1Department of Occupational and Environmental Medicine, Pusan National University, Yangsan Hospital, Yangsan, Korea
2Department of Preventive and Occupational Medicine, Pusan National University, School of Medicine, Yangsan, Gyongnam, Korea
3Occupational Safety & Health Research Institute, Korea Occupational Safety & Health Agency, Ulsan, Korea
4Department of Occupational and Environmental Medicine, Haeundae Paik Hospital, Inje University, Busan, Korea
5Department of Occupational and Environmental Health, Yonsei University Graduate School of Public Health, Seoul, Korea
6Department of Occupational and Environmental Medicine, College of Medicine, the Catholic University, Seoul, Korea
7Department of Occupational and Environmental Medicine, Ajou University School of Medicine, Suwon, Korea
8Department of Preventive Medicine, Ewha Womans University School of Medicine, Seoul, Korea
9Department of Occupational and Environmental Medicine, Wonju Severance Christian Hospital, Wonju College of Medicine, Yonsei University, Wonju, Korea
10Department of Preventive Medicine and Institute of Occupational and Environmental Medicine, Wonju College of Medicine, Yonsei University, Wonju, Korea
Copyright © 2014 Kang et al.; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.