1. Sirindhorn College of Public Health, Trang, Faculty of Public Health and Allied Health Sciences, Praboromarajchanok Institute Nonthaburi 92110 Thailand
2. Department of Health and Environmental Sciences, Kyoto University Graduate School of Medicine, Yoshida Konoe, Sakyo, Kyoto 6068501 Japan
3. Department of Environmental Health Sciences, Faculty of Public Health, Mahidol University, Bangkok 10400 Thailand