Toxicokinetics of 2,2',4,4'- and 3,3',4,4'-tetrachlorobiphenyl congeners in the house cricket.

Recently, investigators have reported bioaccumulation of polychlorinated biphenyls (PCBs) in insects collected at hazardous waste sites. Little is known about differences in bioaccumulation of particular PCB congeners in insects. The authors report on the toxicokinetics of a non-coplanar ortho substituted congener, 2,2',4,4'-tetrachlorobiphenyl (PCB-47) and a coplanar non-ortho substituted PCB, 3,3',4,4'-tetrachlorobiphenyl (PCB-77) in topically treated house crickets. Penetration and excretion were more rapid for PCB-47 than for PCB-77. PCB-47 demonstrated a high affinity for abdomen, gut, and gonads, whereas, PCB-77 had a greater affinity for the head and thorax. Sex differences were observed in excretion and distribution. Females had an increased excretion of PCBs and increased accumulation in gut and gonads compared to males. Differences in lipophilicity can explain differences in distribution between sexes and of compounds within sexes. However, to explain the observed difference in penetration, it is necessary to invoke explanations based on stearic factors associated with coplanarity of the molecules. Differences in excretion are likely related to sex differences in mixed-function oxidase activities. These toxicokinetic data suggest that the more toxic coplanar congener, PCB-77, is likely to be more persistent in crickets compared to PCB-47, despite its lower lipophilicity.