Polychlorinated Biphenyls, Dibenzo-p-dioxins, and Dibenzofurans in Harbor Porpoises (Phocoena phocoena) Stranded on the Dutch Coast Between 1990 and 1993

Congener-specific polychlorinated biphenyl (PCB) concentrations were determined in the blubber, kidney, and liver tissues of 22 harbor porpoises (Phocoena phocoena) stranded on the Dutch coast. For comparison, the PCB concentrations in blubber and liver samples of four porpoises from the vicinity of Greenland were investigated. In ten blubber samples, the non-ortho PCB concentrations were determined, while in four of these the levels of chlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) were analyzed. It is shown that the PCB level increases with age in males, whereas in mature females the levels remain relatively constant. A comparison with earlier data indicates a slight decrease over the last 20 years in the PCB burden of porpoises living near the Dutch coast. The amount of the most prominent and persistent congener, PCB 153, can be related to the feeding pattern of male porpoises; it appears to be completely retained in this species. Bioaccumulation of non-ortho PCBs and PCDD/Fs does not take place. The overall toxicity, expressed as 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalents (TEQ), is mostly covered by di-ortho and mono-ortho PCBs, depending on age and sex, whereas the contribution of the notorious toxic PCDDs and PCDFs to the overall TEQ is at most 0.5%.