First record of mercury concentrations and stable isotopes (13C & 15N) in albacore (Thunnus alalunga) from the Western Equatorial Atlantic Ocean.

This paper reports the first record of total mercury (THg) concentrations in albacore (Thunnus alalunga), one of the main tuna species caught from the Western Equatorial Atlantic Ocean and presents a preliminary comparison with other regions and tuna species. Mean, standard deviation and range of concentrations in T. alalunga (515 ± 145 ng g-1 ww; 294-930 ng g-1 ww) with 92 % being of methyl-Hg, are higher than in albacore from other Atlantic Ocean subregions despite their smaller body size. These concentrations are similar to those from the Pacific and Indian oceans, but lower than in the Mediterranean. Compared to other sympatric tuna species, concentrations are higher than those in T. albacares and similar to T. obesus. These results are discussed considering the potential differences in stable isotope values (13C and 15N) of T. alalunga populations from multiple oceanic areas and compared to other tuna species worldwide.

Mercury distribution, bioaccumulation, and biomagnification in riparian ecosystems from a neotropical savanna floodplain, Araguaia River, central Brazil.

Litterfall is the main source of dry deposition of mercury (Hg) into the soil in forest ecosystems. The accumulation of Hg in soil and litter suggests the possibility of transfer to terrestrial invertebrates through environmental exposure or ingestion of plant tissues. We quantified total mercury (THg) concentrations in two soil layers (organic: 0-0.2 m; mineral: 0.8-1 m), litter, fresh leaves, and terrestrial invertebrates of the Araguaia River floodplain, aiming to evaluate the THg distribution among terrestrial compartments, bioaccumulation in invertebrates, and the factors influencing THg concentrations in soil and invertebrates. The mean THg concentrations were significantly different between the compartments evaluated, being higher in organic soil compared to mineral soil, and higher in litter compared to mineral soil and fresh leaves. Soil organic matter content was positively related to THg concentration in this compartment. The order Araneae showed significantly higher Hg concentrations among the most abundant invertebrate taxa. The higher Hg concentrations in Araneae were positively influenced by the concentrations determined in litter and individuals of the order Hymenoptera, confirming the process of biomagnification in the terrestrial trophic chain. In contrast, the THg concentrations in Coleoptera, Orthoptera and Hymenoptera were not significantly related to the concentrations determined in the soil, litter and fresh leaves. Our results showed the importance of organic matter for the immobilization of THg in the soil and indicated the process of biomagnification in the terrestrial food web, providing insights for future studies on the environmental distribution of Hg in floodplains.

Mercury in Fish and Human Hair and Estimated Dietary Intake in a Riverside Community of the Madeira River Basin in the Brazilian Amazon.

Mercury (Hg) is a chemical element that poses risks to human health due to its high toxicity and environmental persistence. We determined the total Hg (THg) and methyl Hg (MeHg) concentrations in hair samples from residents of the Demarcação District (Porto Velho, Rondônia) in the Brazilian Amazon, as well as in water and fish samples, to evaluate factors influencing human exposure. The average THg concentration in human hair was 7.86 ± 6.78 mg kg-1 and it was significantly higher in men, with an increasing trend related to age. There was no significant difference between female age groups. Human exposure to Hg through water was negligible compared to fish consumption. The average weekly intake estimates in the community varied between 1.54 and 4.62 µg kg-1, substantially higher than the recommended limit. The fish species with the highest amounts safe for daily consumption were herbivores and detritivores. Our results contribute to an understanding of how exposure to Hg affects the health of riverside populations and provide insights for new research to develop methods to mitigate such exposure and thus improve the quality of life of Amazonian people.

A 35-Year Record (1987-2022) of Hg Concentrations in Two of the Fish Species Most Consumed by People Living in the Upper Madeira River Basin, Brazilian Amazon Region.

This study presents a 35-year record of total mercury (Hg) concentrations in the detritivore fish Prochilodus nigricans (Curimatã) and the carnivore Cichla pleiozona (Tucunaré), two of the most widely distributed, ecologically important and consumed fish species in the upper Madeira River Basin in the Western Brazilian Amazon. Fish samples from the major Madeira River and marginal lakes and tributaries were compared. Irrespective of site, Hg concentrations were higher in the carnivore fish compared to the detritivore. Hg concentrations increased 5-fold in C. pleiozona in the past three decades, whereas they remained relatively constant in P. nigricans when analyzing the entire 35-year period. When analyzed separately, fish in the main river and marginal lake and tributaries presented the same pattern of Hg variation, with a significant increase in Hg concentrations in the carnivore and in the detritivore in marginal lakes and tributaries but not in the main river. This was in line with the increase in methyl-Hg production in tributaries, mostly associated with deforestation in the past decade in the basin. Although an increase in direct emissions from artisanal gold mining also occurred in the past decade, this caused virtually no impact on fish Hg concentrations, suggesting atmospheric emission and deposition in forests and further export to water systems as an intermediate link with fish Hg concentrations.

Mercury Contamination as an Indicator of Fish Species' Trophic Position in the Middle Araguaia River, Brazil.

This study evaluates the use of mercury (Hg) concentrations in fish muscle tissue to determine a species' trophic position (TP) in its environment. A campaign conducted in 2019 along 375 km in the middle Araguaia River basin, Brazil, resulted in 239 organisms from 20 species collected. The highest total mercury (THg) concentrations were found in Pellonacastelnaeana (6.93 µg·g-1, wet weight) and in Triportheus elongatus (3.18 µg·g-1, wet weight), whose TPs were different according to the FishBase database. However, they occupied the same trophic level in this study. The intra-specific comparison showed a difference in Hg concentrations between individuals captured in distinct sites. The study of the biota-sediment accumulation factor (BSAF) showed that spatiality interferes with a species' TP. Statistical analyses revealed that when we used a predicted species' TP based on each individual's size, it explained 72% of the variability in THg concentration across all fish species. Multiple regression analysis confirmed that standard length and FishBase values are positively associated with THg (R2 = 0.943). These results point to Hg as a viable indicator of a fish species' TP since it reflects regional, biological, and environmental factors, as demonstrated here for the middle Araguaia River.

Ecological risk of mercury in bottom sediments and spatial correlation with land use in Neotropical savanna floodplain lakes, Araguaia River, Central Brazil.

The Araguaia River floodplain is an important biogeographic boundary between the two largest South American biomes: the Cerrado (Brazilian Savanna) and the Amazon rainforest. The large-scale degradation due to land use conversion experienced in the Araguaia River watershed represents a potential source of mercury (Hg) transport to aquatic ecosystems. However, more information is needed about the dynamics of Hg distribution in savanna floodplains, including the Araguaia River floodplain. We analyzed total mercury (THg) concentrations in the bottom sediments of 30 lakes connected to the Araguaia River and four tributaries, aiming to evaluate the environment's integrity based on the geoaccumulation index (Igeo) and the ecological risk index (ERI). The principal component analysis was applied to examine associations between Hg concentrations, environmental conditions, and land use intensity among lakes associated with different river systems. We used indicator cokriging to identify areas with a greater probability of Hg pollution and ecological risk associated with land use intensity. The land use data showed the predominance of areas used for pasture in the Araguaia River basin. THg concentrations in the sediments varied between 22.6 and 81.9 ng g-1 (mean: 46.5 ± 17.7 ng g-1). Sediments showed no significant pollution (Igeo: 1.35 - 0.50; Classes 1 and 2) and low to considerable ecological risks (ERI: 23.5-85.1; Classes 1 to 3). THg in bottom sediments was associated with land use, water turbidity and electrical conductivity, and sediment organic matter. The indicator cokriging indicates a moderate to strong spatial dependence between land use intensity and Hg, confirming the contribution of anthropic sources to the increment of ecological risk but also the influence of extrinsic factors (such as environmental conditions, geology, and hydrology). Integrating sediment assessment and land use indices with geostatistical methods proved a valuable tool for identifying priority areas for Hg accumulation at a regional scale.

Flood pulse as a driving force of Pb variation in four fish guilds from Puruzinho Lake (western Amazon).

The Brazilian Amazon is heavily impacted by mining activities, especially by gold and cassiterite mining. Pb is a contaminant released during cassiterite extraction, and it stands out for its high toxicity. The present study aimed to evaluate the effect of flood pulse on Pb dynamics in four fish species with different feeding habits (Cichlapleiozona: carnivorous, Mylossomaduriventre: herbivorous, Prochilodus nigricans: detritivorous, and Serrasalmus rhombeus: piscivorous) over four hydrological periods in Puruzinho Lake (Brazilian Amazon), which receives water from the Madeira River. The risk assessment for daily Pb intake through the consumption of these fish by the local riverside population was also carried out. Fish species were sampled during four Amazonian hydrological periods: rising water, high water, falling water, and low water. Pb and stable isotopes (δ15N and δ13C) measurements were carried out on fish muscle. The flood pulse had the same effect on Pb concentrations of all the fish species regardless of their feeding habits, as we found a nonsignificant interaction between these variables. The Pb in fish muscle increased in the flood season (rising and high water) and decreased in the dry season (falling and low water). The Pb concentration in fish increased significantly with their trophic level (δ15N), evidencing the occurrence of biomagnification of the element along the trophic chain (R2 = 0.24). The main food source of the herbivorous fish (δ13C) was very distinct from that of the others, which had a large overlap in their values. Regarding risk assessment, the daily Pb intake through consumption of the herbivorous species during high water (17.82 ± 19.68 µg∙day-1) exceeded the limit determined by the Food and Drug Administration (FDA) of 12.5 µg∙day-1, representing a health risk to the riverside population of Puruzinho Lake.

Evaluating total mercury and methylmercury biomagnification using stable isotopes of carbon and nitrogen in fish from the Madeira River basin, Brazilian Amazon.

The isotopic signatures of carbon in primary consumer fish species in the Madeira River basin (Western Amazon) follow a pattern, with basal species feeding mainly on C3 (e.g., vascular plants and phytoplankton). In this study with 196 specimens of 19 fish species and six trophic guilds, significant differences were found between the two main groups of primary consumers (herbivores and detritivores) in the Madeira River basin. The mercury and δ15N data indicated that the fish specimens collected in Puruzinho and Cuniã Lakes provided greater trophic magnification factors (TMFs) for this metal than those found in the corresponding rivers. In relation to total mercury (0.09-2.07 µg g-1) and methylmercury (0.05-1.91 µg g-1) concentrations, the piscivorous/carnivorous species exceeded the values recommended by the World Health Organization, with a [MeHg:THg] ratio of about 80%. Preventive and educational practices should be adopted to reduce the possible toxic effects of Hg in the riverside population, for whom fish constitutes the main protein source. Also, biomonitoring of the fish species in the Madeira River should be conducted on an ongoing basis to detect possible alterations in mercury concentrations.

Spatial-temporal dynamics of Cr in fish from Puruzinho Lake (Western Amazon) and dietary risk assessment.

Cr contamination is a growing concern in the Amazon. Along with the rise of cattle farming in the region, tanneries are becoming more common and threatening environmental quality, since the effluents from this activity are rich in Cr. The objective of this study was to evaluate the seasonal and spatial dynamics of Cr in fish with different feeding habits from Puruzinho Lake, located in the Madeira River basin, also determining the daily intake of Cr associated with the consumption of these fish by the population that lives around the lake. Seasonality and feeding habits directly affected Cr dynamics in fish (p < 0.0001), with medians of Cr concentration ranging between 0.07 mg kg-1 in the species Cichla pleiozona, a carnivorous fish, and 0.62 mg kg-1 in Mylossoma duriventre, a herbivorous fish. The high Cr concentrations in M. duriventre were related to the biodilution effect of Cr in the trophic chain (R2 = 0.14, p < 0.0001). The consumption of M. duriventre by the population was associated with the highest daily intake of Cr (55.5 µg∙day-1), exceeding the recommended limits of Cr intake (35 µg∙day-1). However, no harmful effects on health are expected due to the ingestion of Cr through the consumption of fish from Puruzinho Lake. Spatial analysis showed an increasing trend in Cr concentrations along the Madeira River, suggesting that contaminants present in the river are being carried over long distances and are reaching preserved areas of the Amazon.

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 in wild animals and fish and health risk for indigenous Amazonians.

Total mercury (T-Hg) was determined in fish and wild animal meat consumed in indigenous villages in the Brazilian Amazon region, where there is no history of gold mining. The analyses were performed in an atomic absorption spectrophotometer by generation of cold vapour. Regardless of the dietary habit, 42.0% of the fish had levels of T-Hg higher than the values considered as safe for human health by the World Health Organisation. Exposure to mercury in the villages was higher due to the consumption of fish compared to the consumption of meat of wild animals. Carnivorous species showed a higher concentration of T-Hg, both in fish and in wild animals. It is preferred to consume meat from fish and non-predatory wild animals, which can reduce the risk of diseases resulting from high concentrations of mercury in the body of the studied indigenous people.

Influence of Iron on Physiological Parameters and Intracellular Microcystin in Microcystis Panniformis Strain Isolated from a Reservoir in the Amazon.

In the Amazon, the leaching from soil left unprotected by deforestation increases the entry of iron, among other elements, in aquatic ecosystems, which can cause cyanobacterial blooms. This study aimed to investigate the physiological response of a strain of Microcystis panniformis to iron variation. The strain was isolated from a reservoir located in the Western Amazon and produces microcystin-LR. After a period of iron deprivation, the cultures were submitted to three conditions: control (223 µgFe.L-1), treatment with 23 µgFe.L-1, and absence of iron. At regular intervals for eight days, the cell density, levels of chlorophyll a and microcystins were determined. On the second and fourth day, transcription of genes responsive to iron limitation was quantified. Starting on the fourth day of the experiment, the different iron concentrations affected growth, and on the eighth day in the iron-free condition cell density was 90% lower than in control. Chlorophyll cell quota in 23 µgFe.L-1 and control presented similar values, while without iron the cells became chlorotic as of the fourth day Toxin concentration in cells grow in 0 µgFe.L-1 in relation to the control. Higher transcription levels of the feo and fut genes were observed in the 0 µgFe.L-1 and 23 µgFe.L-1 treatments, indicating that the cells were activating high-affinity capture systems to reestablish an adequate concentration of intracellular iron. The increasing deforestation in the Jamari River Basin (Amazon region), can contribute to the occurrence of toxic cyanobacterial blooms due to the greater entrance of iron in water bodies.

Mercury biomagnification in an ichthyic food chain of an amazon floodplain lake (Puruzinho Lake): Influence of seasonality and food chain modeling.

Mercury (Hg) biomagnification in fish food chains is a relevant subject due to the high fish consumption of the Amazonian population and the high toxicity of this metal. In the Amazon, floodplain lake hydrodynamics change considerably along the four seasons of the hydrological cycle (rising water, high water, falling water and low water), which can influence Hg bioaccumulation in fish. The main aim of this study was to evaluate if Hg biomagnification is influenced by seasonality in a floodplain lake (Puruzinho Lake) in the Brazilian Amazon. Additionally, the influence of food chain modeling on measurement of Hg biomagnification was tested. Hg concentrations and stable isotope signatures (carbon and nitrogen) were estimated in four species, Mylossoma duriventre (herbivorous), Prochilodus nigricans (detritivorous), Cichla pleiozona (piscivorous) and Serrasalmus rhombeus (piscivorous). The "trophic magnification slope" (TMS) of the food chain composed by the four species was calculated and compared among the four seasons. There was no significant seasonal variation in TMS among rising water, high water, falling water and low water seasons (p = 0.08), suggesting that Hg biomagnification does not change seasonally. However, there was significant variation in TMS among different food chain models. Lower TMS was observed in a food chain composed of detritivorous and piscivorous fish (0.20) in comparison with a food chain composed of the four species (0.26). The results indicate food chain modeling influences TMS results.

Sediment contaminant levels and multibiomarker approach to assess the health of catfish Sciades herzbergii in a harbor from the northern Brazilian Amazon.

The current study combined chemical data on trace elements and polycyclic aromatic hydrocarbons (PAH) from sediment and used a multibiomarker approach in the catfish Sciades herzbergii to evaluate two different sites in São Marcos Bay, Brazil. Higher diffuse contaminations by trace elements and PAH were detected in the sediment of Porto Grande (PG) harbor than in the Ilha dos Caranguejos (IC) reference area. A multibiomarker was used in catfish to evaluate the bioavailability of PAH in bile and the effects of pollutants in target tissues. The parameters considered were oxidative stress biomarkers (SOD, CAT, GSH, GST and LPO) and histopathological alterations and were compared between two seasons. The biological responses revealed adverse effects on the population, as indicated by the presence of trace elements and PAH as stressors. Principal component analysis (PCA) of the biomarkers corroborated these results and indicated that fish from the PG site during the rainy season in 2019 exhibited many biological effects compared to 2018. Overall, the present study showed that environmental contamination increased over the years and provides information on the contamination of sediments in the São Marcos Bay, Brazil. The results showed that the presence of contaminants was correlated with the health status of the catfish S. herzbergii.

Prevalence and factors associated with mercury exposure in riverside communities in the Brazilian Western Amazon.

OBJECTIVE: to verify mercury exposure prevalence and identify its possible associated factors in two riverside communities in the Madeira River basin of the Western Brazilian Amazon. METHOD: a cross-sectional study comprising 95 children and adolescents. Age cycle, school attendance, Bolsa Família, number of siblings, meals, fish consumption, height by age were measured. Binary logistic regression was used to verify relationships between mercury exposure and its possible associated factors. RESULTS: the general prevalence of mercury exposure was 46.3%; children, 35.4%; and adolescents, 57.4%. Associated factors were fish consumption (aOR=1.84; 95%CI 1.56-2.16), age cycle (aOR=2.50; 95%CI 1.09-5.7), parasites (aOR=1.22; 95%CI 1.02-2.71), and short stature (aOR=1.32; 95%CI 1.05-2.02). CONCLUSION: mercury exposure prevalence in riverside children and adolescents was considered worrying, with association with fish consumption, adolescence, parasites, and short stature.

Ecological and biological factors associated to mercury accumulation in batoids (Chondrichthyes: Batoidea) from northeastern Brazil.

The present study aims to understand how ecological and biological factors affect the Hg levels in stingrays occurring in the Northeastern Brazilian coast. Total mercury (Hg), methylmercury (MeHg) and stable isotope (δ13C and δ15N) analyses were performed in five species. Hypanus americanus and Gymnura micrura showed the highest total Hg concentrations (300 and 176 ng.g-1, respectively). Hypanus guttatus exhibited a significant correlation between total Hg and size. Both species of the genus Hypanus presented the highest percentage of MeHg, around 100%, whereas the other species showed median percentages below 50%. The δ13C and δ15N signatures suggest that all studied species present the same foraging habitat but different trophic positions. Trophic position and animal size were the main factors influencing total Hg and MeHg concentrations in batoid species. The genus Hypanus, present in the Brazilian fish markets, showed concentrations above the accepted limits for human consumption.

Dynamics of mercury in the plankton of a hydroelectric reservoir, Western Amazon.

The energy transfer in the aquatic food chain is an important way for mercury (Hg) to enter other trophic levels. The objective of this work was to evaluate the Hg concentrations in plankton upstream and downstream of the Samuel Hydroelectric Reservoir, Rondônia, Brazil. Phytoplankton and zooplankton samples were collected with 20-µm and 68-µm nylon nets. An aliquot was removed for taxonomic analysis and another for total mercury determination, performed by cold vapor atomic absorption spectroscopy. Water physical-chemical parameters were also measured. The Hg concentrations in total plankton (phytoplankton and zooplankton samples) obtained at the three sampling upstream stations showed the same behavior, with the highest values registered in June 2005 (232 µg kg-1, 118 µg kg-1, 128 µg kg-1). The lowest values at stations J1 and M1 were recorded in November 2005 (4 µg kg-1 and 22 µg kg-1, respectively), while the lowest values at stations M4 and M8 were recorded in October 2005 (22 µg kg-1 and 5 µg kg-1, respectively). The Hg results found in the plankton in this study corroborate the results of other recent studies in the same region. The statistical analyses revealed that Hg concentrations in plankton do not explain the distribution of these organisms at the four sampling stations of Samuel Reservoir. Graphical Abstract.

Influence of size on total mercury (THg), methyl mercury (MeHg), and stable isotopes of N and C in green turtles (Chelonia mydas) from NE Brazil.

The green turtle (Chelonia mydas) is known to present an herbivorous diet as an adult; however, juveniles may have an omnivore habit, and these changes in food preference may affect the uptake and accumulation of pollutants, such as mercury (Hg). In order to better understand the influence of this ontogenetic shift on Hg accumulation, this study evaluates the concentrations of total mercury (THg), methyl mercury (MeHg), and stable isotopes of carbon and nitrogen (δ13C and δ15N) in a group of juveniles of the green turtle. Tissue samples (liver, kidney, muscle, and scutes) were sampled from 47 turtles stranded dead on the coast of Bahia, NE, Brazil, between 2009 and 2013. The turtles analyzed showed a size range of 24.9-62.0 cm and an average of 36.4 ± 7.2 cm of curved carapace length. The scutes showed to be a viable method for Hg monitoring in the green turtles. The concentrations of THg and MeHg decreased with increasing size. The isotope values of δ15N and δ13C did not show a clear relationship with the size, suggesting that the green turtles used in our work would be occupying similar trophic levels, and foraging habitat.

Dynamics of (total and methyl) mercury in sediment, fish, and crocodiles in an Amazonian Lake and risk assessment of fish consumption to the local population.

Increasing concerns have been raised about the toxicity of mercury (Hg) to humans, especially for those that consume a great amount of fish. High Hg concentrations have previously been measured in Amazonian waterbodies, both resulting from natural and anthropogenic sources. However, few studies have been conducted so far in Amazonian lakes that are fished by local populations. In addition, few of those studies included methylmercury (MeHg), the most toxic and bioaccumulative Hg form, and evaluated the influence of physico-chemical conditions and season on Hg dynamics. In the present study, total Hg (THg) and MeHg concentrations were measured in bottom sediment as well as in two fish and two crocodile species of the Amazonian Cuniã Lake. Bottom sediment MeHg concentrations were higher in the dry season than in the wet season, which is related to differences in physico-chemical (pH and electrical conductivity) conditions. Diet appeared to be related with animal tissue MeHg concentrations, with the herbivorous fish having lower MeHg levels than the predatory fish and crocodiles. Based on the measured tissue concentrations and published data on local person weight and fish consumption, MeHg risk to Cuniã Lake populations was estimated. Although the MeHg fish tissue concentrations did not exceed national and international standards, a significant risk to the local population is anticipated due to their high fish consumption rates. Graphical abstract.

Prevalence and factors associated with mercury exposure in riverside communities in the Brazilian Western Amazon / Prevalencia y factores asociados a la exposición al mercurio en las comunidades de ribeirina en la Amazonía occidental brasileña / Prevalência e fatores associados à exposição ao mercúrio em comunidades ribeirinhas na Amazônia Ocidental Brasileira

ABSTRACT Objective: to verify mercury exposure prevalence and identify its possible associated factors in two riverside communities in the Madeira River basin of the Western Brazilian Amazon. Method: a cross-sectional study comprising 95 children and adolescents. Age cycle, school attendance, Bolsa Família, number of siblings, meals, fish consumption, height by age were measured. Binary logistic regression was used to verify relationships between mercury exposure and its possible associated factors. Results: the general prevalence of mercury exposure was 46.3%; children, 35.4%; and adolescents, 57.4%. Associated factors were fish consumption (aOR=1.84; 95%CI 1.56-2.16), age cycle (aOR=2.50; 95%CI 1.09-5.7), parasites (aOR=1.22; 95%CI 1.02-2.71), and short stature (aOR=1.32; 95%CI 1.05-2.02). Conclusion: mercury exposure prevalence in riverside children and adolescents was considered worrying, with association with fish consumption, adolescence, parasites, and short stature.

RESUMEN Objetivo: verificar la prevalencia de exposición al mercurio e identificar sus posibles factores asociados en dos comunidades ribereñas en la cuenca del Río Madeira en la Amazonía occidental de Brasil. Método: estudio transversal compuesto por 95 niños y adolescentes. Se midieron las siguientes variables: ciclo de edad, asistencia a la escuela, Bolsa Família, número de hermanos, comidas, consumo de pescado, talla por edad. La regresión logística binaria se utilizó para verificar las relaciones entre la exposición al mercurio y sus posibles factores asociados. Resultados: la prevalencia general de exposición al mercurio fue del 46,3%; para niños, 35,4%; para adolescentes, 57.4%. Los factores asociados fueron consumo de pescado (ORa=1.84; IC95% 1.56-2.16), ciclo de edad (ORa=2.50; IC95% 1.09-5.7), presencia de parásitos (ORa=1.22; IC95% 1.02-2.71) y baja estatura (ORa=1.32; IC95% 1.05-2.02). Conclusión: la prevalencia de exposición al mercurio en niños y adolescentes ribereños se consideró preocupante, con una asociación con el consumo de pescado, la adolescencia, los parásitos y la baja estatura.

RESUMO Objetivo: verificar a prevalência da exposição ao mercúrio e identificar seus possíveis fatores associados em duas comunidades ribeirinhas da bacia do Rio Madeira da Amazônia Ocidental Brasileira. Método: estudo transversal composto por 95 crianças e adolescentes. Foram mensuradas as seguintes variáveis: ciclo de idade, frequência à escola, Bolsa Família, número de irmãos, refeições, consumo de peixe, estatura por idade. A regressão logística binária foi utilizada para verificar relações entre a exposição ao mercúrio e seus possíveis fatores associados. Resultados: a prevalência geral de exposição ao mercúrio foi de 46,3%; para crianças, 35,4%; para adolescentes, 57,4%. Os fatores associados foram consumo de peixe (ORa=1,84; IC95% 1,56-2,16), ciclo de idade (ORa=2,50; IC95% 1,09-5,7), presença de parasitas (ORa=1,22; IC95% 1,02-2,71) e baixa estatura (ORa=1,32; IC95% 1,05-2,02). Conclusão: a prevalência de exposição ao mercúrio em crianças e adolescentes ribeirinhos foi considerada preocupante, com associação ao consumo de peixe, adolescência, ter parasita e baixa estatura.