1. Johns Hopkins Water Institute, Johns Hopkins Bloomberg School of Public Health, 615 N Wolfe St, E6638, Baltimore, MD 21205, USA
2. Center for Research, Evaluation Resources and Development, Ife, Nigeria and University of Western Cape, Cape Town, South Africa
3. Department of Community Medicine, College of Medicine, University of Ibadan, Ibadan, Nigeria
4. School of Public Health, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana