Background: Fish is considered protective for coronary heart disease (CHD), but mercury (Hg) intake from fish may counterbalance beneficial effects. Although neurotoxic effects of methylmercury (MeHg) are well established, cardiovascular effects are still debated. The objective of the present study was to evaluate blood pressure in relation to Hg exposure and fish consumption among a non-indigenous fish-eating population in the Brazilian Amazon.

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Background: Mercury (Hg) is a ubiquitous environmental contaminant with neurodevelopmental and immune system effects. An informative biomarker of Hg-induced immunotoxicity could aid studies on the potential contribution to immune-related health effects.Objectives: Our objectives were to test the hypothesis that methylmercury (MeHg) exposures affect levels of serum biomarkers and to examine interactions between Hg and selenium (Se) in terms of these responses.Methods: This cross-sectional epidemiological study assessed adults living along the Tapajós River, a system long affected by MeHg. We measured antinuclear (ANA) and antinucleolar (ANoA) autoantibody levels and eight cytokines in serum samples (n = 232). Total Hg (including MeHg) and Se were measured in blood, plasma, hair, and urine.Results: The median (range) total Hg concentrations were 14.1 μg/g (1.1–62.4), 53.5 μg/L (4.3–288.9), 8.8 μg/L (0.2–40), and 3.0 μg/L (0.2–16.1) for hair, blood, plasma, and urine, respectively. Elevated titers of ANA (but not ANoA) were positively associated with MeHg exposure (log-transformed, for blood and plasma), unadjusted [odds ratio (OR) = 2.6; 95% confidence interval (CI): 1.1, 6.2] and adjusted for sex and age (OR = 2.9; 95% CI: 1.1, 7.5). Proinflammatory [interleukin (IL)-6 and interferon (IFN)-©], anti-inflammatory (IL-4), and IL-17 cytokine levels were increased with MeHg exposure; however, in the subset of the population with elevated ANA, proinflammatory IL-1®, IL-6, IFN-©, and tumor necrosis factor (TNF)-〈 and anti-inflammatory (IL-4) cytokine levels were decreased with MeHg exposure. Although Se status was associated with MeHg level (correlation coefficient = 0.86; 95% CI: 0.29, 1.43), Se status was not associated with any changes in ANA and did not modify associations between Hg and ANA titers.Conclusions: MeHg exposure was associated with an increased ANA and changes in serum cytokine profile. Moreover, alterations in serum cytokine profiles differed based on ANA response, suggesting a specific phenotype of MeHg susceptibility. Further research on the potential health implications of these observed immunological changes is warranted.

Although high levels of fish consumption and bioindicators of mercury exposure have been reported for traditional populations in the Amazon, little is known about their actual daily intake of Hg. Using an ecosystem approach, calculate daily mercury intake in adult fish-eaters, examine the relations between mercury intake and bioindicators of exposure and the factors that influence these relations. A cross-sectional dietary survey on fish and fruit consumption frequency was carried out with 256 persons from six villages of the Tapajo´s River. Fish portion per meal was determined. Mercury concentration was determined for 1123 local fish specimens. Daily mercury intake (mg/kg/day) was determined for men and women from each village using the average fish-mercury concentration for the fish caught in their fishing zone, the average quantity of fish per meal, fish-species frequency consumption and participants' body weight. Fish-mercury averaged 0.33 mg/g70.33. Daily mercury intake varied between 0 and 11.8 mg/kg/day (mean 0.92 mg/kg/day70.89) and varied by gender and village. Mean blood-and hair-mercury were 58.7736.1 mg/l and 17.9711.5 mg/g, respectively. There was a strong and positive relation between blood-mercury and daily mercury intake, with an inverse relation for fruit intake and schooling; significant variations were observed with immigrant status, and among villages. Hair-mercury was directly associated with daily mercury intake and inversely related to schooling and fruit consumption. Fruit consumption modified the relation between daily mercury intake and blood-mercury levels: for the same daily mercury intake, persons eating more fruit had lower blood-mercury concentrations (ANCOVA Interaction term: F ¼ 10.9, Po0.0001). The median difference of the ratio of blood-mercury to daily mercury intake between low and high fruit consumers was 26, representing a 26.3% reduction. These findings reveal high levels of daily mercury intake. Rigorous studies for developing risk-based reference doses in the Amazon should be undertaken to orient viable risk-management strategies to reduce exposure, while maintaining fish diet.