1. Department of Environmental and Occupational Health, College of Medicine, National Cheng Kung University, Tainan 70428, Taiwan
2. Department of Health Care Management, University of Kang Ning, Tainan 70970, Taiwan
3. Department of Occupational and Environmental Medicine, National Cheng Kung University Hospital, Tainan 70428, Taiwan
4. Department of Environmental Engineering, Dong-A University, Busan 604-714, Republic of Korea