Gender Differences and Effect of Air Pollution on Asthma in Children with and without Allergic Predisposition: Northeast Chinese Children Health Study

BACKGROUND: Males and females exhibit different health responses to air pollution, but little is known about how exposure to air pollution affects juvenile respiratory health after analysis stratified by allergic predisposition. The aim of the present study was to assess the relationship between air pollutants and asthmatic symptoms in Chinese children selected from multiple sites in a heavily industrialized province of China, and investigate whether allergic predisposition modifies this relationship. METHODOLOGY/PRINCIPAL FINDINGS: 30139 Chinese children aged 3-to-12 years were selected from 25 districts of seven cities in northeast China in 2009. Information on respiratory health was obtained using a standard questionnaire from the American Thoracic Society. Routine air-pollution monitoring data was used for particles with an aerodynamic diameter ≤10 µm (PM(10)), sulfur dioxide (SO(2)), nitrogen dioxides (NO(2)), ozone (O(3)) and carbon monoxide (CO). A two-stage regression approach was applied in data analyses. The effect estimates were presented as odds ratios (ORs) per interquartile changes for PM(10), SO(2), NO(2), O(3), and CO. The results showed that children with allergic predisposition were more susceptible to air pollutants than children without allergic predisposition. Amongst children without an allergic predisposition, air pollution effects on asthma were stronger in males compared to females; Current asthma prevalence was related to PM(10) (ORs = 1.36 per 31 µg/m(3); 95% CI, 1.08–1.72), SO(2) (ORs = 1.38 per 21 µg/m(3); 95%CI, 1.12–1.69) only among males. However, among children with allergic predisposition, more positively associations between air pollutants and respiratory symptoms and diseases were detected in females; An increased prevalence of doctor-diagnosed asthma was significantly associated with SO(2) (ORs = 1.48 per 21 µg/m(3); 95%CI, 1.21–1.80), NO(2) (ORs = 1.26 per 10 µg/m(3); 95%CI, 1.01–1.56), and current asthma with O(3) (ORs = 1.55 per 23 µg/m(3); 95%CI, 1.18–2.04) only among females. CONCLUSION/SIGNIFICANCE: Ambient air pollutions were more evident in males without an allergic predisposition and more associations were detected in females with allergic predisposition.