1. Graduate School of Medical Sciences, University of Tsukuba, Tsukuba, Japan
2. Laboratory of Comparative Carcinogenesis, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina, USA
3. Department of Preventive Medicine, St. Marianna University School of Medicine, Kawasaki, Japan
4. Department of Labor Hygiene and Occupational Health, School of Public Health, China Medical University, Shenyang, China
5. Department of Public Health, Asahikawa Medical College, Asahikawa, Japan
6. Department of Environmental Health, Tokai University School of Medicine, Isehara, Japan
7. Department of Dermatology, Kawasaki Medical School, Kurashiki, Japan
8. Department of Public Health, and
9. Department of Environmental Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan