1. Biostatistics and Epidemiology Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, WV, USA
2. Department of Psychology, West Virginia University, Morgantown, WV, USA
3. School of Public Health and Health Professions, Department of Social and Preventive Medicine, State University of New York at Buffalo, Buffalo, NY, USA