[en] For the first time, a study directed by Airparif, in association with LSCE (Environmental and Climate Sciences laboratory, CNRS-CEA) assesses particles produced in the Ile-de-France region out from the surrounding regions. This study also determines their main origins. With the financial contributions from the State, the Ile-de-France Regional Council and the City of Paris, this large scale study has been carried out from 2009 until 2011 and required 90 000 chemical analyses. This study concludes that, next to the traffic, like the Paris Boulevard peripherique porte d'Auteuil, 60% of the particles matters (PM) are locally produced. A main stable 44% of this local production is from the traffic itself. Concerning the Paris agglomeration urban background, far from the traffic, 70% of the particles originate from other French regions or even European regions. The remaining 30% are locally produced, mainly by the traffic and wood burning