COMPARISON OF CHAMBER AND FACE-MASK 6.6-HOUR EXPOSURES TO OZONE ON PULMONARY FUNCTION AND SYMPTOMS RESPONSES

ISSN： 1091-7691

Source： Inhalation Toxicology, Vol.14, Iss.7, 2002-07, pp. : 745-764

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Abstract

Because of increased interest in an 8-h ozone (O₃) federal air quality standard, acute pulmonary function responses to prolonged square-wave O₃ exposure between 0.08 and 0.12 ppm have been examined in several U.S. Environmental Protection Agency (EPA) chamber studies. A low-cost face-mask O₃ exposure system was developed in this laboratory and found to produce closely similar pulmonary responses to those observed in prolonged exposures by U.S. EPA investigators. The primary purpose of the present study was to investigate the pulmonary function and subjective symptoms effects of 6.6-h square-wave exposure to 0.12 ppm O₃ by these two methods using the same group of subjects. In addition, further investigation of pulmonary function and symptoms responses upon 6.6-h exposures to lower levels of O₃ (0.04–0.08 ppm) were studied with the face-mask inhalation system. Thirty young adult subjects completed five 6.6-h exposures with six 50-min periods of exercise at an intensity requiring a minute ventilation rate (V_E) of ~20 L/min/m² of body surface area, each followed by 10 min of rest, except following 3 h when the rest period was lengthened for a lunch break. The total O₃ doses for the chamber and face-mask exposures to 0.12 ppm O₃ were not significantly different from each other, since the additional O₃ dose during the 35 min lunch break in the chamber exposure was offset by a slightly lower average exercise V_E (i.e., 19.1 L/min/m²). The data convincingly demonstrated that the two methods of exposing young adults to nearly identical total inhaled O₃ doses at 0.12 ppm produce very similar pulmonary function, symptoms, and exercise ventilatory pattern responses. On the other hand, results of the 6.6-h face-mask exposures to 0.08 ppm O₃ in the present study, compared to similar U.S. EPA exposure study results, revealed several incongruities that may be due primarily to high individual subject variability in responses to a relatively low O₃ exposure. Thus, a comparison of chamber exposure responses to those elicited via face-mask exposure to 0.08 ppm O₃ in the same subject group seems warranted.