1. Department of Preventive Medicine, Cheju National University College of Medicine, Jeju, Korea.
2. Department of Preventive Medicine, Ulsan University College of Medicine, Seoul, Korea.
3. Department of Social and Preventive Medicine, Sungkyunkwan University School of Medicine, Seoul, Korea.
4. Department of Social Medicine, Hallym University College of Medicine, Seoul, Korea.
5. Institute of Radiation Effect & Epidemiology, Seoul National University College of Medicine, Seoul, Korea.
6. Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea.