Isomer‐specific polychlorinated biphenyl determination in cetaceans from the mediterranean sea: Enantioselective occurrence of chiral polychlorinated biphenyl congeners

Abstract

AbstractIsomer‐specific concentrations of 41 polychlorinated biphenyls (PCBs) and the enantiomeric ratios (ER) of nine chiral PCBs were determined in the liver of four cetacean species—Risso's dolphin (Grampus griseus), bottlenose dolphin (Tursiops truncatus), fin whale (Balaenoptera physalus), and long‐finned pilot whale (Globicephala melaena)—found dead in the Mediterranean Sea. The total PCB concentration (sum of 41 congeners) ranged from 484 to 63,200 ng/g wet weight. The 2,3,7,8 tetra‐chlorodibenzo‐p‐dioxin (TCDD) toxic equivalents (TEQs), as defined by the World Health Organization (WHO), ranged from 4.3 to 1,454 pg/g wet weight. The contribution of mono‐ortho PCBs was consistently higher than non‐ortho PCB congeners, in whale species, whereas in dolphins this predominance was not so clear. The PCB profiles were dominated by congeners 138, 153, and 180 in almost all the investigated samples. Comparison of PCB profiles by using principal component analysis allowed to separate the species into different groups. Polychlorinated biphenyls 170 and 180 seem to be eliminated by the two whale species, and PCB 180 also seems to be eliminated by Risso's dolphins. The PCBs 95, 132, 149, and 176 revealed an enantiomeric excess of the second eluted enantiomer in almost all the cetaceans investigated, where 136 and 174 were racemic or almost racemic. It is the first time that an enantiomeric excess of PCB 84 and 91 has been reported in biological samples. Although it was only possible to calculate them in two dolphin liver samples, the high values of enantiomeric excess found are surprising (86.3 and 32% for PCB 91 and 84, respectively).