1. Department of Preventive Medicine, Yonsei University College of Medicine, Seoul, Korea.
2. Department of Public Health, Graduate School, Yonsei University, Seoul, Korea.
3. Department of Global Economics, Sungkyunkwan University, Seoul, Korea.
4. Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC, USA.
5. The Institute for Occupational Health, Yonsei University College of Medicine, Seoul, Korea.