1. Department of Internal Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
2. Department of Internal Medicine, Hanyang University Medical Center, Hanyang University College of Medicine, Seoul, Korea.
3. Department of Occupational Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
4. Department of Food and Nutrition, Sungshin Women's University, Seoul, Korea.
5. Department of Occupational and Environmental Medicine, Soonchunhyang University College of Medicine, Chunan, Korea.