Short-term health effects of common ambient air pollutants, particularly photochemical oxidants, were investigated under controlled conditions simulating typical ambient exposures. Volunteer subjects were exposed, in an environmental control chamber providing highly purified background air, to single pollutants or mixtures under conditions of realistic secondary stress (heat and intermittent exercise). Normal men exposed to ozone (O3) showed respiratory symptoms, pulmonary function decrement, and alterations in red-cell biochemistry. These effects were dose-related, with apparent 'threshold' for detectable effect levels as low as 0.2-0.3 ppm in a 2-hr exposure for the most sensitive subjects. Addition of 0.3 ppm nitrogen dioxide (NO2) and 30 ppm carbon monoxide (CO) did not noticeably enhance adverse effects of O3, but addition of 0.37 ppm sulfur dioxide (SO2) to 0.37 ppm O3 produced slightly greater effects than did 0.37 ppm O3 alone. Subjects with asthma of clinical airway hyperactivity appeared to experience more severe effects of O3 than normals, and subjects chronically exposed to ambient O3 appeared to be less reactive than those living in non-O3-polluted areas.

"EPA-600/1-77-007." "January 1977." Photocopy.