Effect of short-term exposure to low levels of SO2 and NOx on pulmonary function and methacholine and allergen bronchial sensitivities in asthmatic children.

Air pollution is an inevitable consequence of industrialization. Continuous exposure to air pollution may cause or trigger respiratory allergic diseases. This study was designed to evaluate whether short-term, 5-min exposures to low levels of sulfur dioxide (SO2) and nitrogen oxides (NOx) influence pulmonary function and increase bronchial sensitivity to methacholine and specific allergens. Five male and 1 female mite-sensitive asthmatic children (mean age 12 y) were studied during symptom-free periods. Pulmonary function tests were conducted after breathing 5, 15, 35, 65, and 105 breaths of compressed polluted air, which was collected from the Lin-Sun S. Road tunnel in Taipei city. Concentrations of SO2 and NOx were 70-120 ppb and 450-500 ppb, respectively, and were 6-fold and 20-fold, respectively, higher than those of ambient air. Methacholine and mite allergen bronchial challenges were completed after 105 breaths of polluted air were inhaled. No difference in pulmonary function was noted after polluted air and ambient air were inhaled, and the methacholine and allergen sensitivities of airways were not increased after polluted air was inhaled. The authors concluded that short-term exposures to low concentrations of SO2 and NOx did not affect the lung function and did not increase bronchial sensitivity to methacholine and allergen.