Assessment of Risk to Mink Exposed to PCBs in the Lower Illinois River Watershed

Staff of the Cooperative Wildlife Research Laboratory recently used environmental contaminant concentrations in mink (Mustela vison) to monitor environmental health using Illinois watersheds as a geographical framework. Our results indicated elevated PCBs in mink collected from 6 watersheds with concentrations in those collected from the 'Lower Illinois River Watershed being the greatest (mean= 3.14 mg/kg, range non-detect - 12.30 mg/kg). Although we have no data to indicate that the mink from this watershed are adversely affected by PCBs, the concentrations measured in their tissues indicate potential environmental concentrations of concern and warrants additional study. The goal of the current study was to better define the sources and distribution of PCBs and to evaluate the potential for adverse effects in biota living in streams in the Lower Illinois River Watershed, with the emphasis being risk to mink reproduction. Sediment, crayfish (Cambarus sp.), and fish were collected from Hill, Palmer, Carr, and Fountain creeks where mink with elevated liver PCB concentrations have previously been collected. PCBs were quantified in only 2 of 3 red shiner fish composite samples (57 and 66 ppb) collected at the confluence of Hill and Palmer Creeks. concentrations in all other samples (sediment, crayfish, and fish) were below our analytical detect limits (50 ppb). The current study did not provide information to indicate that PCBs in sediment or major aquatic food items are possible sources for PCB accumulation in mink collected from the Lower Illinois River Watershed. Quite the contrary, our results indicate that the creeks in our study do not appear to be a significant source of PCBs for mink. Because mink have a fairly large home range ( 1 - 5 km of stream length, EPA 1993) and their diet consist of terrestrial as well as aquatic food items, it would be necessary to evaluate habitats in other locations in order to determine the source of PCBs in the mink previously collected from the Lower Illinois River Watershed.