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This study aims to adapt an experimental model based on Franz diffusion cells and porcine skin explants to characterize the diffusion of TiO 2 NPs and to compare the efficacy of different cleansing products, soapy water and a calixarene cleansing nanoemulsion compared with pure water, as a function of the time of treatment. While TiO 2 NPs tend to form agglomerates in aqueous solutions, a diffusion through healthy skin was confirmed as particles were detected in the receptor fluid of Franz cells using sp-ICP-MS. In the absence of treatment, SIMS images showed the accumulation of TiO 2 agglomerates in the stratum corneum, the epidermis, the dermis, and around hair follicles. Decontamination assays showed that the two products tested were comparably effective in limiting Ti penetration, whatever the treatment time. However, only calixarene nanoemulsion was statistically more efficient than water in retaining TiO 2 in the donor compartment (>89%), limiting retention inside the skin (<1%) and preventing NP diffusion through the skin (<0.13%) when treatments were initiated 30 min after skin exposure. When decontamination was delayed from 30 min to 6 h, the amount of Ti diffusing and retained in the skin increased. This study demonstrates that TiO 2 NPs may diffuse through healthy skin after exposure. Thus, effective decontamination using cleansing products should be carried out as soon as possible., Competing Interests: Declaration of competing interest The authors report there are no competing interests to declare., (Copyright © 2024. Published by Elsevier Ltd.)

The Nuclear Medicine Department of Sainte-Anne military hospital in Toulon uses 99mTc, 123I and 18F unsealed sources to provide therapeutic and diagnostic care. For a few years, only ambient air and surface monitoring were performed to check the absence of internal contamination risk for workers. To verify this risk assessment hypothesis, confirmatory monitoring programme including in vivo and in vitro measurements was performed by the French defence radiation protection service (SPRA, Clamart). Here, due to the short half-life of targeted radionuclides, the analytical sensitivity was determined with estimations of minimal detectable activities and derived recording levels. It was shown that sensitivity was sufficient to detect an internal contamination leading to an effective dose of 0.1 mSv for few days post intake. At the same time, around 20 whole-body countings were performed. Results were below minimal detectable activity and were confirmed by 24-hours urine analysis. So, actual working conditions do not lead to measurable internal contamination for nuclear medicine staff., (© The Author(s) 2023. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permission@oup.com.)