Comparison of chamber and face mask 6.6-hour exposure to 0.08 ppm ozone via square-wave and triangular profiles on pulmonary responses

Recently, a stainless-steel air pollution chamber was acquired in this laboratory, and data were obtained in a study that convincingly demonstrated that chamber and face-mask inhalation methods of exposing young adult subjects for 6.6 h to nearly identical total inhaled O-3 doses at 0.12 ppm produced very similar pulmonary function, symptoms, and exercise ventilatory pattern responses. However, the results of a 6.6-h face-mask exposure to 0.08 ppm O-3, compared to some previous chamber exposure study results, revealed several small incongruities that may be due primarily to high individual subject "noise" in responses to a relatively low O-3 exposure. To resolve these differences, it was the primary purpose of this study to compare chamber exposure responses to those elicited via face-mask exposure to 0.08 ppm O-3 for 6.6 h with subjects serving as their own controls. Two types of O-3 exposure patterns were used: (1) the usual square-wave profile, and (2) an acute triangular profile, in which O-3 concentration was increased each hour from 0.03 ppm to 0.15 ppm during h 4 and then decreased each hour to 0.05 ppm (mean = 0.08 ppm). Thirty young adults (15 of each gender) served as subjects. The two exposure methods (i.e., face mask and chamber) yielded near identical total inhaled O-3 doses in both the square-wave and triangular exposure profiles, and produced very similar postexposure pulmonary function, symptoms, and exercise ventilatory pattern responses. However, pulmonary function and symptoms responses became statistically significant from preexposure at the end of h 4 (when [O-3] = 0.15 ppm) in the triangular protocols, but not until h 6 in the square-wave protocols. These results support previous evidence that O-3 concentration has a greater singular effect in the total inhaled O-3 dose than do V-E and exposure duration.