Résumé
The Brazilian Amazon faces seasonal cycles of rising water levels and droughts, which alter dietary patterns and Hg dynamics, impacting Hg exposure and Se intake in riverine populations. This study provides a detailed assessment of total Hg and its species, as well as Se levels, in hair of riverine populations across these two distinct seasons. Mean hair Hg levels remained stable between dry (6.5 ± 5.7 µg/g) and rainy (6.1 ± 7.7 µg/g) seasons, with MeHg accounting for 90 % of total hair Hg and showing a strong positive correlation with fish consumption frequency. In contrast to the stability of Hg hair levels across seasons, Se concentrations were significantly higher (20 %) in samples collected during the rainy season compared to the dry season (median: 0.62 µg/g), likely driven by seasonal changes in dietary sources of Se. Notably, this is the first documentation of a positive correlation between fish consumption frequency and iHg hair excretion, both among Amazonian populations and more broadly in freshwater fish consumers, shedding light on Hg metabolism in humans. This study is the first to comprehensively investigate both Hg species and Se in hair according to Amazonian seasons, providing deeper insights into exposure and interactions in local population.
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•Seasonality did not influence hair Hg levels of the studied Amazonian population.•Hair Hg levels are notably (∼ 45 %) lower than those reported two decades ago.•Both MeHg and iHg hair levels positively correlate with fish consumption frequency.•Hair Se excretion shows no dependence on the frequency of dietary fish intake.