Trace Elements (Pb, Zn, Cu) in Blood of Mute Swan (Cygnus olor) from the Isonzo River Nature Reserve (Italy)

Lead concentrations in blood of 45 specimens of mute swan from the molting area of the Isonzo River Mouth Nature Reserve (Italy) were determined in two consecutive years (2006-2007), some birds were neck ringed to identify their homing behavior. The second sampling included whole body X-ray radiography and Cu and Zn plasma analyses to investigate the health impact of putative Pb exposure. X-ray images of all investigated specimens did not show any radiopacity due to the ingestion of metal bodies. Lead levels (0.08-0.44 μg/ml) were in the range of those reported for swans living in unpolluted or slightly polluted environments and excluded acute intoxication, as confirmed by clinical investigation. Zinc concentrations ranged between 2.93 and 7.59 μg/ml and were one order of magnitude higher than Cu concentrations (0.21-0.42 μg/ml). The negative correlation between Pb and Zn concentrations could be indicative of adverse health effects caused by chronic lead exposure. To our knowledge this is the first study reporting Pb, Zn and Cu blood levels, X-ray radiographies and data on the origin of swan populations.