Selenium and mercury molar ratios in commercial fish from the Baltic Sea: Additional risk assessment criterion for mercury exposure

Background: Mercury content in fish poses risks to the fish and to those who consume them. The aim of the current study was to verify the protective role of selenium against toxic mercury in Baltic fish. The assessment criteria were the Se:Hg molar ratio, its variability depending on species and tissue, and correlations among Se:Hg ratios, mercury concentration, and specimen length. Assays were performed in muscle and liver tissues of Baltic Sea commercial fish species, i.e., cod, herring, sprat, plaice, and turbot Results: Mercury concentrations in fish from the Baltic Sea are at low level. The values of the Se:Hg molar ratio were higher than 1 (with the exception of a few cod specimens), with ranges in muscle tissues as follows: cod 0.75-28.2; herring 2.0-50.3; sprat 14.2-56.2; flatfish 1.5-35.1; and in livers as follows: cod 10.9-268.2; herring 10.7-87.1; flatfish 10.2-232. The values of the Se:Hg ratio in muscle and liver tissues were negatively correlated with mercury content and specimen length. Conclusion: Mercury concentrations in commercial fish from the Baltic Sea are low and do not pose risks to consumers. The high values of the Se:Hg molar ratio confirm that mercury levels are safe, and also that selenium might offer protection against methylmercury toxicity, which could increase the safety of fish consumption. The values of the Se:Hg molar ratio could be an additional criterion, in addition to measuring Hg concentrations, for evaluating the risk of mercury exposure in fish from the Baltic Sea. (C) 2014 Elsevier Ltd. All rights reserved.