No abstract

This paper describes an attempt to derive a median effect level (EC50) of PCBs for reproduction of mink based on experimental literature data. Unfortunately, the conditions of the mink studies carried out during the last two decades vary widely, which makes it difficult to establish unequivocal dose‐effect relationships. This study describes an attempt to correct for the differences in exposure time using a one‐compartment bioaccumulation model. This model estimates the whole‐body concentration of PCBs in mink. Two approaches are tested. First, the whole‐body concentration of 10 isomer groups of PCBs in mink were estimated and compared with reproduction data to calculate an EC50 value. Alternatively, estimates for the whole‐body concentration in mink of 11 individual biologically active PCB congeners were made. With these, the toxic equivalent concentration (TEC) in mink was estimated using the 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) equivalent factor (TEF) approach. Whole‐body dose‐effect relationships were estimated and EC50 values for litter size and kit survival were calculated. The application of the one‐compartment bioaccumulation model of the first approach resulted in a significant improvement in the dose‐effect relationship in comparison to the raw data set. A further improvement in this relationship was achieved using the congener‐specific bioaccumulation model in combination with the TEF approach. This study proposes a critical body residue (EC50) for mink litter size of 1.2 μg/g (total PCBs/wet weight). From the second approach a critical body residue (EC50) expressed in TCDD equivalency for litter size of 160 pg/g (TCDD equivalence/wet weight) and 200 ng/g (TCDD equivalence/wet weight) for kit survival is proposed.