Evaluation of Alveolar Macrophage Particle Burden in Individuals Occupationally Exposed to Inorganic Dusts

Abstract

Alveolar macrophages recovered by bronchoalveolar lavage from individuals with occupational inorganic dust exposure are laden with particles. We evaluated 42 non-smoking males with long-term exposure to asbestos (27), coal (7), or silica (8), and normals (8) to determine a particle burden per 10⁶ alveolar macrophages. Scanning/transmission electron microscopy and energy-dispersive x-ray analysis were utilized to evaluate the particles following bleach digestion of the cells, or of alveolar macrophage sections. There was a four-fold (p<0.01) increase in the number of particles in the dust-exposed. There was also a striking increase in silica particle number in the silica-exposed (p<0.02) but not in the other dust-exposed groups. One-third of the coal miner's cells contained silica particles predominantly <0.5 μm. In the asbestos-exposed, there was one chrysotile fiber per 35 cells, and one amosite fiber per 215 cells consistent with the known mixed exposure of workers exposed to insulation products in the United States. No crocidolite was observed in any of the cells and tremolite was identified in two controls and two workers. Computer-generated maps of elements comprising the particles demonstrated the in situ localization of the particles and identified many very small alumino-silicates, particularly in coal miners. Particle analysis is a useful technique to evaluate type and amount of exposure, to evaluate alveolar clearance, and may be useful to investigate macrophage activation.