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 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.

Impact of pesticides use in agriculture: their benefits and hazards

“…Exposure to great concentrations of persistent, bioaccumulative, and toxic contaminants such as DDT (1,1,1-trichloro-2,2-bis[ p -chlorophenyl]ethane) and PCBs has been shown to elicit adverse effects on reproductive and immunological functions in captive or wild aquatic mammals (Helle et al ., 1976; Reijnders, 1986; Ross et al ., 1995; Martineau et al ., 1987; Kannan et al ., 1993; Colborn and Smolen, 1996). Aquatic mammals inhabiting freshwater systems, such as otters and mink, have been reported to be sensitive to chemical contamination (Leonards et al ., 1995; Leonards et al ., 1997). 2,4-D or 2,4-D containing products have been shown to be harmful to shellfish (Cheney et al ., 1997) and other aquatic species (U.S. EPA, 1989; Sanders, 1989) The weed-killer trifluralin is moderately to highly toxic to aquatic invertebrates, and highly toxic to estuarine and marine organisms like shrimp and mussels (U.S. EPA, 1996).…”

Congener‐specific model for polychlorinated biphenyl effects on otter (Lutra lutra) and associated sediment quality criteria

“…Reproduction effects on relative litter size (RLS) of the related mustelid mink (Mustela vison) were calculated for TEQ by Leonards et al [6] as…”

“…A safe effect level, motivated on a no-effect consideration, of 1% reduction and a critical level of 50% reduction of RLS for female otters was derived from Equation 7, assuming equal sensitivity of mink and otters [6,18]. For lipid to wet weight conversion of otter tissue, a lipid weight fraction of 0.023 g lw/g wet wt was used.…”

“…The purpose of this study is the prediction of effects on adult otters for several locations in The Netherlands, ranging from relatively clean to contaminated and, conversely, to derive sediment quality criteria (SQC) based on dose-response studies for dioxin-like toxicity of PCBs to otters [5] or mink [6]. The uncertainty in these species-specific quality criteria is an important issue in decision making related to the high cost of sediment cleanup (e.g., by dredging and storage at controlled sites).…”

“…The predicted congener patterns in otter tissue are finally converted to 2,3,7,8-tetrachlorodibenzo-p-dioxin 206 Environ. Third, potential effects of PCBs on otters are estimated with dose-response functions for reproduction of mink [6] and hepatic retinoid levels [5] based on toxic equivalent concentration (TEQ). Chem.…”