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.