Silica, silicosis, and progressive systemic sclerosis.

An inquiry into the relation between exposure to silica dust, the presence of silicosis, and progressive systemic sclerosis was conducted in white South African gold miners by means of a case-control study. Seventy nine cases of progressive systemic sclerosis were matched by year of birth with an equal number of control miners selected randomly but bearing in mind the administrative channel through which the case had come to be identified. Analysis showed no association between silicosis and PSS but did show that the cumulative life time silica exposure was significantly higher in the cases compared with controls. This difference was due to a difference in the intensity of exposure to silica during mining service rather than a difference in duration of service. The results are discussed in the context of current thought on the aetiology of progressive systemic sclerosis, particularly in relation to autoimmune and genetic factors.