Brazil: Dam disaster risk means independent reviews a must: Researchers

Independent scientific reviews of mining disasters are vital to help authorities avoid future catastrophes.

This is one of the lessons learned after the collapse of a tailings dam at Brumadinho in southeast Brazil, in January 2019. Tons of mud and iron ore poured into Paraopeba River, which was the water source for the area.

The rupture of the tailings dam was one of the region’s worst socio-environmental disasters, killing over 270 people and affecting 40,000 nearby residents. It drastically increased heavy metals in the Paraopeba River, and destroyed large areas of Atlantic Forest and protected areas along its watercourses.

“Independent studies are important because they tend to be an impartial source of information, which may be consulted both by decision-makers and the affected population,” Alex Bastos, a geologist at Espírito Santo Federal University (Ufes), tells SciDev.Net.

“Many data may be generated, but if the population is not aware of them and do not believe in the results, there is an escalation of conflicts, so it is not only a matter of carrying out independent studies, but also of creating a data management and communication model capable of properly informing the population affected by this sort of disaster.”

To Vivian de Mello Cionek, a biologist at the State University of Santa Catarina, independent studies provide scientific bases to better assess the environmental impacts of dam failures and the lack of safety culture in risky operations.

For Cybelle Longhini, a biologist at Ufes, studies of mining disasters are “important to understand the responses of huge metal contamination at the ecosystem level, and the results can guide future studies for management and conservation strategies of the affected areas”.

Bastos says every environmental study after a high impact event is important to create impartial and high quality data for decision-makers.

“The role of the public universities at a time of serious environmental disaster is to support public authorities and the population in order to be a source of information that can be consulted and considered impartial,” he says.

An unusable river and an ongoing catastrophe

A week after the Brumadinho disaster, a research team from the State University of Northern Rio de Janeiro carried out biogeochemical, microbiological and ecotoxicological analyses across 464km of Paraopeba River.

Their research was published in the February issue of Science of the Total Environment and tallies with other reports on the need for independent impact studies.

The researchers found that immediately after the tailings dam failure, the river’s water quality was 30 times lower than the Brazilian Resolution for Water Quality standard.

The mercury values were up to 21 times above the acceptable level. Mercury is a toxic metal that may be harmful to the environment, humans and animals.

When they repeated these tests four months later, the quality parameters showed that water from the Paraopeba was still dangerous for human use and even for fishing.

The team also found a 60-fold increase in iron tolerant bacterial at a point 115 km downstream of the dam failure, which indicates that the ore tailings stimulated the growth of pathogenic and toxic microbes.

“It also suggests that waters are highly toxic and may pose a threat to public health” Omar Yazbek Bitar,a geologist at the Institute of Technological Research in São Paulo, tells SciDev.Net.

For Bastos, the study is important because it presents simple data that shows that the river’s health is compromised, and that the impacts are not over yet.

Studies carried out by SOS Mata Atlântica Foundation in January, at 21 points along 356km of the riverbed, found that the river remains contaminated and that, due to high rainfall, heavy metals had washed downstream.

Bastos says the extent of the impacts of the dam collapse may still be unknown.

Researchers also observed a high mortality level of zebrafish embryo across the study area.

Tailings dam failures used to be considered rare events in Brazil, but since 2015, two iron tailings disasters have hit the state of Minas Gerais, which has a history of poorly regulated resource extraction.

The risk of future dam disasters remains high. A 2018 Annual Dam Report  warned that 45 Brazilian dams are at high risk of failure, including five mining tailings dams.