A New Study Finds Dangerous Levels of Mercury From Amazon Fish

A new study reveals that almost a third of the fishes in Amapa, Brazil contains dangerous levels of Mercury (Hg), leaving them dangerous for human consumption.

The joint research team from the World Wildlife Fund (WWF), Escola Nacional de Saúde Pública Sérgio Arouca, Instituto de Pesquisas Científicas e Tecnológicas do Amapá, and the Iepé-Instituto de Pesquisa e Formação Indígena conducted the study. Published in the International Journal of Environmental Research and Public Health, the team claimed that 77.6 percent of carnivorous fish, 20 percent of omnivores, and 2.4 percent of herbivores contained mercury that "surpassed safety limits."

Traditional Amazon Fishing Community Continues To Live In Stilt Houses — SAO LUIS, BRAZIL - NOVEMBER 24: A resident talks on his phone on an elevated pathway between homes in the traditional fishing community of Sao Francisco, where some residents live in wooden homes constructed on stilts above the water, on November 24, 2014 in Sao Luis, Brazil. Photo by Mario Tama/Getty Images

Monitoring Amazon Fishes

For the study, researchers collected tissue samples from 428 fishes, covering 45 species across 18 sites. Fishes were caught from five regions of Amama, bordering French Guiana in the Northwest. The river systems that supplied the samples were close to environmentally protected areas in the continent.

For tracing the presence of mercury, the research team subjected the samples to cold vapor atomic fluorescence spectrometry to determine total mercury (THg) content. Testing was done at the Analytical Chemistry Laboratory of the Pontific University of Rio de Janeiro.

In the analysis of their samples, the study noted: "Four of the seven species with the highest Hg concentrations are among the most consumed species in the region." The highest levels were detected in pirapucu (Boulengerella cuvieri), tucunare (Cichla monoculus), and traírão (Hoplias aimara), carnivorous fishes often used in native Brazilian cuisine.

For the pirapucu, for example, scientists found 2.1 micrograms of Hg per gram. An adult person who eats more than 200g of these Mercury-laced fishes could pose health risks. In a week, this equates to 1.4 μg/kg/week for a 70 kg adult.

Also noted in the study is that fishes from the inland zone had higher mercury levels compared to fishes taken from the coastal sites.

Human Activities in the Region

In the report's introduction, it noted how artisanal small-scale gold mining (ASGM) has expanded in the Amazon regions over the last twenty years. ASGM was cited as a major cause behind habitat degradation and deforestation in the northern Amazon, inside Brazilian borders.

Amapa, the state covering the northern areas of Brazil, shares the border with French Guiana and Suriname - 72% of the state's area is also formally protected. Unfortunately, "weak governance, lack of financial resources for protective management, and different anthropogenic pressures" have negatively affected protection efforts in the area.

With the prevalence of ASGM in the region, so is the use of mercury. In small-scale mining efforts, mercury is used to recover grams of pure gold mixed in rock and soil. Gold attaches itself to mercury and extracted together from the mixture. Later, gold is isolated by vaporizing mercury.

An earlier report points to the local ASGM sector as the lead source of Hg "emissions, contamination, and consumption in Latin American and the Caribbean." ASGM has negatively affected the health of riverside communities, mostly of indigenous people. These people have a diet that relies largely on fishes as their main protein source.