Combined effects of ozone and nitrogen dioxide on respiratory function in man.

Ten young adult males were exposed to either filtered air or 0.50 ppm ozone plus 0.50 ppm NO2 in filtered air under four environmental conditions: 25 degree C, 45 % rh; 30 degrees C, 85% rh; 35 degrees C, 40% rh; and 40 degrees C, 50% rh. There were eight 2-hour exposures per subject. After 1 hour of sitting exposure the subjects exercised for 30 minutes (35-40% predicted maximum capacity) which increased ventilatory exchange to approximately 40 L/min (BTPS). Pulmonary function tests were performed before, during, and after exposure. Metabolism and ventilation were determined during the last 15 minutes of exercise. A symptom questionnaire was completed at the termination of each exposure following reexamination by a physician. There was a decrease in vital capacity, inspiratory capacity, and several flow-related measures of lung function during exposure. The response to exposure to the combined pollutants (O3 and NO2) was similar to that observed in ozone exposures alone. No synergism was observed.