Association between long-term PM2.5 exposure and risk of urticaria and allergic rhinitis in Korean children: a nationwide longitudinal cohort study

OBJECTIVES: Exposure to air pollutants is well established as being associated with the development and exacerbation of asthma. However, relatively few studies have examined the relationship between fine particulate matter (PM2.5) exposure and the risk of urticaria and allergic rhinitis (AR). Therefore, this study aimed to investigate the associations between long-term PM2.5 exposure and the risks of urticaria and AR. METHODS: We analyzed data from the Korean National Health Insurance Service-National Sample Cohort spanning 2002 to 2019. The cohort included individuals enrolled from birth and followed until the onset of urticaria or AR. Annual PM2.5 exposure was estimated using validated machine learning-based prediction models with high spatial resolution across mainland Korea. At the initial healthcare visit, urticaria and AR were identified based on primary diagnostic codes from the 10th revision of the International Classification of Diseases. Cox proportional hazards models with time-varying exposures and confounders were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the risks associated with a 5 μg/m3 increase in annual PM2.5 concentration. RESULTS: During follow-up, 364,227 individuals aged 0-18 years at enrollment were included, among whom 151,508 developed urticaria and 258,041 developed AR. The mean PM2.5 concentration at baseline was 29.6 μg/m3 (standard deviation, 3.1). The HR per 5 μg/m3 increase in annual PM2.5 concentration was 1.02 (95% CI, 1.01 to 1.03) for urticaria and 1.06 (95% CI, 1.05 to 1.07) for AR. CONCLUSIONS: In this nationwide cohort, long-term exposure to PM2.5 was associated with the incidence of urticaria and AR. These findings provide important evidence for strategies aimed at preventing urticaria and AR in children.