Takahashi, S.; Aono, D.; Anh, HQ.; Watanabe, I.; Tomioka, K.; Kuwae, M.; Kunisue, T.; Sakai, S. (2019) 39th International Symposium on Haloganated Persistent Organic Pollutants, pp. 236-239

Polychlorinated biphenyls (PCBs) were commercially synthesized and widely used in numerous industrial
applications such as additives in dielectric fluids in transformers and capacitors, heat transfer fluids and hydraulic fluids in partially closed-industrial systems, as well as other open applications like lubricants, casting waxes, surface coatings, adhesives, plasticizers, and inks1. On the other hand, PCBs can be unintentionally produced during combustion, chlorination bleaching of wood pulp, and different industrial production processes, especially in paint pigment manufacturing2,3. PCBs are extremely persistent in the environment and they have been detected in various environmental media in virtually all parts of the world1. Marine sediments have been considered as an important sink of PCBs and other organic micro-pollutants; and the vertical distributions of these contaminants in sediment cores can provide relevant information on their historical trends and emission sources4-6.

Before 1950s, PCBs were imported into Japan. In Japan, technical PCB mixtures (Kanechlor) were produced since 1954, and these production activities were stopped in 1972. The total amount of commercial PCBs produced in Japan was estimated to be 59,319 tonnes with a peak production between 1965 and 19697. The issues regarding technical PCBs has received great attention in Japan due to incidental exposures (e.g., the Yusho incidence) to these toxic compounds and their related analogues since the late 1960s8,9. The use and disposal of industrial PCB products (including those kept in depositories for a long time) as well as incineration of industrial and domestic wastes have released considerable amounts of dioxin-like PCBs (dl-PCBs) in Japan10. A certain level of 3,3'-dichlorobiphenyl (CB-11, an impurity in commercial paints and pigments) was also observed in the air of several urban and industrial areas in Japan, implying the current emission of PCBs3. Several studies on the temporal trends of PCB contamination were performed by using sediment cores collected from different Japanese coastal areas6,11-13; however, these researches focused on a subset of PCB congeners and did not investigate novel substances (e.g.,CB-11) In the present study, we analyzed concentrations of all 209 PCBs in a representative sediment core obtained from Beppu Bay, southwestern Japan in order to provide a new and detailed insight into the environmental occurrence and historical profile of this chemical class.