1. National Institute for Occupational Safety and Health, Morgantown, West Virginia 26505, Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201, Division of Toxicology and Environmental Medicine, Agency for Toxic Substances and Disease Registry (ATSDR/CDC), 1600 Clifton Road NE, F-32, Atlanta, Georgia 30333, and School of Pharmacy, West Virginia University, Morgantown, West Virginia 26506