Contamination of Dioxins and PCBs in Sediment Core in Tokyo Bay

An analysis was conducted of the concentration and composition of dioxin (PCDD/Fs, Co-PCBs) and total PCBs (PCBs) in the sediment core of Tokyo Bay that area administrated by the Tokyo Metropolitan Government (35°30'19'' N, 139°50'58'' E) . Sedimentary records for these distributions were investigated over the years 1900-2000. It was revealed that contamination from PCBs and Co-PCBs has increased since the 1950's, reaching its maximum in the 1970's, and gradually decreasing after that. There is a connection to the time period between the peak concentration of PCBs and Co-PCBs residue and the maximum production level of commercial PCBs, with the results of principle component analysis of the congener profile indicating that the main source of Co-PCBs is a release of commercial PCBs. Total PCDD/Fs concentration levels were low before the 1950's, the homologue and congener profiles showing similarities in combustion and atmosphere. After that, the contamination level elevated rapidly, the profile suggesting that the cause of this rise was due mainly to the impurity of PCP and CNP. Recently, the levels of individual homologue and congener has decreased or leveled off, implying that pesticide impurities, especially PCP are continuously being released into Tokyo Bay.