Toxic Assessment of PCBs by the 2,3,7,8-Tetrachlorodibenzo-p-Dioxin Equivalent in Common Cormorant (Phalacrocorax carbo) from Japan K. S. Guruge, 1 S. Tanabe, 1 M. Fukuda 2 1 Center for Marine Environmental Studies, Ehime University, Tarumi 3-5-7, Matsuyama 790-8566, Japan 2 Tokyo Sea Life Park, Edogawa-ku, Rinkai 6-2-3, Tokyo 134, Japan Received: 29 January 1999/Accepted: 30 November 1999 Abstract. Common cormorants collected from three colonies and their fish diet were analyzed for PCB congeners and 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQs) were estimated. The highest total PCBs (40 mg/g wet weight) found in adult cormorants from Shinobazu Pond located in Central Tokyo, was sevenfold higher than that from Lake Biwa. IU- PAC 153 was the most abundant congener in adults and eggs, whereas IUPAC 28 1 31 was higher in some chicks and exhibited growth-related congeneric enrichment. The estimated metabolic index (MI) for PCB congeners revealed that mono- and non-ortho coplanars had higher bioaccumulation in cor- morant liver and were expected to cause toxic effects. Among non-ortho coplanars, IUPAC 126 was predominant, and total non-ortho coplanars and TEQs in cormorants were threefold higher in Shinobazu Pond than those from Lake Biwa. The non-ortho IUPAC 126 contributed a higher portion to the total TEQs followed by IUPAC 105 and IUPAC 77. The hepatic IUPAC 169/126 ratio increased significantly with TEQs, im- plying a potential induction of drug-metabolizing enzymes in Shinobazu Pond cormorants. Based on the available data, PCB contamination in cormorants is enough to pose sublethal ef- fects, especially in Shinobazu Pond and Godaiba Island, To- kyo, Japan. This could be a reason for recently observed high chick and juvenile mortality in those colonies in Tokyo. Polychlorinated biphenyls (PCBs) are commercial products used widely in industrial applications. PCB residues have been reported even in regions of nonindustrial activities and are routinely detected in all the compartments of environment due to their worldwide usage and dispersible nature. The high lipophilicity and persistency of PCBs also contribute to their bioaccumulation and biomagnification in the food chain. Similar to marine mammals, fish-eating birds have been adversely affected by PCB contamination. High PCB residues have been reported in the livers of dead seabirds (Koeman et al. 1973; Walker 1990). The reduced capacity to detoxify and higher exposure via dietary intake enable some seabirds to accumulate high levels of PCBs (Walker et al. 1984). The fish-eating birds from the Great Lakes showed serious terato- genic and reproductive dysfunctions as a result of high PCB accumulation (Gilbertson et al. 1991; Tillitt et al. 1992; Ya- mashita et al. 1993) and most of the effects were generally believed to have due to dioxin-like planar PCBs. Japan is the most developed nation in the far east and used large quantities of organochlorines during the postwar period to promote agricultural and industrial production. Total amount of PCBs produced in Japan is estimated to be about 60,000 metric tons, which is greater than other developed countries, per unit area. The production of PCBs was banned in the early 1970s due to the Kanemi rice oil incident. Loganathan et al. (1989) reported a decline of PCB residues in freshwater fish from contaminated rivers in Japan after banning of PCBs. Neverthe- less, the environmental concentration is still high enough to alter several biochemical reactions in marine mammals and fish-eating birds (Yamashita et al. 1992; Tanabe et al. 1994; Guruge and Tanabe 1997). The data on organochlorine levels in cormorants from Japan are few and only documented recently (Guruge et al. 1997). Therefore, as a continuation of the earlier study, the present study is aimed at assessing the PCB concentrations especially in various life stages of dead cormorants found in some colo- nies around Tokyo, Japan. Additionally, hepatic TEQs were determined, and possible PCB-related toxic impacts were dis- cussed. Materials and Methods Sample Collection Ten adult birds from the Lake Biwa were collected by shooting, 14 carcasses from Shinobazu Pond, and five carcasses and three un- hatched eggs from Godaiba Island in Tokyo Bay were employed for the present study. The PCB accumulation in cormorants from the Lake Biwa was reported elsewhere (Guruge and Tanabe 1997). The car- casses were collected during fortnightly visits to each colony after observing the number of dead birds have been increased during last few years. The growth stage of birds was identified by their weight, Correspondence to: S. Tanabe Arch. Environ. Contam. Toxicol. 38, 509 –521 (2000) DOI: 10.1007/s002449910067 ARCHIVES OF Environmental Contamination and T oxicology © 2000 Springer-Verlag New York Inc.