Cobalt Exposure and Lung Disease in Tungsten Carbide Production: A Cross-sectional Study of Current Workers

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Abstract
A cross-sectional study of 1,039 tungsten carbide (TC) production workers was carried out. The purposes were (1) to evaluate the prevalence of interstitial lung disease (ILD) and work-related wheezing, (2) to assess correlations between cobalt exposure and pulmonary disease, (3) to compare lung disease in grinders of hard carbide versus nongrinders, and (4) to evaluate the effects of new and previous threshold limit values for cobalt of 50 and 100 .mu.g/m3. We obtained medical and occupational histories, flow-volume loops, single breath carbon monoxide diffusing capacity (DLCO), and chest radiographs. Time-weighted averave cobalt levels were determined at every step in the production process. Work-related wheeze occurred in 113 participants (10.9%). Profusion .gtoreq. 1/0 occurred in 26 (2.6%) and interstitial lung disease (defined as profusion .gtoreq. 1/1, FVC or DLCO .ltoreq. 70%, and FEV1/FVC% .gtoreq. 75) in 7 (0.7%). The relative odds of work-related wheeze was 2.1 times for present cobalt exposures exceeding 50 .mu.g/m3 compared with exposures .ltoreq. 50 .mu.g/m3. The relative odds of profusion .gtoreq. 1/0 was 5.1 times for average lifetime cobalt exposures exceeding 100 .mu.g/m3 compared with exposures .ltoreq. 100 .mu.g/m3 in those with latency exceeding 10 yr. ILD was found in three workers with very low average lifetime exposures (less than 8 .mu.g/m3) and shorter latencies. Grinders of hard carbide had lower mean DLCO than nongrinders, even though their cobalt exposures were lower. These findings suggest that a small percentage of TC workers is at risk for ILD. Individuals with increased susceptibility may develop ILD after relatively shorter and lower exposures than less susceptible individuals.