[Short-term effects and seasonal variation of ozone on daily hospital outpatient visits for childhood asthma in Lanzhou].

Objective: To analyze the effects of ozone (O ₃ ) concentrations measured with different approaches across different seasons on the total number of childhood asthma-related clinical visits, as well as the differentiation of such effects across different groups of patients.
Methods: The outpatient data of three grade A tertiary hospitals in Lanzhou City spanning from 1 January 2014 to 31 December 2017, as well as air pollution and meteorological data during the same period were collected. Considering the nonlinear relationship between O ₃ concentrations and the total number of childhood asthma-related clinical visits and meteorological factors, a generalized additive temporal sequence model was employed to analyze the short-term association between changes in O ₃ concentrations and the total number of childhood asthma-related clinical visits. Taking into account of the variations in O ₃ concentrations within 1 day, this study adopted different measurement approaches to address the three types of O ₃ exposures, namely, the maximum 1 h daily concentration (O ₃ max1h), the maximum 8 h daily concentration (O ₃ 8h) and the mean 24 h daily concentration (O ₃ 24h) as the short term exposure indicators to O ₃ , followed by a model-based analysis.
Results: The increase in short-term exposure levels to O ₃ in summer had a significant effect on the increase in the total number of childhood asthma-related clinical visits. With lag0 for the current day, every 10 μg/m ³ increase in atmospheric concentration of O ₃ max1h was associated with an increase in the total number of childhood asthma-related clinical visits by 3.351% (95% CI : 1.231%-5.516%); for every 10 μg/m ³ increase in O ₃ 8h concentration, the total number of childhood asthma-related clinical visits increased by 3.320% (95% CI : 0.197%-3.829%); for every 10 μg/m ³ increase in O ₃ 24h concentration, the total number of childhood asthma-related clinical visits in summer increased by 6.600% (95% CI : 0.914%-12.607%); moreover, an increase in exposure to O ₃ max1h also led to a significant rise in the total number of childhood asthma-related clinical visits among the males.
Conclusion: The increase in short-term exposure levels to O ₃ in summer in Lanzhou City has a significant effect on the increase in the total number of childhood asthma-related clinical visits; O ₃ max1h is more closely correlated with the increase in the total number of childhood asthma-related clinical visits.