ASSESSMENT OF EXPERIMENTAL DATA ON PCB-INDUCED REPRODUCTION INHIBITION IN MINK, BASED ON AN ISOMER- AND CONGENER-SPECIFIC APPROACH USING 2,3,7,8-TETRACHLORODIBENZO-p-DIOXIN TOXIC EQUIVALENCY

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 ECSO value. Alternatively, estimates for the whole-body concentration in mink of 1 1 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 doseeffect 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 pg/g (total PCBs/wet weight). From the second approach a critical body residue (EC5O) 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.

Toxic equivalency factors (TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife.

“…(18) with the NOAEL calculated from a mink laboratory reproductive study in which the diets were subject to complete chemical characterization (151). These two independent analyses of the TEF approach, utilizing different effects data sets and the same set of international TEFs (1,20) …”

Environmental contaminants in freshwater fish and their risk to piscivorous wildlife based on a national monitoring program

“…Total PCB concentrations exceeded NEHCs for bald eagle and mink at multiple sites. Mink are among the most sensitive organisms to PCBs with their survival and reproduction affected by small dietary PCB doses (Leonards et al 1995). Risk associated with total PCBs to mink generally was greatest in industrialized watersheds and near historical production and formulation facilities.…”

Using the dioxin receptor–calux in vitro bioassay to screen marine harbor sediments for compounds with a dioxin‐like mode of action

“…A well-known AhR-mediated response is the induction of the biotransformation enzyme cytochrome P4501A. Direct and indirect AhR-mediated effects of dioxinlike compounds also interfere with retinoid and thyroid hormone homeostasis [10], in severe cases producing adverse biological effects, such as reduced fertility and immunotoxicity in wildlife [11,12]. Humans may also be adversely affected [13].…”