Air pollution and children's respiratory symptoms in six cities of Northern China

Objective: The associations between air pollution and children's respiratory health in the high pollution range have not yet been clearly characterized. We evaluated the effects of outdoor air pollution on respiratory morbidity in children selected from multiple sites in a heavy industrial province of northeastern China.

Methods: The study included 11,860 children aged 3-12 years, selected from 18 districts of 6 cities in Liaoning province, the participation rate is 89.9%. Informed consent and written responses to surveys about children's historic and current health status, personal and household characteristics, and other information were obtained from parents. A two-stage regression approach was applied in data analyses.

Results: There were wide gradients for TSP (188-689 μg/m(3)), SO(2) (14-140 μg/m(3) and NO(2) (29-94 μg/m(3)) across the 18 districts of 6 cities. The three air pollutants significantly increased the prevalence of persistent cough (21-28%), persistent phlegm (21-30%) and current asthma (39-56%) for each interquartile range increment (172 μg/m(3) for TSP, 69 μg/m(3) for SO(2), 30 μg/m(3) for NO(2)), showing larger between-city effects than within-city. Rates of respiratory symptoms were significantly higher for children with younger age, atopy, respiratory disease in early age, family history of asthma or chronic bronchitis, and tobacco smoke exposure.

Conclusion: The high levels of outdoor air pollution in north China are positively associated with children's respiratory symptoms, the associations with TSP appear to be stronger than SO(2) and NO(2).