Congener profile and toxicity assessment of polychlorinated biphenyls in dolphins, sharks and tuna collected from Italian coastal waters

Bottlenose and Rissoʹs dolphins found dead along the Italian coast in 1992 were analysed for the presence of PCB isomers and DDT. High concentrations of PCBs (90–1400 μg/g wet wt) were detected in the blubber of stranded carcasses. The concentrations were higher than those found in animals showing reproductive failure and physiological impairment following prolonged PCB exposure, suggesting that the contamination by PCBs as well as DDT may be a major causative factor for the large-scale deaths of dolphins in the Mediterranean Sea. The 2,3,7,8-TCDD toxic equivalents estimated for bottlenose and Rissoʹs dolphins were 18.8 and 20.8 ng/g, respectively, with a major contribution from mono-ortho PCBs. The monoortho congeners of IUPAC Nos 105, 118 and 156 accounted for most of the toxicity exerted by PCBs in these dead dolphins. An increase in the proportion of non-ortho coplanar PCB congener of IUPAC No. 169 to No. 126 with an increase in the total PCB concentration in the blubber suggested a strong induction of drug metabolizing enzymes. It is possible to use CB-169/CB-126 concentration ratio to indicate whether there has been a strong activation of cytochrome P450 enzyme system in severely exposed/contaminated dolphin populations. The total PCB concentrations in the adipose fat of sharks from Italian coasts ranged from 70 to 4000 ng/g wet wt and that of DDT from 14 to 300 ng/g wet wt. In bluefin tuna, the total PCB and DDT concentrations were 170–2200 and 56–780 ng/g wet wt, respectively. These values were comparable to those reported for the same species in the Mediterranean Sea during the 1970s, suggesting the existence of PCB sources near this marine ecosystem.