1. Department of Occupational and Environmental Medicine, Chungbuk National University Hospital, Cheongju 28644, Republic of Korea
2. Department of Public Health, Graduate School, Yonsei University, Seoul 03722, Republic of Korea
3. Department of Preventive Medicine, College of Medicine, Chungbuk National University, Cheongju 28644, Republic of Korea
4. Department of Hygienic Chemistry, Graduate School of Biomedical Science, Nagasaki University, Nagasaki 852-8521, Japan