1. Department of Environmental Engineering, Kyoto University, C-1 Kyotodaigaku Katsura, Nishikyo, Kyoto 615-8540, Japan
2. Water, Sanitation, Hygiene and Health, World Health Organization, 20 Avenue Appia, 1211 Geneva 27, Switzerland
3. National Health and Medical Research Council, GPO Box 1421, Canberra ACT 2601, Australia
4. Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Rosenau 162B, 135 Dauer Drive, CB #7431, Chapel Hill, NC 27599-7431, USA