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

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Abstract
O3 and NO2 are common components of photochemical smog. Ten young adult males were exposed to filtered air or 0.50 ppm O3 plus 0.50 ppm NO2 in filtered air under 4 environmental conditions: 25.degree. C, 45% rh [relative humidity]; 30.degree. C, 85% rh; 35.degree. C, 40% rh; and 40.degree. C, 50% rh. There were eight 2-h exposures/subject. After 1 h of sitting exposure the subjects exercised for 30 min (35-40% predicted maximum capacity) which increased ventilatory exchange to .apprx. 40 l/min (BTPS). Pulmonary function tests were performed before, during and after exposure. Metabolism and ventilation were determined during the last 15 min 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 O3 exposures alone. No synergism was observed.