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

Total Mercury Content in the Tissues of Freshwater Chelonium (Podocnemis expansa) and a Human Health Risk Assessment for the Amazon Population in Brazil

Researchers recognize the silent, negative and deleterious effects caused by mercury pollution in gold mining areas. Freshwater turtles are culturally part of the diet of riverside populations in the Amazon region and this area presents mercury (Hg) pollution issues mainly due to gold mining activities. Thus, this research aimed to evaluate the total mercury (THg) content in the different organs of Amazonian giant river turtle (Podocnemis expansa) and carry out a human health risk assessment associated with the consumption of these animals. This study was conducted in the Vila Balbina, municipality of Presidente Figueiredo, state of Amazonas, Brazil. Skin (n = 28), muscle (n = 19) and brain (n = 2) samples were analyzed by Atomic Absorption Spectrometry (TDA-AAS) and a DMA-80™ mercury analyzer was used for the total mercury determinations. The average values found for THg in the skin, muscle and brain samples were, respectively, 0.1045 mg·kg-1, 0.1092 mg·kg-1 and 0.0601 mg·kg-1. Thus, THg was observed even though the P. expansa were kept in captivity, possibly due to previous contamination by air, water and food. The Hazard Quotient (HQ) was calculated considering a 9.07 g·day-1 intake dose of P. expansa and the consumption of turtles once a week showed an HQ = 2.45, which may cause long-term injuries to human health. Although the muscle concentrations were below the maximum limit established by the World Health Organization (WHO) and Brazilian regulatory agencies, it is important to evaluate consumption factors such as amount ingested, frequency and animal gender, which may cause a potential risk to regular consumers due to mercury bioaccumulation. The WHO may consider various aspects in order to warn the Amazon population about the severity and silent hazard of this metal, especially due to the importance of this matrix in the region. This region urgently needs government actions to inhibit clandestine mining and to prevent future serious, chronic health problems of the entire population.

Atmospheric mercury in forests: accumulation analysis in a gold mining area in the southern Amazon, Brazil

The spatial distribution and dispersion of mercury (Hg) is associated with the structural conditions of the environment, primarily land use and vegetation cover. Man-made emissions of the metal from activities such as artisanal and small-scale gold mining (ASGM) can influence this distribution. Forest ecosystems are of particular importance as they constitute one of the most active environments in the biogeochemical cycle of Hg, and understanding these dynamics is essential to better understand its global cycle. In this study, we determined the content of Hg present in different forest strata (soil, leaf litter, herbaceous, underwood/bush, and arboreal), as well as the relationship between the presence of Hg and the landscape heterogeneity, percentage of gold mines, and ground slope. This study was carried out in tropical forest areas of the southern Brazilian Amazon. Accumulation and transport of Hg between forest strata was assessed in order to understand the influence of these forest environments on Hg accumulation in areas where ASGM occurs. We verified that there is a difference in Hg content between forest strata, indicating that atmospheric Hg is accumulated onto the arboreal stratum and transported vertically to strata below the canopy, i.e., underwood/bush and herbaceous, and subsequently accumulated in the leaf litter and transferred to the soil. Leaf litter was the stratum with the highest Hg content, characterized as a receptor for most of the Hg load from the upper strata in the forest. Therefore, it was confirmed that Hg accumulation dynamics are at play between the areas analyzed due to the proximity of ASGMs in the region. This indicates that the conservation of forest areas plays an important role in the process of atmospheric Hg deposition and accumulation, acting as a mercury sink in areas close to man-made emissions.

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.