Objectives To understand the status of atmospheric Ozone pollution in different areas of Hebei province, and to clarify the impact of Ozone on the outpatient visits of children with respiratory diseases.

Methods The number of children outpatients with respiratory diseases in Hebei Provincies Children's Hospital from 2015 to 2017 was collected and environmental and meteorological data during the same period were obtained. The distribution lag non-linear model (DLNM) was used to calculate the excess risk ER and 95%CI of Ozone for volume of respiratory system outpatients, described by the lag (1~16) day effect and the cumulative (1~16) day effect, and the maximum effect is used as an estimate of the effect of Ozone on the number of outpatients.

Results ① From 2015 to 2017, the number of days with unqualified concentration of ozone in Shijiazhuang, Tangshan, and Zhangjiakou increased year by year, and the pollution level increased year by year. ② The daily average concentration of Ozone in Shijiazhuang, Tangshan, and Zhangjiakou was statistically correlated with the number of outpatients (P < 0.01); ③ Ozone in Shijiazhuang, Tangshan, and Zhangjiakou have a lag effect on the number of children outpatients with respiratory system, with the daily average concentration of atmospheric Ozone increased by 10 μg/m³, the number of respiratory disease outpatients increases by 0.25% (0.14%, 0.36%), 0.16% (0%, 0.31%), 0.53% (0.12%, 0.94%), respectively. Zhangjiakou has the greatest impact, and the impact variation trend of Ozone on the lag effect of children's respiratory system outpatient visits in 3 cities is consistent. ④ Ozone in Shijiazhuang and Zhangjiakou have a cumulative effect on outpatients of children's respiratory diseases lasts for 16 days, reaching a maximum at (13~14) d, with an increase in atmospheric Ozone daily concentration of 10 μg/m³, the number of outpatients with respiratory disease increased by 0.82% (0.63%, 1.01%) and 2.37% (1.03%, 3.74%), respectively. Zhangjiakou had the greatest impact, and the impact variation trend of Ozone on the cumulative effect of the number of respiratory diseases outpatient visits in the three cities was consistent. ⑤ Ozone in Shijiazhuang and Zhangjiakou had lag and cumulative effects on children's respiratory diseases J00-J06 and symptom R07 outpatient visits, and the cumulative effect of Ozone on J00-J06 and R07 lasted longer, and showing a gradual upward trend.

Conclusions There are regional differences in the impact of Ozone on children's health in different regions of Hebei province. It is extremely urgent to further explore the causes of Ozone in different regions and its impact on human health.