1Department of Occupational Health, Graduate School of Health Science and Management Yonsei University, Korea. chang@wonju.yonsei.ac.kr
2Department of Preventive Medicine and Institute of Occupational Medicine, Wonju College of Medicine Yonsei University, Korea.
3Department of Preventive Medicine and Public Health, College of Medicine Yonsei University, Korea. JFIF d d Ducky d qhttp://ns.adobe.com/xap/1.0/