A Dose-Response Study of Healthy, Heavily Exercising Men Exposed To Ozone At Concentrations Near the Ambient Air Quality Standard

Twenty-four healthy, well-conditioned young adult male volun teers, free of asthma or clinical respiratory allergies, were exposed to purified air containing ozone (03) at 0.16, 0.14, 0.12, 0.10, 0.08, and 0.00 part per million (ppm). Exposures were separated by 2- week intervals, occurred in random order, and lasted 2 hours each. Temperature was 32 ± 1° C and relative humidity was 38 ± 3%, simulating Los Angeles area smog conditions. Subjects exercised 15 minutes of each half hour, attaining ventilation rates averaging 68 L/min (∼35 L/min per m2 body surface area). Lung function was measured pre-exposure and after 1 hr and 2 hr of exposure. Airway responsiveness to a cold-air challenge was measured immediately following the 2-hr exposure. Symptoms were recorded before, dur ing, and for one-week periods following exposures. For the group as a whole, no meaningful untoward effects were found except for a mild typical respiratory irritant response after 2 hr exposure to 0.16 ppm 03. Two individual subjects showed possible responses at 0.14 ppm, and one of them also at 0.12 ppm. In comparison to some previous investigations, this study showed generally less response to 03. The comparative lack of response may relate to the favorable clinical status of the subjects, the pattern of exercise dur ing exposure, or some other factor not yet identified.