1. Water and Health Research Centre, Faculty of Health Sciences, University of Johannesburg, P.O. Box 17011, 2028 Auckland Park, South Africa
2. Environment and Health Research Unit, Medical Research Council of South Africa, P.O. Box 87373, Houghton 2041, South Africa
3. Department of Environmental Health, Faculty of Health Science, University of Johannesburg, P.O. Box 17011, 2028 Auckland Park, South Africa