Toxicity of Lead-Contaminated Sediment to Mute Swans

Abstract

Most ecotoxicological risk assessments of wildlife emphasize contaminant exposure through ingestion of food and water. However, the role of incidental ingestion of sediment-bound contaminants has not been adequately appreciated in these assessments. This study evaluates the toxicological consequences of contamination of sediments with metals from hard-rock mining and smelting activities. Lead-contaminated sediments collected from the Coeur d'Alene River Basin in Idaho were combined with either a commercial avian maintenance diet or ground rice and fed to captive mute swans (Cygnus olor) for 6 weeks. Experimental treatments consisted of maintenance or rice diets containing 0, 12 (no rice group), or 24% highly contaminated (3,950 microg/g lead) sediment or 24% reference (9.7 microg/g lead) sediment. Although none of the swans died, the group fed a rice diet containing 24% lead-contaminated sediment were the most severely affected, experiencing a 24% decrease in mean body weight, including three birds that became emaciated. All birds in this treatment group had nephrosis; abnormally dark, viscous bile; and significant (p <or= 0.05) reductions in hematocrit and hemoglobin concentrations compared to their pretreatment levels. This group also had the greatest mean concentrations of lead in blood (3.2 microg/g), brain (2.2 microg/g), and liver (8.5 microg/g). These birds had significant (alpha = 0.05) increases in mean plasma alanine aminotransferase activity, cholesterol, and uric acid concentrations and decreased plasma triglyceride concentrations compared to all other treatment groups. After 14 days of exposure, mean protoporphyrin concentrations increased substantially, and mean delta-aminolevulinic acid dehydratase activity decreased by more than 95% in all groups fed diets containing highly contaminated sediments. All swans fed diets that contained 24% lead-contaminated sediment had renal acid-fast intranuclear inclusion bodies, which are diagnostic of lead poisoning in waterfowl. Body weight and hematocrit and hemoglobin concentrations in swans on control (no sediment) and reference (uncontaminated) sediment diets remained unchanged. These data provide evidence that mute swans consuming environmentally relevant concentrations of Coeur d'Alene River Basin sediment developed severe sublethal lead poisoning. Furthermore, toxic effects were more pronounced when the birds were fed lead-contaminated sediment combined with rice, which closely resembles the diet of swans in the wild.

Effects of lead exposure on oxidative stress biomarkers and plasma biochemistry in waterbirds in the field

“…This effect was also observed in previous studies with mallard ducklings experimentally exposed to Pb with sediment contaminated with Pb acetate (828 mg/g Pb dry weight; Hoffman et al, 2000), adult mute swans exposed to Pb contaminated sediment (700 mg/g Pb dry weight; Day et al, 2003) and mallard ducks with Pb contaminated food (1840 mg/g Pb dry weight; Mateo et al, 2003b). Alkaline phosphatase is an indicator of osteoblastic activity (Campbell, 1986), and Pb exposure has been associated with altered bone mineralization in birds (Gangoso et al, 2009).…”

“…In the erythrocyte, O 2 · human epidemiological studies, which suggest that kidney function may be altered even at the lowest levels of PbB o 5 mg/dl (Ahamed and Siddiqui, 2007b). The decrease of ALT activity in plasma observed in coots has been reported previously in mute swans exposed to low Pb contaminated sediment (Day et al, 2003). However, increases of ALT have been reported in mallards exposed to high Pb levels, which can be related to hepatic alterations (Mateo et al, 2003a).…”

The effect of lead poisoning on hematologic and biochemical values in trumpeter swans and Canada geese

“…Waterfowl, in particular swans, appear predisposed to acute lead poisoning due to high marshland contamination with lead pellets and the feeding habits of the birds. Severe lead intoxication in birds results in neurologic impairment that can interfere with flight and ability to prehend food 10–12. Lead accumulates in lipid, with particularly high concentrations in myelin.…”

Toxicity of Pb‐contaminated soil to Japanese quail (Coturnix japonica) and the use of the blood–dietary Pb slope in risk assessment

“…Hoffman et al () reported that Pb from contaminated sediment in feed was 44% as available as Pb acetate in feed when fed to ducklings. Blood Pb concentrations were found to be greater when waterfowl were fed suboptimal diets (Hoffman et al ; Day et al ), possibly due to nutritional deficiencies, such as a reduced level of Ca (Scheuhammer ), or to a greater rate of ingestion. Compounds may bind Pb to soil and sediment; the addition of phosphoric acids to Pb‐contaminated sediments decreased the rate of absorption by subadult mallards (Heinz et al ; Furman et al ).…”