Titre 25 mots 25 DNA damage after in vitro exposure to very low concentration of combusted cerium nanoparticles (CoCeO 2 NPs) and to CoCeO 2 NPs + Benzo(a)pyrene in rat and human gametes. Study question 25 mots 23 Do in vitro gametes exposures to very low concentration of CoCeO 2 NPs and to CoCeO 2 NPs + Benzo(a)pyrene induce significant and similar DNA damage ? Summary answer 25 mots 22 In vitro gametes co-exposure to CoCeO 2 NPs + Benzo(a)pyrene induced statistically higher DNA damage than exposure to CoCeO 2 NPs alone in rat and human. What is known already 100 mots 100 Cerium dioxide nanoparticles (CeO 2 NPs) are widely used as diesel additive and are released in the air after engine combustion. The Organization for Economic Cooperation and Development included CeO 2 NPs in the priority list of nanomaterials requiring urgent evaluation. In vitro exposure of human and mouse sperm and cumulus oocyte complexes (COC) to very low concentrations of pristine CeO 2 NPs induce significant DNA damage. Benzo(a)pyrene (BaP) is also released in the air by diesel combustion and is known to induce DNA damage in sperm and COC. Nevertheless, pristine CeO 2 NPs are modified by combustion; the impact of CoCeO 2 NPs exposure and to CoCeO 2 NPs+BaP remains unexplored. Study design, size, duration 75mots 66 Pristine CeO 2 NPs were extracted from Envirox TM diesel additive and combusted at 850°C, (average combustion temperature in a diesel engine), to obtain CoCeO 2 NPs. Crystalline structure of CoCeO 2 NPs was analysed by X-ray Diffraction. Rat gametes were sampled in epididymis and oviducts after euthanasia of five mature males and fourty 4 weeks old females (after ovarian stimulation). Human frozen sperm from fertile donors were purchased from Germetheque biobank (France).