Pulmonary function and peripheral airway disease in patients with mineral dust or fume exposure

Cigarette smoking and mineral dust exposure combined result in small airways function abnormalities difficult to distinguish from smoking effects alone. To determine if mineral dust or fume exposure in smokers results in additional changes in small airways structure and function, we studied small airways disease and pulmonary function in 25 persons (62.4 +/- 8.8 yr) with exposure to mineral dust or fume for 10 yr or more and compared them individually with control subjects without dust exposure (61.8 +/- 8.5 yr) matched for age, smoking history, and lobe resected. All subjects were patients undergoing surgical resection for isolated coin lesions. Occupational histories and measurements of lung volumes, flow rates, small airways function, diffusing capacity, and pressure-volume relationships were obtained preoperatively. Membranous bronchioles were graded for the presence and degree of mural inflammation, fibrosis, muscle, pigment, and squamous and goblet cell metaplasia. Respiratory bronchioles were similarly graded for inflammation, fibrosis, muscle, pigment, and lumenal macrophages. The dust-exposed group had increased fibrous tissue deposition and goblet cell metaplasia in the membranous bronchioles (p less than 0.05). When the exposed group was divided according to occupation into miners (n = 13) and nonminers exposed in other dusty jobs (n = 12), the pathologic changes were evident in both exposed groups. No differences in pulmonary function were seen between the 2 groups. We conclude that occupational exposure to mineral dust and fume produces structural changes in peripheral airways that are greater than those seen with smoking alone, but these changes were not associated with a greater deterioration in lung function.