1. Department of Occupational and Environmental Medicine, International St. Mary’s Hospital, Catholic Kwandong University, Incheon, Korea
2. Department of Statistics, Dongguk University, Seoul, Korea
3. Occupational Safety and Health Research Institute, Korea Occupational Safety and Health Agency, Ulsan, Korea
4. Department of Occupational and Environmental Medicine, Inha University, Incheon, Korea
5. Department of Occupational Health, Catholic University of Daegu, Daegu, Korea
6. Department of Environmental Health, Korea National Open University, Seoul, Korea