Sub-acute Inhalation Exposure to Aluminum Oxide Nanoparticles and its Effects on Wistar Rats as Opposed to the Micro-sized Chemical Analog.

Introduction: Aluminum oxide nanoparticles (Al₂O₃ NPs) are widely used in various productions. Simultaneously, many research works report the toxic effects of this nanomaterial. Given that, there is a growing risk of negative effects produced by Al₂O₃ NPs on public health.

Aims: This study aims to investigate the toxic effects of Al₂O₃ NPs as opposed to the micro-sized chemical analogue under sub-acute inhalation exposure.

Materials and methods: We identified the physical properties of Al₂O₃ NPs as opposed to the micro- sized chemical analogue, including size, specific surface area, and total pore volume. Inhalation exposure to Al₂O₃ NPs was simulated on Wistar rats in a chamber for whole-body. The animals were exposed for 4 hours each day for 28 days. NPs and MPs concentrations in the chamber were kept at ~ 1/4000 from LC₅₀. Rats' behavior was examined prior to the exposure period and after it; after the last daily exposure, we examined biochemical and hematological blood indicators, NPs and MPs bioaccumulation, and pathomorphological changes in organ tissues.

Results: The tested Al₂O₃ sample is a nanomaterial according to its analyzed physical properties. Rats' behavior changed more apparently under exposure to NPs compared to MPs. Aluminum levels, which were 1.62-55.20 times higher than the control, were identified in the lungs, liver, brain, and blood under exposure to NPs. These levels were also 1.55-7.65 times higher than the control under exposure to MPs. Biochemical indicators of rats' blood also changed under exposure to NPs against the control. We identified more active ALT, AST, ALP, and LDH, elevated levels of GABA, MDA, and conjugated bilirubin, and a lower level of Glu. As opposed to exposure to MPs, ALT, AST, and ALP were more active; GABA and MDA levels were higher; Glu level was lower. Under exposure to NPs, the number of platelets grew, whereas no similar effect occurred under exposure to MPs. We established pathomorphological changes in tissues of the lungs, brain, heart, and liver under exposure to Al₂O₃ NPs; similar changes occurred only in the lungs under exposure to MPs. Exposure to NPs induced changes in tissue structures in a wider range of various organs, and these changes were more apparent than under exposure to MPs.

Conclusion: Greater toxicity of Al₂O₃ NPs as opposed to MPs is evidenced by a wider range of organs where their bioaccumulation occurs, more apparent pathomorphological and pathological functional changes. Established peculiarities of toxic effects produced by the analyzed nanomaterial should be considered when developing hygienic recommendations aimed at preventing and mitigating adverse impacts of Al₂O₃ NPs on human health under inhalation exposure.