Chronic effects of ambient air pollution on respiratory morbidities among Chinese children: a cross-sectional study in Hong Kong

BACKGROUND: The chronic health effects from exposure to ambient air pollution are still unclear. This study primarily aims to examine the relationship between long-term exposure to ambient air pollution and respiratory morbidities in Chinese children. METHODS: A cross-sectional study was conducted among 2,203 school children aged 8–10 in three districts with different air pollution levels in Hong Kong. Annual means for ambient PM(10), SO(2), NO(2) and O(3) in each district were used to estimate participants’ individual exposure. Two questionnaires were used to collect children’s respiratory morbidities and other potential risk factors. Multivariable logistic regression was fitted to estimate the risks of air pollution for respiratory morbidities. RESULTS: Compared to those in the low-pollution district (LPD), girls in the high-pollution district (HPD) were at significantly higher risk for cough at night (OR(adj.) = 1.81, 95% CI: 1.71-2.78) and phlegm without colds (OR(adj.) = 3.84, 95% CI: 1.74-8.47). In addition, marginal significance was reached for elevated risks for asthma, wheezing symptoms, and phlegm without colds among boys in HPD (adjusted ORs: 1.71-2.82), as well as chronic cough among girls in HPD (OR(adj.) = 2.03, 95% CI: 0.88-4.70). CONCLUSIONS: Results have confirmed certain adverse effects on children’s respiratory health from long-term exposure to ambient air pollution. PM(10) may be the most relevant pollutant with adverse effects on wheezing and phlegm in boys. Both PM(10) and NO(2) may be contributing to cough and phlegm in girls.