Exposure to ozone alters regional function and particle dosimetry in the human lung

Effects of experimental exposure to O[sub 3] (0.33 ppm) or filtered air on regional lung function were assessed in nine healthy male subjects. Immediately after 2-h chamber exposures, regional ventilation and particle dosimetry were measured by gamma camera imaging. The vertical distributions of a radiolabeled gas ([sup 133]Xe) and aerosol (3.5-[mu]m-diam insoluble [sup 99m]T[sub c]-tagged Fe[sub 2]O[sub 3] particles) were quantified for upper, middle, and lower lung regions; distribution data were corrected for regional differences in lung volume and tissue attenuation. Indexes of mechanical function, inspiratory capacity, and mid-maximal expiratory flow rates were significantly reduced after O[sub 3], but functional residual capacity remained unchanged. Exposure to O[sub 3] significantly enhanced the fraction of respired aerosol retained by the lung and altered the distribution pattern of deposited aerosol by increasing particle deposition to the middle lung region (P < 0.05). Aerosol penetration indexes, i.e., ratio of particle deposition in central lung regions to that in peripheral lung regions, and particle retention 24 h postinhalation (an index of aerosol deposition within alveoli and slowly clearing bronchioles) indicated that particle filtration efficiency had increased for tracheobronchial and parenchymal lung regions. For seven of the nine subjects, regional ventilation after O[sub 3] was reducedmore » by 14% to the lung base and enhanced by 8 and 6% to the upper and middle lung regions, respectively; these changes were significant (P < 0.02) compared with ventilation after filtered air. These data suggest that there is a vertical gradient in deposition for 3.5-[mu]m aerosol (particle burdens/unit lung volume are lowest for the lung apex and highest for the middle lung regions) and that O[sub 3] alters regional ventilation and particle filtration efficiency of the respiratory tract. 37 refs., 7 figs., 4 tabs.« less