TOXICITY 



AQUATIC ORGANISMS 



LC-50 values of sensitive species of freshwater and marine organisms 

 subjected to various Aroclor PCBs varied from 0.1 to 10.0 ug/1 during exposure 

 of 7 to 38 days (Table 3). In general, toxicity increased with increasing 

 exposure, crustaceans and younger developmental stages were the most sensitive 

 groups tested, and lower chlorinated biphenyls were more toxic than higher 

 chlorinated biphenyls. In most toxicity tests, mortality patterns in 

 PCB-exposed fish did not stabilize within 30 days (Johnson and Finley 1980). 



BIRDS 



As a group, birds were more resistant to acutely toxic effects of PCBs 

 than mammals (Table 4). LD-50s for various species of birds varied from 604 

 to more than 6,000 mg Aroclor/kg diet, and for mallards more than 2,000 mg/kg 

 body weight administered orally (Table 4). Signs of PCB poisoning among birds 

 included morbidity, tremors (which may become continuous), beak pointed 

 upwards, and muscular incoordination. At necropsy, the liver frequently 

 contained hemorrhagic areas and the gastrointestinal tract was filled with 

 blackish fluid (Stickel et al. 1984). 



For all avian species, PCB residues of 310 mg/kg fresh weight or higher 

 in brain were associated with an increased likelihood of death from PCB 

 poisoning. Residues in brains of starlings, red-winged blackbirds ( Agejaius 

 phoeniceus ), common grackles ( Quiscalus quiscula ), and brown-headed cowbi rds 

 ( MolothruT ater ), that died after eating diets containing 1,500 mg Aroclor 

 1254/kg, varied from 349 to 763 mg/kg; surviving birds, at the 50% mortality 

 point, contained 54 to 301 mg/kg (Stickel et al. 1984). Similar results are 

 reported for ringed turtle-doves ( Streptopelia risoria ) after 105 days fed a 

 10 mg Aroclor 1254/kg diet, chickens fed Phenoclor, Clophen, and Aroclor PCBs, 

 and finches and cormorants fed Aroclor 1254 (as quoted in Stickel et al . 

 1984). In the field, PCBs were the probable cause of mortality of many 

 ring-billed gulls that died in southern Ontario in late summer and early 

 autumn of 1969 and 1973; PCB residues in brains were 310 to 1,110 mg/kg fresh 

 weight in 67% of the samples analyzed, and 200 to 310 in the remainder (as 

 quoted in Stickel et al. 1984). 



36 



