Relationships of Lung Structural and Functional Changes to Accumulation of Diesel Exhaust Particles

Abstract

Abstract Relationships between accumulated lung burdens of diesel soot, altered lung morphology and impaired respiratory function were examined. Rats were exposed 7 hr/day, 5 days/wk for 24 months to diluted exhaust at soot concentrations of 0.35, 3.5 or 7.0 mg/m 3 or to clean air. Soot lung burdens were measured by light absorption. Excised lung weights and volumes and mean linear intercepts of terminal airspaces were measured and histopathology was evaluated. Respiratory function was measured in vivo. Soot accumulated in lungs of all exposed rats, but no other abnormalities were seen at the lowest level. At the higher levels, focal proliferative, fibrotic and emphysematous changes were reflected in increased lung weight, density and mean linear intercept. Reduced in vivo lung volume and compliance paralleled reduced weight-specific lung volume. Gas exchange impairment paralleled reduced internal surface area. A difference between surface area calculated from internal and external lung volumes was demonstrated.