Exploring mercury and selenium dynamics in Amazonian human populations: Insights from urine, blood, and plasma...

The Amazonian riverside population is one of the most impacted by mercury, interestingly, with distinct selenium values in blood, generally among the highest worldwide. The interaction between Hg and Se remains to be thoroughly investigated and could provide insights into the fate of these elements and the potential for selenium-mediated detoxification. The current study explores the levels of both elements, determined by inductively coupled plasma mass spectrometry (ICP-MS), in blood, plasma, and urine, of 1089 adult individuals from communities of Tapajós and Amazon River. A large inter-individual variability was found for Hg levels (0.2-139; 0.2-27; 0.1-19 μg Hg.L^-1 respectively in blood, plasma, and urine), while Se contents show rather homogenous status in blood (arithmetic mean = 183 ± 78 μg Se.L^-1) and plasma (AM = 103 ± 34 μg Se.L^-1). Hg content in blood was positively correlated with Hg level in plasma, both increasing with the frequency of fish intake. In contrast, Se levels remained stable in blood regardless of how often fish was consumed. However, a positive correlation was observed between Hg and Se excreted in urine. This work represents the largest human cohort in the region, pioneering the evaluation of the levels of both elements simultaneously in blood, plasma, and urine, laying the foundations for understanding the dynamics of Hg and Se in Amazonian riverside populations.