Concentrations of PCBs, DDTs, and TCDD equivalents in cyprinids of the middle Po River, Italy

The concentrations of non-ortho; mono-ortho-, di-ortho-substituted polychlo rinated biphenyls (PCBs) and DDTs (pp'-DDT and pp'-DDE) were measured in fi sh and bed sediments of the Po River. Three species of cyprinids, nase (Cho ndrostoma 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 barb el, were found to be the most contaminated, showing muscle tissue concentra tions up to eightfold higher than the corresponding upstream fish. DDT conc entrations were parallel to PCB changes although at lower values. Despite t he increased contamination caused by the input from the Lambro tributary, w hen fish PCB loads are converted to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TC DD) 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 R iver, the presence of other organochlorines and halogenated hydrocarbons is very probable in the downstream area, and a more exhaustive hazard assessm ent, based on further studies, should be undertaken.