Association of air pollution with outpatient visits for respiratory diseases of children in an ex-heavily polluted Northwestern city, China

BACKGROUND: A great number of studies have confirmed that children are a particularly vulnerable population to air pollution. METHODS: In the present study, 332,337 outpatient visits of 15 hospitals for respiratory diseases among children (0–13 years), as well as the simultaneous meteorological and air pollution data, were obtained from 2014 to 2016 in Lanzhou, China. The generalized additive model was used to examine the effects of air pollutants on children’s respiratory outpatient visits, including the stratified analysis of age, gender and season. RESULTS: We found that PM(2.5), NO(2) and SO(2) were significantly associated with the increased total respiratory outpatient visits. The increments of total respiratory outpatient visits were the highest in lag 05 for NO(2) and SO(2), a 10 μg/m(3) increase in NO(2) and SO(2) was associated with a 2.50% (95% CI: 1.54, 3.48%) and 3.50% (95% CI: 1.51, 5.53%) increase in total respiratory outpatient visits, respectively. Those associations remained stable in two-pollutant models. Through stratification analysis, all air pollutants other than PM(10) were significantly positive associated with the outpatients of bronchitis and upper respiratory tract infection. Besides, both NO(2) and SO(2) were positively related to the pneumonia outpatient visits. PM(2.5) and SO(2) were significantly related to the outpatient visits of other respiratory diseases, while only NO(2) was positively associated with the asthma outpatients. We found these associations were stronger in girls than in boys, particularly in younger (0–3 years) children. Interestingly, season stratification analysis indicated that these associations were stronger in the cold season than in the transition or the hot season for PM(10), PM(2.5) and SO(2). CONCLUSIONS: Our results indicate that the air pollution exposure may account for the increased risk of outpatient visits for respiratory diseases among children in Lanzhou, particularly for younger children and in the cold season.