Title: Bioassay monitoring study in the PCB degradation process using metallic sodium dispersion

Auteur(s): Takigami H ; Mitsuhara Y ; Matsuyama K ; Sakai S ;  ; 

Year: 2003

Journal: Organohalogen Compounds

Subject(s): bioassay ; monitoring ; PCB ; PCBs ; extraction ; clean-up ; Reporter gene ; CALUX ; TEQ ;  ; 

Summary: The PCB treatment technology presented in this paper uses chemical methods to dechlorinate PCB oil or PCB-contaminated oil by finely dispersed sodium as the active agent under inert atmosphere (nitrogen gas). PCB-sodium reaction (replacement of chlorine atom of PCB molecule with sodium atom) can be done at comparatively lower temperatures. For PCB oil with low concentrations (greater than tens of ppm and less than 10,000 ppm), the reaction is conducted at 50-60°C and then followed by the addition of water to treated oil for the two-phase separation of the residual hydrophobic byproduct (e.g., biphenyl as major byproducts) and sodium chloride/hydroxide. On the other hand, high-temperature (160°C) treatment is performed for the degradation of PCBs with high concentrations greater than 10,000 ppm. In this case, polymerization of dechlorinated biphenyls occurs and the polybiphenyls can be separated from oil together with sodium chloride/hydroxide. Basically, PCB-sodium reaction occurs quickly and detailed time-course reaction mechanism could be hardly clarified. Furthermore, toxicological risk assessment for PCB treatment using this process has not been fully conducted, to the best of our knowledge.In this study, Kanechlor 400, one of the Japanese commercial PCB products was applied to the sodium dispersion process on comparatively slow reaction conditions at low temperature (60°C). Seven treated samples were taken with time and processed to the extraction and clean-ups for two in vitro bioassays: DR-CALUX® AhR reporter-gene bioassay (CALUX) and enzyme-linked immunosorbent assay adopting monoclonal antibody against 2,3', 4,4', 5-pentachlorobiphenyl (PCB #118-ELlSA). Labile (crude) fraction containing hydrophobic byproducts and stable fraction containing persistent compounds such as PCBs resistant to acid treatment were prepared from the sampled oils. The two bioassays were applied according to their own assay characteristics. The CALUX was adopted to evaluate total biological TEQ in complex mixtures. The ELISA was used to simply and rapidly grasp the concentration of residual major PCB congeners (e.g., #118).