Fine particle (PM₁) pollution is a major health issue in the city of Marseille, which is subject to numerous pollution sources. Sampling carried out during the summer enabled a fine characterization of the PM₁ sources and their oxidative potential, a promising new metric as a proxy for health impact. PM₁ came mainly from combustion sources, secondary ammonium sulfate, and organic nitrate, while the oxidative potential of PM₁ came from these sources and from resuspended dust in the atmosphere.