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 fit for human consumption. The world in Linhares, Espírito Santo, has been uncovered to iron mining waste because the Fundão tailings dam collapsed in Minas Gerais in November 2015.
The workforce targeted 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 recommend that consuming bananas grown in contaminated soil might current a possible well being danger for kids six years previous and youthful.
“Our group has been learning 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 danger of contamination of vegetation, soil, water, and fish. However the query remained: Does this contamination pose a danger 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, printed in Environmental Geochemistry and Well being, explains how vegetation soak up probably poisonous parts (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 Greater Schooling Personnel (CAPES). Duim acquired assist from FAPESP by 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 instantly hyperlinks human well being danger to the motion of PTEs from soil into crops. “The iron oxide content material within the soil, which is the primary 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 parts 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 completely different species accumulate PTEs in another way,” she says. “The thought was to seek out one of the best native species for cleansing up contaminated environments, and we discovered a couple of species that may fulfill this perform, with outcomes already printed. 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 had been floor individually for evaluation. “We dissolved the ‘plant powder,’ remodeling it into an answer utilizing numerous 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 had been present in greater quantities beneath floor, in roots and tubers. Cocoa behaved in another 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 workforce found that some edible parts contained PTE ranges above advisable requirements, they performed a proper well being danger evaluation.
Well being Threat Evaluation for Youngsters and Adults
The scientists calculated the chance quotient (RQ), danger index (RI), and complete danger 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 day by day consumption of a substance to a reference dose thought of secure. The TRI helps decide potential non-carcinogenic well being danger from publicity to PTEs. A TRI beneath 1 signifies low danger.
“These parts exist naturally within the setting. 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. Normal strategies consider how bioavailable these parts are, since sure concentrations can result in kidney and coronary heart issues, gastrointestinal discomfort, and lung injury if inhaled. Brief-term results can also embody pores and skin irritation and eye issues.
The researchers factored in how a lot domestically grown meals residents devour, utilizing knowledge from the Brazilian Institute of Geography and Statistics (IBGE). In addition they thought of how lengthy people may be uncovered, variations in physique weight between kids and adults, and the time required for dangerous results to develop.
“In keeping with the reference day by 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 had been beneath 1, indicating no important non-carcinogenic danger for adults consuming these meals from the Doce River estuary. Nevertheless, the TRI for bananas exceeded 1 for kids, signaling attainable well being issues. Elevated lead ranges had been the first driver, and cadmium concentrations in bananas additionally surpassed FAO suggestions. The researchers be aware that long-term publicity to steer, even at low ranges, can completely have an effect on mind growth, probably decreasing IQ and contributing to consideration and behavioral issues.
Lengthy-Time period Most cancers Issues and Ongoing Publicity
The workforce 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 danger since there is a risk of direct and oblique DNA injury,” says Cherubin. Such genetic injury might enhance the chance of cancers affecting the central nervous system, digestive tract, and blood-forming tissues. “All of it is dependent upon the human physique’s capacity to soak up and metabolize these parts which might be accessible within the setting,” she provides.
