Toxicity and Hazard of Vanadium to Mallard Ducks (Anas platyrhynchos) and Canada Geese (Branta canadensis)

Abstract

A recent Canada goose (Branta canadensis) die-off at a petroleum refinery fly ash pond in Delaware was attributed to vanadium (V) toxicity. Because of the paucity of V toxicity data for wild birds, a series of studies was undertaken using the forms of V believed to have resulted in this incident. In 7-d single oral dose trials with mallard drakes (Anas platyrhynchos), the estimated median lethal dose (LD50) for vanadium pentoxide was 113 mg/kg body weight, while the LD50 for sodium metavanadate was 75.5 mg/kg. Sodium metavanadate was found to be even more potent (LD50 = 37.2 mg/kg) in male Canada geese. The most distinctive histopathological lesion of both forms of V was lympho-granulocytic enteritis with hemorrhage into the intestinal lumen. Vanadium accumulation in liver and kidney was proportional to the administered dose, and predictive analyses based on these data suggest that V concentrations of 10 μg/g dry weight (dw) in liver and 25 μg/g dw in kidney are associated with mortality (>90% confidence that exposure is >LD50) in mallards acutely exposed to sodium metavanadate. Chronic exposure to increasing dietary concentrations of sodium metavanadate (38.5 to 2651 ppm) over 67 d resulted in V accumulation in liver and kidney (25.2 and 13.6 μg/g dw, respectively), mild intestinal hemorrhage, blood chemistry changes, and evidence of hepatic oxidative stress in mallards, although some of these responses may have been confounded by food avoidance and weight loss. Dietary exposure of mallards to 250 ppm sodium metavanadate for 4 wk resulted in modest accumulation of V in liver and kidney (<5 μg/g dw) and mild intestinal hemorrhage. Based on these data and other observations, it is unlikely that chronic low-level dietary exposure to V poses a direct lethal hazard to wildlife. However, point sources, such as the V-laden fly ash pond encountered by geese at the petroleum refinery in Delaware, may pose a significant hazard to water birds.

Acknowledgements

We thank Betty K. Ackerson, Kinard Boone, Dr. Patty Bright, Lynda J. Garrett, Dr. Jeff S. Hatfield, Vera Hudson, Katie R. Schoen, and Pamela C. Toschik for assistance with this work, and Drs. Gary H. Heinz and W. Nelson Beyer for reviewing a draft of this article.

Notes

The logistic distribution (logit transformation) is virtually indistinguishable from the normal distribution (probit transformation) except with very large sample sizes. Given the complexity of the models we subsequently considered and the insensitivity of the inference to the choice, we chose the logit transformation for its superior operating characteristics.

Credible intervals are the Bayesian analog of confidence intervals.

^aEstimated median lethal dose significantly different (p = .044, maximum likelihood analysis) from that of mallards receiving sodium metavanadate.

^aLiver and kidney V concentrations observed at goose die-off.

^aDietary concentrations were increased each week, starting at 38.5 ppm and ending at 2651 ppm.

^bSignificant at p < .05.

^aDietary concentrations were increased each week, starting at 38.5 ppm and ending at 2651 ppm.

^bnmol NADPH oxidized/min/mg of 10,000 g supernatant protein.

^cnmol/min/mg of 10,000 g supernatant protein.

^dSignificant at p < .05.

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