ObjectivesTo investigate the prevalence of respiratory diseases and lung function of school-age children in Chongqing and to compare them with that of children in 25 years ago and to explore the possible causes of this change.MethodsAccording to the air quality data of Chongqing from 1998 to 2016, the annual variation of air quality days and pollutant concentrations were plotted. 2 126 school-age children in two districts of Chongqing were selected by random cluster sampling for questionnaires. 771 children were randomly selected from the children who completed the questionnaire for pulmonary function tests. The results were compared with that of 25 years ago.ResultsFrom 1998 to 2016, the number of days with good air quality in Chongqing increased annually, and the concentration of SO2 decreased significantly. The main air pollution composition changed from SO2 to PM10 and PM2.5. The prevalence of bronchitis (P<0.05) was higher than that of 25 years ago. After adjusting for confounding factors by multivariate logistic regression, the OR value of bronchitis in children was 1.667 (P<0.05) compared with 25 years ago. After adjusting for age, sex, height and weight by multiple linear regression, the results showed that the subjects' lung function indexes (FVC, FEV1, PEF and FEV3) were lower than that of 25 years ago. In this survey, there were differences in lung function indexes between children with different frequency of eating fruits and dairy products (P<0.05), and those with high frequency consumption were higher than low frequency. In terms of exercise time, subjects exercising ≥1 hour/day had greater FVC and FEV3 values than those exercising <1 hour/day (P<0.05).ConclusionsThe overall air quality in Chongqing has improved from 1998 to 2016; The respiratory health of children has decreased when compared with that of 25 years ago. Changes in the composition of air pollutants may endanger children's respiratory health, and fruit and dairy foods and exercise may be protective factors for children's respiratory health.