1. National Food Safety and Toxicology Center, Department of Zoology, Institute of Environmental Toxicology, Michigan State University, East Lansing, Michigan 48824, U.S. Geological Survey, National Wildlife Health Center, 6006 Schroeder Road, Madison, Wisconsin 53711-6223, Department of Environmental Toxicology, Clemson University, 509 Westinghouse Road, P.O. Box 709, Pendleton, South Carolina 29670-0709, and 3M Environmental Laboratory, 935 Bush Avenue, St. Paul, Minnesota 55133