Feasibility study of prolonged ozone inhalation exposure via face mask

Because of the interest attendant to establishing an 8-h ozone (O-3) federal air quality standard, acute pulmonary function responses to prolonged (6.6 to 8 h) O(3)exposure between 0.08 and 0.24 ppm have been examined in chamber studies. Given time constraints for O-3 concentration changes in room-sized chambers and the need to simulate rapid fluctuations in O-3 levels, such as occurs when one goes from indoors to outdoors during an air pollution episode, mouthpiece or face-mask exposure systems offer potential advantages over chamber exposure systems. In a recent study in this laboratory, subjects indicated that over 2 h of continuous exposure via an obligatory mouthpiece inhalation system (with noseclip) was more than they could tolerate with this type of exposure system. The purpose of this study was to compare O-3-induced responses observed following 2-h exposures via an obligatory mouthpiece inhalation system and a newly devised face-mask exposure system, and to determine whether the latter could be tolerated during 4-h exposures. Six young adults completed 5 experimental protocols (three 2-h and two 4-h) while exposed to O-3 concentrations ranging from 0.00 ppm (filtered air) to 0.24 ppm. Exercise and resting minute ventilation (V-E) were measured continuously, Pulmonary function, subjective symptoms (SS) of breathing discomfort, and exercise ventilatory pattern responses were obtained. Exposure to 0.24 ppm O-3 with intermittent exercise (IE) for 2 h via a newly devised inhalation system, consisting of a nylon plastic non-rebreathing respiratory valve and a silicone rubber face mask with Teflon overlay on the inner surface, yielded pulmonary function, SS and exercise ventilatory pattern responses nearly identical to those obtained in the same O-3 exposure effected via a Teflon-coated Hans-Rudolph respiratory valve obligatory mouthpiece inhalation system. It was concluded that the newly devised face-mask inhalation system was well tolerated by all subjects during the 4-h exposure protocols, with each subject indicating that longer 6.6-h exposures with this system would be tolerable.