摘要Background The high risks for childhood respiratory diseases are associated with exposure to ambient air pollution.How-ever,there are few studies that have explored the association between air pollution exposure and respiratory diseases among young children(particularly aged 0-2 years)based on the entire population in a megalopolis.Methods Daily hospital admission records were obtained from 54 municipal hospitals in Wuhan city,China.We included all children(aged 0-2 years)hospitalized with respiratory diseases between January 2017 and December 2018.Individual air pollution exposure assessment was used in Land Use Regression model and inverse distance weighted.Case-crossover design and conditional logistic regression models were adopted to estimate the hospitalization risk associated with air pollutants.Results We identified 62,425 hospitalizations due to respiratory diseases,of which 36,295 were pneumonia.Particulate matter with an aerodynamic diameter less than 2.5 μm(PM2.5)and nitrogen dioxide(NO2)were significantly associated with respiratory diseases and pneumonia.ORs of pneumonia were 1.0179(95％CI 1.0097-1.0260)for PM2 5 and 1.0131(95％CI 1.0042-1.0220)for NO2 at lag 0-7 days.Subgroup analysis suggested that NO2,Ozone(O3)and sulfur dioxide(SO2)only showed effects on pneumonia hospitalizations on male patients,but PM2.5 had effects on patients of both genders.Except O3,all pollutants were strongly associated with pneumonia in cold season.In addition,children who aged elder months and who were in central urban areas had a higher hospitalization risk.Conclusions Air pollution is associated with higher hospitalization risk for respiratory diseases,especially pneumonia,among young children,and the risk is related to gender,month age,season and residential location.