I will expand the ongoing SPARTAN (Surface PARTiculate mAtter Network) project to include measurements of PM2.5 oxidative potential at 13 locations around the globe. Recent evidence suggests that PM2.5 oxidative potential (i.e. the ability of PM2.5 to cause oxidative stress) may be a more biologically relevant exposure compared to traditional mass-based measurements. Incorporating this parameter into SPARTAN will allow us to evaluate which components of PM2.5 are the most important predictors of oxidative potential around the world.