Contaminated Soil Poses Health Risks to Children Near Doce River Estuary

A recent study reveals that consuming bananas grown in soil contaminated by the 2015 Fundão tailings dam disaster in Brazil may pose a health risk to children six years old and younger. Researchers from the University of São Paulo (USP), the Federal University of Espírito Santo (UFES), and the University of Santiago de Compostela investigated the presence of potentially toxic elements (PTEs) in crops near the Doce River estuary in Linhares, Espírito Santo.

The Fundão Dam Disaster and Initial Concerns

On November 5, 2015, the Fundão tailings dam, operated by Samarco Mineração S.A., failed, releasing between 55 and 62 million cubic meters of iron mining tailings into the Doce River watershed . Immediately following the disaster, scientists recognized the potential for widespread contamination of plants, soil, water, and fish . The key question became whether this contamination presented a tangible risk to human health.

Study Focus: Bananas, Cassava, and Cocoa

The research team focused on three locally cultivated crops: bananas, cassava, and cocoa. They analyzed levels of cadmium, chromium, copper, nickel, and lead – metals commonly associated with iron oxides, the primary component of the tailings. Their analysis examined how plants absorb these elements from the contaminated soil and whether they accumulate in edible tissues.

How Contamination Moves from Soil to Plants

The study highlights the correlation between iron oxide content in the soil and its presence within the plants. Researchers traced the movement of PTEs from the tailings in the soil to the water, and then from the water to the plant, including its leaves and fruits. Different plant species accumulate PTEs at varying rates.

Measuring Contamination Levels

Researchers meticulously collected soil and plant samples, carefully washing, weighing, and drying them. Plant tissues – roots, stems, leaves, and peeled fruits – were ground separately for analysis. A process of dissolving the “plant powder” using acids allowed researchers to determine the concentration of PTEs in milligrams per kilogram of dry biomass.

Findings: Elevated PTE Levels in Crops

In bananas and cassava, most PTEs (except chromium) were found in higher concentrations below ground, in the roots and tubers. Cocoa exhibited a different pattern, with elevated levels in stems, leaves, and fruits. Notably, copper and lead concentrations in cocoa pulp exceeded limits set by the Food and Agriculture Organization of the United Nations (FAO).

Health Risk Assessment: Children at Greater Risk

A formal health risk assessment, calculating the risk quotient (RQ), risk index (RI), and total risk index (TRI), was conducted for both children (under six years of age) and adults (over 18 years of age). While TRI values were generally below 1 for adults, indicating low non-carcinogenic risk, the TRI for bananas exceeded 1 for children, raising potential health concerns. Elevated lead levels were the primary driver, with cadmium concentrations in bananas also surpassing FAO recommendations.

Long-Term Exposure and Potential Cancer Risks

The researchers caution that long-term consumption of food grown in contaminated soil could lead to cumulative effects, potentially increasing the risk of cancer due to possible DNA damage. The body’s ability to absorb and metabolize these elements plays a crucial role in determining the extent of the risk. Long-term exposure to even low levels of lead can permanently affect brain development, potentially lowering IQ and contributing to attention and behavioral problems.

Ongoing Research and Environmental Restoration

The study builds upon years of research following the dam collapse, with initial samples collected just seven days after the accident . Ongoing research continues to evaluate the geochemistry and toxicity of water and sediments in the Doce River Basin, aiming to support environmental restoration efforts and inform decision-making regarding the disaster .