1. National Institute for Occupational Safety and Health (NIOSH), Health Effects Laboratory Division (HELD), Exposure Assessment Branch, Morgantown, West Virginia
2. Industrial and Management Systems Engineering, West Virginia University, Morgantown, West Virginia
3. NIOSH, HELD, Biostatistics and Epidemiology Branch, Morgantown, West Virginia
4. School of Medicine, West Virginia University, Morgantown, West Virigina