1Department of Occupational and Environmental Medicine, Yeungnam University Hospital, Korea. jsakong@med.yu.ac.kr
2Department of Preventive Medicine and Public Health, College of Medicine, Yeungnam University, Korea.
3Department of Occupational Medicine, Good Morning Hospital, Korea.
4Department of Preventive Medicine, College of Medicine, Seoul National University, Korea.
5Department of Preventive Medicine, College of Medicine, Chosun University, Korea.
6Department of Occupational Medicine, Busan National University Yangsan Hospital, Korea.
7Department of Preventive Medicine, College of Medicine, Dankook University, Korea.