1. Department of Pulmonary and Critical Care Medicine, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea.
2. Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea.
3. Department of Pathology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea.
4. Department of Clinical Epidemiology and Biostatistics, University of Ulsan College of Medicine, Seoul, Korea.
5. Graduate School of Public Health, Seoul National University, Seoul, Korea.
6. Department of Environmental Health, Korea National Open University, Seoul, Korea.