1. Department of Environmental Medicine, Ewha Womans University College of Medicine, Seoul, Korea.
2. Department of Occupational and Environmental Medicine, Hanyang University College of Medicine, Seoul, Korea.
3. Department of Occupational and Environmental Medicine, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
4. Department of Occupational and Environmental Medicine, Kosin University College of Medicine, Busan, Korea.
5. Occupational Safety and Health Research Institute, Occupational Safety and Health Agency, Ulsan, Korea.