The chronic inhalation of airborne PM2.5 caused time-dependent early AD-like changes in mice, such as an increase in Aβ40, BACE (beta-site amyloid precursor protein (APP)-cleaving enzyme), and COX-2, as well as a decrease in APP, with a minimal change of phosphorylated tau [77]. The gene discussed is PTGS2; the disease is Alzheimer disease.