Effects of Exposure to 0.06 ppm Ozone on FEV 1 in Humans: A Secondary Analysis of Existing Data

Abstract

Ozone is a potent photochemical oxidant that produces transient, reversible decrements in the lung function of acutely exposed individuals. A recent study provided previously unavailable clinical data for 30 healthy young adults exposed to O3 at 0.06 ppm. That study showed significant effects of 0.08 ppm on lung function, confirming the findings of others. However, exposure to 0.06 ppm O3 was not reported to significantly affect lung function. We conducted this analysis to reevaluate the existing lung function data of the volunteers previously exposed to 0.06 ppm O3. We obtained pre- and postexposure data on forced expiratory volume in 1 sec (FEV1) for all subjects who were previously exposed for 6.6 hr to filtered air or to 0.06 ppm or 0.08 ppm O3. We used standard statistical methods appropriate for paired comparisons to reanalyze FEV1 responses after exposure to 0.06 ppm O3 relative to filtered air. Controlling for filtered air responses, 24 of the 30 subjects experienced an O3-induced decrement in FEV1. On average, 0.06 ppm O3 exposure caused a 2.85% reduction in FEV1 (p < 0.002), which was consistent with the predicted FEV1 response from existing models. Although the average response was small, two subjects had > 10% FEV1 decrements. Exposure to 0.06 ppm O3 causes a biologically small but highly statistically significant decrease in mean FEV1 responses of young healthy adults.