Altered biologic activities of commercial polychlorinated biphenyl mixtures after microbial reductive dechlorination.

Abstract

The reductive dechlorination of polychlorinated biphenyls (PCBs) by anaerobic bacteria has recently been established as an important environmental fate of these compounds. This process removes chlorines directly from the biphenyl ring with replacement by hydrogen, resulting in a product mixture in which the average number of chlorines per biphenyl is reduced. In this study, dechlorination of commercial PCB mixtures (Aroclors 1242 and 1254) by microorganisms eluted from PCB-contaminated sediments of the River Raisin (Michigan) and Silver Lake (Massachusetts) caused a depletion in the proportion of highly chlorinated PCB congeners and an accumulation of lesser-chlorinated congeners. Dechlorination occurred primarily at the meta and, to a much lesser extent, para positions of biphenyl. The concentrations of the coplanar congeners including 3,3',4,4',5-pentachlorobiphenyl, the most potent dioxinlike congener, were significantly lowered by reductive dechlorination. Microbial reductive dechlorination of commercial PCB mixtures caused a substantial reduction in biologic activity in several instances. It significantly lowered or eliminated the inhibitory effects of Aroclors on fertilization of mouse gametes in vitro. Similarly, the dechlorinated product mixtures had substantially lower ethoxyresorufin-Odeethylase induction potencies and showed less ability to induce activating protein 1 transcription factor activity as compared to the unaltered Aroclors. In other assays the same dechlorinated product mixtures demonstrated biologic activities similar to the nondechlorinated Aroclors, including the ability of PCB mixtures to stimulate insulin secretion and cause neutrophil activation. The data presented here establish that the biologic activities of commercial PCB mixtures are altered by microbial reductive dechlorination and that an assessment of their toxic potential requires an array of tests that include the different mechanisms associated with PCBs.

Development and Characterization of Stable Sediment-Free Anaerobic Bacterial Enrichment Cultures That Dechlorinate Aroclor 1260

“…Multiple adverse health effects have been attributed to them, and they are suspected human carcinogens (62). Microbial reductive PCB dechlorination provides a natural means of detoxifying PCBs in aquatic sediments because it reduces their persistence and increases their biodegradability and metabolism by other prokaryotes and by higher organisms (14,16,50,51,55).There have been numerous reports of microbial dechlorination of Aroclors observed in situ and in laboratory experiments with sediment slurries (3,9,17,18,24,34,35,47,48,53,54,66).Furthermore, eight microbial PCB dechlorination processes have been described (8, 9). Each of these dechlorination processes dechlorinates multiple PCB congeners in commercial PCB mixtures such as Aroclors, but they differ in the PCB congeners that are substrates, the PCB congeners that are products, and the chlorine positions targeted.…”

“…Multiple adverse health effects have been attributed to them, and they are suspected human carcinogens (62). Microbial reductive PCB dechlorination provides a natural means of detoxifying PCBs in aquatic sediments because it reduces their persistence and increases their biodegradability and metabolism by other prokaryotes and by higher organisms (14,16,50,51,55).…”

DDT and its metabolites alter gene expression in human uterine cell lines through estrogen receptor-independent mechanisms.

“…Organochlorine compounds, such as DDT, the polychlorinated biphenyls 2´,4´,6´-trichloro-and 2´,3´,4´,5´-tetrachloro-4-biphenylol, β-hexachlorohexane, and heptachlor, activate multiple kinase pathways (45)(46)(47)(48)(49)(50)(51)(52). The weakly estrogenic polychlorinated biphenyl Arochlor 1254 has been reported to induce AP-1 activity (53,54). In neurons, the endocrine disruptor β-hexachlorohexane up-regulates expression of c-fos (55).…”

Evaluation of the Eological Management and Enhancement Alernative for Remediation of the K1007-P1 Pond

“…With the discontinuation of routine use and discharge of bioaccumulative contaminants such as PCBs and chlordane, and the subsequent burial of contaminated sediments with cleaner sediments in downstream reservoirs, PCBs and chlordane concentrations have decreased at many sites nationally, including in Watts Bar (DOE 2005). Also, the dechlorination of meta-and para-chlorinated arochlors could result in relative detoxification of a PCB mixture through lower concentrations of coplanar congeners and via the transformation of more toxic, more extensively chlorinated congeners (Mousa et al 1998, Magar et al 2005a). …”