1Department of Occupational and Environmental Medicine, College of Medicine, Kyung Hee University, Korea.
2Department of Occupational and Environmental Medicine, Konkuk University Chungju Hospital, Korea.
3Department of Family Medicine, College of Medicine, Kyung Hee University, Korea.
4Department of Preventive Medicine, Ewha Women's University School of Medicine, Korea. jungchoikh@gmail.com JFIF d d Ducky d qhttp://ns.adobe.com/xap/1.0/