Mercury Exposure through Fish Consumption in Traditional Communities in the Brazilian Northern Amazon

Mercury in aquatic ecosystems of two indigenous communities in the Piedmont Ecuadorian Amazon: evidence from fish, water, and sediments

Mercury is a highly toxic element present in water, soil, air, and biota. Anthropogenic activities, such as burning fossil fuels, mining, and deforestation, contribute to the presence and mobilization of mercury between environmental compartments. Although current research on mercury pathways has advanced our understanding of the risks associated with human exposure, limited information exists for remote areas with high diversity of fauna, flora, and indigenous communities. This study aims to deepen our understanding of the presence of total mercury in water, sediments, and fish, within aquatic ecosystems of two indigenous territories: Gomataon (Waorani Nationality) and Sinangoé (Ai´Cofán Nationality) in the Ecuadorian Amazon. Our findings indicate that, for most fish (91.5%), sediment (100%) and water (95.3%) samples, mercury levels fall under international limits. For fish, no significant differences in mercury levels were detected between the two communities. However, eight species exceeded recommended global limits, and one surpassed the threshold according to Ecuadorian legislation. Piscivore and omnivore fish exhibited the highest concentrations of total mercury among trophic guilds. Only one water sample from each community's territory exceeded these limits. Total mercury in sediments exhibited greater concentrations in Gomataon than Sinangoé. Greater levels of mercury in sediments were associated with the occurrence of total organic carbon. Considering that members of the communities consume the analyzed fish, an interdisciplinary approach, including isotopic analysis, methylmercury sampling in humans, and mercury monitoring over time, is imperative for a detailed risk assessment of mercury exposure in Amazonian communities.

Global mercury concentrations in biota: their use as a basis for a global biomonitoring framework

An important provision of the Minamata Convention on Mercury is to monitor and evaluate the effectiveness of the adopted measures and its implementation. Here, we describe for the first time currently available biotic mercury (Hg) data on a global scale to improve the understanding of global efforts to reduce the impact of Hg pollution on people and the environment. Data from the peer-reviewed literature were compiled in the Global Biotic Mercury Synthesis (GBMS) database (>550,000 data points). These data provide a foundation for establishing a biomonitoring framework needed to track Hg concentrations in biota globally. We describe Hg exposure in the taxa identified by the Minamata Convention: fish, sea turtles, birds, and marine mammals. Based on the GBMS database, Hg concentrations are presented at relevant geographic scales for continents and oceanic basins. We identify some effective regional templates for monitoring methylmercury (MeHg) availability in the environment, but overall illustrate that there is a general lack of regional biomonitoring initiatives around the world, especially in Africa, Australia, Indo-Pacific, Middle East, and South Atlantic and Pacific Oceans. Temporal trend data for Hg in biota are generally limited. Ecologically sensitive sites (where biota have above average MeHg tissue concentrations) have been identified throughout the world. Efforts to model and quantify ecosystem sensitivity locally, regionally, and globally could help establish effective and efficient biomonitoring programs. We present a framework for a global Hg biomonitoring network that includes a three-step continental and oceanic approach to integrate existing biomonitoring efforts and prioritize filling regional data gaps linked with key Hg sources. We describe a standardized approach that builds on an evidence-based evaluation to assess the Minamata Convention's progress to reduce the impact of global Hg pollution on people and the environment.

Influence of genetic polymorphisms of Hg metabolism and DNA repair on the frequencies of micronuclei, nucleoplasmic bridges, and nuclear buds in communities living in gold mining areas

Fishing communities living near gold mining areas are at increased risk of mercury (Hg) exposure via bioaccumulation of methylmercury (MeHg) in fish. This exposure has been linked to health effects that may be triggered by genotoxic events. Genetic polymorphisms play a role in the risk associated with Hg exposure. This study evaluated the effect of single nucleotide polymorphisms (SNPs) in metabolic and DNA repair genes on genetic instability and total hair Hg (T-Hg) levels in 78 individuals from "La Mojana" in northern Colombia and 34 individuals from a reference area. Genetic instability was assessed by the frequency of micronuclei (MNBN), nuclear buds (NBUDS), and nucleoplasmic bridges (NPB). We used a Poisson regression to assess the influence of SNPs on T-Hg levels and genetic instability, and a Bayesian regression to examine the interaction between Hg detoxification and DNA repair. Among exposed individuals, carriers of XRCC1Arg399Gln had a significantly higher frequency of MNBN. Conversely, the XRCC1Arg194Trp and OGG1Ser326Cys polymorphisms were associated with lower frequencies of MNBN. XRCC1Arg399Gln, XRCC1Arg280His, and GSTM1Null carriers showed lower NPB frequencies. Our results also indicated that individuals with the GSTM1Nulland GSTT1null polymorphisms had a 1.6-fold risk for higher T-Hg levels. The Bayesian model showed increased MNBN frequencies in carriers of the GSTM1Null polymorphism in combination with XRCC1Arg399Gln and increased NBUDS frequencies in the GSTM1Null carriers with the XRCC3Thr241Met and OGG1Ser326Cys alleles. The GSTM1+ variant was found to be a protective factor in individuals carrying OGG1Ser326Cys (MNBN) and XRCC1Arg280His (NPB); the GSTT1+ polymorphism combined with XRCCArg194Trp also modulated lower MNBN frequencies, while GSTT1+ carriers with the XRCC1Arg399Gln allele showed lower NPB frequencies. Consistent with GSTM1, GSTT1Null carriers with XRCC3Thr241Met showed increased NBUDS frequency. With the rise of gold mining activities, these approaches are vital to identify and safeguard populations vulnerable to Hg's toxic effects.

The GSTP1 rs1695 Polymorphism Is Associated with Mercury Levels and Neurodevelopmental Delay in Indigenous Munduruku Children from the Brazilian Amazon

Genetic polymorphisms may influence mercury (Hg) toxicity. The aims of this study were to evaluate individual factors, such as the presence of the GSTP1 rs1695 polymorphism, associated with internal Hg dose and child neurodevelopment in indigenous people from the Brazilian Amazon chronically exposed to Hg. Eighty-two indigenous children were clinically evaluated, hair Hg was measured, and the GSTP1 rs1695 polymorphism was genotyped. The mean age was 4.8 years, the median Hg was 5.5 µg/g, and 93.8% of children exceeded the safe limit (2.0 µg/g). Fish consumption was associated with Hg levels (p = 0.03). The GSTP1 rs1695 A>G polymorphism was in the Hardy-Weinberg equilibrium and the highest prevalence of the GSTP1 AA genotype (80%) was found in Sawré Aboy, which had the highest Hg levels (10 µg/g) among the studied villages. The Hg levels tended to increase over the years in males and in carriers of the GSTP1 AA genotype (0.69 µg/g and 0.86 µg/g, respectively). Nine children failed the neurodevelopmental test, all of whom had Hg > 2.0 µg/g, and 88.9% carried the GSTP1 AA or AG genotypes, previously associated with the highest internal Hg doses and neurocognitive disorders. The genetic counseling of this population is important to identify the individuals at greater risk for neurodevelopmental disorders resulting from chronic Hg exposure.

Genomic investigation on genes related to mercury metabolism in Amazonian indigenous populations

Studies have identified elevated levels of mercury in Amazonian Indigenous individuals, highlighting them as one of the most exposed to risks. In the unique context of the Brazilian Indigenous population, it is crucial to identify genetic variants with clinical significance to better understand vulnerability to mercury and its adverse effects. Currently, there is a lack of research on the broader genomic profile of Indigenous people, particularly those from the Amazon region, concerning mercury contamination. Therefore, the aim of this study was to assess the genomic profile related to the processes of mercury absorption, distribution, metabolism, and excretion in 64 Indigenous individuals from the Brazilian Amazon. We aimed to determine whether these individuals exhibit a higher susceptibility to mercury exposure. Our study identified three high-impact variants (GSTA1 rs1051775, GSTM1 rs1183423000, and rs1241704212), with the latter two showing a higher frequency in the study population compared to global populations. Additionally, we discovered seven new variants with modifier impact and a genomic profile different from the worldwide populations. These genetic variants may predispose the study population to more harmful mercury exposure compared to global populations. As the first study to analyze broader genomics of mercury metabolism pathways in Brazilian Amazonian Amerindians, we emphasize that our research aims to contribute to public policies by utilizing genomic investigation as a method to identify populations with a heightened susceptibility to mercury exposure.

Human exposure to elements through consumption of raw and cooked fish in an urban region of the central Brazilian Amazon biome: Health risks

Fish is an important source of animal protein for local communities in the Amazon basin, whose food safety must be assured. However, certain potential toxicants elements, can bioaccumulate in fish species, which inhabit anthropogenically polluted waters, ultimately posing a risk to human health. In the present study, the concentrations of nine elements (Al, As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) were determined in raw and cooked samples of eight fish species consumed in Santarém (northern Brazil, Amazon biome). The potential for non- carcinogenic human health risks linked to the consumption of cooked fish were evaluated for adults and children in two different scenarios. Four carnivores, three omnivores and one detritivore, all of them regularly marketed and consumed by the Santarém population, were the target species. The safety reference values set by national and international guidelines for humans, in both raw and cooked preparations, were used. In most cases, the cooking process showed a trend to increase elements concentrations compared to raw samples, however the differences were not significant. Moreover, the risk assessment showed danger for children in relation to Hg from the consumption of fish, in both scenarios evaluated. For adults, in one of the scenarios, there was a health risk associated to Hg as a result of carnivorous fish consumption. In a context of combined exposure to all elements, children were at risk when consuming fish, especially carnivorous and omnivorous species. For adults, the mixture of elements posed a risk to health human only for carnivorous fish consumption. The results reveal an environmental scenario of Hg contamination, which requires monitoring actions to preserve the aquatic biodiversity and human health in the Brazilian Amazon biome.

Methylmercury neurotoxicity: Beyond the neurocentric view

Mercury is a highly toxic metal widely used in human activities worldwide, therefore considered a global public health problem. Many cases of mercury intoxication have occurred in history and represent a huge challenge nowadays. Of particular importance is its methylated form, methylmercury (MeHg). This mercurial species induces damage to several organs in the human body, especially to the central nervous system. Neurological impairments such as executive, memory, motor and visual deficits are associated with MeHg neurotoxicity. Molecular mechanisms involved in MeHg-induced neurotoxicity include excitotoxicity due to glutamatergic imbalance, disturbance in calcium homeostasis and oxidative balance, failure in synaptic support, and inflammatory response. Although neurons are largely affected by MeHg intoxication, they only represent half of the brain cells. Glial cells represent roughly 50 % of the brain cells and are key elements in the functioning of the central nervous system. Particularly, astrocytes and microglia are deeply involved in MeHg-induced neurotoxicity, resulting in distinct neurological outcomes depending on the context. In this review, we discuss the main findings on astroglial and microglial involvement as mediators of neuroprotective and neurotoxic responses to MeHg intoxication. The literature shows that these responses depend on chemical and morphophysiological features, thus, we present some insights for future investigations, considering the particularities of the context, including time and dose of exposure, brain region, and species of study.

Comparative analysis between mercury levels in fish tissues evaluated using direct mercury analyzer and inductively plasma-coupled mass spectrometer

Recent ecotoxicological studies have indicated mercury (Hg) contamination in aquatic ecosystems in the Amazon Basin. Although Hg contamination can be associated with small-scale gold mining, the soils of the Amazon region have naturally high Hg concentrations, and can be transported to aquatic ecosystems via deforestation and mining activities. Biomagnification of Hg can pose risks to the local human population; therefore, its concentration in fish tissues must be monitored consistently. Fast and sensitive Hg determination is required for continuously monitoring ecosystems impacted by mineral exploration. The direct mercury analyzer (DMA-80) is widely used for determining total Hg levels in tissue samples; it is fast and cost-effective, without requiring sample preparation. Here, we determined the sensitivity and specificity of Hg detection accomplished using DMA-80, and whether these results are reliable compared to those obtained using Inductively Coupled Plasma Mass Spectrometer (ICP-MS), which is the gold standard. We obtained 106 paired dried samples of muscle tissue from fish species occupying different trophic levels in the Lower Amazon region, and analyzed them using both equipment (DMA-80 and ICP-MS). The results obtained using DMA-80 had an overall Hg mean of 1.90 ± 0.18 mg/kg which was higher (p < 0.05) than the mean of those obtained using ICP-MS (1.55 ± 0.13 mg/kg). Linear regression analysis comparing the Hg levels obtained using both devices was within the 95% prediction interval, and a high coefficient of correlation showed agreement between the devices (r = 0.979; 0.069 to 0.986, 95% CI). Bland-Altman analysis showed that DMA-80 had a positive bias of 6.5% in relation to ICP-MS, which is more evident in samples with high Hg concentrations. DMA-80 was efficient in determining whether the Hg levels exceeded the maximum allowed levels required by the European Union, USA, and Brazil, showing a specificity and sensitivity of above 95%.

Mercury exposure in riverine populations of Terra do Meio Extractive Reserves in the Xingu basin, Amazon, Brazil

Amazon is a hotspot for mercury (Hg) contamination and Terra do Meio region, despite its protected status for sustainable use, has never been monitored for this element. Looking to address this gap, this study aimed to quantify capillary Hg concentration in riverine populations of Terra do Meio (Xingu Basin, Central Amazon, Brazil) and associated factors with high Hg levels (90 percentile). Hair samples from 182 individuals from Iriri, Riozinho do Anfrísio and Xingu Extractive Reserves (RESEX), aged between 18 and 70 years old, were collected to measure total mercury levels (HgT), and socioeconomic, demographic, and clinical-epidemiological data were annotated. Overall, high levels of Hg were observed (mean 4.985 µg/g, median 3.531 µg/g) with significant differences between localities. Among the factors related to high capillary Hg levels, male gender, smoking habit, work in agriculture, livestock or extractivism, and residence in Iriri and Riozinho do Anfrísio RESEX were highlighted. A high prevalence of symptoms related to Hg intoxication, including anxiety, memory deficit, and lower limb problems, was observed. Overall, the results reveal that communities in these RESEXs are exposed to Hg and appear to be suffering from chronic health effects. Considering the increased anthropogenic alterations observed recently in the Amazon region and the subsequent amplified environmental bioavailability of Hg, further studies and mitigating actions are critical. This includes better surveillance of illegal anthropic activities and provision of ongoing education on this matter and incentives for dietary adaptations.

Risk Assessment of Mercury-Contaminated Fish Consumption in the Brazilian Amazon: An Ecological Study

Mercury is one of the most dangerous contaminants on the planet. In recent years, evidence of mercury contamination in the Amazon has significantly increased, notably due to gold-mining activities. Although mercury contamination in fish has consistently been documented, little is known about the risk associated with fish consumption by populations in urban areas of the Amazon. We sampled 1010 fish sold in public markets in six state capitals and 11 additional cities. Mercury levels were determined for each specimen, and the evaluation of the health risks associated with consuming mercury-contaminated fish was conducted according to the methodology proposed by the World Health Organization (WHO). Our study reveals that more than one-fifth (21.3%) of the fish sold in urban centers had mercury levels above the safe limits (≥0.5 µg/g) established by the Brazilian Health Surveillance Agency (ANVISA). The prevalence of Hg contamination ≥0.5 µg/g was approximately 14 times higher in carnivorous than in noncarnivorous fish. The analysis of the risk attributable to fish consumption reveals that daily mercury intake exceeded the reference dose recommended by the U.S. EPA in all population groups analyzed, reaching up to 7 and 31 times in women of childbearing age and children from 2 to 4 years old, respectively. However, these risks are diverse depending on the type of fish consumed and must be considered to formulate appropriate nutritional guidelines for safe fish consumption by the local community.

Vulnerabilities to illnesses in women living on the border of the Guiana Shield mines

OBJECTIVE

To analyze the the vulnerabilities to illnesses in women living on the border of the Guiana Shield mines: Brazil, French Guiana, and Suriname.

METHOD

Descriptive, exploratory field study with a qualitative approach. Data collection took place with 19 women who were living in the mining context, in April 2018. The interviews were recorded and transcribed in full and subsequently analyzed in the light of the concept of vulnerability.

RESULTS

Women aged between 30 and 39 years, predominantly black and brown, on a common-law marriage, multiparous, of low level of education, and with work activities related to mining. Three empirical categories emerged: Exposure to environmental and life conditions in the mines: vulnerabilities to illnesses in women; Sexual and reproductive health in the context of borders: the invisibility between legality and illegality; Gendered facets of violence in the mines on the border of the Guiana Shield.

CONCLUSION

Vulnerability is marked in the three dimensions of the concept: in the difficult access to health services, in the discontinued treatment, and in the disparity in health policies within countries, which are important aspects of vulnerability and health conditions.

Genotoxicity biomarkers on native fish species from the Araguari River (Amazon biome)

The Araguari River, one of the most important waterways in the Brazilian state of Amapá, is ecologically relevant and essential for the conservation of Amazonian fish biodiversity. Our previous studies demonstrated contamination of water and fish by metals. In particular, water samples showed genotoxic damage in Danio rerio. Here, we extended our studies of potential genotoxic damage to native fish from sampling sites located in the Araguari River lower section. To accomplish this, we collected samples of fish with different feeding behaviors, but in the same sampling sites, and evaluated the same genotoxicity biomarkers in erythrocytes. All eleven species of fish collected in the Araguari River lower section showed profiles and frequencies of genotoxic damage similar to those previously observed in tests with D. rerio, confirming that genotoxic pollutants present in these waters are also causing damage to native fish species.

Intestinal bacteria diversity of suckermouth catfish (Pterygoplichthys pardalis) in the Cd, Hg, and Pb contaminated Ciliwung River, Indonesia

The contamination of aquatic environments with heavy metals poses a serious threat to fish, potentially leading to diseases or even death. Therefore, there is an urgent need for studies to investigate the adaptability of fish in heavy metal-contaminated environments. Several studies have explored the adaptability of suckermouth catfish (P. pardalis) to survive in the contaminated Ciliwung River. The findings obtained showed that the presence of intestinal bacteria helped these fish overcome the heavy metals in their intestines, thereby enabling the fish to survive. Analysis using the Next Generation Sequencing (NGS) technology has succeeded in identifying diversity of these bacteria in P. pardalis living in the Ciliwung River, which contaminated with Cd (0.3-1.6 ppm in the water & 0.9-1.6 ppm in the sediment), Hg (0.6-2 ppm in the water & 0.6-1.8 ppm in the sediment), and Pb (59.9-73.8 ppm in the water & 26.1-58.6 ppm in the sediment). Diversity index of intestinal bacteria in P. pardalis was relatively high, but it had a negative correlation with the presence of these contaminants. Actinobacteria, Firmicutes, and Proteobacteria were abundant in the intestines of P. pardalis from the upstream to downstream of the river, with an overall abundance range of 15-48%. Furthermore, Mycobacterium along with 6 other genera were identified as core intestinal bacteria. The presence of these bacterial communities in all the samples affected their survival in heavy metals-contaminated rivers. The fish's adaptability to live in this harsh environment indicated that it has the potential to be utilized as a bioremediator of heavy metals in river sediments.

Metal bioaccumulation in fish from the Araguari River (Amazon biome) and human health risks from fish consumption

Recently, high concentrations of metals have been found in the waters from sampling sites located in the Araguari River lower section. These metals can be bioaccumulated by fish, but also biomagnified, representing a potential risk through human consumption. Here, we aimed to (1) determine the metal concentrations in muscle samples from fish; (2) evaluate bioaccumulation of metals in muscle tissue of fish species with different feeding behaviors; and (3) investigate the risks of single metals, as well as mixture of metals, to human fish consumption. Eleven fish species were sampled (3 carnivorous, 5 omnivorous, and 3 detritivorous). In four fish species, Cd and Pb concentrations exceeded the Brazilian maximum limits (MLs) for human consumption. Individually, Pb and Cd concentrations in the muscle of these fish indicate risks to human health. When considering the mixture of metals, the consumption of all fish species represents risks. The highest risks implicate detritivorous species. For all fish species evaluated, the estimated daily intake (EDI) of Hg shows values above its reference dose (RfD). Our results suggest the need to establish an environmental monitoring program that aims to preserve environmental quality, biodiversity, and human health. It is also necessary to develop actions that aim to educate Amazonian populations on safe fish preparation and consumption.

Impairment in Working Memory and Executive Function Associated with Mercury Exposure in Indigenous Populations in Upper Amazonian Peru

The Matsigenka people living traditional lifestyles in remote areas of the Amazon rely on a fish-based diet that exposes them to methylmercury (MeHg) at levels that have been associated with decreased IQ scores. In this study, the association between Hg levels and working memory was explored using the framework of the Multicomponent Model. Working memory tasks were modified to fit the culture and language of the Matsigenka when needed and included measures for verbal storage (Word Span) visuospatial storage (Corsi Block Task) and a measure of executive functions, the Self-Ordered Pointing Task (SOPT). An innovation of the Trail Making Tests A & B (TMT A & B) was pilot tested as another potential measure of executive functions. The mean hair Hg levels of 30 participants, ages 12 to 55 years, from three different communities (Maizal, Cacaotal and Yomibato) was 7.0 ppm (sd = 2.40), well above the World Health Organization (WHO) limit for hair of 2.0 ppm and ranged from 1.8 to 14.2 ppm, with 98% of a broader sample of 152 individuals exceeding the WHO limit. Hair Hg levels showed significant associations with cognitive performance, but the degree varied in magnitude according to the type of task. Hg levels were negatively associated with executive functioning performance (SOPT errors), while Hg levels and years of education predicted visuospatial performance (Corsi Block accuracy). Education was the only predictor of Word Span accuracy. The results show that Hg exposure is negatively associated with working memory performance when there is an increased reliance on executive functioning. Based on our findings and the review of the experimental research, we suggest that the SOPT and the Corsi Block have the potential to be alternatives to general intelligence tests when studying remote groups with extensive cultural differences.

Health Risk Assessment Attributed to Consumption of Fish Contaminated with Mercury in the Rio Branco Basin, Roraima, Amazon, Brazil

The aim of this study was to assess the health risk attributable to the consumption of mercury-contaminated fish for the urban and non-urban populations living in the Roraima state, Amazon, Brazil. Seventy-five fish specimens distributed across twenty different species, comprising four trophic levels (i.e., herbivore, omnivore, detritivore, and carnivore), were collected at four locations in the Branco River Basin. The fish samples were sent to the Toxicology Laboratory at Evandro Chagas Institute to determine the total-Hg levels by using the cold vapor atomic system (CVAAS). The total-Hg levels ranged from 0 to 3.159 µg/g. The average concentration in non-carnivorous species (n = 32) was 0.116 µg/g, and among carnivorous fish (n = 43), it was 0.869 µg/g. The weighted average of contamination levels for all samples was 0.545 µg/g. The health risk assessment was conducted according to the methodology proposed by the World Health Organization and different scenarios of human exposure were considered, based on three levels of fish consumption (low: 50 g/day; moderate: 100 g/day and high: 200 g/day). Women of childbearing age ingest 5 to 21 times more mercury than the dose considered safe by the U.S. EPA and intake a dose from 2 to 9 times higher than the safe dose proposed by FAO/WHO. Children under 5 years of age ingest from 18 to 75 times the dose proposed by the U.S. EPA and from 8 to 32 more mercury than the limit proposed by FAO/WHO. In summary, regardless of the level of fish consumption, type of residency (urban or non-urban), and the subset of the population analyzed, anyone who consumes fish from the locations sampled is at high risk attributable to mercury ingestion, with the only exception of adult men, who consume an average of 50 g of fish per day.

Fish consumption habits of pregnant women in Itaituba, Tapajós River basin, Brazil: risks of mercury contamination as assessed by measuring total mercury in highly consumed piscivore fish species and in hair of pregnant women

The Tapajós River basin in the Amazon region, Brazil is one of the most active gold mining areas in the world. In this study, we evaluated fish consumption habits and mercury exposure in 110 pregnant women in the city of Itaituba by measuring their total hair mercury concentrations. In addition, we investigated seasonal differences in mercury concentrations in two highly consumed piscivorous fish species, tucunaré (Cichla spp.) and pescada (Plagioscion squamosissimus). Total fish mercury concentrations (THg) during the dry season were 0.62±0.07 mg/kg for Cichla spp. and 0.73±0.08 mg/kg for P. squamosissimus. During the rainy season they were 0.39±0.04 and 0.84±0.08 mg/ kg, respectively. Of our participants 44 % declared that they ate Cichla spp. and 67 % P. squamosissimus. Mean mercury concentration in their hair was 1.6±0.2 mg/kg and was above the US Environmental Protection Agency (US EPA) reference dose of 1 mg/kg in 48 % of them. Mean fish THg concentrations were also above the joint Food and Drug Administration and US EPA safety limit of 0.5 mg/kg for P. squamosissimus during both seasons and for Cichla spp. during the dry season only. These results show that pregnant women should avoid consumption of these piscivorous fish species during pregnancy and call for a regular programme to monitor Hg levels in that area.

Landscape composition and inorganic contaminants in water and muscle tissue of Plagioscion squamosissimus in the Araguari River (Amazon, Brazil)

Amazonian aquatic environments are seriously impacted by dam-building and deforestation, among other threats. Therefore, the present study aimed to examine water quality in the middle and lower course of the Araguari River with respect to the composition of vegetative cover and the concentration of As, Cd and Hg in order to determine risks to the preservation of biota and risks to human health from consumption of P. squamosissimus contaminated with these inorganic elements. To accomplish this, water samples and fish specimens were collected in the middle and lower Araguari River in 2019. The concentration of inorganic contaminants was analyzed by atomic absorption spectrophotometry. These stretches of the Araguari River presented higher proportions of forest fragments and evident expansion of buffalo pastures. According to Brazilian legislation, the concentrations of Cd and Hg in the water samples represented risk quotient values > 1, indicating risk to the preservation of aquatic biota. In particular, the concentrations of Cd in the muscle tissue of P. squamosissimus in the lower Araguari River also indicated risks to human health. The bioaccumulation factor indicated that Hg is bioavailable in the water. It can be concluded that water imbalances in the middle and lower Araguari River compromise the health of both aquatic and human life.

Exposição ao mercúrio e anemia em crianças e adolescentes de seis comunidades da Amazônia Brasileira

Resumo O mercúrio (Hg) é uma substância tóxica, sendo o consumo de pescados uma das principais fontes de exposição da população. Este artigo visa avaliar a associação entre anemia e exposição ao Hg na população infanto-juvenil de seis comunidades ribeirinhas da Amazônia Brasileira. Realizou-se a análise secundária de dados de estudos seccionais, incluindo 1.318 indivíduos, divididos em dois grupos segundo a influência do garimpo (grupo A sob influência, e grupo B sem influência). Métodos de análise multivariada foram realizados para verificar a associação entre variável de exposição (Hg no cabelo) e anemia, estratificando pelos grupos. Foram observados 348 casos de anemia (27,1%), sendo 206 entre o grupo B e 142 no grupo A. Houve diferença na mediana dos níveis de Hg entre os grupos (A = 12,8µg/g e B = 4,3µg/g, p = 0,01). Foi observada associação entre Hg no cabelo ≥ 6,0µg/g e anemia (OR = 1,38; IC95% = 1,02-1,87), fato que foi magnificado para o grupo A quando realizada estratificação (OR = 2,23; IC95% = 1,28-3,90). O estudo mostrou elevados níveis de Hg, principalmente no grupo A, e que essa substância pode ser um possível fator de risco para anemia. Além disso, as áreas geográficas pareceram modificar esse efeito, apontando para influência de outros fatores, fato que deve ser melhor avaliado.

Risk of exposure to Hg and pesticides residues in a traditional fishing community in the Amazon: a probabilistic approach based on dietary pattern

Exposure to mercury (Hg) and pesticides (o.p'DDT, p.p'DDT, o.p'DDE, and p.p'DDE) in the Amazon through eating fish is of concern due to the large participation of this food in the diet of traditional fishing communities. The aim of this study was to evaluate the estimated daily intake (EDI) and the incremental lifetime cancer risk associated with Hg and o.p'DDT, p.p'DDT, o.p'DDE, and p.p'DDE in an Amazonian community. The results showed that for Hg, the EDI from carnivorous and detritivorous fish had the highest values, while for pesticides, the EDI from detritivorous fish intake had the highest value. The incremental lifetime cancer risk was below the permitted limit. A recommendation for controlling the high risk of exposure includes the reduction of detritivorous fish ingestion and/or replacement with herbivorous fish, which had lower EDI. We highlight the importance of investigating the human dietary patterns when estimating risk of exposure to Hg and pesticides.

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

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.

Efficacy of Hair Total Mercury Content as a Biomarker of Methylmercury Exposure to Communities in the Area of Artisanal and Small-Scale Gold Mining in Madre de Dios, Peru

Total mercury content (THg) in hair is an accepted biomarker for chronic dietary methylmercury (MeHg) exposure. In artisanal and small-scale gold mining (ASGM) communities, the validity of this biomarker is questioned because of the potential for contamination from inorganic mercury. As mining communities may have both inorganic and organic mercury exposures, the efficacy of the hair-THg biomarker needs to be evaluated, particularly as nations begin population exposure assessments under their commitments to the Minamata Convention. We sought to validate the efficacy of hair THg for public health monitoring of MeHg exposures for populations living in ASGM communities. We quantified both THg and MeHg contents in hair from a representative subset of participants (N = 287) in a large, population-level mercury exposure assessment in the ASGM region in Madre de Dios (MDD), Peru. We compared population MeHg-THg correlations and %MeHg values with demographic variables including community location, sex, occupation, and nativity. We observed that hair MeHg-THg correlations were high (r > 0.7) for all communities, regardless of location or nativity. Specifically, for individuals within ASGM communities, 81% (121 of 150 total) had hair THg predominantly in the form of MeHg (i.e., >66% of THg) and reflective of dietary exposure to mercury. Furthermore, for individuals with hair THg exceeding the U.S. EPA threshold (1.0 μg/g), 88 out of 106 (83%) had MeHg as the predominant form. As a result, had urine THg solely been used for mercury exposure monitoring, approximately 59% of the ASGM population would have been misclassified as having low mercury exposure. Our results support the use of hair THg for monitoring of MeHg exposure of populations in ASGM settings where alternative biomarkers of MeHg exposure are not feasible.

High concentrations of metals in the waters from Araguari River lower section (Amazon biome): Relationship with land use and cover, ecotoxicological effects and risks to aquatic biota

The Araguari River is one of the most important water body in the Brazilian state of Amapá. However, the quality of its waters has been deteriorating and, recently, high concentrations of metals were found in water samples collected from its lower section. Overall, we aimed to evaluate land use and cover around three sampling sites located in the Araguari River lower section and its contribution to water pollution by metals; correlate land use pattern with detected metal concentrations; assess acute toxicity using the Daphnia similis test and genotoxicity using the Danio rerio bioassay of water samples from the three sampling sites; and investigate the risks arising from metals present in waters to aquatic biota. Riparian forest around all sampling sites is fragmented owing to the expansion of pasture areas, which showed a significant positive correlation (p < 0.05) with the concentrations of Hg and Cu in water samples. Water samples from sampling sites 2 and 3 presented acute toxicity for D. similis, and the D. rerio bioassay confirmed the presence of genotoxic pollutants in the waters from all sampling sites. Our preliminary risk assessment showed that individual concentrations and the mixture of metals posed a high risk to aquatic biota. Taken together, our results demonstrate that the conversion of native forest to pastureland contributes to water contamination by metals, which contributes to the risks to aquatic biota.

Fish Sellers Knowledge on Exposure of Mercury from Fish in the Kenjeran Beach Area, Surabaya

The development in industrialization and human activities causing public health problems related to the safety of fish consumed in areas where industrialization is taking place especially in Surabaya city. One of the concerns on food safety especially in fish is the contamination of mercury. This study aimed to measure and identify the mercury contamination in fish especially in freshwater and saltwater fish and to assess the mercury contamination knowledge level among fish sellers in Kenjeran Beach area, Surabaya. A number of 36 sellers from eight traditional markets located near Kenjeran Beach area were randomly selected and 72 fish were taken to the laboratory to assess the mercury concentration. The sellers were given a questionnaire to assess their knowledge of mercury pollution in fish. The result showed that 55.5% of saltwater fish were contaminated with mercury (mean=0.00686 ppm). The mean score of questionnaires was 7.69 out of 19. There was no significant association between the questionnaire score and fish’s mercury concentration. This study highlights the association between sellers buying fish from Kenjeran Beach and fish’s mercury contamination. The increased risk of contamination from food can occur due to the low awareness among citizens and food sellers. Therefore, direct and indirect strategies to empower people who live near Kenjeran Beach Area to choose low mercury concentrated fish are needed.

Economic Impacts on Human Health Resulting from the Use of Mercury in the Illegal Gold Mining in the Brazilian Amazon: A Methodological Assessment

Artisanal small-scale gold mining (ASGM) in the Amazon results in the dumping of tons of mercury into the environment annually. Despite consensus on the impacts of mercury on human health, there are still unknowns regarding: (i) the extent to which mercury from ASGM can be dispersed in the environment until it becomes toxic to humans; and (ii) the economic value of losses caused by contamination becomes evident. The main objective of this study is to propose a methodology to evaluate the impacts of ASGM on human health in different contexts in the Brazilian Amazon. We connect several points in the literature based on hypotheses regarding mercury dispersion in water, its transformation into methylmercury, and absorption by fish and humans. This methodology can be used as a tool to estimate the extent of environmental damage caused by artisanal gold mining, the severity of damage to the health of individuals contaminated by mercury and, consequently, can contribute to the application of fines to environmental violators. The consequences of contamination are evaluated by dose-response functions relating to mercury concentrations in hair and the development of the following health outcomes: (i) mild mental retardation, (ii) acute myocardial infarction, and (iii) hypertension. From disability-adjusted life years and statistical life value, we found that the economic losses range from 100,000 to 400,000 USD per kilogram of gold extracted. A case study of the Yanomami indigenous land shows that the impacts of mercury from illegal gold mining in 2020 totaled 69 million USD, which could be used by local authorities to compensate the Yanomami people.

Non-Lethal Concentration of MeHg Causes Marked Responses in the DNA Repair, Integrity, and Replication Pathways in the Exposed Human Salivary Gland Cell Line

In Brazilian northern Amazon, communities are potentially exposed and vulnerable to methylmercury (MeHg) toxicity through the vast ingestion of fish. In vivo and in vitro studies demonstrated that the salivary glands as a susceptible organ to this potent environmental pollutant, reporting alterations on physiological, biochemical, and proteomic parameters. However, the alterations caused by MeHg on the gene expression of the exposed human salivary gland cells are still unknown. Therefore, the goal was to perform the transcriptome profile of the human salivary gland cell line after exposure to MeHg, using the microarray technique and posterior bioinformatics analysis. The cell exposure was performed using 2.5 µM MeHg. A previously published study demonstrated that this concentration belongs to a range of concentrations that caused biochemical and metabolic alterations in this linage. As a result, the MeHg exposure did not cause lethality in the human salivary gland cells line but was able to alter the expression of 155 genes. Downregulated genes (15) are entirety relating to the cell metabolism impairment, and according to KEGG analysis, they belong to the glycosphingolipid (GSL) biosynthesis pathway. On the other hand, most of the 140 upregulated genes were related to cell-cycle progression, DNA repair, and replication pathway, or cellular defenses through the GSH basal metabolism. These genomic changes revealed the effort to the cell to maintain physiological and genomic stability to avoid cell death, being in accordance with the nonlethality in the toxicity test. Last, the results support in-depth studies on nonlethal MeHg concentrations for biomarkers identification that interpret transcriptomics data in toxicological tests serving as an early alert of physiological changes in vitro biological models.

Mercury Exposure in Munduruku Indigenous Communities from Brazilian Amazon: Methodological Background and an Overview of the Principal Results

The Amazonian indigenous peoples depend on natural resources to live, but human activities' growing impacts threaten their health and livelihoods. Our objectives were to present the principal results of an integrated and multidisciplinary analysis of the health parameters and assess the mercury (Hg) exposure levels in indigenous populations in the Brazilian Amazon. We carried out a cross-sectional study based on a census of three Munduruku indigenous villages (Sawré Muybu, Poxo Muybu, and Sawré Aboy), located in the Sawré Muybu Indigenous Land, between 29 October and 9 November 2019. The investigation included: (i) sociodemographic characterization of the participants; (ii) health assessment; (iii) genetic polymorphism analysis; (iv) hair mercury determination; and (v) fish mercury determination. We used the logistic regression model with conditional Prevalence Ratio (PR), with the respective 95% confidence intervals (CI95%) to explore factors associated with mercury exposure levels ≥6.0 µg/g. A total of 200 participants were interviewed. Mercury levels (197 hair samples) ranged from 1.4 to 23.9 μg/g, with significant differences between the villages (Kruskal-Wallis test: 19.9; p-value < 0.001). On average, the general prevalence of Hg exposure ≥ 6.0 µg/g was 57.9%. For participants ≥12 years old, the Hg exposure ≥6.0 µg/g showed associated with no regular income (PR: 1.3; CI95%: 1.0-1.8), high blood pressure (PR: 1.6; CI95%: 1.3-2.1) and was more prominent in Sawré Aboy village (PR: 1.8; CI95%: 1.3-2.3). For women of childbearing age, the Hg exposure ≥6.0 µg/g was associated with high blood pressure (PR: 1.9; CI95%: 1.2-2.3), with pregnancy (PR: 1.5; CI95%: 1.0-2.1) and was more prominent among residents in Poxo Muybu (PR: 1.9; CI95%: 1.0-3.4) and Sawré Aboy (PR: 2.5; CI95%: 1.4-4.4) villages. Our findings suggest that chronic mercury exposure causes harmful effects to the studied indigenous communities, especially considering vulnerable groups of the population, such as women of childbearing age. Lastly, we propose to stop the illegal mining in these areas and develop a risk management plan that aims to ensure the health, livelihoods, and human rights of the indigenous people from Amazon Basin.

Mercury in blood, hair, and feces from subsistence fish-eating riverines of the Madeira River Basin (Western Amazon)

BACKGROUND

The Madeira River (Amazon Basin) has been impacted by activities related to artisanal and small-scale gold mining (ASGM), deforestation and burning (for timber, agriculture, and hydroelectric dam projects). All these activities contribute to environmental mercury (Hg) release and cycling into the Amazon ecosystem and thus to changing lifestyles.

METHOD

We assessed exposure to total and MeHg in two small riverine communities of the Madeira River (Amazon): Lago Puruzinho (LP, n = 26 families) and São Sebastião do Tapurú (SST, n = 31 families). Samples of human hair (n = 137), blood (n = 39), and feces (n = 41) were collected from adults and children (0-15 years of age).

RESULTS

In women of childbearing age from LP village, the mean blood total-Hg (THg) (45.54 ± 24.76 μg.L^-1) and MeHg (10.79 ± 4.36 μg.L^-1) concentrations were significantly (p = 0.0024; p < 0.0001, respectively) higher than in women from SST village (THg: 25.32 ± 16.75 μg.L^-1; MeHg: 2.32 ± 1.56 μg.L^-1) village; the trend in hair-Hg persisted but was statistically significant (p < 0.0145) only for THg (LP, 11.34 ± 5.03 μg. g^-1; SST, 7.97 ± 3.51 μg. g^-1). In women, the median hair:blood ratio of total Hg was 269. In children, the mean hair THg concentrations were 6.07 ± 3.60 μg. g^-1 and 6.47 ± 4.16 μg. g^-1 in LP and SST; thus, not significantly different (p = 0.8006). There was a significant association (p < 0.001) between hair-Hg concentrations of mothers and their respective children. The excretion of Hg in feces of women (0.52 μg. g^-1 dw) was not significantly different from children (0.49 μg. g^-1 dw). The only statistically significant correlation between Hg in feces and in hair was found in children, (n = 16, r_s = 0.38, p = 0.005). Significant relationship was seen between the levels of THg in blood and hair of women from LP and SST. Based on hair-Hg concentrations, fish consumption rate ranged from 94.5 to 212.3 g.day^-1.

CONCLUSION

Women and children excrete THg in feces in comparable concentrations. However, the mean fish consumption rate and blood MeHg are higher in the most remote villagers. Mother`s hair-Hg concentration is a good predictor of children's hair-Hg.

Genetic Polymorphism of Delta Aminolevulinic Acid Dehydratase (ALAD) Gene and Symptoms of Chronic Mercury Exposure in Munduruku Indigenous Children within the Brazilian Amazon

Genetic polymorphisms involved in mercury toxicokinetics and toxicodynamics may be associated with severe mercury toxicity. This study aimed to investigate the impact of an ALAD polymorphism on chronic mercury exposure and the health situation of indigenous children from the Brazilian Amazon. One-hundred-and-three indigenous children (under 15 years old) were included and genotyped (rs1800435) using a TaqMan validated assay. The mean age was 6.6 ± 4.5 years old, 60% were female, 49% presented with anemia, and the mean hair mercury concentration was 7.0 ± 4.5 (1.4-23.9) µg/g, with 49% exceeding the reference limit (≥6.0 µg/g). Only two children were heterozygous ALAD, while the others were all wild type. Minor allele frequency (ALAD G) and heterozygous genotype (ALAD CG) were 1% and 2%, respectively. The two children (12 and 14 years old) with the ALAD polymorphism had mercury levels above the average as well as had neurological symptoms related to chronic mercury exposure, such as visual field alterations, memory deficit, distal neuropathy, and toe amyotrophy. Both children also reported frequent consumption of fish in the diet, at least three times a week. In conclusion, our data confirm that an ALAD polymorphism can contribute to mercury half-life time, harmful effects, and neuropsychological disorders in indigenous children with chronic mercury exposure to gold mining activity.

Associations between perfluoroalkyl acids in serum and lead and mercury in whole blood among US children aged 3-11 years

Data for 639 US children aged 3-11 years who participated in the National Health and Nutrition Examination Survey during 2013-2014 were analyzed by fitting regression models with log10-transformed values of blood lead and methyl and total mercury as dependent variables and log10-transformed values of perfluoroalkyl acids (PFAA) as one of the independent variables. PFAAs considered were 2-(N-methyl-perfluorooctane sulfonamido) acetic acid (MPAH), linear isomer of perfluorooctanoic acid (NPFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluorohexane sulfonic acid (PFHxS), linear isomer of perfluorooctane sulfonic acid (NPFOS), and monomethyl branch isomer of perfluorooctane sulfonic acid (MPFOS). Adjusted regression slopes (β) indicating associations between the concentrations of PFAAs with blood lead and mercury were estimated. Statistically significant associations between concentrations of each PFAA and blood lead were observed. For 10% increases in concentrations of MPAH, NPFOA, PFNA, PFDA, PFHxS, NPFOS, and MPFOS, percent increases in the concentrations of blood lead were 0.45%, 1.59%, 0.78%, 0.32%, 0.65%, 1.32%, and 0.89% respectively. For 10% increases in concentrations of MPAH, PFNA, PFDA, and NPFOS, percent increases in the concentrations of total mercury in the blood were 1.62%, 1.44%, and 3.24% respectively. For 10% increases in concentrations of PFDA and NPFOS, percent increases in the concentrations of methyl mercury in the blood were 2.07% and 4.57% respectively. While concentrations of each of the seven PFAAs were positively associated with the concentrations of blood lead, concentrations of only PFDA and NPFOS were positively associated with increases in total and methyl mercury. PFAAs having positive associations with lead and mercury imply co-exposure and/or co-existence of high concentrations of PFAAs and lead/mercury. Since PFAAs as well as lead/mercury are known to be neurotoxic, nephrotoxic, and endocrine disruptors, their co-existence/co-exposure may lead to neurodevelopmental deficits that are additive/synergistic than neurodevelopmental deficits associated with exposures to PFAAs and lead/mercury alone. Future studies are needed to investigate additive/synergistic neurodevelopmental deficits associated with co-exposures to PFAAs and lead/mercury.

Mercury: What can we learn from the Amazon?

Mercury is among the ten most dangerous chemicals for public health, and is a priority concern for the 128 signatory countries of the Minamata Convention. Mercury emissions to the atmosphere increased 20% between 2010 and 2015, with South America, Sub-Saharan Africa and Southeast Asia as the main contributors. Approximately 80% of the total mercury emissions in South America is from the Amazon, where the presence of the metal is ubiquitous and highly dynamic. The presence of this metal is likely increasing, with global consequences, due to events of the last two years including extensive biomass burning and deforestation, as well as mining activities and the construction of large-scale projects, such as dams. Here we present a concise profile of this mobilization, highlighting the human exposure to this metal in areas without mining history. Mercury reaches the food chain in its most toxic form, methylmercury, intoxicating human populations through the intake of contaminated fish. Amazonian populations present levels over 6 ppm of hair mercury and, according to the 175:250:5:1 ratio for methylmercury intake : mercury hair : mercury brain : mercury blood, consume 2-6 times the internationally recognized reference doses. This exposure is alarmingly higher than that of other populations worldwide. A possible biphasic behavior of the mercury-related phenomena, with consequences that may not be observed in populations with lower levels, is hypothesized, supporting the need of improving our knowledge of this type of chronic exposure. It is urgent that we address this serious public health problem in the Amazon, especially considering that human exposure may be increasing in the near future. All actions in this region carry the potential to have global repercussions.