1. Department of Occupational and Environmental Medicine, Ewha Womans University Mokdong Hospital, Seoul, Korea.
2. Department of Occupational and Environmental Medicine, Catholic Kwandong University International St. Mary’s Hospital, Incheon, Korea.
3. Department of Preventive Medicine, College of Medicine, Hanyang University, Seoul, Korea.
4. School of Public Health, Hanyang University, Seoul, Korea.
5. Ewha Medical Research Institute, Ewha Womans University School of Medicine, Seoul, Korea.