Association between ozone exposure and allergic diseases in Hohhot: an analysis based on generalized additive model

Objective To quantitatively assess the relationship between ozone exposure and number of outpatient visits for allergic diseases (such as allergic rhinitis, allergic asthma, and allergic conjunctivitis) in Hohhot city from 2023 to 2024, and to explore the potential impact of O₃-8 h exposure on public health.

Methods The number of outpatient visits for allergic diseases, atmospheric pollutant concentrations, and meteorological data from January 1, 2023 to December 31, 2024 in Hohhot city were collected. The generalized additive model (GAM) was employed to quantitatively analyze the exposure-response relationship between O₃-8 h exposure levels and number of outpatient visits.

Results The mean O₃-8 h concentration in Hohhot city from 2023 to 2024 was 94.1 μg/m³, with a non-compliance rate of 7.0%. Single-day lag analysis revealed that for every 10 μg/m³ increase in O₃-8 h, the ERs for allergic conjunctivitis and allergic asthma increased by 3.62% (95%CI: 0.39%–6.95%) and 2.16% (95%CI: 0.68%–3.67%), respectively, two days after exposure (lag 2). The ER for allergic rhinitis at lag 1 was 1.94% (95%CI: 0.23%–3.68%). Cumulative lag effect analysis revealed that the effect values for allergic asthma and allergic rhinitis both peaked at lag 01. For every 10 μg/m³ increase in O₃-8h, the ERs for allergic asthma and allergic rhinitis were 1.22% (95%CI: 0.36%–2.08%) and 1.10% (95%CI: 0.10%–2.11%), respectively, with cumulative lag effects diminishing as cumulative lag time increased.

Conclusions Elevated O₃-8 h exposure levels in Hohhot city may increase outpatient visits for allergic diseases with a lag effect. A tiered response mechanism based on high O₃ concentration alerts should be established. Coordinated emission reduction measures should be implemented before pollution events and during high-incidence periods to reduce peak exposure, accompanied by differentiated health protection guidelines.