A survey of black mineworkers of the Cape crocidolite mines.

Between 1974-1978, a study group 970 mineworkers exposed from before July 1962 only to Cape crocidolite were traced: 755 were alive and 215 dead. Of those still alive, 66.1% showed no radiological abnormalities of the chest; 8.9% had irregular small opacities only; 17.7% had pleural abnormalities only; and 7.3% had both. Five pleural mesotheliomas were found in living ex-workers; although only one was reported in those who had died, this was considered to be an underestimate. The incidences of pleural mesotheliomas in ex-employees of the mining industry outside of the study group are also described.