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Objective-Occupational exposure to silica dust is associated with significant impairment oflung function. The present study investigates which pathological changes in the lung are associated with impairment oflung function in silica dust exposed workers who were life-long nonsmokers. Methods-242 South African white gold miners who were lifelong non-smokers and who had a necropsy at death were studied. The pathological features identified at necropsy were the degree and type of emphysema, the presence of airway disease, and the degree of silicosis in the lung parenchyma and pleura. These features were related to lung function tests done a few years before death, to type of impairment (obstructive or restrictive), and to cumulative silica dust exposure. Results-The degree of emphysema found at necropsy was not associated with a statistically significant impairment of lung function or with dust exposure. The degree of silicosis in the lung parenchyma and the large airways disease (based on mucus gland hyperplasia) were associated with a statistically significant impairment of lung function. The large airway disease was, however, not positively associated with dust exposure or silicosis. In miners with a moderate or a higher degree of limitation of airflow the main findings were silicosis, heart disease, and obesity. The presence of small airways disease could not be established from the necropsy material. Conclusion-The results indicate that the level of exposure to silica dust to which these miners were exposed, without a confounding effect of tobacco smoking, is not associated with a degree of emphysema that would cause a statistically significant impairment of lung function. Silicosis of the lung parenchyma was associated with loss of lung function. Other factors that may play a part in impairment of lung function in these miners are obesity and heart disease.(Occup Environ Med 1994;51:557-563) It has been shown in experimental animals' and also in humans2-4 that exposure to silica or mineral dust containing a large percentage of silica can result in pathological changes in the lung parenchyma other than silicosis and that these changes result in impairment of lung function. The changes are emphysema,5 6 thickening of small airways,' and pronounced fibrosis and pigmentation of the respiratory bronchioles.2It is uncertain whether the impairment of lung function in workers exposed to silica dust is due to the change in the alveoli (emphysema) or in the small airways. The American Thoracic Society suggests that in subjects at risk of developing chronic obstructive pulmonary disease (COPD), pathological changes in the peripheral airways precede the development of emphysema and that these changes on their own, without emphysema, may be responsible for subtle abnormalities in pulmonary function tests that are not associated with physical impairment.7Workers in South African gold mines are exposed to low levels of respirable dust ( % 0 4 mg/m3) containing a high percentage of crystalline silica (-30%). Epide...

In order to assess the effect of silicosis on lung function, 61 gold miners with radiological silicosis were compared with 61 controls. Each pair was matched for age, dust exposure, and smoking habits. A full range of lung function tests was performed, and with two exceptions the results showed no significant differences between the two groups. The exceptions are the slope of the alveolar plateau (phase 3) and the closing volume, for which the silicotic cases had significantly higher values. The reason for the higher readings in the silicotic patients remains unexplained.

Evidence is presented which indicates that electric alternation is frequently associated with pericardial effusion; that this alternation is of a unique type; and that it is caused by movement of the heart in the fluid filled pericardial sac.

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