Abstract

In evaluating 03 toxicity in humans, the effective dose, expressed as the simple product of concentration, exposure duration, and ventilation volume (VE), has been applied only to resting or intermittent exercise (IE) exposures. In the present study, we examined the validity of effective dose inpredicting pulmonary function impairment when effective dose was determined both as a simple product and as a weighted function via multiple regression. Eight trained male subjects (ages 22-46) completed 18 protocols, including exposure (via mouthpiece) to filtered air and three levels of 03 concentration(0.20, 0.30, and 0.40 ppm), while exercising continuously for durations ranging from 30 to 80 min. The 03 effective dose was significantly related to pulmonary function impairment and exercise ventilatory pattern alteration. Multiple regression analysis, however, substantiated the predominant importance of 03 concentration, with the threshold for 03 toxicity during exercise at a moderately heavy work load shown to be between 0.20 and 0.30 ppm. Although considerable individual variability in 03 toxicity response was noted, group mean responses in our continuous exercise mouthpiece exposures were similar to those previously observed with IE in chamber exposures. Verf.-Referat