More than 20 percent of the fish sold at supermarkets and fishmongers in six of Brazil’s Amazon states was found to be contaminated with mercury above the level considered acceptable by the World Health Organization (WHO).
This was the main finding of a study released on Tuesday, carried out by researchers from the Oswaldo Cruz Foundation (Fiocruz), the Federal University of Western Pará (UFOPA), Greenpeace Brasil, Iepé, Instituto Socioambiental, and WWF-Brasil.
The study concludes that illegal gold mining in the Amazon is to blame for the contamination levels.
Researchers purchased 1,010 fish of 80 different species in 17 Amazonian cities between March 2021 and September 2022. In Brazil’s northernmost state of Roraima, 40 percent of the samples had more than 0.5 micrograms of mercury per gram (µg/g) — levels deemed harmful by the WHO.
Protected indigenous lands make up almost half of Roraima state — including the vast Yanomami territory, where illegal mining ventures increased by 46 percent in 2021 alone.
Wildcat gold mining in the Amazon typically uses barges to suck up water from rivers, from which sediment is extracted and then mixed with mercury, which bonds to any gold fragments. Once the gold is separated, the highly poisonous mercury is burned away from the precious metal and the toxic by-products are dumped into the river.
The study also raises the alarm in Acre and Rondônia — where 35.9 percent and 26.1 percent of fish samples, respectively, were contaminated with mercury.
“It reinforces an alert for an already known, but unresolved issue, which is the risk to food security in the Amazon region generated by the use of mercury in illegal gold mining,” said Decio Yokota, coordinator of Iepé’s Information Management Program. “It is worrisome that the territory’s main source of protein, if ingested without control, can cause damage to health because it is contaminated.”
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