BACKGROUND: Asthma is a common respiratory disease in children, and air pollution is a risk factor for pediatric asthma. However, how air pollution affects blood cells in pediatric patients with asthma remains unclear. METHODS: This retrospective observational study, performed in 2007-2018 at a medical center, enrolled non-trauma patients aged <
17 years who visited the emergency department and had asthma. Medical records and blood cell counts, including absolute neutrophil count (ANC), eosinophil count, and platelet count were extracted. The concentrations of PM RESULTS: One-unit increases in PM CONCLUSIONS: PM