Hard metal disease: eight workers with interstitial lung fibrosis due to cobalt exposure.

Eight hard metal workers exposed to cobalt containing dust (four producers of stone-cutting cobalt-diamond wheels and four grinders of hard metal tools) and affected by interstitial lung fibrosis have been examined. A close relationship between cobalt exposure and clinical findings was observed in six patients who were still working. The clinical picture ranged from minor symptoms to manifestations resembling those of hypersensitivity pneumonitis, with fever, weight-loss, non-productive cough and dyspnea. A restrictive impairment of the ventilatory function was prevalent. The chest roentgenogram of one patient showed a diffuse reticular nodular pattern, while the others presented a mild reticular accentuation of the interstitium. In five patients, bioptic specimens of the lung parenchyma showed interstitial collagenic fibrosis with inflammatory cells infiltrating the alveolar septa. An increased number of lymphocytes and polymorphs was reported in the bronchoalveolar lavage (BAL) fluid from seven patients. Giant multinucleated cells were present in the BAL of four subjects while an inversion of the helper-suppressor ratio was evident in those patients who were still exposed to cobalt when BAL was performed. In this study, the causal role of metallic cobalt inhalation in the etiology of the lung disease is examined and discussed.