A computational study on the translocation of inhaled ultrafine particles to the brain
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Date
2026-07-07
Authors
Παπανικολάου, Κωνσταντίνος
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Abstract
Inhaled ultrafine particles pose a great threat to human health. Their deposition to the nasal cavity and specifically the olfactory region, eventually causes their translocation to the brain, where, due to their high oxidative potential, they cause significant damage. The quantification of their deposi-tion efficiency and daily doses is crucial in evaluating human exposure levels. A computational in-vestigation is performed, in which the deposition fractions of particles are quantified in a patient-specific geometry during resting conditions. A parametric study also explores how the deposition efficiency changes for different breathing parameters. Computational findings are combined with atmospheric data to determine the daily doses in the total nasal cavity and the olfactory region in different environments. The results suggest that the olfactory deposition efficiency of ultrafine par-ticles is close to 1% for the smaller particles and drops dramatically with increasing size. The dep-osition efficiency of ultrafine particles decreases with increasing volumetric flow rate, suggesting that mass convection is enhanced and mass diffusion becomes less significant. The quantification of the daily doses suggests that olfactory uptake can be a significant particle translocation pathway to the brain and that particles of smaller size have a higher tendency to deposit to the cavity and the olfactory region. The findings also point out “maximum zones” during the day for the local environ-ments studied, when peaks in the daily doses are observed.
In the introductory chapter (Chapter 1) the causes of air pollution are discussed and the primary air pollutants are presented. Ultrafine particles are explored in greater depth, as their physico-chemical characteristics are analyzed, as well as their impact on human health. Great focus is given on the influence of inhaled ultrafine particles on the brain. Finally, the possible translocation path-ways are presented and the olfactory route is suggested to be the dominant one.
In the methodology chapter (Chapter 2), after a brief review of the previous studies on the ol-factory deposition of particles, the main deposition mechanisms are analyzed, and the dominant mechanism in the ultrafine regime is selected. The different physiological breathing parameters used are analyzed. Afterwards, the procedure through which the anatomic geometry was recon-structed is presented. Following that, the physical model is analyzed along with the mathematical expressions used for different calculations. The experimental procedure for the air quality data ac-quisition is finally presented.
In the results chapter (Chapter 3) the results of a steady-state simulation aiming to evaluate the model used are presented. After that, the results of transient simulations are given, analyzing the air flow profiles and the deposition fractions of particles of varying size in the ultrafine regime. A parametric analysis is also conducted to investigate the influence of the physiological breathing parameters on the deposition fractions of different particles. The daily doses of particles in different environments are also quantifying, revealing important insight concerning exposure levels and pub-lic health. Lastly, local daily doses are calculated in two major cities, by combining computational results with air quality data obtained experimentally.
In the conclusions chapter (Chapter 4) the results are further discussed and important conclu-sions are made. In the appendix, the numerical method used to solve the physical model is further described, and the geometry reconstruction steps are presented analytically.
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Keywords
Air pollution, Human health, Computational fluid dynamics (CFD), Multiphysics modelling, Doses