Before the Dam: A Fish-Mercury Contamination Baseline Survey at the Xingu River, Amazon Basin Before the Belo Monte Dam

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.

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.

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

This study aimed to evaluate the sociodemographic, behavioral, and biological profile and its relationship with the emergence of chronic non-communicable diseases in riverside populations in the Xingu region, Pará, Brazil. Characteristics related to health indicators and which risk factors are considered most important were analyzed. This is a cross-sectional, exploratory, and descriptive study. The sample consisted of riverside people of over 18 years of both sexes. The sample size (n = 86) was calculated with a confidence level of 95% and a sample error of 5%. The K-means clustering algorithm was adopted through an unsupervised method to divide the groups, and the values were expressed as a median. For continuous and categorical data, the Mann-Whitney and chi-square tests were used, respectively, and the significance level was set at p < 5%. The multi-layer perceptron algorithm was applied to classify the degree of importance of each variable. Based on this information, the sample was divided into two groups: the group with low or no education, with bad habits and worse health conditions, and the group with opposite characteristics. The risk factors considered for cardiovascular diseases and diabetes in the groups were low education (p < 0.001), sedentary lifestyle (p < 0.01), smoking, alcoholism, body mass index (p < 0.05), and waist-hip ratio, with values above the expected being observed in both groups. The factors considered important so as to be considered to have good health condition or not were the educational and social conditions of these communities, and one part of the riverside population was considered healthier than the other.

Investigating spatial-temporal contamination for two environments of the Amazon estuary: A multivariate approach

An assessment of environmental quality in Amazonian estuaries utilizing histological and immunohistochemical biomarkers concomitantly with analyses of trace metals in the tissues of Sciades herzbergii, also considering physical chemical analyzes of the water. 352 animals were captured from two sites and during two periods (dry and rainy). Site 1: São Marcos Bay - heavy anthropic influence and Site 2: Caeté estuary-preserved estuary. In the laboratory, the fish were weighed (g) and measured (cm). Fragments of gills and liver were analyzed using histology and immunohistochemistry (Caspase 3). The specimens from Site 1 presented a low-value condition factor, with the highest concentrations of Al, Cd, and Hg appearing in the muscle, and most severe damages to gills and liver. In contrast, individuals from Site 2 presented a high-value condition factor and showed low metal concentrations in the muscle with only slight tissue lesions. Furthermore, our results demonstrated that seasonal changes affect metal modulation and pathologies in fish at Site 1. The sentinel species chosen in this study is considered a strong bioindicator of pollution and the combination of different biomarkers was efficient in providing a clear view of the signs of exposure to pollutants, and the risks posed to fish health by the presence of metals in the environment, especially in Site 1.