1. School of Nursing, National Taiwan University, and Center for Medical Employee Safety and Health, Taipei, Taiwan, ROC
2. Yong Loo Lin School of Medicine, National University of Singapore
3. College of Medicine, National Cheng Kung University, Tainan, Taiwan, ROC
4. Department of Occupational and Environmental Medicine, College of Medicine, National Taiwan University, Section 1, Jen-Ai Road, Taipei 10051, Taiwan. Tel: +886 2 3322 8215; Fax: +886 2 2394 7998