Levels and toxicokinetic behaviors of PCDD, PCDF, and coplanar PCB congeners in common cormorants from Lake Biwa, Japan

Concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (Co-PCBs) were determined in the liver and pectoral muscle of common cormorants (Phalacrocorax carbo) collected from Lake Biwa, Japan. To clarify the toxicokinetic behaviors and potential toxicities of these chemicals, the present study addresses life-stage- and tissue-specific accumulation of the congeners. Total 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalents (TEQs) were in the range of 360 to 50 000 pg/g lipid weight in the liver and 310 to 12 000 pg/g lipid weight in the pectoral muscle. Among congeners, for which toxic equivalency factors were assigned, PCB126, 2,3,4,7,8-P5CDF, and 1,2,33,8-P5CDD made a greater contribution to total TEQs in the liver. Hepatic concentrations of T-4- to H6CON, P-5- and H(6)CDFs, and Co-PCBs (except PCB77) significantly increased with growth of cormorants, leading to life-stage-related compositional changes. The concentration ratios of liver to pectoral muscle revealed preferential accumulation of higher chlorinated congeners in hepatic tissue. For most congeners, concentration ratios significantly increased with an increase in hepatic total TEQs, suggesting their con centration-dependent hepatic sequestration. These results imply the presence of hepatic binding protein(s) such as cytochrome P450, inducible by these chemicals, which may function as a binding species different from aryl hydrocarbon receptor. On the basis of these results, we conclude that the toxicokinetic behavior of each congener is life-stage-, tissue-, and concentration-dependent. TEN in wildlife populations exposed to multiple congeners with varying concentrations should be used with caution for risk assessment, even within a species.