Influence of Experimental Pulmonary Emphysema on Toxicological Effects from Inhaled Nitrogen Dioxide and Diesel Exhaust

This report describes a study by Dr. Mauderly and colleagues to examine the influence of preexisting pulmonary emphysema on adverse health effects induced by chronic exposure of rats to diesel engine exhaust (DEE) or NO₂. Rats were exposed 7 hours/day, 5 days/week for 24 months to 9.5 ppm NO₂ or 3.5 mg soot/m³ DEE. Prior to exposure, a subset of rats was instilled with the proteolytic enzyme elastase to induce pulmonary emphysema. At 12, 18, and 24 months of exposure the following measures were taken: respiratory function, clearance of inhaled radiolabeled particles, pulmonary immune response to instilled antigen, biochemistry and cytology of airway fluid, total lung collagen, histopathology, lung morphometry, and lung burdens of diesel soot.