Pulmonary function, airway responsiveness, and respiratory symptoms in asthmatics following exercise in NO2. Toxicol Ind Health

Two experiments were conducted to determine respiratory responses of persons with asthma performing intermittent moderate exercise while exposed to low concentrations of NO,. In the first, preliminary experiment, 13 male subjects, aged 19-35, with mild asthma were ex-posed on separate days in a chamber (natural breathing, 20”C, 40% RH) to 0.30 ppm NO2 and to a control or “clean air ” exposure (0.0 ppm NO,). Exposure included three 10-min periods of moderate treadmill exercise (VE = 44.5 literlmin), each followed by symptom measurement and pulmonary function testing. The average decrease in FEV, following the initial 10 min exercise in 0.30 ppm was I I % which was signijicantly greater (p < 0.05) than that observed in clean air (7%). Differences in FVC and SRaw were not signiJicantly differ-ent at this time. Slight cough and dry mouth and throat were apparent only afer the first exercise in NO2. After the second and third exer-cises, decreases in FEV, and FVC and increases in SRaw were signif-icantly greater in 0.30 than in 0.0ppm NO2. Individual subject re-sponses were variable. These results suggested that some asthmatics who perform moderate exercise while exposed to 0.30 ppm NO2 may experience bronchoconstriction and reduction in spirometric perfor-mance