Small Airways Disease Caused by Mineral Dusts

Abstract

Recent studies have made it clear that mineral dusts can produce a distinctive pattern of fibrosis of the walls of the small airways. This process can be reliably identified microscopically by the appearance of characteristic lesions in the respiratory bronchioles and alveolar ducts, but the membranous bronchioles are affected as well. With sufficiently high dust exposure, the fibrosing process becomes severe enough to both narrow and distort the airway, leading to flow abnormalities. These lesions have been documented in the lungs of persons exposed to many different types of inorganic dusts, including asbestos, silica, iron oxide, aluminum oxide, sheet silicates such as talc and mica, and coal. The pathologic changes are probably a result of progressive deposition and translocation of dust through the airway epithelium into the interstitium with a resulting inflammatory response that leads to the release of fibrogenic mediators.