1. Graduate School of Public Health, Yonsei University, Seoul, Korea.
2. Institute for Occupational Health, Yonsei University College of Medicine, Seoul, Korea.
3. Division of Allergy and Immunology, Department of Internal Medicine, Institute of Allergy, Yonsei University College of Medicine, Seoul, Korea.
4. Department of Preventive Medicine, Yonsei University College of Medicine, Seoul, Korea.