Peculiarities of toxic effects produced by aluminum oxide nano- and microparticles under multiple inhalation exposure

Introduction. Aluminum oxide nanoparticles (Al₂O₃ NPs) are widely used in nanotechnologies employed in various branches including chemical, food, and medical industry and perfume and cosmetics production. This high demand for Al₂O₃ NPs, given the wide-scale development of nanoindustries, can, in its turn, lead to ambient air pollution that creates public health risks under long-term exposure to it. Given that, it seems relevant to perform profound investigation with its focus on pathogenetic features of toxic effects produced by these nanoparticles and comparatively analyze them with effects produced by a micro-sized chemical analog under inhalation exposure to introduce more effective prevention.

Materials and methods. We examined chemical properties of Al₂O₃, nano- and microparticles (MPs) in an experiment on Wistar rats, comparatively analyzed the results and described pathogenetic features of toxic effects produced by the examined particles under multiple inhalation exposure. 

Results. The examined samples were a nanomaterial judging by such parameters as particle size, shape, surface area, and total pore volume. They differed substantially from their micro-sized analog. Exposure to Al₂O₃ NPs causes more pronounced changes in the behaviour of rats relative to MPs. Under exposure to Al₂O₃ NPs, aluminum concentrations were statistically significantly by 1.62–55.2 times higher in the lungs, liver, brain and blood. The concentration of the examined elements was by 1.55–7.65 times higher in these organs as compared to exposure to the micro-sized particles. Exposure to Al₂O₃ NPs induced changes in biochemical indicators of negative effects against the control (exposure to micro-sized particles). We established higher activity of ALT, AST, AP, LDH, and elevated levels of direct bilirubin, GABA, glutamine acid, and MDA against the same indicators in the control group. Pathomorphological changes were identified in the lungs, brain, heart, and liver under exposure to Al2O3 NPs whereas exposure to the micro-sized analog induced such changes only in the lungs. Exposure to NPs induced more apparent changes in tissue structures in many organs. 

Limitations. The study involved only multiple inhalation exposure to Al₂O₃ NPs and MPs in an experiment on Wistar rats.

Conclusion. Al₂O₃ NPs are more toxic than their micro-sized chemical analog; this is evidenced by a greater number of organs where bioaccumulation occurs, more apparent pathomorphological changes and pathological functional disorders. The study results should be considered when developing hygienic recommendations aimed at preventing and minimizing negative effects produced by Al₂O₃ NPs on human health.

Compliance with ethical standards. The study was accomplished in accordance with the European Convention for the Protection of Vertebrate Animals used for Experimental and other Scientific Purposes (ETS No. 123) and requirements of the Local Committee on Ethics of the Federal Scientific Center for Medical and Preventive Health Risk Management Technologies (the Meeting Report No. 5 issued on January 20, 2021).

Contribution:
Zemlyanova М.А. — the study concept and design, data analysis, writing;
Zaitseva N.V. — the study concept and design, statistical data analysis, editing;
Stepankov М.S. — data collection and analysis.
All the authors have approved the final variant of the article and bear full responsibility for its integrity. 

Conflict of interest. The authors declare no conflict of interest.

Acknowledgement. The research was granted financial support from the federal budget.

Received: March 31, 2023 / Accepted: May 31, 2023 / Published: June 20, 2023