1. Occupational Medicine Division, School of Public Health, University of Cape Town, Cape Town, Western Cape, South Africa
2. Discipline of Occupational and Environmental Health, University of KwaZulu-Natal, Durban, KwaZulu-Natal, South Africa
3. Discipline of Public Health Medicine, University of KwaZulu-Natal, Durban, KwaZulu-Natal, South Africa
4. National Institute for Occupational Health, National Health Laboratory Service, Johannesburg, Gauteng, South Africa
5. School of Health Systems and Public Health, University of Pretoria, Pretoria, South Africa
6. Department of Environmental Health, University of Johannesburg, Johannesburg, Gauteng, South Africa
7. Medical Bureau for Occupational Diseases, National Department of Health, Pretoria, South Africa