Acute toxicity and sublethal effects of white phosphorus in mute swans, Cygnus olor

Among the waterfowl affected by white phosphorus (P₄) at a military base in Alaska are tundra (Cygnus columbianus) and trumpeter (C. buccinator) swans. To estimate the toxicity of P₄ to swans and compare the toxic effects to those of mallards (Anas platyrhynchos), we dosed 30 juvenile mute swans (C. olor) with 0 to 5.28 mg P₄/kg body weight. The calculated LD₅₀ was 3.65 mg/kg (95% CI: 1.40 to 4.68 mg/kg). However, many of the swans still had P₄ in their gizzards after dying, as determined by “smoking gizzards” and characteristic odor, and a lower LD₅₀ might be calculated if all of the P₄ had passed into the small intestines. We attribute the retention of P₄ in swans to the possibility that P₄ pellets were mistaken for the similarly sized grit in their gizzards. Most swans took 1 to 4.5 days to die in contrast to the few hours normally required in mallards and death appeared to be related more to liver dysfunction than to hemolysis. White phosphorus affected several plasma constituents, most notably elevated aspartate aminotransferase, blood urea nitrogen, lactate dehydrogenase, and alanine aminotransferase.