||Northrop Services, Inc., Research Triangle Park, NC. ;Duke Univ. Medical Center, Durham, NC.;Health Effects Research Lab., Research Triangle Park, NC.
Pulmonary function was examined in juvenile and young adult Fischer-344 rats continuously exposed to NO2 (0.5, 1.0 or 2.0 ppm) for up to 6 weeks with twice daily 1 hr spikes equal to 3X the baseline concentration. The spike to baseline ratio was chosen to simulate morning and evening urban rush hour conditions. Juvenile rats were examined after 3 and 6 weeks of NO2 exposures, while young adult rats were examined after 1, 3, and 6 week intervals. Lung volumes, compliance, and efficiency of ventilation were evaluated. Lung volumes increased in the juvenile rats after 3 and 6 week exposures to 1.0 and 2.0 ppm, but were unchanged in young adult rats. Lung compliance increased in juvenile rats exposed to 1.0 or 2.0 ppm for 3 weeks, however, was unchanged in juvenile rats exposed for 6 weeks, as well as in the young adult rats exposed for 1 and 3 weeks. Compliance decreased in young adult rats exposed to 2.0 ppm for 6 weeks, and was correlated to an overall thickening of alveolar interstitium and spetal tissues.