In this study, the means of the Se:THg and Se:MeHg molar ratios in human blood were 60.7 ± 27.1 and 110 ± 53.6 respectively. All blood samples had Se:THg and Se:MeHg molar ratios N10, which indicated lessMeHg neurotoxicity. The major form of Se in blood is seleno-cysteine, which could form a stronger complex with MeHg than cysteine (Chen et al., 2006; Khan and Wang, 2009) and could make MeHg less available and less able to cross blood-brain barriers.