The Relationship Between Air Pollution, Meteorological Factors, and Eosinophil Counts in Peripheral Blood of Patients With Allergic Rhinitis: A Cross-Sectional Study.

Objective: To evaluate the relationship between air pollution, meteorological factors, and eosinophils in the peripheral blood of allergic rhinitis (AR) patients. Methods: We conducted a retrospective study of medical records from the Ninth Medical Center of PLA General Hospital in Beijing. A review of medical records (1^st January 2014-31^th August 2022) of 1080 AR patients who underwent peripheral blood eosinophil count tests. Patients were stratified into elevated and normal eosinophil count groups. Daily meteorological data (mean temperature and relative humidity) and ambient pollutant levels (PM2.5, PM10, NO₂, SO₂, CO, and ozone [O₃]) were collected. The mean pollutant levels and meteorological factors on the day of eosinophil count measurement were calculated separately for each group. Linear regression was performed to analyze the association between eosinophil counts and both meteorological factors and pollutant levels among AR patients. Results: In 1080 AR patients, 11.85% had elevated eosinophil counts. Higher temperature (16.88 ± 9.09°C), humidity (57.75 ± 17.22%), and O₃ levels (116.54 ± 54.92 μg/m³) correlated significantly (p < 0.05) with elevated eosinophil counts. Linear regression confirmed positive associations between eosinophil count and temperature (β = 0.003), humidity (β = 0.001), and O₃ (β = 0.0004) (p < 0.05). Other pollutants showed no significant differences. Conclusion: Elevated eosinophil counts in AR patients correlated significantly with higher temperature, humidity, and O₃ levels. Linear regression confirmed positive associations between eosinophil count and these meteorological factors.