Dr. Drechsler-Parks and colleagues at the Institute of Environmental Stress sought to examine the effects of nitrogen dioxide, ozone, and peroxyacetyl nitrate on metabolic and pulmonary function. Because it is possible that two or more pollutants could interact in ambient air and cause effects that could not be predicted from the effects observed with the individual pollutants, the investigators examined varying levels of different pollutants in 32 non-smoking men and women (8 men and 8 women 18-26 years of age and 8 men and 8 women 51-76 years of age). Subjects alternated between rest and periods of exercise. Functional residual capacity (FRC) and forced vital capacity (FVC) were determined before and after exposure, in addition to 5 minutes after each exercise period for FVC. Heart rate and ventilatory minute volume were also monitored.