Heavy metals (copper, cadmium, lead, mercury) in mute swans from Denmark

During the severe winter of 1978-79, large numbers of mute swans died in coastal areas of Denmark. Of these, 2111 were collected for examination. The analyses confirm previous findings of relatively high copper levels in mute swans (mean for 178 livers was 2680 mg/kg dry weight (Dw) and for 110 kidneys 34 mg/kg Dw) (Table I, Fig. 1). The copper content was not related to sex or age (Table II). The highest liver levels of copper were found in swans from Western Jutland. Cadmium was found at the same relatively low levels as recorded for waterfowl elsewhere (mean for 178 livers was 12 mg/kg Dw, for 110 kidneys 24 mg/kg Dw) (Table I, Fig. 2). The cadmium content was not sex-related, but it increased with age (Table II). The mean mercury content (liver) was 1.4 mg/kg Dw in the 10 birds analysed (Table I). The mean lead content was 15 mg/kg Dw in the 178 livers analysed and 31 mg/kg Dw in 110 sternum (Table I and Fig. 3). The lead content was not sex-related. In sternum, but not in livers, it was related to age (Table II). One third of the swans were found lead-contaminated probably after ingestion of lead pellets. None of the swans carried high levels of both copper, cadmium, and lead (Table III).