Alveolar destruction in guinea pigs chronically exposed to diesel engine exhaust. A light- and electron-microscopic morphometry study.

Guinea pigs were exposed 16 h a day, 6 d a week, for 6, 12, 18, or 24 mo to filtered air or diesel-exhaust at low (NO2 = 0.22 +/- 0.03 ppm; SO2 = 0.60 +/- 0.19 ppm; particles = 0.21 +/- 0.07 mg/m3), medium (NO2 = 1.07 +/- 0.09; SO2 = 2.83 +/- 0.73; particles = 1.14 +/- 0.26) or high (NO2 = 2.88 +/- 0.29; SO2 = 6.49 +/- 1.75; particles = 2.94 +/- 0.69) concentrations, or at a medium concentration without particles (NO2 = 1.01 +/- 0.09; SO2 = 2.66 +/- 0.64; particles = 0.01 +/- 0.01). We quantitated the holes in the alveolar wall and alveolar size by using scanning electron microscopy (SEM). After 12 mo of exposure, the ratio of the area of alveolar holes to that of the alveolar wall, and the number of holes per alveolus, rose as the concentration and duration of exposure increased. There were no differences in alveolar size between the study groups. Animals exposed to the medium concentration of diesel exhaust without particles showed less of an increase in the development of holes than animals exposed to the same concentration of diesel exhaust with particles. These findings suggest that diesel exhaust causes alveolar destruction (alveolar holes) without an enlargement in alveolar size in a concentration- and duration-dependent manner. Particulate matter in diesel exhaust may play some role in the development of these lesions.