Comparison of the Toxicokinetics and Bioaccumulation Potential of Mercury and Polychlorinated Biphenyls in Goldfish (Carassius auratus)

Both mercury (Hg) and polychlorinated biphenyls (PCBs) demonstrate food web biomagnification in aquatic ecosystems, yet their toxicokinetics have not been simultaneously contrasted within a common fish species. This study quantifies uptake and elimination rates of Hg and PCBs in goldfish. Fish were exposed to contaminated food containing PCBs and Hg to determine dietary chemical assimilation efficiencies (AEs) and elimination coefficients (k_tot). To test first-order kinetics, three exposure regimes were established by varying the proportion of contaminated fish incorporated into the food. Dietary AEs were 98 ± 10, 75 ± 12, and 40 ± 9% for MeHg, THg, and PCBs, respectively. The k_tot values were 0.010 ± 0.003 and 0.010 ± 0.002 day^–1 for THg and MeHg, respectively. No significant differences were found in k_tot among the dosing levels for either THg or MeHg, confirming that Hg elimination is a first-order process. For PCB, k_tot ranged from 0.007 to 0.022 day^–1 and decreased with an increase in hydrophobicity. This study revealed that Hg had an AE higher than that of PCBs, while the k_tot of Hg was similar to those measured for the most hydrophobic PCBs. We conclude that Hg has a bioaccumulation potential in goldfish 118% higher than the highest PCB BMF observed for congeners with a log K_OW of >7.