1. a U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, Public Health Service, 4676 Columbia Parkway, Mail Stop R-5, Cincinnati, OH 45226-1099
2. b Murray State University, Department of Occupational Safety and Health, Faculty Hall, Suite 6A, Murray, KY 42071
3. c University of Cincinnati, College of Engineering, Department of Civil and Environmental Engineering, Cincinnati, OH 45221-0071