Study of lung reactions in six asymptomatic workers occupationally exposed to hard metal dusts.

The description of one case of pulmonary fibrosis in a group of workers occupationally exposed to hard metal dusts with high concentrations of cobalt (50-90%), followed for five years, prompted us to perform a cytological examination on the bronchoalveolar lavage fluid plus determination of the lymphocytic subpopulations in six asymptomatic workers with the longest exposure. Bronchoalveolar lavage performed 16 hours (3 cases) or 48 hours (3 cases) after the end of the workshift showed a lymphocytosis with inversion of the helper/suppressor ratio in 3 cases. This demonstrates an immune response at deep lung level. No difference was observed between a subject with ascertained interstitial fibrosis and the other subjects. Furthermore, bronchoscopy revealed marked inflammatory reaction of the tracheobronchial mucosa.