Adaptations to Ozone in Reference to Mucociliary Clearance

Adaptation to ozone in respiratory tract mucociliary clearance was investigated in this study. Eighty rats inhaled insoluble radioactively labeled particles in order to permit monitoring of clearance. The respiratory tract and the feces were counted for radioactivity at fixed intervals to determine clearance rates. A brief challenge to 1.2 ppm of ozone following particle deposition caused a substantial delay in rapid (mucociliary) clearance. This delay (or "ozone effect") however, was eliminated by brief pre-exposure to 0.8 ppm of ozone 3 days prior to deposition of particles. When a 13-day period intervened between the ozone pre-exposure and challenge, a substantial delay (or "ozone effect") was again seen. Thus, the pre-exposure to ozone appeared to afford essentially complete protection at 3 days, and no protection by 13 days.