Background: Fine particulate matter (PM) (PM with an aerodynamic diameter <2.5 mu m, PM2.5) exposure contributes to respiratory disease development and exacerbation. Objective: We sought to investigate the effect of PM2.5 exposure on mucociliary function in primary human nasal epithelial cells (HNECs) and the underlying mechanism. Methods: HNECs derived from control subjects and patients with chronic rhinosinusitis with nasal polyps were established as air-liquid interface cultures. Confluent cultures were exposed to 100 or 200 mu g/mL PM2.5 for 24 h and assessed for expression of specific mucociliary-associated factors, the percentage of beta-tubulin IV-positive and MUC5AC-positive cells, expression of epidermal growth factor receptor (EGFR) ligand and activation of phosphoinositide 3-kinase (PI3K)-AKT/ERK. In addition, cultures pretreated for 30 min with AG1478 (an EGFR inhibitor) or LY294002 (a PI3K inhibitor) following PM2.5 exposure were assessed for MUC5AC mRNA and protein expression. Results: PM2.5 exposure at 100 or 200 mu g/mL for 24 h did not affect geminin coiled-coil domain containing, multiciliate differentiation and DNA synthesis associated cell cycle protein, FOXJ1, or DNAI2 mRNA expression or the percentage of beta-tubulin IV-positive cells. However, 200 mu g/mL PM2.5 exposure significantly increased mRNA expression of SAM-pointed domain-containing ETS transcription factor and MUC5AC and the percentage of MUC5AC-positive cells. PM2.5 also increased expression of EGFR ligands, including heparin-binding EGF-like growth factor and amphiregulin. Furthermore, PM2.5induced activation of PI3K, AKT, and ERK, and pretreatment of HNECs with AG1478 or LY294002 attenuated PM2.5-induced MUC5AC mRNA and protein expression.