1. 1Department of Public Health, Keimyung University, 1000 Shindang-Dong, Dalseo-Gu, Daegu 704-701, Korea
2. 2Graduate School of Public Health, Seoul National University, Seoul 110-799, Korea
3. 3Department of Environmental Health, Yongin University, Yongin 449-714, Korea
4. 4Korea Health Industry Development Institute, Seoul 156-050, Korea
5. 5National Institute of Health Sciences, Tokyo 158, Japan