1Department of Occupational & Environmental Medicine, School of Public Health, Seoul National University, Korea.
2Occupational Health Center, KajwaSungmo Hospital, Korea.
3Department of Occupational & Environmental Medicine, Hangang Sacred Heart Hospital, Hallym University, Korea.
4Dept. of Preventive Medicine, Industrial Medical Center, The Catholic University of Korea, Korea.
5Department of Preventive Medicine, The Catholic University of Korea, Korea. JFIF d d Ducky d qhttp://ns.adobe.com/xap/1.0/