When suspended in the air, microplastics undergo atmospheric aging due to exposure to oxidants (e.g. O3) and UV light, which can change their chemical and physical properties, including ice nucleating properties. To investigate the effect of atmospheric aging on the ice nucleation activity of microplastics, we exposed the microplastics to O3 using a flow-tube reactor and measured the change in ice activity. The O3 exposures in our experiments corresponded to 16.3 days at 30 ppbv (background PBL conditions). We also conducted UVC+O3 experiments, which represented an upper limit to photooxidation in the troposphere. Figure shows the freezing curves in the form of boxplots before and after the aging experiments, and Table summarizes all T50 values including 83% confidence intervals before and after oxidation experiments.