Relationship between Daily Pediatric Outpatient Visits for Respiratory Diseases and Air Pollution in Lanzhou

Objective To study the relationship between daily pediatric outpatient visits for respiratory diseases and air pollution in Lanzhou.

Methods The data of daily pediatric outpatient visits for respiratory diseases were collected from two general hospitals, two health service centers and two maternal and child care service centers in two urban areas of Lanzhou, and the data of air pollution in Lanzhou were collected also. Wilcoxon rank sum test between two independent samples was used to analyze the concentration of pollutants in Chengguan district and Xigu district, as well as to analyze the concentration of pollutants between overall Lanzhou and these two districts. A time-series analysis using a generalized addictive model (GAM) was applied to assess the association between pediatric outpatient visits for respiratory diseases and air pollution of Lanzhou after adjustment for long-term trend, the day of a week and meteorological factors.

Results In Chengguan and Xigu areas of Lanzhou, the average concentration of SO₂ was 26.52 and 28.78 μg/m³ respectively; the average concentration of NO₂ was 48.56 and 51.84 μg/m³ respectively; the average concentration of PM₁₀ was 115.82 and 129.31 μg/m³ respectively; and the average concentration of PM_2.5 was 51.34 and 62.86 μg/m³ respectively. Using Wilcoxon rank sum test to analyse the difference between two independent samples, the average concentration of SO₂, PM₁₀ and PM_2.5 in Xigu district was higher than those in Chengguan district(P < 0.01); the concentration of pollutants in these two districts was higher than that of overall Lanzhou (P < 0.01). Using GAM time-series analysis, the concentration of SO₂, NO₂, PM₁₀ and PM_2.5 had a positive impact on pediatric outpatient visits for respiratory diseases. Using a multiple pollutant model analysis, there was no difference between the RR value of single pollutant models and multiple pollutant models.

Conclusion The concentration of ambient air pollutants could positively associated with an increase of daily pediatric outpatient visits for respiratory diseases in Lanzhou, and there was a hysteresis effect in the association.