BACKGROUND: Air pollution, particularly particulate matter, has been linked to various health issues, including respiratory infections in children. This study investigates the impact of long-term PM2.5 exposure on acute otitis media (AOM), sinusitis, pharyngitis, and tonsillitis in a large Korean cohort. While children are known to be more vulnerable due to anatomical factors, the relationship between prolonged PM2.5 exposure and these infections has been insufficiently explored in large populations. METHODS: We aimed to examine the association of long-term exposure to PM RESULTS: Our study included 364,227 people aged 0-18 years at enrollment and total of onset of each disease was 196,762 with acute otitis media, 253,248 with sinusitis, 275,160 with pharyngitis, and 315,367 with tonsillitis. Estimated hazard ratios (HR) per 5 μg/m CONCLUSIONS: This study demonstrates a significant link between long-term PM2.5 exposure and increased risks of AOM, sinusitis, pharyngitis, and tonsillitis, especially in younger individuals. Highlighting the effects of prolonged exposure, it emphasizes the importance of public health strategies to protect vulnerable populations and provides insights for policies addressing air pollution-related health risks.