Chemical alteration of UO2 micro-particles in model lung systems
Journal
Journal of Hazardous Materials
Journal Volume
497
Start Page
139670
ISSN
0304-3894
Date Issued
2025-10
Author(s)
Khng, You Cheng
Vettese, Gianni F.
Ang, Joyce W.L.
Walker, Jessica M.
Parker, Julia
Neill, Thomas
Morris, Katherine
Abrahamsen–Mills, Liam
Sarparanta, Mirkka
Law, Gareth T.W.
Abstract
Uranium dioxide (UO2) particles can be released from mines, nuclear fuel manufacturing, reactor accidents, and weapons use. They pose inhalation risks, yet their behavior in the human lung remains poorly understood. This study investigates the long-term chemical alteration and dissolution of µm-sized UO2 particles in two model lung fluids: Simulated Lung Fluid (SLF) and Artificial Lysosomal Fluid (ALF), representing extracellular and intracellular lung environments, respectively. Particles were exposed to each fluid at 37°C for up to 180 days (SLF) and 900 days (ALF). In SLF, UO2 showed low apparent solubility (<2 % U released to solution), but solid-phase analyses revealed significant oxidation of U(IV) (∼50 %) and formation of autunite-like sheets on the UO2 surface. Secondary phase formation may lessen overall UO2 dissolution, promoting long-term particle retention, whilst modifying particle chemical toxicity and cell uptake. In contrast, Monte Carlo simulations indicate that the SLF-induced surface alteration would reduce (>50 %) external radiation dose from the particles. In contrast, UO2 readily dissolved in ALF (∼75 % U released to solution in 60 days, ∼100 % by 900 days). There was no evidence of secondary phase formation in ALF, but extensive particle matrix dissolution/disaggregation was observed by 30 days. Fragmentation of the UO2 polycrystalline matrix may lead to release of smaller UO2 crystallites, which could translocate more readily. Overall, this work provides new mechanistic insight into the fate of inhaled UO2 under physiologically relevant conditions, highlighting a possible need to consider particle reactivity and alteration processes in health risk assessments.
Subjects
Dissolution
Inhalation
Lung fluid
Macrophage
Particle alteration
U-particles
Publisher
Elsevier BV
Type
journal article