Exposição ao mercúrio em comunidades da Região do Baixo Tapajós

Abstract

Mercury (Hg) is a highly toxic element for human health. It can be derived from sources in the Earth's crust and from anthropogenic sources. The biotransformation, biomagnification and bioaccumulation of this metal in the ecosystem affects humans. One of its chemical forms, methylmercury, has the ability to accumulate in aquatic plants and fish and, thus, promote chronic exposure to Hg in people. Thus, the objective of this study is to characterize exposure to Hg in communities in the riverside region of the lower Tapajós, state of Pará. This is a cross-sectional, descriptive and quantitative research. The data in this study refer to collections carried out in 2022, in the communities of the lower Tapajós region. People of both sexes, aged 18 and over, with fixed residence in the riverside area for more than one year were included in this research. To collect the data, a questionnaire with sociodemographic, dietary and health questions was applied. In addition, 5 mL of venous blood was collected from each volunteer to measure total mercury (HgT). HgT measurements were performed using a DMA-80 Direct Mercury Analyzer, which quantifies Hg levels using atomic absorption spectrometry. For this study, the safety limit for Hg of 10 μg/L established by the World Health Organization (WHO) was considered. Descriptive analysis, daily Hg intake estimation, risk ratio calculation, Hg comparison tests (Kruskal-Wallis and Mann-Whitney tests) and Spearman correlation were performed. Statistical analyses were performed using JASP software, version 0.19.2.0. R software was used for Mann-Whitney analyses and to prepare boxplot graphs using the ggplot2 package. In this study, a significance level of p < 0.05 was adopted. Of the 570 individuals, females were the most present (63.33%). HgT levels were higher among men (median = 26.28 μg/L). Daily fish consumption was reported by 36.84% of participants, with a median HgT of 27.49 μg/L. Hg exposure is directly related to the total amount of fish consumed, with a strong positive correlation (ρ = 0.947, p < 0.001). A weak and negative correlation was observed between Hg levels and fruit consumption (ρ = -0.104, p = 0.013). There was a health risk, especially for women of childbearing age and based on the consumption of carnivorous fish. The risk estimate associated with fish consumption revealed that women of childbearing age have a risk ratio (RR) of 5.4, while adults of both sexes have a RR of 2.6. A statistically significant difference was found in the symptom of numbness in the hands (p = 0.0173) with median = 23.63 μg/L and body tremor (p = 0.047) with median = 23.43 μg/L. The riverside dwellers presented Hg levels above the WHO safety limit and are at risk to their health. Dietary patterns influenced Hg exposure. Hg exposure in the Tapajós River basin continues to be a public health concern, especially for riverside populations, as they depend on fish as their main food source. Therefore, mitigation measures, such as diversifying the diet with species from different trophic levels, encouraging the consumption of foods rich in antioxidants, and implementing educational campaigns on the risks of Hg exposure, are essential to reduce the health impacts of these populations. In addition, there is an urgent need to implement public policies aimed at environmental and health monitoring of populations exposed to Hg in the Amazon. Finally, further studies need to be carried out to clarify the association between the presence of symptoms that may be caused by the toxic and neurotoxic effects of Hg and exposure levels, as well as research that may determine possible risk markers for vulnerable populations.