1. Department of Environmental Health, Faculty of Health Sciences, Doornfontein Campus, University of Johannesburg, Johannesburg, South Africa
2. School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, Johannesburg, South Africa
3. Department of Environmental Sciences, College of Agriculture and Environmental Sciences, University of South Africa, Johannesburg, South Africa
4. Department of Toxicology and Biochemistry, National Institute for Occupational Health, Division of the National Health Laboratory Service, Johannesburg, South Africa