Exposure and risk of polychlorinated biphenyls to mink (Mustela vison) at the Kalamazoo River Superfund site, Michigan.

摘要

125 kilometers of the Kalamazoo River, located in southwestern Michigan, has been designated a Superfund site with polychlorinated biphenyls (PCBs) as the contaminant of concern. Mink are of special concern due to their trophic status and sensitivity to PCBs. A top-down risk assessment was conducted by measuring concentrations of total PCBs and TEQs in tissues of mink collected from the Kalamazoo River area of concern (KRAOC). Mink were caught from areas within the KRAOC and from Fort Custer Recreation Area (FC), an upstream reference area on the same river system. Total PCB concentrations, in livers of mink, averaged 2.7 and 2.3 mg PCB/kg ww from the KRAOC and FC, respectively. Total TEQs in livers of mink averaged 300 and 110 pg TEQ/g ww from KRAOC and FC respectively. Previously conducted studies in which mink were fed PCB-contaminated diets were used to calculate a range of hazard quotients (HQs) based on the no observed adverse effect level (NOAEL) and the lowest observed adverse effect level (LOAEL). For mink livers from KRAOC, total PCB-based HQs ranged from 0.37 to 0.88 and total TEQ-based HQs ranged from 1.1 to 1.4 (based on a comparison of the mean exposure level and the LOAEL). For mink livers from FC, total PCB-based HQs ranged from 0.31–0.73 and total TEQ-based HQs ranged from 0.39–0.49 (based on a comparison of the mean exposure level and the LOAEL).; The extent to which mink (Mustela vison), were exposed to PCBs through their diet and the resulting potential risk was estimated using three different dietary models. Fish, crayfish, and mammalian species were collected from two sites: Trowbridge (TB), a former impoundment within the KRAOC and FC. Prey items were analyzed for total PCB and TEQ concentrations. Total PCB and TEQ concentrations were greatest in fish species. Identified contents from gastrointestinal tracts of mink collected from the sites yielded the following dietary composition: 72% mammals, 14% fish, and 14% crayfish, and was used as one of the dietary models. At TB, LOAEL-based HQs for total PCBs and TEQs are less than 1.0 for all dietary models except the literature-based model in which fish comprise 85% of the mink's diet. Calculated risk, based on dietary models, was slightly less than risk calculations based on site-specific mink tissue residues. Both approaches were in agreement that the degree of exposure to PCBs and TEQs were near the threshold for effects on reproduction in mink.; Multiple lines of evidence were considered, including the habitat quality, number of animals trapped per territory, age and sex distributions, gross morphology, liver histology, bacculum weight, and body weight. Based on these multiple lines of evidence, the observed concentrations of PCBs measured in the livers of mink in the KRAOC are unlikely sufficient to cause a reduction in the number of mink inhabiting the KRAOC.