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(644) Effects of anaerobic dechlorination on PCB toxicity.
Smithwick, Ashley*,1, Quensen, John2, Smith, Andrew1, London, Lucille1, Morris, Pamela1, 1 Medical University of South Carolina, Charleston, SC2 Michigan State University, East Lansing, MI
ABSTRACT- Polychlorinated biphenyls (PCBs) are environmental contaminants that persist in soil and sediments. Upon entering the environment, PCBs can be degraded by microorganisms via a process of reductive dechlorination, in which chlorines are removed preferentially from meta and para positions of biphenyl, resulting in a mixture enriched in ortho substitutions. However, little is known about the impact of reductive dechlorination on PCB toxicity. In this study, Aroclor 1242 was anaerobically dechlorinated using inoculum from Hudson River and Silver Lake. Dechlorination of Aroclor 1242 decreased average meta plus para chlorines per biphenyl from 1.89 to 0.82 and 1.17 for Hudson River and Silver Lake, respectively, while ortho chlorines per biphenyl persisted for both dechlorinated mixtures. Immunotoxicity was examined using lymphocytes from spleens of C57BL/6J mice and was assessed by viability, LPS-induced splenocyte proliferation, and antibody secretion following PCB exposure. No change in viability was observed following PCB exposure. Single congener studies revealed PCB immunotoxicity resides in multi-ortho substituted congeners, which persist following dechlorination. Accordingly, a 30% decrease in LPS-induced proliferation was observed at 10 ppm following Aroclor 1242 exposure, and similar inhibition was observed with dechlorinated mixtures. Inhibition of antibody secretion was also noted at similar concentrations of Aroclor 1242 and dechlorinated mixtures. These studies support our hypothesis of the dependence of immunotoxicity on the presence of ortho chlorines, since removal of meta and para chlorines from Aroclor 1242 by reductive dechlorination did not result in a significant change in PCB toxicity.
Key words: polychlorinated biphenyls, immunotoxicity, anaerobic reductive dechlorination
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