HEALTH EFFECTS OF OZONE EXPOSURE IN ASTHMATICS

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Abstract
To investigate whether ambient air quality standards for O3 adequately protect high-risk populations, pulmonary and biochemical respones of 22 asthmatic volunteers to 2 h controlled exposures to O3 at concentrations approximating 0.2 ppm were assessed, with secondary stresses of heat and intermittent exercise. All subjects had physician-diagnosed asthma; clinically, they covered a range from minimal wheezing to persistent marked abnormality in forced expiratory performance. Control experiments included repeated sham exposures (to purified air with no O3 added) as well as brief exposures to the odor of O3 followed by purified air. No meaningful changes in forced expiratory measures, lung volumes or single-breath N2 indices were found after O3 exposure relative to control. Symptoms, scored semiquantitatively, increased slightly but not significantly with exposure to O3. Small but significant (P < 0.05) group mean blood biochemical changes occurred with exposure to O3; these included increased glucose-6-phosphate dehydrogenase and lactate dehydrogenase activities, increased erythrocyte fragility and decreased concentration of reduced glutathione. Hb concentration and acetylcholinesterase activity decreased with O3 and decreased to a lesser extent in control studies. Concentrations of O3 readily attainable in smog episodes thus appear to be capable of affecting blood biochemistry in at least some asthmatic persons, in the absence of obvious adverse pulmonary responses. Whether the biochemical effects represent harm to health or a normal response to stress remains to be determined.

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