1. Department of Occupational and Environmental Medicine, Severance Hospital, Yonsei University Health System, Seoul, Korea.
2. The Institute for Occupational Health, Yonsei University College of Medicine, Seoul, Korea.
3. Department of Public Health, Yonsei University Graduate School, Seoul, Korea.
4. Federation of Korean Trade Unions, Seoul, Korea.
5. Graduate School of Public Health, Yonsei University, Seoul, Korea.
6. Department of Preventive Medicine, Yonsei University College of Medicine, Seoul, Korea.