ALTERED TOXICITY OF COMMERCIAL PCB MIXTURES AFTER MICROBIAL REDUCTIVE DECHLORINATION
|L.J. Fischer(1), S.A. Boyd(2), P.E. Ganey(3), M. Mousa(2), J.F. Quensen(2), B.V. Madhukar(4), K. Chou(5), and J.P. GIesy(6), Michigan State University, (1)Institute for Environmental Toxicology, (2)Crop and Soil Science, (3)Pharmacology and Toxicology, (4)Pediatrics/Human Development, (5)Animal Science, and (6)Fisheries and Wildlife, East Lansing, MI 48824||
The goal of this project is to assess changes in the spectrum of toxicity of contaminants resulting from biological or chemical remediation processes. Initial efforts have focused on commercial PCB mixtures (Aroclors) that have undergone microbial reductive dechlorination. This process involves removal of chlorine directly from biphenyl and replacement with hydrogen.
Generally, chlorines in the meta and para positions are more easily removed leaving products containing ortho chloro substitution. The toxicity of PCBs dechlorinated by anaerobic bacteria from different PCB-contaminated river sediments was assessed using a variety of in vitro biological test systems. Microbial dechlorination of Aroclors 1242 and 1254 reduced or eliminated the inhibitory effect of these mixtures on fertilization of mouse gametes.
A significant decrease in Ah-receptor mediated activity (EROD-induction) was also observed for dechlorinated Aroclors. This was likely due to the greater than 90% 1088 of coplanar PCBs as a result of dechlorination. PCBs activate PKC isoenzymes causing an induction of AP-1 activity and this was found to be attenuated by dechlorination. Each of these results indicate that the toxic effects of PCB mixtures may be mitigated by microbial reductive dechlorination.
In contrast, dechlorinated Aroclors had similar or slightly greater potential for producing insulin release from the cell line RINm5F when compared to the commercial mixtures. Also, neutrophil activation by Aroclor 1242 was not found to be altered when the products of anaerobic dechlorinated were evaluated.
Together, these data indicate the potential for PCB toxicity from the products of bioremediation is dependent on the biological test system. A variety of biological test systems which measure activities of the various types of compounds in the dechlorination product mixture must be employed for adequate toxicity evaluation.
Key words: biphenyls, biodegradation products, toxicity, dechlorination, PCBs
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