Respiratory symptoms and pulmonary function in coal miners: looking into the effects of simple pneumoconiosis

Although severe impairment of pulmonary function is believed to occur commonly in complicated pneumoconiosis, the relationships of simple coal workers' pneumoconiosis (CWP) to pulmonary function and respiratory symptoms have remained under debate. The study aims to investigate if simple pneumoconiosis is associated with significant impairment of pulmonary function and increased risk of respiratory symptoms.

Spirometry and diffusing capacity were performed in 205 miners with simple CWP and 289 without X ray evidence of pneumoconiosis, who were selected from a large underground coal mine in China. A questionnaire on occupational history and respiratory symptoms including breathlessness, chronic cough, and phlegm was administered. The presence or absence of emphysema on their X-ray films was also evaluated. Logistic regression and multiple linear regression analysis were applied to estimate the independent effect of CWP on respiratory symptoms and parameters of pulmonary function.

On the average, the miners with CWP had lower values of pulmonary function and higher prevalences of respiratory symptoms, and emphysema than did those without. The simple CWP was associated with increased risk of the respiratory symptoms after adjusting for age, smoking, and years underground. Regression analysis showed that the CWP had significantly independent effects on parameters of pulmonary function. Even when the effects of emphysema, respiratory symptoms indicating chronic bronchitis were taken into consideration, the significant relationship between CWP and decrements in FVC and diffusing capacity remained.

The findings of this study are consistent with simple CWP being a contributor to significant decrements in pulmonary function, and to increased risk of respiratory symptoms.