1. Department of Public Health, Juntendo University Faculty of Medicine, Japan
2. Department of Public Health, Dokkyo Medical University, Japan
3. Department of Public Health, Showa University, Japan
4. Department of Epidemiology and Environmental Health, Juntendo University Faculty of Medicine, Japan
5. Department of Safety and Health, Tokyo Gas Co. Ltd., Japan
6. Teikyo University Graduate School of Public Health, Japan