1 Department of Health Risk Control, Atomic Bomb Disease Institute, Nagasaki University, Nagasaki, Japan.
2 Department of Health Risk Control, Atomic Bomb Disease Institute, Nagasaki University, Nagasaki, Japan; Cambodia University of Technology and Science (CamTech), Phnom Penh 121003, Cambodia; Hiroshima University, Hiroshima, Japan. Electronic address: bengmealea@yahoo.com.