Micronodules and emphysema in coal mine dust or silica exposure: relation with lung function

The aim of this study was to investigate the respective effects of micronod ules and pulmonary emphysema, detected by computed tomography (CT), on lung function in workers exposed to silica and coal mine dust. Eighty-three subjects exposed to silica (n=35) or to coal mine dust (n=48), without progressive massive fibrosis, were investigated by high-resolution and conventional CT scans to detect micronodules and to quantify pulmonary emphysema by measuring the relative area of the lung with attenuation valu es lower than -950 Hounsfield units. Sixty-six (54.5%) subjects had evidence of micronodules an CT scans. Smoker s had micronodules more rarely than nonsmokers. Significant correlations we re found between the forced expiratory volume in one second (FEV1; % predic ted) (r=-0.41, p<0.001), FEV1/vital capacity (VC) (r=-0.61, p<0.001), diffu sing capacity of the lung for carbon monoxide (DL,CO) (r=-0.36, p<0.001) an d the extent of emphysema, No difference was demonstrated in the linear rel ationships between the extent of emphysema and the pulmonary function accor ding to the type of exposure or the presence of micronodules on CT scans. This study suggests that micronodules detected by computed tomography have no influence, by themselves, on pulmonary function and that they should onl y be considered as a marker of exposure.