Biological activity associated with noncoplanar polychlorinated biphenyls after microbial dechlorination of Aroclor 1242® and Aroclor 1254®

Bioremediation of polychlorinated biphenyls (PCBs) by anaerobic microbial dechlorination occurring naturally in the subsurface and in engineered systems results in mixtures of lower-chlorinated, primarily ortho-substituted biphenyls. The purpose of this study was to determine whether this process of bacterial dechlorination results in a mixture that differs in biological activity from that of the parent PCB mixture. Two biological assays sensitive to the action of ortho-substituted PCBs were employed: insulin release by RINm5F cells, and superoxide anion (O-2) production by rat neutrophils. The PCB mixtures Aroclor 1242(R) and Aroclor 1254(R) were incubated for nine months with microbes from PCB-contaminated sites (Silver Lake, MA, USA, or River Raisin, MI, USA), and the products of dechlorination were then extracted. Exposure of RINm5F cells to dechlorinated Aroclor 1242 or 1254 product mixtures caused an increase in insulin release similar to the hormone release from cells exposed to non-dechlorinated Aroclors. When tested alone, several of the major products identified in the dechlorination mixture (i.e., 2,2', 4,4'-tetrachlorobiphenyl, 2,2',4-trichlorobiphenyl [TCB], 2,3',4-TCB, 2,3',5-TCB, and 2,2'-dichlorobiphenyl) caused an increase in insulin release. In studies using neutrophils isolated from rat peritoneum, the amount of O-2 produced on exposure to product mixtures resulting from dechlorination of Aroclor 1242 was not different from the amount produced in nondechlorinated controls. The product mixture resulting from Aroclor 1254 dechlorination by organisms from River Raisin increased generation of O-2 relative to the parent Aroclor. Taken together, these results suggest that anaerobic dechlorination of Aroclor mixtures of PCBs does not reduce the biological activities associated with lightly chlorinated and ortho-substituted PCBs. This observation has implications For the usefulness of PCB bioremediation efforts that involve only anaerobic dechlorination.