| Summary: | Among nanomaterials (NMs), titanium dioxide (TiO<sub>2</sub>) is one of the most manufactured NMs and can be found in many consumers’ products such as skin care products, textiles and food (as E171 additive). Moreover, due to its most attractive property, a photoactivation upon non-ionizing UVA radiation, TiO<sub>2</sub> NMs is widely used as a decontaminating agent. Uncontrolled contaminations by TiO<sub>2</sub> NMs during their production (professional exposure) or by using products (consumer exposure) are rather frequent. So far, TiO<sub>2</sub> NMs cytotoxicity is still a matter of controversy depending on biological models, types of TiO<sub>2</sub> NMs, suspension preparation and biological endpoints. TiO<sub>2</sub> NMs photoactivation has been widely described for UV light radiation exposure, it could lead to reactive oxygen species production, known to be both cyto- and genotoxic on human cells. After higher photon energy exposition, such as X-rays used for radiotherapy and for medical imaging, TiO<sub>2</sub> NMs photoactivation still occurs. Importantly, the question of its hazard in the case of body contamination of persons receiving radiotherapy was never addressed, knowing that healthy tissues surrounding the tumor are indeed exposed. The present work focuses on the analysis of human normal bronchiolar cell response after co-exposition TiO<sub>2</sub> NMs (with different coatings) and ionizing radiation. Our results show a clear synergistic effect, in terms of cell viability, cell death and oxidative stress, between TiO<sub>2</sub> NMS and radiation.
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