Abstract
Methyl mercury in the aquatic food web poses significant health risks to both wildlife and humans. One primary source of mercury contamination for both the aquatic and terrestrial systems is atmospheric deposition of inorganic mercury from industrial emissions. Once in the environment, inorganic mercury is converted to methyl mercury that enters the food web and bioaccumulates in prey species. Top level predators including piscivorous birds and humans are at greatest risk. Methyl mercury is the most toxic form of mercury, and is associated with behavioral changes, neurological impairment, reproductive failure and death. There is concern that methyl mercury may threaten populations of many wildlife species.
In this study the American kestrel was exposed to dietary methyl mercury in a controlled setting at the United States Geological Survey (USGS) Patuxent Wildife Research Center (PWRC). The purpose of this pilot study was to determine sensitivity and pathological change of this species to the toxicant, and gather information about methyl mercury absorption and distribution. Results from this study will help 1) design a reproductive study and 2) develop a physiologically-based toxicokinetic model of bioaccumulation of mercury in kestrels.
Though the concern for methyl mercury in avian species is primarily in piscivores, the American kestrel was chosen as the animal model for study since it can be kept and bred in captivity and is a top level carnivore. Information from the kestrel studies will also provide needed information to better understand risks from methyl mercury to wild pisivorous birds.
Dosage of birds included control, 3,6, and 12 ppm methyl mercury chloride (dry weight) mixed with Nebraska brand Bird of Prey diet for 1, 2, 4 or 8 weeks. Tissues examined histopathologically were kidney, liver, spinal cord and brain. Lesions were found only in the cerebellum of 12 ppm birds; all birds at this dose had similar lesions. Changes included neuronal degeneration, loss of myelin and mild inflammation.
This project is a collaboration with the United States Environmental Protection Agency and the USGS.