PULMONARY-FUNCTION RESPONSE TO EQUIVALENT DOSES OF OZONE CONSEQUENT TO INTERMITTENT AND CONTINUOUS EXERCISE

The effects on pulmonary function of inhaling the same effective dose of ozone, as well as subjective responses during continuous exercise a nd intermittent exercise, were studied in 12 aerobically trained men. Each subject completed 1 h of continuous exercise at work rates that e licited a mean minute ventilation of 60 l/min, and two additional 2-6 intermittent exercise exposures eliciting a mean exercise minute venti lation of 45-47 l/min (i.e., total minute ventilation for each protoco l was approximately 3600 l). Subjects were exposed in randomized seque nce to 0.30 ppm ozone on three occasions and to filtered air on three occasions. Forced expiratory volume in 1 s decrements of -17.6%, -17.0 %, and -17.9%, respectively, for the 1-h continuous exercise exposure and the two 2-h intermittent exercise exposures to 0.30 ppm ozone were significantly different. Exposure to ozone caused significant differe nces between postexposure subjective symptom responses; that is, respo nses associated with continuous exercise were greater than those for e ither intermittent exercise protocol. However, the overall symptom sev erity responses during the last minute of exercise for the two intermi ttent exercise protocols (at 90 and 105 min, respectively) were not si gnificantly different from the continuous exercise postexposure value. The findings indicate that when the ozone effective dose is equivalen t at a given ozone concentration, there is no difference between pulmo nary function responses to continuous exercise or intermittent exercis e exposures of 2-h duration (or less), although subjective symptoms ar e reduced somewhat during the last rest period of intermittent exercis e.