Supplementary Material for: Impact of Airborne Pollen on Allergic Rhinitis and Asthma in an Arid Chinese City: A Time-Series Study from Lanzhou

Airborne pollen has emerged as a critical environmental driver of allergic respiratory diseases, particularly under the accelerating influence of global climate change. This study investigates the short-term effects of daily airborne pollen concentrations on the incidence of allergic rhinitis (AR) and bronchial asthma (BA) in Lanzhou, a representative arid city in northwestern China. Utilizing outpatient visit data from a Class A tertiary hospital between April and October 2024, along with daily records of pollen concentrations, meteorological indicators, and air pollutant levels, we employed a Distributed Lag Non-linear Model (DLNM) to examine the non-linear and lagged relationships between pollen exposure and disease risk. Our findings reveal a significant association between elevated pollen levels and increased risks of both AR and BA, with the strongest effects observed within 1–3 days after exposure. Stratified analyses show that females and individuals aged 0–19 years are particularly susceptible. Moreover, health impacts were more pronounced during the late summer to autumn pollen season, likely due to the presence of highly allergenic species such as Artemisia and Chenopodiaceae. Thunderstorm events were also found to coincide with spikes in pollen concentrations and disease incidence, suggesting a potential link to thunderstorm-related allergic exacerbations. These results underscore the urgent need for region-specific pollen monitoring systems, early warning mechanisms, and targeted public health interventions to mitigate the burden of allergic respiratory diseases in vulnerable populations, particularly under increasingly volatile climatic conditions.