The effects of ozone on the respiratory epithelium of mice II. Ultrastructural alterations.

Ultrastructural alterations in the tracheal and bronchial epithelium of mice exposed to 0.8 ppm ozone for varying periods of time were examined with scanning electron microscopy. The lesions were apparent in the ciliated cells. Examination of tissue from control mice showed that the ciliated cells were arranged in groups and the cilia were uniform in length. After six days of exposure to ozone, shortened cilia were occasionally observed by day 10, more pronounced changes were observed. Cilia were either absent or became short and blunt. The lesions observed after 20 days in ozone were similar to those seen on day 10. After ozone-exposed mice had been returned to ambient air for 10 days, ciliary regeneration occurred and, the major airways had a surface appearance approaching the normal state.