1. Department of Preventive Medicine, College of Medicine, Ewha Medical Research Center, Ewha Womans University, Seoul, South Korea
2. Department of Epidemiology and Biostatistics and Institute of Health and Environmental Sciences, School of Public Health, Seoul National University, Seoul, South Korea
3. Department of Occupational and Environmental Medicine, College of Medicine, Inha University, Incheon, Korea
4. Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts