A large body of evidence demonstrates dose-response relationships of cumulative coal mine dust exposure with lung function impairment and with small opacity profusion. However, medical literature generally holds that simple coal workers’ pneumoconiosis (CWP) is not associated with lung function impairment. This study examines the relationship between small opacity profusion and lung function in U.S. underground coal miners with simple CWP.
Miners were examined during 2005–2013 as part of the Enhanced Coal Workers’ Health Surveillance Program. Work histories were obtained, and chest radiographs and spirometry were administered. For those with multiple Program encounters, the most recent visit was used. Lung parenchymal abnormalities consistent with CWP were classified according to International Labour Organization guidelines, and reference values for FEV1 and FVC were calculated using reference equations derived from the 3rd National Health and Nutrition Examination Survey. Differences in lung function were evaluated by opacity profusion, and regression models were fit to characterize associations between profusion and lung function.
A total of 8,230 miners were eligible for analysis; 269 had category 1 or 2 simple CWP. Decrements in FEV1 percent predicted were nearly consistent across profusion subcategories. Clear decrements in FVC percent predicted and FEV1/FVC were also observed, although these were less consistent. Controlling for smoking status, BMI, and mining tenure, each one-unit subcategory increase in profusion was associated with decreases of 1.5% (95% CI 1.0% to 1.9%), 1.0% (95% CI 0.6% to 1.3%), and 0.6% (95% CI 0.4% to 0.8%) in FEV1 percent predicted, FVC percent predicted, and FEV1/FVC, respectively.
We observed progressively lower lung function across the range of small opacity profusion. These findings address a longstanding question in occupational medicine, and point to the importance of medical surveillance and respiratory disease prevention in this workforce.