1. Department of Environmental Medicine (Y.A., A.K., M.K., S.Y., K.I., F.K.), Center for Community Medicine, Jichi Medical School, Tochigi 329-0498
2. School of Agriculture (M.K., M.Y.), Ibaraki University, Ibaraki 300-0393
3. Graduate School of Medicine (A.I.), Osaka City University, Osaka 545-8585
4. Fourth Department of Internal Medicine (S.Y., S.W.), Saitama Medical School, Saitama 350-0495; Core Research for Evolutional Science and Technology, Japan Science and Technology Corporation, Saitama 332-0012, Japan