Concentration of organochlorines (PCBs and DDTs) and Toxic Equivalents (TEQs) in cyprinids of the middle river Po, Italy

The concentrations of non-ortho-, mono-ortho-, di-ortho-substituted polychlorinated biphenyls (PCBs) and DDTs (pp'-DDT and pp'-DDE) were measured in fish and bed sediments of the Po River. Three species of cyprinids, nase (Chondrostoma soetta), chub (Leuciscus cephalus), and barbel (Barbus plebejus), were captured in the major Italian river, upstream and downstream from the confluence of the Lambro River. The two carnivorous species, chub and barbel, were found to be the most contaminated, showing muscle tissue concentrations up to eightfold higher than the corresponding upstream fish. DDT concentrations were parallel to PCB changes although at lower values. Despite the increased contamination caused by the input from the Lambro tributary, when fish PCB loads are converted to 2,3,7,8-tetrachlorodibenzo-p- dioxin (TCDD) equivalents using piscine toxic equivalency factors (TEFs), no specific hazard can be associated to the limited toxic potentials of PCBs. Although these results seem to minimise the risk for the fish community of the Po River, the presence of other organochlorines and halogenated hydrocarbons is very probable in the downstream area, and a more exhaustive hazard assessment, based on further studies, should be undertaken.