Short-term association among meteorological variation, outdoor air pollution and acute bronchiolitis in children in a subtropical setting

Objectives To examine the association among acute bronchiolitis-related hospitalisation in children, meteorological variation and outdoor air pollution. Methods We obtained the daily counts of acute bronchiolitis-related admission of children≤2 years old from all public hospitals, meteorological data and outdoor air pollutants’ concentrations between 1 January 2008 and 31 December 2017 in Hong Kong. We used quasi-Poisson generalised additive models together with distributed lag non-linear models to estimate the associations of interest adjusted for confounders. Results A total of 29 688 admissions were included in the analysis. Increased adjusted relative risk (ARR) of acute bronchiolitis-related hospitalisation was associated with high temperature (ambient temperature and apparent temperature) and was marginally associated with high vapour pressure, a proxy for absolute humidity. High concentration of NO 2 was associated with elevated risk of acute bronchiolitis admission; the risk of bronchiolitis hospitalisation increased statistically significantly with cumulative NO 2 exposure over the range 66.2–119.6 µg/m 3 . For PM 10 , the significant effect observed at high concentrations appears to be immediate but not long lasting. For SO 2 , ARR increased as the concentration approached the 75th percentile and then decreased though the association was insignificant. Conclusions Acute bronchiolitis-related hospitalisation among children was associated with temperature and exposure to NO 2 and PM 10 at different lag times, suggesting a need to adopt sustainable clean air policies, especially to target pollutants produced by motor vehicles, to protect young children’s health.