Asbestos exposure and mesothelioma in South Africa

Objectives. To describe the exposure experiences of South African mesothelioma cases, with emphasis on the contribution made to the caseload by different fibre types, the proportion of subjects with no recall of asbestos exposure and only environmental contact, and the importance of putative causes other than asbestos. Design. A multicentred case-control study. Subjects and setting. 123 patients with mesothelioma interviewed by trained interviewers in study centres established in Johannesburg, Kimberley, Pretoria, Bloemfontein, Cape Town and Port Elizabeth. Results. A convincing history of asbestos exposure was obtained in the overwhelming majority of cases (only 5 cases had unlikely asbestos exposure). Twenty-three subjects had worked on Cape crocidolite mines, 3 at Penge tan amosite mine), 3 on mines producing amosite and Transvaal crocidolite and 1 on a Transvaal crocidolite mine. Exclusively environmental exposure accounted for at least 18% of cases; 91% of these cases (20/22 subjects) had had contact with Cape crocidolite. There was a relative paucity of cases linked to amosite and no convincing chrysotile case. Non-asbestos causes occur rarely, if at all, in South Africa. Conclusion. The preponderance of crocidolite cases, followed by amosite and then chrysotile cases, is consistent with the view that there is a fibre gradient of mesotheliomagenic potential for South African asbestos (crocidolite > amosite > chrysotile).