1Institute for Occupational Health, Yonsei University College of Medicine, Korea. jhroh@yumc.yonsei.ac.kr
2Graduate School of Public Health and Management, Yonsei University, Korea.
3Department of Preventive Medicine and Industrial Medical Center, The Catholic University of Korea, Korea.
4Department of Preventive Medicine and Institute of Occupational Medicine, Wonju College of Medicine, Yonsei University, Korea. JFIF d d Ducky d qhttp://ns.adobe.com/xap/1.0/