Different effects of long-term exposures to SO₂ and NO₂ air pollutants on asthma severity in young adults

Numerous studies demonstrated that exposure to ambient air pollutants contributes to severity and frequency of asthma exacerbations. However, whether common air pollutants, such as nitrogen dioxide (NO₂) and sulfur dioxide (SO₂), exert differential effects on asthma occurrence and severity is unclear. The aim of this investigation was to determine whether exposure to NO₂ and/or SO₂ may initiate different long-term effects on prevalence and severity of asthma in young adults. Medical records of 137,040 males, 17 years old, who underwent standard premilitary service health examinations during 1999–2008 were examined. Air-pollution data for NO₂ and SO₂ were linked to the place of residence of each subject. The influence of specific air pollutants on asthma prevalence and severity was evaluated using bivariate logistic regression, controlling for individuals’ sociodemographic attributes. For both ambient air pollutants, there was a significant dose-response effect on severity of asthma at ambient concentrations below the current National Ambient Air Quality Standards. However, in residential areas with high levels of SO₂ (13.3–592.7µg/m³) and high levels of NO₂ (27.2–43.2µg/m³) the risk of asthma occurrence was significantly higher than that in residential areas with high levels of NO₂ (27.2–43.2 µg/m³) and intermediate levels (6.7–13.3 µg/m³) of SO₂ pollution. The effects of exposure to SO₂ and NO₂ air pollutants on the respiratory airways system appear to differ, with possible implications regarding medical management, even in cases of exposure to mixtures of these pollutants.