1. a The University of Michigan, School of Public Health, Industrial Hygiene Program, Ann Arbor, MI 48109-2029
2. b Beijing Medical University, School of Public Health, Beijing 100083, People's Republic of China
3. c U.S. DHHS, PHS, CDC, NIOSH, DSHEFS, HETAB, IHS, 4676 Columbia Parkway, Cincinnati, OH 45226