Asthma and respiratory irritants (ozone).

Asthmatics appear to be more susceptible to the effects of air pollutants than nonasthmatics. The present studies were undertaken to examine the effects of exposing asthmatics to ozone concentrations that occur in the environment. Seventeen well-documented male and female asthmatics have been exposed for 2 hr in an environmental chamber to 0.25 ppm of ozone on one occasion (ozone) and to air on another occasion (air). Effects were assessed by measurements of pulmonary function obtained prior to (0 hr), every half-hour during and at the end of all exposures (2 hr). Paired t-test analysis of lung volumes, forced expiratory volume in 1 sec (FEV1.0), and maximum expiratory flow rates at 50% of vital capacity (V50%VC) showed no significant changes (p greater than 0.05) when the following comparisons were made: 0 hr air vs 0 hr ozone, 0 hr air vs. 2 hr air, 0 hr ozone vs. 2 hr ozone, 2 hr air vs. 2 hr ozone. There was variability in severity of asthma and pulmonary function status; most subjects were taking some form of medication at the time of study. Some asthmatics showed no change or improvement with both air and ozone and others developed greater reductions in pulmonary function with ozone than with air. Approximately one-third of the asthmatics demonstrated greater changes in V50%VC with exposure to 0.25 ppm of ozone relative to air exposure. These studies indicate that acute exposures to ozone at realistic concentrations in the environment can produce adverse responses in some asthmatics.