Mercury contamination in the Amazon Basin: fish consumption, co-exposures, and health implications for indigenous and riverside communities

Overview

This review examines mercury contamination in the Amazon Basin, focusing on fish consumption as the primary exposure pathway for indigenous and riverside communities. Fish total mercury (Hg) concentrations range from 0.10 to 4.73 µg/g (wet weight) across Amazonian species, with piscivorous predators (surubim, tucunaré/peacock bass, piranha) at the high end. Human hair mercury concentrations in documented exposed populations range from 3.07 to 24.6 µg/g, substantially exceeding the WHO guidance value of 1 µg/g. The review also addresses co-exposures with agrochemicals, microplastics, and artisanal gold mining (ASGM) byproducts, noting synergistic effects that may amplify neurotoxic risk. Nutritional trade-offs (omega-3 benefits vs. Hg risk) are discussed in the context of food security for communities dependent on river fish.

Key numbers

Fish total mercury (tHg) range: 0.10–4.73 µg/g (wet weight), species-dependent; piscivorous predators highest. Human hair Hg: 3.07–24.6 µg/g in documented exposed Amazonian populations (WHO guidance: 1 µg/g). ASGM (artisanal small-scale gold mining) identified as the dominant anthropogenic source. Co-exposures with organochlorines, glyphosate, and microplastics reported. methylmercury (MeHg) is the speciated form driving exposure (estimated >90% of total Hg in freshwater fish muscle).

Methods (brief)

Narrative review. Sources drawn from peer-reviewed epidemiological and environmental chemistry literature on Amazonian Hg. No pooled meta-analytic estimates; concentration ranges cited from tabular data in contributing studies. Annals of Global Health, CC BY.

Implications

Certification: Freshwater Amazon fish species are not direct HMT&C product categories, but the review establishes the highest documented fish Hg concentrations in a food consumption context. Relevant to comparative benchmarking for marine fish Hg standards. Courses: Core reference for the mercury-in-fish module, particularly for discussing MeHg speciation, vulnerable populations (pregnant women, young children), and the nutritional trade-off dilemma. App: Contributes to the freshwater fish contamination profile for tHg and MeHg; piscivorous freshwater species should be flagged at higher risk than small or herbivorous species. Microbiome: Hg-induced gut microbiota disruption is reviewed; relevant for microbiome/mercury-gut-axis crosswalk.

Related evidence

• Mercury
• Fish
• Freshwater Fish
• Vulnerable populations and metal exposure

Update history

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