OZONE RESPONSE RELATIONSHIPS IN HEALTHY NONSMOKERS

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Abstract
Significant concentration responses were observed in FVC [forced vital capacity], FEV1 [forced expiratory volume in 1 s], FEF25-75 [forced expiratory flow rate between 25 and 75% FVC], SGaw [specific airway conduction], IC [inspiratory capacity] and TLC [total lung capacity] in 20 healthy, nonsmoking volunteers exposed randomly to 0.00, 0.10, 0.15, 0.20 and 0.25 ppm O3. Significant response changes for FVC1, FEV1 and FEF25-75 were shown with time over the 2-h exposure. Intermittent, heavy exercise (.ovrhdot.VE [expiratory ventilation] 68 l/min) lasting 14 min was employed every 30 min during exposure. Inspection of the concentration and time response curves suggests that the threshold for the group response is < 0.15 ppm O3. Six subjects experienced decreases > 5% in FEV1 or > 15% in SGaw at 0.15 ppm. This concentration is only slightly higher than the 1-h O3 National Ambient Air Quality Standard. A dose-related response was also seen for cough, nose and throat irritation and chest discomfort. The work load, length of exposure and individual sensitivity must be considered for establishing a safe O3 exposure level.