Dietary Exposure of Mink to Carp from Saginaw Bay. 3. Characterization of Dietary Exposure to Planar Halogenated Hydrocarbons, Dioxin Equivalents, and Biomagnification

Abstract

Mink are known to be very sensitive to the toxic effects of planar polychlorinated biphenyls (pPCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs), collectively known as planar halogenated hydrocarbons (PHHs). Previously, we reported the reproductive effects in mink fed a diet containing 10, 20, or 40% fish taken from Saginaw Bay, Lake Huron. The present study reports the chemical characterization of the diets and the adult mink livers, along with a comparison of an additive model of toxicity with the results of the H4IIE bioassay on these samples. The assessment of dietary or tissue-based exposure of the mink to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds revealed that TCDD equivalents of the PHH mixtures largely followed an additive model of toxicity as compared with the H4IIE bioassay. Consistent dietary and liver tissue-based threshold concentrations for reproductive toxicity in mink were determined regardless of whether PHHs were quantified as TEQs (additive toxicity) or TCDD-EQs (H4IIE bioassay). Significant reproductive effects were observed in the lowest treatment group (10% fish or 19.4 pg of H4IIE bioassay-derived TCDD-EQs/g). Consumptionnormalized mink liver biomagnification factors (BMFs) were 6.4-74.2 for PCDDs, <1-75.8 for PCDFs, <1-15.9 for PCBs, and in general, increased with degree of chlorination within each class. Based on TEQs or TCDD-EQ, this study confirms that mink are among the most, if not the most, sensitive mammalian species to the reproductive toxicity of TCDD and related compounds.

Environmental Contaminants in Fish and Their Associated Risk to Piscivorous Wildlife in the Yukon River Basin, Alaska

“…All PCB concentrations were less than conservative wildlife guidelines (100-110 ng/g) available for fish (IJC 1987;Newell et al 1987). TCDD-EQ was less than or equal to the LOD (1.7 pg/g) in all samples (i.e., dioxin-like activity was not detected in any sample), and all TCDD-EQs were less than the dietary toxicity thresholds for mammals (4.4 pg/g; Heaton et al 1995;Tillitt et al 1996) and birds (5.0 pg/g; Nosek et al 1992). …”

The H4IIE Cell Bioassay as an Indicator of Dioxin-like Chemicals in Wildlife and the Environment

“…Studies have used the H4IIE bioassay to identify areas where fish have accumulated high concentrations of TCDD-EQs relative to fish from reference locations. These regional comparisons have revealed PHH contamination in fish from industrial regions of the Great Lakes Giesy et al, 1995;Tillitt et al, 1996) and in fish inhabiting areas near pulp and paper mill effluents (van den Heuvel et al, 1996;Whyte et al, 1998). In one of the few studies that report TCDD-EQs in aquatic invertebrates, McDonald et al (1994) and Kennicutt et al (1995) reported 10-fold greater TCDD-EQs in clams from the heavily PCB-contaminated Winter Quarters Bay, Antarctica, as compared to clams collected from a uncontaminated reference location (Table 11).…”

“…Mink (Mustela vison) are highly sensitive to the effects of PHHs (Aulerich et al, 1973(Aulerich et al, , 1985Tillitt et al, 1996). This was clearly demonstrated when farm-raised mink were fed diets containing increasing proportions of Saginaw Bay carp (Cyprinus carpio).…”

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

“…Dietary-based toxicity reference values (TRVs) based on no observed adverse effect levels (NOAELs) from the scientific literature were used for most contaminants (Linder et al 1980;Hill and Camardese 1986;Sample et al 1996;Tillitt et al 1996;USEPA 1995). An adjustment factor for differences in body size was applied when the mammal NOAEL TRV was not based on a mink study; a scaling factor of 1 was used for interspecies extrapolation among birds (Sample et al 1996).…”

“…The toxicity of PCBs to mink, bald eagles, and other organisms is largely attributable to relatively few congeners, specifically the highly toxic non-ortho-and mono-ortho-chloro substituted compounds that can assume a planar molecular configuration (Aulerich and Ringer 1977;Peterson et al 1993;Tillitt et al 1996). These compounds are structurally similar to 2,3,7, and are among the compounds collectively known as planar halogenated hydrocarbons (PHHs).…”