Pulmonary functional and morphological changes induced by a 4-week exposure to 0.7 PPM ozone followed by a 9-week recovery period

Male Fischer‐344 rats (control, C = 12; experimental, E = 11) were subjected to pulmonary‐function testing procedures. The experimental group was then exposed to 0.7 ppm ozone for 28 d, 20 h/d, and both groups were tested at the termination of the exposure and after 4 and 9 wk of recovery in clean filtered air. Another group of animals (C = 6, E = 12) was similarly treated, but at each test point one‐third were sacrificed for microscopic evaluation. When percent changes from preexposure values were compared to controls at each time point, the ozone exposure produced obstructive changes in the lung, including significant decreases (p < 0.05) in forced expiratory flows (MEF 25 40.3%, MEF 10 70.7%), lung volumes (IC 22.5%, FVC 21.8%), and DLCO (20.7%) and a significant increase in functional residual capacity (FRC 61.1%). The total lung capacity (IC + FRC) was not significantly changed by the ozone. Microscopic examination revealed characteristic lesions in the region of terminal bronchioles and central acin...