Respiratory disease in tungsten carbide production workers

We carried out a medical and environmental survey to evaluate respiratory disease at two tungsten carbide (TC) production plants. The study population of 290 subjects (19.2 percent of the total work force) was chosen to focus on those with the greatest potential exposures to cobalt, a binding agent which is probably the cause of interstitial fibrosis and airways disease in TC workers. We found peak air concentrations of cobalt exceeding 500 micrograms/m3 during many major steps in TC production. Nine subjects at plant A and two at plant B had interstitial infiltrates. Two of these nine from plant A had restriction (total lung capacity less than 80 percent of predicted). A lung biopsy specimen in one showed interstitial fibrosis. Two nonsmokers at plant A and one nonsmoker at plant B had obstructive defects. These results suggest that interstitial and obstructive lung disease occur in TC workers in association with elevated peak air concentrations of cobalt.