Emphysema and airway obstruction in non-smoking South African gold miners with long exposure to silica dust.

Abstract

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...

Occupational chronic obstructive pulmonary disease: a systematic literature review

“…As with the studies of airway obstruction and coal mining, the studies on gold mining have the inherent challenge of disentangling the restrictive deficits associated with the dust exposure from obstructive deficits. The dust exposure with high silica concentration has been associated with different respiratory health outcomes: asthma (23), bronchial hyper-responsiveness (24), emphysema (25), silicosisassociated dysfunction, chronic airflow limitation, and chronic bronchitis (26), and studies among gold miners have found loss in lung function associated with pulmonary tuberculosis (27). The diversity in respiratory health outcome associated with the same exposure pinpoints a diagnostic uncertainty.…”

HETA 93-0794-2621, Unimin Specialty Minerals, Inc. - Tamms, Tamms, Illinois.

“…(31,32,33) A NIOSH evaluation at this same plant in 1979 found that 7 (27%) of 26 participating current and former workers with one or more years exposure had chest x-ray changes consistent with silicosis. (34) Three cases were identified among 15 current workers and four cases were identified among 11 former workers.…”

Silicose

“…(25)(26) As alterações clínicas e funcionais observadas, embora guardem certa relação com as alterações radiográficas, podem ser encontradas em indiví-duos expostos sem evidências radiográficas de silicose.…”