The interaction of the Multidisciplinar Institute of Vegetal Biology (IMBIV) at CONICET with RI-URBANS is related to the ongoing project “Source apportionment of size-resolved atmospheric particulate matter and their oxidative potential in Córdoba (Argentina) and Leipzig (Germany)” funded by DFG, Germany. The main objective of this project is to assess the association of size-resolved PM chemical composition and source contributions with size-resolved PM toxicity in two medium-sized urban locations in South America and Europe. Limited available data from these cities have shown that emission sources and their contributions are very different for ultrafine, fine, and coarse particle sizes, therefore, particle toxicity is expected to vary.