Mercury and Polychlorinated Biphenyl Bioaccumulation Dynamics in Fish

Global contamination by mercury (Hg) and polychlorinated biphenyls (PCBs) coupled with high health risks to humans requires exposure models. The models must correctly predict Hg and PCB concentrations in fish, which in turn, requires accurate estimates of model parameters. This dissertation first quantified assimilation efficiencies (AE) and elimination coefficients (ktot) of Hg and PCBs in Goldfish (Carassius auratus). Then, a non-steady state toxicokinetic model, combined with a Wisconsin bioenergetics model, was developed to simulate Hg and PCB bioaccumulation in Silver Carp (Hypophthalmichthys molitrix), Bighead Carp (Hypophthalmichthys nobilis), and Bluegill (Lepomis macrochirus) from multiple locations. Finally, a sensitivity analysis was performed for these three modeled species to evaluate the relative contribution of each parameter to the model outcomes. The results indicated that dietary AEs were 98±10 % and 40±9 % for MeHg and PCBs, respectively, thus, Hg had a higher AE compared to PCBs. The ktot of MeHg was 0.010±0.002 d-1, which was equivalent to those measured for highly hydrophobic PCBs with log KOW =7.2. In addition, using the tissue specific growth rate, the non-steady state bioenergetics/kinetics model was generally able to simulate differences in the bioaccumulation trends of PCBs and Hg for the study species. The sensitivity analysis indicated that toxicokinetic parameters representing tissue growth rate are as influential as model parameters associated with ontogenetic diet shifts in terms of explaining age specific Hg and PCB bioaccumulation. Overall, this dissertation was the first to directly compare chemical toxicokinetics between Hg and PCBs within the same organism, and to quantify the effect of tissue specific growth rate on bioaccumulation of these contaminants by fish using a non-steady state bioenergetics/ toxicokinetics model. It was concluded that Hg has a higher bioaccumulation potential than PCBs, and suggested tissue growth rates should be incorporated in future bioaccumulation models especially as they apply to modelling PCB dynamics in fish