We investigated the change of coronary atherosclerosis with long-term exposure to fine particulate matter of aerodynamic diameter <2.5 ​μm (PM2.5) using coronary computed tomography angiography (CCTA).Subjects undergoing serial CCTAs between January 2007 and December 2017 (n ​= ​3,127) were analyzed. Each individual's cumulative amount of PM2.5 exposure between the two CCTAs was evaluated by Kriging interpolation and zonal analysis, considering the time interval between the two CCTAs. The main outcome was progression of coronary artery calcium (CAC) with additional semiquantitative analysis on the changes in the severity and composition of atherosclerotic plaques.The CAC scores increased by 30.8 Agatston units per-year under a median PM2.5 concentration 24.9 ​μg/m3 and tended to increase with the cumulative amount of PM2.5 exposure (r ​= ​0.321, p ​<0.001). The CAC progressed in 1,361 (43.5%) subjects during a median 53 months follow-up. The cumulative amount of PM2.5 exposure was independently associated with CAC progression (adjusted OR 1.09, p ​<0.001). By random forest analysis, the relative impact of cumulative amount of PM2.5 exposure on CAC progression was higher than that of traditional cardiovascular risk factors and the average concentration of PM2.5. The extent of coronary atherosclerosis and newly developed calcified plaque on follow-up were also significantly associated with the cumulative amount of PM2.5 exposure.Cumulative exposure to air pollution is associated with the progression of diffuse coronary calcification, the importance of which may be more significant than other traditional cardiovascular risk factors. Further investigations into the causality between PM2.5 and coronary atherosclerosis are warranted to improve global cardiovascular health.