species tested in the laboratory (Table 2). The main source of PCBs at that 

 location was a diecasting plant. Granular oil absorbent material behind the 

 plant contained up to 120,000 ppm of PCBs; runoff and seepage from rain and 

 floodwaters carried PCBs into the river, subsequently contaminating fish, 

 especially carp ( Cyprinus carpio ). Whole fresh carp from the Sheboygan River 

 contained more than 155 ppm of ^PCBs (as quoted in Heinz et al. 1984), 

 suggesting that fish-eating birds may be especially at risk. 



In 1981 and 1982, duck hunters in New York and New Jersey were cautioned 

 about the consumption of wild waterfowl. At the time, waterfowl from the 

 Hudson and Niagara rivers contained PCBs in excess of tolerances established 

 by FDA for poultry (more than 5 ppm fresh weight), although PCB concentrations 

 found in these waterfowl were below the levels associated with reproductive 

 impairment or decreased survival of birds (Fleming et al. 1983). 



Residues of PCBs in birds are modified by numerous biotic factors 

 including fat content, tissue specificity, sex, and developmental stage. PCB 

 residues in birds may also reflect levels due to aerosol transport of these 

 compounds (Weber 1983), as well as water transport (Norheim and Kjos-Hanssen 

 1984). Highest PCB residues were in birds with low fat content and in poor 

 condition on capture (Falandysz and Szefer 1984). Sexual differences in PCB 

 content are pronounced due to the female's ability to shed a significant 

 portion of the PCB burden into eggs (Lemmetyinen and Rantamaki 1980). 

 Developmental stage is an important consideration when collecting bird samples 

 for PCB analysis (Lemmetyinen and Rantamaki 1980); for example, PCB level is 

 reduced from egg to fledgling (Fimreite and Bjerk 1983). Finally, residues in 

 brain appear to be good indicators of PCB stress in birds (Stickel et al . 

 1984). Concentrations greater than 300 ppm of PCBs in brain (fresh weight) 

 were consistently recorded in dead or dying ring-billed gulls ( Larus 

 delawarensis ) and ring-necked pheasants ( Phasianus colchicus ) poisoned by 

 PCBs, as quoted in Heinz et al . (1984). 



MAMMALS 



Among mammals, the mink is especially sensitive to PCBs; only 0.64 ppm 

 PCBs in their diets caused reproductive failure, and 1.0 ppm caused death (as 

 quoted in Fleming et al . 1983). In western Maryland and in northern Oregon 

 during 1978-1979 (areas with no recognized large-scale PCB pollution), levels 

 of PCBs in livers of some wild mink were comparable to those reported for 

 female ranch mink that failed to reproduce after eating a diet contaminated 

 with 0.64 ppm of PCBs for 160 days (O'Shea et al . 1981; Henny et al . 1981). 

 Some fish from the Oregon collection sites contained PCB residues (0.24-2.8 

 ppm fresh weight) that were equivalent to, or higher, than dietary levels fed 

 to mink under controlled conditions (Henny et al. 1981). 



PCB concentrations in river otters from the Columbia River, Oregon, 

 during 1978 and 1979, were substantially higher than those reported in the 

 same species from Alabama. The significance of this is not clear, but 



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