Mercury Contamination: A Growing Threat to Riverine and Urban Communities in the Brazilian Amazon

Abstract

In recent decades, widespread and uncontrolled use of mercury (Hg) in artisanal small-scale gold mining has released thousands of tons of mercury-contaminated waste in the Amazon biome, endangering the largest tropical rainforest worldwide. In this study, we assessed and compared blood Hg levels in individuals living in urban and riverine areas in the lower Tapajós basin and examined the association between Hg exposure and specific biochemical parameters. In total, 462 adults from eight riverine communities and one urban area were assessed. Overall, 75.6% of the participants exhibited Hg concentrations exceeding the safe limit (10 µg/L). Hg exposure was higher in the riverine population (90%) than in urban areas (57.1%). Mean Hg levels were 21.8 ± 30.9 µg/L and 50.6 µg/L in urban and riverine residents, respectively. The mean Hg level was higher in those aged 41–60 years in both urban and riparian areas, with riparian residents exhibiting a mean double that of urban residents. The highest glucose and hepatic biomarker levels were detected in the urban area, whereas the highest levels of renal biomarker occurred in the riverine population. Our results indicate that Hg contamination remains a persistent challenge for the urban population of Santarém, a major city in the Brazilian Amazon.

Sociobehavioral, Biological, and Health Characteristics of Riverside People in the Xingu Region, Pará, Brazil

“…The population studied presented a typical food profile of riverside populations in the Amazon region, in which riverine people reported having a good diet (natural food) based on vegetables, Brazil nuts, fruits, and mainly fish, the latter item being consumed three to four times per week [ 55 , 72 ]. We highlight the “fish consumption” factor for two interesting aspects: (i) a positive aspect, since there is a high concentration of unsaturated fats and omega-3 fatty acids in this food, which can substantially contribute to the prevention of cardiovascular diseases in this population, since this nutrient has been proven to prevent this disease [ 38 , 73 ]; and (ii) a negative aspect, since there is a strong possibility that this food is contaminated by methylmercury, which in turn can bioaccumulate in riverine people who consume them [ 39 , 40 , 41 , 42 ]. Indeed, Souza-Araujo and collaborators (2022) [ 42 ] identified fish contamination and mercury biomagnification in food webs in the Belo Monte Hydroelectric Power Plant, in the middle of Xingu River, Pará state.…”

“…Indeed, Souza-Araujo and collaborators (2022) [ 42 ] identified fish contamination and mercury biomagnification in food webs in the Belo Monte Hydroelectric Power Plant, in the middle of Xingu River, Pará state. Recent studies have reported mercury contamination of traditional (e.g., riverine and indigenous) and urban communities in the lower Tapajós basin and in the Tucurí Lake influence area, Pará state [ 40 , 41 , 74 ]. Therefore, it is possible that the population studied may be at risk of methylmercury contamination, since they may be consuming contaminated fish.…”

“…The variable “fish consumption” was emphasized, since this food is rich in omega-3 fatty acid, which is a nutrient known to be associated with the prevention and protection of cardiovascular diseases [ 38 ]. On the other hand, the consumption of fish by the population studied may be a risk factor for mercury contamination, since it has been reported that many species of fish in the Xingu River have levels of methylmercury concentration (the organic form of the metal heavy mercury) far above what is tolerable by the human body and which has a high power of bioaccumulation along the food chain [ 39 , 40 , 41 , 42 ].…”

Effects of illegal gold mining on Hg concentrations in water, Pistia stratiotes, suspended particulate matter, and bottom sediments of two impacted rivers (Paraíba do Sul River and Muriaé River), Southeastern, Brazil

“…In this context, this study aimed to evaluate the impact of garimpo activities on Hg contamination in three environmental compartments (sediment, water, and aquatic macrophytes) along a 106-km transect, starting from the point where the mining rafts were seized. Monitoring the impact of small-scale alluvial mining gold mining on Hg contamination is paramount, as garimpo remains the main source of Hg contamination for aquatic ecosystems in Latin America (Meneses et al, 2022 ). Higher Hg concentrations near the points where garimpo rafts were seized and/or seen are expected, as (I) the Hg 0 used in the amalgamation of gold is insoluble in water, and (II) the effects of garimpo are spatially limited (Lechler et al, 2000 ; Guimaraes, 2020 ).…”

Trace element accumulation in different edible fish species from the Bolivian Amazon and the risk for human consumption

“…Monomethyl-mercury is closely related to fish consumption since it is highly available in aquatic environments, despite constituting only around 1 % of the total mercury pool. This happens because of its highly persistent and lipid-soluble nature, being very bioavailable to fish and easily accumulated especially in fatty tissue, accruing in aquatic food webs and biota in general ( Mataba et al., 2016 ; Govaerts et al., 2018 ; Meneses et al., 2022 ). The consequences of this have been reported in several studies ( Lee et al., 2021 ; Vasconcellos et al., 2021 ; Meneses et al., 2022 ) where people from indigenous communities of the Amazon and, more specifically, the Beni River ( Lee et al., 2021 ) have shown high concentrations of mercury in their bodies.…”