Impact of coal mine dust exposure and cigarette smoking on lung disease in Appalachian coalminers.

Introduction: Interactions have been demonstrated between cigarette smoking (CS) and occupational exposures to several particles. This study tested the postulate that CS interacts with coal mine dust exposure to impact and change radiological and histological endpoints of coal mine dust lung disease.

Methods: A retrospective evaluation of coalminers with a high-resolution computed tomography (HRCT) of the chest was conducted at West Virginia University Hospital (2015- 2022). There was a consensus review of both radiology and histology findings and their comparative analysis with a non-miner surgical resection cohort collected from thoracic oncology clinic.

Results: The study cohort (n=556) was divided into groups: coal-/smoking- (8.3%), coal-/smoking+ (26.6%), coal+/smoking- (22.3%), and coal+/smoking+ (42.8%). Miners were older males with a median duration of coal mine work (CMW) of 30-years. Ever-smokers (66% of miner cohort and 76% of non-miner cohort) smoked 35 and 28 composite pack years (CPY) respectively, where miners had greater intensity of smoking (22 vs 18 cigarettes/day) compared to non-miners. On HRCT, 1/3^rd and 1/5^th of miners had simple and complicated coal workers' pneumoconiosis (sCWP and cCWP), respectively. 35% of ever-smoking miners had radiologic patterns for probable usual interstitial pneumonitis, nonspecific interstitial pneumonitis, desquamative interstitial pneumonitis, and combined pulmonary fibrosis and emphysema. Radiologically, both coal-/smoking+ and coal+/smoking+ showed excessive emphysema (70-80%). Histologically, miners had more fibrosis (47% and 50% in coal+/smoking- and coal+/smoking+ vs. 11% and 28% in coal-/smoking- and coal-/smoking+). Never-smoking miners demonstrated more histological evidence of CWP than ever-smokers (60% and 27%); in addition, they had radiologic and histologic emphysema (30%), radiologic interstitial lung disease (ILD) (14.5%) and histologic evidence of fibrosis (47%). Ever-smokers demonstrated histologic emphysema more frequently (33% and 67% in coal+/smoking- and coal+/smoking+ vs. 24% and 72% in coal-/smoking- and coal-/smoking+). Logistic regression modeling showed the following associations: radiologic and histologic emphysema with CPY; histologic fibrosis, any ILD (not including RB-ILD), CPFE and anthracosis with both CPY and CMW; radiologic RB-ILD inclusive of small-opacities, cCWP with both CMW and silica; and sCWP and pulmonary artery dilation with CMW. Interestingly, CPY≥30 negatively correlated with radiologic cCWP and histologic CWP. Mortality was increased in smokers (14% and 29% in coal+/smoking- and coal+/smoking+ vs. 4% and 20% in coal-/smoking- and coal-/smoking+) with predictors being radiologic ILD, histologic CWP, and related co-morbid diseases including COPD, chronic kidney disease, and gastroesophageal reflux.

Conclusion: CS demonstrated a major impact on miners' health including changing radiologic and histologic endpoints of interstitial lung diseases and emphysema.