The relationship between rheumatoid arthritis and silicosis was studied by means of a case-control study in South African goldminers. One hundred and fifty seven miners with rheumatoid arthritis classified as "definite" (91) or "probable" (66) were individually matched by year of birth with miners who had no evidence of rheumatoid arthritis. Unmatched analysis of the case-control status for "probable" and "definite" cases yielded an odds ratio of 2-84 (p = 0-0001). Separate analyses yielded an odds ratio of 3 79 (p = 00006) for "definite" cases, a non-significant odds ratio for "probable" cases, and an odds ratio of 500 (p = 00003) for the presence of rheumatoid factor. These results could not be explained on the basis of cumulative dust exposure or intensity of exposure. The rate of progression of silicosis in both the "definite" and the "probable" groups was greater than for the control patients with silicosis, as was the probability of silicosis presenting at the start with larger nodules (type r).The radiological and histological features of silicosis are sometimes modified in a characteristic manner in miners with rheumatoid arthritis1-a phenomenon seen also in coalminers' pneumoconiosis.2 3 The question of whether silicosis occurs more readily in individuals with rheumatoid arthritis exposed to silica has not, however, been addressed.Silicosis occurs in South African gold miners, who may be exposed to dust containing high levels of free silica. The main objective of this study was to determine whether silicosis was present more often in miners with rheumatoid arthritis than in miners without, and to determine whether any differences found in the prevalence of silicosis could be explained by differences in the amount or intensity of exposure to silica dust. Miners with silicosis and rheumatoid arthritis were compared with those without rheumatoid arthritis to establish whether the rate of progression and other features of silicosis were different under conditions of equal exposure to silica dust. Index subjects with silicosis who were seropositive for rheumatoid factor were compared with the control subjects with silicosis to determine whether the presence of rheumatoid factor was relevant to the progression of silicosis.

All white and mixed race men who were employed in South African asbestos mines and mills between 30 November 1970 and 30 November 1975 were studied. The men who had two radiographs available, the first taken some time between the above two dates and the latest available radiograph which had to be at least two years after the first one numbered 1454: 793 continued exposure after the first radiograph and 661 did not. The films were read by a panel of three readers. Data available included age, years of exposure to asbestos and other mining, intensity of exposure to asbestos and other dust, and smoking habit. Progression was expressed as the difference between the average readings of radiograph 2-radiograph 1 in minor categories per year of irregular opacities. Changes in pleural abnormality were also measured. No differences ofprogression in the profusion or change in size of the irregular opacities were found between the two groups or in the number of zones affected. "New attacks" appeared equally frequently between the two groups. No difference in the change in extent of any type of pleural change was seen. It appears that once a dose of asbestos sufficient to initiate the disease has been retained it is inexorably progressive.The effect of removal from exposure to asbestos dust on progression ofradiological change has been studied by several authors working on relatively small groups of exposed men who have usually been exposed to chrysotile or chrysotile with a small admixture of amphibole.'"9 In one study the exposure was purely to Western Australian crocidolite.'°T he present study was performed on men whose predominant exposure was to South African amphibole (crocidolite and amosite) asbestos. The objectives were:(1) to determine if the progression of irregular opacities was slowed down or stopped or reversed after exposure to asbestos ceased, particularly in the case of low profusion of irregular opacities; and (2) to determine whether irregular opacities appeared de novo after exposure ceased and if so how commonly. sectional study were chosen for this study if they had had a follow up radiograph taken at least two years after the radiograph used for the cross sectional study. The maximum follow up time was up to mid-1987. Workers with missing exposure data or no follow up radiograph were excluded. The group remaining for the progression study amounted to 1454 men. Of these, 793 had exposure after the first radiograph and 661 did not. Eighty five men had exposure to chrysotile only. Methods RADIOLOGICAL READINGSA panel of three experienced radiograph readers read the films using the full 1980 ILO classification of Radiographs of the Pneumoconioses, the standard films and the side by side reading method. The films were marked to indicate the chronological order, the film used in the original cross sectional study (marked 1) and the latest available film (marked 2), but the dates of the films were covered so that the readers were blinded as to the duration of the period between the two films. The r...

A cross-sectional radiological survey of 2,245 men who were employed in South African asbestos mines was conducted in 1976. Since 1976, the lungs of 172 of these men who died have been examined to establish the presence of asbestosis or other pneumoconiosis. The x-ray readings (ILO/UC 1971) were compared with the pathological findings. A high prevalence of false positive readings, particularly for two of the three readers, was found. False negative readings were also very prevalent. Detailed information about asbestos and other mining exposure, smoking habit, age, height, and weight were examined to determine what influence they may have had in inducing false positive findings. Other dust exposure and smoking appeared to be possible factors, whereas age and obesity were probably not. It is suggested that the term "small irregular opacities" requires more precise definition.