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.

Study of an adsorption method for trace mercury based on Bacillus subtilis

In order to decrease the difficulty in trace mercury determination, an adsorption method for trace mercury based on Bacillus subtilis cells was proposed in this article. The adsorption process was characterized by optical microscopy and SEM. The adsorption mechanism was analyzed by IR. The adsorption performance was studied by measuring the concentration of supernate and calculating the adsorption efficiency. When adsorbing Hg2+, Bacillus subtilis cells gathered and their structure turned coarse. The IR results illustrated that functional groups bound with Hg for complexation during adsorption. Bacillus subtilis completed adsorption for trace Hg2+ in 15 min. The adsorption efficiency was maintained above 80% under low Hg2+ concentrations (<200 µg/L). The proposed study illustrates that Bacillus subtilis cells are highly efficient and easily obtained material for the adsorption of trace mercury, which shows potential to be further used in the pretreatment of trace Hg2+ detection.

Simple mercury determination using an enclosed quartz cell with cold vapour-atomic absorption spectrometry

A simple method for determining total inorganic mercury (Hg) in solution using an enclosed quartz cell applying cold vapour-atomic absorption spectrometry (CV-AAS) can reduce sample volume, reductant, and cost compared with those of official methods.

Hg(II) Analysis Using Poly(cysteine)-rGO Electrode

In the present work, we have developed a sensitive platform for the selective determination of Hg(II) ions based on reduced graphene oxide (rGO) electrode modified with poly cysteine (Poly-Cys). The Poly-Cys/rGO modified electrode was characterised by SEM, ATR-IR and its electrochemical behaviour was investigated through cyclic voltammetry and square wave voltammetry. The synergistic effect of rGO and poly-cysteine favoured the complexation of Hg(II) ions onto the surface of the modified electrode. The ions were then anodically stripped and the corresponding voltammograms recorded. The process of complexation followed by stripping was repeated with increasing concentrations of the metal ion. The linear range for the electrochemical determination of Hg(II) using the modified electrode was found to be from 0.05 to 2.7 μM with a detection limit of 0.006 μM. In addition, the electrode also exhibited good stability with negligible sensitivity towards interfering metal ions. The analytical applicability of the modified electrode was investigated by carrying out mercury determination in water samples obtained from various sources.

Mercury Determination in Natural Zeolites by Thermal Decomposition Atomic Absorption Spectrometry: Method Validation in Compliance with Requirements for Use as Dietary Supplements

Natural zeolites are hydrated aluminosilicate minerals that, due to their remarkable physical-chemical properties of being molecular sieves and cation exchangers, have applications in different areas such as environmental protection, catalysis, animal feed, and dietary supplements. Since natural zeolites may contain traces of undesirable compounds such as toxic metals, the accurate quantification of these elements is necessary. In this study, a direct method for Hg determination in zeolite samples based on the thermal desorption atomic absorption spectrometry (TD-AAS) technique is fully validated, taking into account the legislative requirements in the field. The chosen quantification limit was 0.9 µg kg-1, which is satisfactory for intended use. Trueness was evaluated by recovery rate using certified reference materials containing mercury, with satisfactory results. Other figures of merit, such as repeatability and measurement uncertainty, also fulfill the legislative requirements related to the analysis of dietary supplements. This paper presents, for the first time, a fully validated method for mercury determination in zeolite samples, and the obtained results reveal that the method can be applied successfully for the intended purpose.