Organochlorine residues (PCBs and DDTs) in two Torpedinid species liver from the Southeastern Mediterranean Sea

PCB and DDT concentrations were determined in the liver of two torpedinid species, electric ray and marbled electric ray from the Adriatic Sea (South-Eastern Mediterranean Sea). In both species PCB contents were higher than those of DDTs. Contaminant load was higher in electric ray (PCBs: 1040 ng g-1 lipid weight; DDTs: 234 ng g-1 lipid weight) than in marbled electric ray (PCBs: 434 ng g-1 lipid weight; DDTs: 78 ng g-1 lipid weight). The examination of congener profiles showed that hexachlorinated molecules were dominant (hexa-CBs: 63.7-64.5%), followed by hepta-PCB 180 (20.9-22.3%) and penta-CBs (13.1-15.4%). PCB 138, 153 and 180 were the prominent congeners constituting from 84.6 to 86.8% of the total PCBs. Among the compounds of DDT, p,p’-DDE was the most dominant molecule (electric ray: 92.9%; marbled electric ray: 85.4%), demonstrating the old age of these compounds in the environment. The high ratios PCBs/DDTs indicated predominantly industrial versus agrarian activities in the area. TEQs concentrations (marbled electric ray: 15.4 pg-TEQ g-1 lipid weight, electric ray: 28.5 pg-TEQ g-1 lipid weight) were comparable with those encountered in other elasmobranch and teleost fish. Further studies are needed to better evaluate the toxicological significance of the organochlorine levels measured in these organisms.