Short term effects of air pollutants on hospital admissions for respiratory diseases among children: A multi-city time-series study in China

Evidence concerning short-term acute association between air pollutants and hospital admissions for respiratory diseases among children in a multi-city setting was quite limited. We conducted a time-series analysis to evaluate the association of six common air pollutants with hospital admissions for respiratory diseases among children aged 0–14 years in 4 cities (Guangzhou, Shanghai, Wuhan and Xining), China during 2013–2018. We used generalized additive models incorporating penalized smoothing splines and random-effect meta-analysis to calculate city-specific and pooled estimates, respectively. The exposure-response relationship curves were fitted using the cubic spline regression. Subgroup analyses by gender, age, season and disease subtype were also performed. A total of 183,036 respiratory diseases hospitalizations were recorded during the study period, and 94.1% of the cases were acute respiratory infections. Overall, we observed that increased levels of air pollutants except O3, were significantly associated with increased hospital admissions for respiratory disease. Each 10 μg/m3 increase in PM2.5, SO2 and NO2 at lag 07, PM10 at lag 03 and per 1 mg/m3 increase in CO at lag 01 corresponded to increments of 1.19%, 3.58%, 2.23%, 0.51% and 6.10% in total hospitalizations, respectively. Generally, exposure-response relationships of PM2.5 and SO2 in Guangzhou, SO2, NO2 and CO in Wuhan, as well as SO2 and NO2 in Xining with respiratory disease hospitalizations were also found. Moreover, the adverse effects of these pollutants apart from PM2.5 in certain cities remained significant even at exposure levels below the current Chinese Ambient Air Quality Standards (CAAQS) Grade II. Children aged 4–14 years appeared to be more vulnerable to the adverse effects of PM2.5, SO2 and NO2. Furthermore, with the exception of O3, the associations were stronger in cold season than in warm season. Short-term exposure to PM2.5, SO2, NO2 and CO were associated, in dose-responsive manners, with increased risks of hospitalizations for childhood respiratory diseases, and adverse effects of air pollutants except PM2.5 held even at exposure levels below the current CAAQS Grade II in certain cities.