Organic aerosols undergo changes when exposed to oxidants like ozone or UV (ultraviolet) light. This study looks at how both aging processes affect particle properties, using trans-aconitic acid as a proxy for secondary organic aerosols. We found that exposure to UV light and ozone causes mass loss and changes viscosity significantly, up to 4 orders of magnitude. This suggests that aged particles may take much longer than untreated particles to equilibrate under dry conditions.