Inorganic Dust Exposure Causes Pulmonary Fibrosis in Smokers: Analysis Using Light Microscopy, Scanning Electron Microscopy, and Energy Dispersive X-Ray Spectroscopy

Abstract

Smoking is alleged to cause pulmonary fibrosis, but the role of inorganic dust particulates has not been adequately examined. The authors hypothesize that inorganic dust exposure is an independent risk factor for the development of fibrosis in smokers. They studied a prospective series of 34 subjects with open lung biopsies, 18 of whom had adequate lung parenchyma for evaluation. They also examined the relationships between smoking (pack-years), respiratory bronchiolitis (RB), inorganic dusts, and interstitial fibrosis. They graded RB, fibrosis, and particulate dust by means of light microscopy. They performed a semiquantitative analysis of dust burden by using scanning electron microscopy with energy-dispersive X-ray spectroscopy. A logistic regression analysis demonstrated a significant association between smoking and RB (p = .03), but not between smoking and fibrosis or between RB and fibrosis. Fibrosis was significantly associated with silica (pp = .004) and titanium (pp = .0006) concentrations. The results support the authors' hypothesis.

Keywords:

• inorganic dust
• pulmonary fibrosis
• smoking