Respiratory impairments due to dust exposure: a comparative study among workers exposed to silica, asbestos, and coalmine dust.

We conducted a comparative study of pulmonary dysfunction among workers who were exposed to silica, asbestos, or coalmine dust. The results showed that all three groups of dust-exposed workers, even those without radiographic signs of pneumoconiosis, had decreased spirometric parameters and diffusing capacity (DLco) in both nonsmokers and smokers. Pulmonary function was further decreased when pneumoconioses were present in the three groups. In accord with increasing radiographic categories, pulmonary function in the workers with either silicosis or asbestosis was even lower, whereas in those with coal workers' pneumoconiosis (CWP), it changed relatively little. Workers with mild to moderate (radiographic category I-II) silicosis or asbestosis showed similarly decreased DLco, but those with silicosis showed lower FEV1/FVC than those with abestosis. The workers with CWP also showed a lower FEV1/FVC than those with asbestosis. The major impairment patterns for silica workers, asbestos workers, and coal miners were mixed, restrictive and mixed, and obstructive, respectively. Smoking obviously increased the prevalence of obstruction for all the groups. We conclude from the present study that all the three dusts cause functional abnormalities that precede radiographic changes of pneumoconiosis. We should pay more attention to respiratory impairment in the initial stage of silicosis and CWP.