1. Department of Occupational and Environmental Medicine, Severance Hospital, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
2. The Institute for Occupational Health, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
3. Graduate School, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
4. Department of Preventive Medicine, Yonsei University College of Medicine, Seoul 03722, Republic of Korea