Abstract
In contrast to mercury, an extremely toxic element, selenium is an essential micronutrient, which by complexing with mercury can mitigate its toxicity. In this regard, we quantified mercury and selenium concentrations in samples (n = 309) of fish tissues and analyzed the Se:Hg molar ratio and HBVSe as toxicological risk biomarkers. The data indicated that mercury levels in planktivorous fish (0.630 ± 0.202 mg kg(-1)) and carnivorous fish (1.196 ± 0.513 mg kg(-1)) were above the Brazilian limits considered safe for daily consumption. The highest selenium concentrations were observed in planktivores (0.272 ± 0.093 mg kg(-1)) and the lowest in herbivores (0.099 ± 0.092 mg kg(-1)). Molar ratios greater than one and positive HBVSe values were found in 42% of the fish samples (n = 131). As a result, we found that (i) the trophic level influences the risk of mercury exposure through the intake of fish in the diet; (ii) the approach presented in our study (model II) involves greater rigor concerning intake and exposure via fish consumption, since it considers the antagonistic Se:Hg ratio; and (iii) selenium can attenuate mercury toxicity, but safe thresholds vary depending on the species.