BACKGROUND CONCENTRATIONS 



GENERAL 



PCB concentrations have been determined for a variety of flora and fauna, 

 and in certain nonbiological materials (Table 2). These selected data seem to 

 represent current state-of-the-art analytical procedures for accurate and 

 precise measurement of PCBs at detection limits of less than 0.01 ppm for most 

 isomers. Characterization of Aroclor PCB residues in living and nonliving 

 resources is difficult due to the chemical, physical, and metabolic 

 transformations between product manufacture and detection in environmental 

 samples. Schmitt et al . (1985) suggest that total PCBs in samples is a more 

 reliable measure of environmental contamination than measurements of any 

 commercial PCB mixtures such as Aroclor PCBs. Also, Brown et al . (1985) 

 indicated that only a few PCB congeners (i.e., those most toxic) are 

 appropriate for meaningful interpretation of PCB residues in biota. 



There is general agreement that more samples from recent collections have 

 detectable PCB residues, that absolute concentrations seem to be declining in 

 some areas of known high PCB contamination, and that lower chlorinated 

 PCBs--resembling Aroclor 1242--are disappearing. Nevertheless, many fish and 

 wildlife species, including salmon, trout, turtles, eagles, herons, 

 fish-eating birds, mink ( Mustela vison ), river otters ( Lutra canadensis ), and 

 bats, all contain measurable, and in some cases potentially harmful, PCB 

 residues, especially in adipose (fatty) tissues. 



ALGAE AND TERRESTRIAL MACROPHYTES 



In the Great Lakes, atmospheric deposition of PCBs is the most 

 significant source of contamination. More than 90% of atmospheric PCBs are 

 transported in the vapor phase and deposited by turbulent impaction. 

 Deposition of PCBs is also associated with particulate matter, as well as 

 direct partitioning from the vapor phase into the surface organic microlayer 

 at the air-water interface, and these account for the remaining input (Rohrer 

 et al. 1982). Once in the water column, the hydrophobic PCBs partition into 

 the more apolar compartments of the ecosystem or are physically adsorbed on 

 particulate matter. Transfer of PCBs on microparticulate materials and into 

 phytoplankton is well documented, as is partitioning from aqueous solution 

 into algal lipids (Rohrer et al . 1982). PCBs incorporated into phytoplankton 



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