron mining waste for the reason that Fundão tailings dam collapsed in Minas Gerais in November 2015.
The crew centered on bananas, cassava, and cocoa pulp cultivated in soil affected by the catastrophe. They examined ranges of cadmium, chromium, copper, nickel, and lead, metals linked to iron oxides, that are the first part of the tailings. Their findings counsel that consuming bananas grown in contaminated soil could current a possible well being threat for kids six years previous and youthful.
“Our group has been finding out the impacts of the dam collapse for years. We obtained the primary samples seven days after the accident and instantly understood that there was an imminent threat of contamination of vegetation, soil, water, and fish. However the query remained: Does this contamination pose a threat to human well being?” remembers Tiago Osório, an agronomist and professor within the Division of Soil Science on the Luiz de Queiroz Faculty of Agriculture on the College of São Paulo (ESALQ-USP).
The research, revealed in Environmental Geochemistry and Well being, explains how vegetation soak up probably poisonous components (PTEs) from mining waste and retailer them in edible tissues. It additionally outlines how these substances can transfer into the human meals provide. The analysis kinds a part of Amanda Duim’s doctoral work at ESALQ. Her thesis has produced seven worldwide publications and earned two main awards in 2025: the USP Thesis Award in Sustainability and the Capes Thesis Award, granted by the Brazilian Ministry of Schooling’s Coordination for the Enchancment of Increased Schooling Personnel (CAPES). Duim obtained help from FAPESP by way of a doctoral scholarship.
How Contaminated Soil Transfers Metals Into Vegetation
Duim, the research’s lead writer, says the analysis stands out as a result of it immediately hyperlinks human well being threat to the motion of PTEs from soil into crops. “The iron oxide content material within the soil, which is the principle constituent of the tailings, correlates with its content material within the plant. We studied the passage of constituents from the tailings within the soil to the water, after which from the water to the plant, together with its leaves and fruits.”
“First, we have to know which components are there and in what portions with a view to perceive the biochemical dynamics of their launch,” Osório explains.
Duim started her doctoral analysis in 2019 by exploring whether or not vegetation from flood-prone areas might assist restore contaminated environments. She evaluated each cultivated crops and native species. “We evaluated cultivated and native species. Within the case of the latter, we needed to understand how they have an effect on the dissolution of iron oxide and, on this course of, perceive if and the way the PTEs related to this waste enter the plant, since totally different species accumulate PTEs in a different way,” she says. “The thought was to search out the very best native species for cleansing up contaminated environments, and we discovered a couple of species that may fulfill this perform, with outcomes already revealed. Within the case of cultivated species, we needed to know if PTEs can be transferred to the fruits and edible elements of the vegetation.”
To measure contamination, the researchers rigorously collected soil and plant samples. They washed and weighed the contemporary vegetation, then dried them and weighed them once more. Roots, stems, leaves, and peeled fruits have been floor individually for evaluation. “We dissolved the ‘plant powder,’ reworking it into an answer utilizing varied acids, and decided the focus within the resolution. We transformed the calculation of the focus of fabric within the resolution and in contrast it with the burden of the diluted materials, thus acquiring the PTE focus in milligrams per kilogram of dry biomass,” Duim describes.
In bananas and cassava, practically all PTEs besides chromium have been present in greater quantities beneath floor, in roots and tubers. Cocoa behaved in a different way, with elevated ranges in stems, leaves, and fruits. In cocoa pulp, copper and lead concentrations exceeded limits set by the Meals and Agriculture Group of the United Nations (FAO).
When the crew found that some edible parts contained PTE ranges above beneficial requirements, they carried out a proper well being threat evaluation.
Well being Danger Evaluation for Youngsters and Adults
The scientists calculated the chance quotient (RQ), threat index (RI), and complete threat index (TRI) for individuals consuming bananas, cassava rhizomes, and cocoa pulp. They evaluated kids (beneath six years of age) and adults (over 18 years of age) individually. The RQ compares an individual’s estimated each day consumption of a substance to a reference dose thought-about protected. The TRI helps decide potential non-carcinogenic well being threat from publicity to PTEs. A TRI beneath 1 signifies low threat.
“These components exist naturally within the atmosphere. We’re uncovered to them in decrease concentrations. However within the case of a catastrophe just like the one in Mariana, when publicity is predicted to extend, we have to train additional warning,” says Tamires Cherubin, a well being sciences Ph.D. and co-author of the research. Commonplace strategies consider how bioavailable these components are, since sure concentrations can result in kidney and coronary heart issues, gastrointestinal discomfort, and lung harm if inhaled. Quick-term results might also embrace pores and skin irritation and eye issues.
The researchers factored in how a lot regionally grown meals residents eat, utilizing knowledge from the Brazilian Institute of Geography and Statistics (IBGE). In addition they thought-about how lengthy people is likely to be uncovered, variations in physique weight between kids and adults, and the time required for dangerous results to develop.
“Based on the reference each day consumption doses for contaminants coated by the literature, we think about the bounds of 0.05 mg/kg-1 for the presence of cadmium in fruits and 0.1 mg/kg-1 in tubers, 0.5-1.0 mg/kg-1 for the presence of chromium, 20.0 mg/kg-1 for copper, 0.5-1.0 mg/kg-1 for nickel, 0.8-2.3 mg/kg-1 for lead, and 50.0 mg/kg-1 for zinc,” Cherubin explains.
For many metals, TRI values have been beneath 1, indicating no important non-carcinogenic threat for adults consuming these meals from the Doce River estuary. Nonetheless, the TRI for bananas exceeded 1 for kids, signaling attainable well being issues. Elevated lead ranges have been the first driver, and cadmium concentrations in bananas additionally surpassed FAO suggestions. The researchers observe that long-term publicity to guide, even at low ranges, can completely have an effect on mind improvement, probably reducing IQ and contributing to consideration and behavioral issues.
Lengthy-Time period Most cancers Issues and Ongoing Publicity
The crew cautions that consuming meals grown in contaminated soil over a few years might result in cumulative results. “Over time, contemplating the life expectancy in Brazil of round 75 years, there could also be a carcinogenic threat since there is a risk of direct and oblique DNA harm,” says Cherubin. Such genetic harm could enhance the probability of cancers affecting the central nervous system, digestive tract, and blood-forming tissues. “All of it is dependent upon the human physique’s skill to soak up and metabolize these components which are obtainable within the atmosphere,” she provides.
