Biological activity associated with noncoplanar polychlorinated biphenyls after microbial dechlorination of Aroclor 1242((R)) and Aroclor 1254((R))

Bioremediation of polychlorinated biphenyls (PCBs) by anaerobic microbial d echlorination occurring naturally in the subsurface and in engineered syste ms results in mixtures of lower-chlorinated, primarily ortho-substituted bi phenyls. The purpose of this study was to determine whether this process of bacterial dechlorination results in a mixture that differs in biological a ctivity from that of the parent PCB mixture. Two biological assays sensitiv e to the action of ortho-substituted PCBs were employed: insulin release by RINm5F cells, and superoxide anion (O-2) production by rat neutrophils. Th e 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 extrac ted. Exposure of RINm5F cells to dechlorinated Aroclor 1242 or 1254 product mixtures caused an increase in insulin release similar to the hormone rele ase from cells exposed to non-dechlorinated Aroclors. When tested alone, se veral 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 rele ase. In studies using neutrophils isolated from rat peritoneum, the amount of O-2 produced on exposure to product mixtures resulting from dechlorinati on of Aroclor 1242 was not different from the amount produced in nondechlor inated controls. The product mixture resulting from Aroclor 1254 dechlorina tion by organisms from River Raisin increased generation of O-2 relative to the parent Aroclor. Taken together, these results suggest that anaerobic d echlorination of Aroclor mixtures of PCBs does not reduce the biological ac tivities associated with lightly chlorinated and ortho-substituted PCBs. Th is observation has implications For the usefulness of PCB bioremediation ef forts that involve only anaerobic dechlorination.