The intake of fish and the mercury concentration of fishing families at the city of Imperatriz (MA), Brazil

Levels of Potentially Toxic and Essential Elements in Water and Estimation of Human Health Risks in a River Located at the Interface of Brazilian Savanna and Amazon Biomes (Tocantins River)

The Tocantins-Araguaia basin is one of South America's largest river systems, across three Brazilian states (Maranhão, Tocantins, and Pará), within the Legal Amazon region. Despite draining extensive Cerrado savanna and rainforest ecosystems, it has suffered significant degradation, notably in the past 40 years. Human activities, including agricultural expansion, deforestation, and the introduction of non-native species, have worsened the environmental damage, which is alarming since many residents and villages along the middle Tocantins River rely on it for water supply, recreation, and fishing. This study assessed the concentration of potentially toxic and essential elements in water samples from four sampling sites distributed along the middle Tocantins River. The monitoring occurred throughout 2023, involving the measurement of parameters both on-site and in the laboratory. Water quality and its health implications were evaluated using the Weighted Arithmetic Water Quality Index (WAWQI), the Water Quality Index (WQI), and the health risk assessment index. The levels of aluminum, copper, iron, magnesium, and selenium exceeded legal standards. Seasonal fluctuations indicate a complex dynamic influenced by climatic or seasonal factors, with February showing the highest values. Site P1, located in urban areas, exhibited elevated mean concentrations for conductivity, total dissolved solids (TDS), and chlorophyll, indicating the need for continuous monitoring. The nitrogen concentrations at P1 raise concerns regarding drinking water quality, which is a concern for the region's residents who use untreated river water. Despite seasonal variations in element concentrations, the overall WAWQI categorized all sections as "Excellent," and the WQI rated as "Good." Human health risk assessments detected no risks, but continuous monitoring and interventions are crucial for sustained water quality improvement.

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.

Mercury chloride toxicity in juveniles Prochilodus argenteus a species from southeastern Brazil

The aim of this study was to determine the 96-h LC₅₀ (lethal concentration for 50% of the test population in 96 h of observation) of mercury chloride (HgCl₂) and evaluated its absorption in the gills, liver, and muscle of juvenile "curimatã-pacu," Prochilodus argenteus. The fish were exposed for 4 days to different concentrations of HgCl₂: 0.000, 0.0375, 00.075, 0.150, 0.225, 0.300, and 0.400 mg L^-1 to get the 96-h LC₅₀, and the concentration of Hg in the tissues. The fish were exposed to different levels of HgCl2 (0.000, 0.0375, 00.075, 0.150, 0.225, and 0.300 mg L^-1), for 4 and 7 days, when different tissues (gills, liver, and muscle) were sampled. The mercury concentration values obtained were compared between tissues, days, and concentration of mercury in the water. The 96-h LC₅₀ for P. argenteus was 0.339 mg L^-1 of HgCl₂, within the range found for other neotropical and tropical species, showing a medium sensitivity. The concentration of Hg in the tissues increased from the muscle to the gills and liver, and according to the increasing concentration of HgCl₂ in the water. The fish liver is the most suitable tissue for environmental monitoring and for the evaluation of the consumed fished. Despite being the tissue that least accumulated mercury, the muscle must be evaluated because it is the part consumed by the population.

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.

Assessment of Mercury Concentration in Turtles (Podocnemis unifilis) in the Xingu River Basin, Brazil

Many studies on mercury contamination in aquatic biota deal with the effect of consuming metal-contaminated organisms on human health. In this study, we examined the factors that cause mercury contamination in Podocnemis unifilis in the Xingu River Basin of Mato Grosso and Pará States, Brazil. We quantified by atomic absorption spectroscopy with cold vapor the total mercury (THg) content in the liver and muscle samples of 50 Podocnemis unifilis specimens collected from the basin. The liver and muscle samples contained 134.20 ± 119.30 ng g−1 THg and 24.86 ± 26.36 ng g−1 THg, respectively. Each chelonian or meal has, on average, 5.34× more Hg than the highest level established as acceptable. From the results it can be inferred that, given the weekly consumption of chelonians, the riverine and indigenous communities in the Xingu River Basin are at risk of chronic consumption of Hg in amounts beyond the acceptable limit. The potential high risk to the health of this population is evident; however, the risk classification needs to be further studied.