Asbestos exposure and mesothelioma in South Africa

Objectives. To describe the exposure experiences of South African mesotheli oma cases, with emphasis on the contribution made to the caseload by differ ent fibre types, the proportion of subjects with no recall of asbestos expo sure 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, Pret oria, Bloemfontein, Cape Town and Port Elizabeth. Results. A convincing history of asbestos exposure was obtained in the over whelming majority of cases (only 5 cases had unlikely asbestos exposure). T wenty-three subjects had worked on Cape crocidolite mines, 3 at Penge tan a mosite mine), 3 on mines producing amosite and Transvaal crocidolite and 1 on a Transvaal crocidolite mine. Exclusively environmental exposure account ed for at least 18% of cases; 91% of these cases (20/22 subjects) had had c ontact with Cape crocidolite. There was a relative paucity of cases linked to amosite and no convincing chrysotile case. Non-asbestos causes occur rar ely, 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 g radient of mesotheliomagenic potential for South African asbestos (crocidol ite > amosite > chrysotile).