Effectiveness of various exposure metrics in defining dose-response relationships for mink (Mustela vison) exposed to polychlorinated biphenyls.

We conducted a quantitative analysis of published results from more than 50 tests of polychlorinated biphenyl (PCB) effects on mink reproduction, which provided a basis for evaluating how well different methods of measuring and assessing PCB concentrations can approximate a toxicologically relevant dose for this endpoint. Several dose metrics were identified for comparison. Dietary dose metrics included the daily intake of total PCBs and the daily intake of 2,3,7,8-tetrachlorodibenzo-p-dioxin toxicity equivalence concentrations (TECs), calculated using World Health Organization toxicity equivalence factors (TEFs). Internal dose metrics included whole-body total PCBs, whole-body TECs calculated using World Health Organization TEFs, and whole-body TECs calculated using alternative TEFs specifically identified for internal dose assessment. Accounting for the bioaccumulative potential (i.e., internal dose) of ingested PCBs proved to be more important than accounting for the concentrations of dioxin-like PCB congeners in explaining the observed variation in reproductive success. This was true regardless of whether internal doses were estimated from dietary data based on homolog concentrations (whole-body total PCBs) or congener concentrations (whole-body TECs). For each of the PCB dose metrics, a range of toxicity reference values is identified based on the species-specific PCB toxicity database compiled for this evaluation.