Impact of particulate matter 2.5 exposure on severity of pediatric chronic rhinitis: A prospective cohort study.

BACKGROUND: Particulate matter with a diameter of ≤2.5 micrometers (PM2.5) is associated with respiratory and allergic diseases. However, the longitudinal impact on pediatric rhinitis control remains limited. OBJECTIVES: To determine the association between PM2.5 exposure and symptom control in pediatric patients with chronic rhinitis. METHODS: This prospective longitudinal study (July 2024-August 2025) followed children with chronic rhinitis in the Bangkok Metropolitan Region. Rhinitis symptom severity was assessed weekly using a visual analog scale (VAS), with covariates such as medication use and concurrent respiratory infections. A 1-week average PM2.5 concentration preceding VAS assessment (via Inverse Distance Weighting interpolation) was estimated. Associations between PM2.5 exposure and VAS were analyzed using multivariable mixed-effects and fixed-effects linear regression models. Additional analyses were stratified by aeroallergen sensitization status (allergic rhinitis versus nonallergic rhinitis). RESULTS: Among 146 children followed for a median of 52 weeks, higher PM2.5 exposure (per 10 μg/m3) was consistently associated with increased VAS (β coefficient; 95% confidence interval = 0.260; 0.215-0.306, p < .001). Wet season, concurrent respiratory infections, and medication use were also associated with increased VAS. These associations were observed in both allergic rhinitis and nonallergic rhinitis. CONCLUSION: Higher short-term ambient PM2.5 exposure was associated with greater rhinitis symptom severity in children with chronic rhinitis. These findings support consideration of ambient air pollution as an environmental factor in pediatric rhinitis management.