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Inhaled particulate matter is associated with nasal diseases such as allergic rhinitis, rhinosinusitis and neural disorders. Its health risks on humans are usually evaluated by measurements on monkeys as they share close phylogenetic relationship. However, the reliability of cross-species toxicological extrapolation is in doubt due to physiological and anatomical variations, which greatly undermine the reliability of these expensive human surrogate models. This study numerically investigated in-depth microparticle transport and deposition characteristics on human and monkey (Macaca fuscata) nasal cavities that were reconstructed from CT-images. Deposition characteristics of 1-30μm particles were investigated under resting and active breathing conditions. Similar trends were observed for total deposition efficiencies and a single correlation using Stokes Number was fitted for both species and both breathing conditions, which is convenient for monkey-human extrapolation. Regional deposition patterns were carefully compared using the surface mapping technique. Deposition patterns of low, medium and high inertial particles, classified based on their total deposition efficiencies, were further analyzed in the 3D view and the mapped 2D view, which allows locating particle depositions on specific nasal regions. According to the particle intensity contours and regional deposition profiles, the major differences were observed at the vestibule and the floor of the nasal cavity, where higher deposition intensities of medium and high inertial particles were shown in the monkey case than the human case. Comparisons of airflow streamlines indicated that the cross-species variations of microparticle deposition patterns are mainly contributed by two factors. First, the more oblique directions of monkey nostrils result in a sharper airflow turn in the vestibule region. Second, the monkey's relatively narrower nasal valves lead to higher impaction of medium and high inertial particles on the nasal cavity floor. The methods and findings in this study would contribute to an improved cross-species toxicological extrapolation between human and monkey nasal cavities., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Air conditioning in the nasal airways plays an important role in regulating ambient atmospheric temperature and humidity conditions of the inhaled air. Inevitably, it may alter the behaviour and fate of inhaled ambient aerosols within the human respiratory airways due to hygroscopic growth and droplet evaporation, which is a phenomena of variations in particle sizes due to physical and chemical reactions on particle surfaces in different temperature and humidity fields. Although laboratory animals have been widely used to predict health effects of human exposure to ambient substances, the nasal temperature and humidity responses in animal surrogates and human nasal cavities are still less-investigated. This paper provides a comparative study between two monkey and two human nasal subjects under the same ambient temperature and humidity conditions, where nasal models were reconstructed from CT images and the heat and mass transfer process incorporating with the intricate nose anatomy were modelled by the computational fluid dynamics (CFD) approach. Present model comparison revealed that the monkey nasal models can reach equilibrium temperature and moisture state for inhaled ambient air in a much shorter distance compared to the human models. This indicate that heat transfer in the monkey models is more effective compared to the human models due to having a higher complexity coefficient and a smaller hydraulic radius. Hence, in order to achieve comparable or similar inhalation exposure patterns in animal surrogates, corresponding adjustments such as changing the size of released particles, or the inhalation flow rates, to achieve comparable particle Stokes number are needed. The outcomes of this study would provide informative insights for future inhalation toxicology studies related to hygroscopic materials and targeted drug delivery through nasal airways., (Copyright © 2022. Published by Elsevier Ltd.)

As a primary determinant of nasal physiological functions, the nasal morphology and its effects on the airflow dynamics have been extensively studied in literature. However, gross flow features reported in literature are mostly obtained from subjects at similar ages, while studies focusing on nasal subjects with distinct age differences are significantly less. To advance current understandings of nasal airflow dynamics in the context of age diversity, this study employed three anatomically accurate nasal cavity models with distinct age features (5-, 24- and 77-year-old models) and numerically compared the physiological nasal airflow fields within these nasal cavity models. To demonstrate the validity of the present numerical models, in vivo rhinomanometry measurement was conducted on the 24-year-old female nasal model, and key anatomical features and pressure-flow curves of all three models were compared with models with similar age features in literature work. Apart from results comparison based on conventional velocity flow fields and wall shear stress distributions, a method for quantifying flow partitions in confined airway spaces was developed to reveal the proportions of fractional flow that enters the olfactory region. Our results revealed dramatic intersubject discrepancies between considered nasal cavity models, especially for the fractional flow that enters the olfactory region. Specifically, the 5-year-old girl nasal model received the highest proportion of fractional flow, which accounts for 13.3% ~ 15% of overall inhalation flow rates under different activity levels. For the 24-year-old female model, on the contrary, the olfactory fractional flow was dramatically reduced (with a local to overall percentage around 4.3%-7.7%). Finally, for the elderly subject-77-year-old male model, minimum level of olfactory flux was observed with a local to overall percentage ranging between 3.1% and 4.9% for considered wide range of inhalation flow rates. Therefore, the local flow intersubject variation can reach nearly fourfold. The vast local flow difference is mainly due to the inherent anatomical features (e.g., immature nasal turbinate structure in the child model, the partial narrowing superior nasal valve in the elder model). The results may further lead to discrepant health effects associated with inhalation exposure to airborne particles., (© 2021 John Wiley & Sons Ltd.)

Nonhuman primates are occasionally used as laboratory models for sophisticated medical research as they bear the closest resemblance to humans in morphometry and physiological functions. A range of nonhuman primate species have been employed in the inhalation toxicity, nasal drug delivery and respiratory viral infection studies, and they provided valuable insight to disease pathogenesis while other laboratory animals such as rodents cannot recapitulate due to the lesser degree of similarity in metabolism, anatomy and cellular response to that of humans. It is anticipated that nonhuman primate models of respiratory diseases will continue to be instrumental for translating biomedical research for improvement of human health, and the confidence in laboratory data extrapolation between species will play a pivotal role. From the morphometry and flow dynamics point of view, this study performed a detailed comparative analysis between human and a cynomolgus monkey nasal airway, with intention to provide high-fidelity qualitative and quantitative linkage between the two species for more effective laboratory data extrapolation. The study revealed that cynomolgus monkey could be a good human surrogate in nasal inhalation studies; however, care should be given for interspecies data extrapolation as subtle differences in anatomy and airflow dynamics were present between the two species., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

In this study, we present a detailed flow analysis using an anatomically accurate rat nasal cavity model, in which the anatomy and physiology of the nasal airway was thoroughly examined. Special efforts were given to the swirling flow structures in the nasal vestibule (anterior section of the nose, lined by squamous epithelium), fractional flow patterns in the olfactory (posterior superior section of the rat nose, lined by olfactory epithelium), and a designated method to precisely quantify flow apportionment in the olfactory region was developed. Results revealed distinct inspiratory flow patterns in the anterior vestibule region, where the accelerated airflow undergoes two sharp turns as traveling through the tortuous airway, making a route in a shape of 8. Besides this, exceptionally large flow apportionment was observed at the interface of the olfactory recess, which can be as much as 15 times greater than that in the human nose. The thorough understanding of the airflow dynamics in the rat nasal cavity is necessary to avoid potential misinterpretation of rat-derived inhalation toxicity results. Research findings are expected to play a fundamental role in developing unbiased rat to human interspecies data extrapolation schemes., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Background: A major issue among computational respiratory studies is the wide variety of nasal morphologies being studied, caused by both inter-population and inter-subject variations., Method: Six nasal cavity geometries exhibiting diverse geometry variations were subjected to steady inhalation flow rate of 15L/min. to determine if any consistent flow behaviour could be found., Findings: Despite vastly different geometries we were able to identify consistent flow patterns including relatively high velocity in the nasal valve region, followed by flow continuing predominantly in the inferior half of the airway. We also found conformity among models where the inhaled air reached a near-conditioned state by the middle of the nasal cavity. Air from the front of the face reached the olfactory regions while air from the lateral sides of the face moved through the inferior half of the nasal cavity., Interpretation: The ability to predict gross flow features provides a baseline flow field to compare against. This contributes towards establishing well defined flow predictions and be used as a comparison for future larger studies., (Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.)

Intranasal drug delivery has attracted significant attention because of the opportunity to deliver systemic drugs directly to the blood stream. However, the mucociliary clearance poses a challenge in gaining high efficacy of intranasal drug delivery because cilia continuously carry the mucus blanket towards the laryngeal region. To better understand mucus flow behaviour on the human nasal cavity wall, we present computational model development, and evaluation of mucus motion on a realistic nasal cavity model reconstructed from CT-scans. The model development involved two approaches based on the actual nasal cavity geometry namely: (i) unwrapped-surface model in 2D domain and (ii) 3D-shell model. Conservation equations of fluid motion were applied to the domains, where a mucus production source term was used to initiate the mucus motion. The analysis included mucus flow patterns, virtual saccharin tests and quantitative velocity magnitude analysis, which demonstrated that the 3D-shell model results provided better agreement with experimental data. The unwrapped-surface model also suffered from mesh-deformations during the unwrapping stage and this led to higher mucus velocity compared to experimental data. Therefore, the 3D-shell model was recommended for future mucus flow simulations. As a first step towards mucus motion modelling this study provides important information that accurately simulates a mucus velocity field on a human nasal cavity wall, for assessment of toxicology and efficacy of intranasal drug delivery., (Crown Copyright © 2019. Published by Elsevier Ltd. All rights reserved.)

Increased computational resources provide new opportunities to explore sophisticated respiratory modelling. A survey of recent publications showed a steady increase in the number of mesh elements used in computational models over time. Complex geometries such as the nasal cavity exhibit sharp gradients and irregular curvatures, leading to abnormal flow development across their surfaces. As such, a robust method for examining the near-wall mesh resolution is required. The non-dimensional wall unit y + (often used in turbulent flows) was used as a parameter to evaluate the near-wall mesh in laminar flows. Mesh independence analysis from line profiles showed that the line location had a significant influence on the result. Furthermore, using a single line profile as a measure for mesh convergence was unsuitable for representing the entire flow field. To improve this, a two-dimensional (2D) cross-sectional plane subtraction method where scalar values (such as the velocity magnitude) on a cross-sectional plane were interpolated onto a regularly spaced grid was proposed. The new interpolated grid values from any two meshed models could then be compared for changes caused by the different meshed models. The application of this method to three-dimensional (3D) volume subtraction was also demonstrated. The results showed that if the near-wall mesh was sufficiently refined, then narrow passages were less reliant on the overall mesh size. However, in wider passages, velocity magnitudes were sensitive to mesh size, requiring a more refined mesh., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A major functional role of the nasal cavity is air conditioning of the inspired environmental air to near alveolar conditions. It is well known that the anatomical disparities among nasal passages can change airflow patterns to a great extent. However, its effect on nasal air conditioning performance remains largely unexplored. This research investigated the nasal air conditioning performance among nasal models with distinct vestibule phenotypes, including subjects with and without vestibule notches. For the mass transfer, we used a two-film theory model to determine the species transport. Airflow patterns, heat and mass transfer between the inhaled airflow and the nasal mucosa were analysed and compared. Results showed that the nasal air conditioning performance is closely related to nasal passage structures. The anatomical variations, especially the geometry changes in the anterior vestibule region, can increase both heat and mass transfer rate between nasal mucous and respiratory air at the vicinity of the notched regions, while for other regions such as the anterior superior nasal cavity, the heat transfer is greatly reduced to even zero heat flux due to lack of active airflow passing., (Copyright © 2018 IPEM. Published by Elsevier Ltd. All rights reserved.)

The complex nasal structure poses obstacles for efficient nasal drug administration beyond the nasal valve, especially when targeting the olfactory region. This study numerically detailed the naturally inhaled nanoparticle transport process from the initial releasing locations to the final deposited sites using a realistic human nasal passage. Dispersed nanoparticles at different coronal cross-sections were partitioned into multiple groups according to their final deposited locations. Results showed inhaled nanoparticles are more likely to move along the septum. Olfactory deposited particles entered the nose through the inner superior corner of the nostril; the middle meatus deposited particles entered the nose through the top third of the nostril; the inferior deposited particles entered via the bottom floor regions of the nostril. Therefore, targeted nasal inhalation therapies that intentionally release therapeutic particles from these recognized regions at the nostril plane can considerably improve the resultant topical disposition doses. However, it remains challenging to completely prevent undesired particle depositions as particles coming from the same location may produce multiple-sites depositions due to partition overlapping. Nevertheless, the fraction of undesired particle deposition is anticipated to be reduced at a great extent compared to unplanned releasing approaches., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Rats have been widely used as surrogates for evaluating the health effects of inhaled airborne particulate matter. To provide a thorough understanding of particle transport and deposition mechanisms in the rat nasal airway, this article presents a computational fluid dynamics (CFD) study of particle exposure in a realistic rat nasal passage under a resting flow condition. Particles covering a diameter range from 1 nm to 4 µm were passively released in front of the rat's breathing zone, and the Lagrangian particle tracking approach was used to calculate individual particle trajectories. Detailed particle deposition analysis shows the deposition of inertial particles >2 µm is high in the rat nasal vestibule and more than 70% of all inhaled inertial particles were trapped in this region. While for diffusive nanoparticles, the vestibule filtration effect is reduced, only less than 60% of inhaled nanoparticles were blocked by the anterior nasal structures. The particle exposure in the olfactory region only shows notable deposition for diffusive nanoparticles, which peaks at 9.4% for 5 nm particles. Despite the olfactory deposition remains at a low level, the ratio between the olfactory and the main passage is kept around 30-40% for 10-800 nm particles, which indicates a particle-size-independent distribution pattern in the main nasal passage and olfactory. This study provides a deep understanding of particles deposition features in a rat nasal passage, and the research findings can aid toxicologist in inter-species exposure-response extrapolation study.

In this study, the effects of nasal drug delivery device and the spray nozzle orientation on sprayed droplets deposition in a realistic human nasal cavity were numerically studied. Prior to performing the numerical investigation, an in-house designed automated actuation system representing mean adults actuation force was developed to produce realistic spray plume. Then, the spray plume development was filmed by high speed photography system, and spray characteristics such as spray cone angle, break-up length, and average droplet velocity were obtained through off-line image analysis. Continuing studies utilizing those experimental data as boundary conditions were applied in the following numerical spray simulations using a commercially available nasal spray device, which was inserted into a realistic adult nasal passage with external facial features. Through varying the particle releasing direction, the deposition fractions of selected particle sizes on the main nasal passage for targeted drug delivery were compared. The results demonstrated that the middle spray direction showed superior spray efficiency compared with upper or lower directions, and the 10µm agents were the most suitable particle size as the majority of sprayed agents can be delivered to the targeted area, the main passage. This study elaborates a comprehensive approach to better understand nasal spray mechanism and evaluate its performance for existing nasal delivery practices. Results of this study can assist the pharmaceutical industry to improve the current design of nasal drug delivery device and ultimately benefit more patients through optimized medications delivery., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

To gain a better understanding of nanoparticle exposure in human nasal cavities, laboratory animals (e.g. rat) are used for in vivo studies. However, due to anatomical differences between human and rodent nasal cavities, direct particle deposition comparisons between species are difficult. This paper presents a comparative nanoparticle (1 nm, 10 nm, and 100 nm) deposition study using anatomically realistic models of a human and rat nasal cavity. The particle deposition fraction was highest consistently in the main nasal passage, for all nanoparticles tested, in the human model; whereas this was only the case for 10 nm, and 100 nm particles for the rodent model, where greater deposition was found in the anterior nose for 1 nm particles. A deposition intensity (DI) term was introduced to represent the accumulated deposition fraction on cross-sectional slices. A common and preferential deposition site in the human model was found for all nanoparticles occurring at a distance of 3.5 cm inside the nasal passage. For the rodent model maximum DI occurred in the vestibule region at a distance of 0.3 cm, indicating that the rodent vestibule produces exceptionally high particle filtration capability. We also introduced a deposition flux which was a ratio of the regional deposition fraction relative to the region's surface area fraction. This value allowed direct comparison of deposition flux between species, and a regional extrapolation scaling factor was found (e.g. 1/10 scale for vestibule region for rat to human comparison). This study bridges the in vitro exposure experiments and in vivo nanomaterials toxicity studies, and can contribute towards improving inter-species exposure extrapolation studies in the future., (© The Author 2016. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Background: To evaluate the deposition efficiency of spray droplets in a nasal cavity produced from a spray device, it is important to determine droplet size distribution, velocity, and its dispersion during atomization. Due to the limiting geometric dimensions of the nasal cavity airway, the spray plume cannot develop to its full size inside the nasal vestibule to penetrate the nasal valve region for effective drug deposition., Methods: Particle/droplet image analysis was used to determine local mean droplet sizes at eight regions within the spray plume under different actuation pressures that represent typical hand operation from pediatric to adult patients., Results: The results showed that higher actuation pressure produces smaller droplets in the atomization. Stronger actuation pressure typical of adult users produces a longer period of the fully atomized spray stage, despite a shorter overall spray duration. This produces finer droplets when compared with the data obtained by weaker actuation pressure, typical of pediatric users., Conclusion: The experimental technique presented is able to capture a more complete representation of the droplet size distribution and the atomization process during an actuation. The measured droplet size distribution produced can be related to the empirically defined deposition efficiency curve of the nasal cavity, allowing a prediction of the likely deposition.

Micron-sized particle deposition in anatomically realistic models of a rat and human nasal cavity was numerically investigated. A steady laminar inhalation flow rate was applied and particles were released from the outside air. Particles showing equivalent total particle deposition fractions were classified into low, medium and high inertial particle. Typical particle sizes are 2.5, 9 and 20 μm for the human model and 1, 2 and 3 μm for the rat model, respectively. Using a surface-mapping technique the 3D nasal cavity surface was "unwrapped" into a 2D domain and the particle deposition locations were plotted for complete visual coverage of the domain surface. The total surface area comparison showed that the surface area of the human nasal model was about ten times the size of the rat model. In contrast, the regional surface area percentage analysis revealed the olfactory region of the rat model was significantly larger than all other regions making up ∼55.6% of the total surface area, while that of the human nasal model only occupying 10.5%. Flow pattern comparisons showed rapid airflow acceleration was found at the nasopharynx region and the nostril region for the human and rat model, respectively. For the human model, the main passage is the major deposition region for micro-particles. While for the rat model, it is the vestibule. Through comparing the regional deposition flux between human and rat models, this study can contribute towards better extrapolation approach of inhalation exposure data between inter-subject species.

Airflow analysis can assist in better understanding the physiology however the human nasal cavity is an extremely complicated geometry that is difficult to visualize in 3D space, let alone in 2D space. In this paper, an anatomically accurate 3D surface of the nasal passages derived from CT data was unwrapped and transformed into a 2D space, into a UV-domain (where u and v are the coordinates) to allow a complete view of the entire wrapped surface. This visualization technique allows surface flow parameters to be analyzed with greater precision. A UV-unwrapping tool is developed and a strategy is presented to allow deeper analysis to be performed. This includes (i) the ability to present instant comparisons of geometry and flow variables between any number of different nasal cavity models through normalization of the 2D unwrapped surface; (ii) visualization of an entire surface in one view and; (iii) a planar surface that allows direct 1D and 2D analytical solutions of diffusion of inhaled vapors and particles through the nasal walls. This work lays a foundation for future investigations that correlates adverse and therapeutic health responses to local inhalation of gases and particles., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Recent advances in nanotechnology have seen the manufacture of engineered nanoparticles for many commercial and medical applications such as targeted drug delivery and gene therapy. Transport of nanoparticles is mainly attributed to the Brownian force which increases as the nanoparticle decreases to 1 nm. This paper first verifies a Lagrangian Brownian model found in the commercial computational fluid dynamics software Fluent before applying the model to the nasal cavity and the tracheobronchial (TB) airway tree with a focus on drug delivery. The average radial dispersion of the nanoparticles was 9x greater for the user-defined function model over the Fluent in-built model. Deposition in the nasal cavity was high for very small nanoparticles. The particle diameter range in which the deposition drops from 80 to 18% is between 1 and 10 nm. From 10 to 150 nm, however, there is only a small change in the deposition curve from 18 to 15%. A similar deposition curve profile was found for the TB airway.

Aspiration efficiencies from nose and mouth inhalations are investigated at low and high inhalation rates by using the commercial Computational Fluid Dynamics (CFD) software CFX 11. A realistic human head with detailed facial features was constructed. Facial features were matched to represent the 50th percentile of a human male, aged between 20 and 65 years old, based on anthropometric data. The constant freestream velocity was 0.2 ms(-1), normal to the face, and inhalation rates through the mouth and nose were 15 liters per minute (LPM) for light breathing and 40 LPM for heavy breathing. It was found that the flow field in the near breathing region exhibited vertical direction caused by the presence of the torso where the airstream diverges as it flows around and over the body. The critical area concept was used as a tool to determine the aspiration efficiency of particles. Comparisons between critical areas for the nose and mouth inhalations show similar geometric properties such as the area's shape, and its vertical distance location on the x-z plane located at y = 80 cm upstream. The critical area sizes were found to be slightly larger for the mouth inhalation mainly due to the larger mouth area and also the aligned orientation of the mouth to the upstream flow, whereas the nose is perpendicular to the upstream flow. This study was undertaken to establish the flow field in the near breathing region that will help to characterize the flow and particle field for initial boundary conditions leading to a more holistic modeling approach of respiration through the internal nasal cavity and mouth.

Nasal physiology is dependent on the physical structure of the nose. Individual aspects of the nasal cavity such as the geometry and flow rate collectively affect nasal function such as the filtration of foreign particles by bringing inspired air into contact with mucous-coated walls, humidifying and warming the air before it enters the lungs and the sense of smell. To better understand the physiology of the nose, this study makes use of CFD methods and post-processing techniques to present flow patterns between the left and right nasal cavities and compared the results with experimental and numerical data that are available in literature. The CFD simulation adopted a laminar steady flow for flow rates of 7.5 L/min and 15 L/min. General agreement of gross flow features were found that included high velocities in the constrictive nasal valve area region, high flow close to the septum walls, and vortex formations posterior to the nasal valve and olfactory regions. The differences in the left and right cavities were explored and the effects it had on the flow field were discussed especially in the nasal valve and middle turbinate regions. Geometrical differences were also compared with available models.

Although many parametric studies have been conducted in developing standardized nasal geometry and analysing associated airflow dynamics, most of them are based on symmetrical nasal chambers assumption, while the inter-chamber variations due to the morphological asymmetry of the two nasal chambers are much less investigated. To address this issue, this paper presents an inter-chamber anatomical variability study by developing a shape comparison method to quantify inter-chamber anatomical differences. Then the anatomical deviation is correlated with the flow apportionment and the associated nanoparticle deposition patterns using CFD method. Results show that noticeable inter-chamber difference is observed especially in the inferior and middle passages where most inhaled flow is distributed to. Additionally, the shape of vestibule notch and septum deviation contributes to the discrepancy flow behaviour between two chambers. Consequently, these differences lead to variations in regional nanoparticle deposition, especially for 1 nm particles in the olfactory region, where the inter-chamber differences can reach up to 400%. Our results suggest that the inter-chamber anatomical variation should be considered when developing standardized nasal models. [ABSTRACT FROM AUTHOR]

Micropollutants (MPs) have increasingly become a matter of concern owing to potential health risks associated with human inhalation exposure, particularly in densely-occupied indoor environments. This study employed numerical simulations in a traditional built indoor workspace and a public transport cabin to elucidate the transport dynamics and health impacts of particulate and gaseous type of indoor MPs on varying groups of occupants. The risk of infection from pathogen-bearing MPs was evaluated in the workspace using the integrated Eulerian-Lagrangian and modified Wells-Riley model. In the cabin environment, the health impact of inhaled TVOC within the human nasal system was assessed via the integrated nasal-involved manikin model and cancer/non-cancer risk model. The results demonstrated that when ventilation layout was in favour of restricting particulate MPs spread, considerably high health risks (up to 17.22% infection possibility) were generally found in near-fields of emission source (< 2.25 m). Conversely, if the ventilated flow interacts robustly with emission source, every occupant has a minimum 5% infection risk. Incorporating the nasal cavity in the human model offers a nuanced understanding of gaseous MP distributions post-inhalation. Notably, the olfactory and sinus regions displayed heightened vulnerability to TVOC exposure, with a 62.5%–108% concentration increase compared to other nasal areas. Cancer risk assessment plausibly explained the rising occurrence of brain and central nervous system cancer for aircrew members. Non-cancer risk was found acceptable. This study was expected to advance the understanding of environmental pollution and the health risks tied to indoor MPs in densely-populated environments. [Display omitted] • MP transport characteristics in densely occupied workspace and cock-pit are analysed. • Control cabin environment is analysed with 3D scanned nasal-involved manikin models. • Occupants' health risk in workspace was evaluated using modified Wells-Riley model. • Pilots' cancer and non-cancer risk was assessed using in-nasal TVOC concentration. • High TVOC level in olfactory and sinus region links to plausibly rising brain cancer. [ABSTRACT FROM AUTHOR]

Understanding the inhalation, transport and deposition of smoke particles during fire missions are important to evaluating the health risks for firefighters. In this study, measurements from Underwriters Laboratories' large-scale fire experiments on smoke particle size distribution and concentration in three residential fire scenes were incorporated into models to investigate the fate of inhaled toxic ultrafine particulates in a realistic firefighter nasal cavity model. Deposition equations were developed, and the actual particle dosimetry (in mass, number and surface area) was evaluated. A strong monotonic growth of nasal airway dosages of simulated smoke particles was identified for airflow rates and fire duration across all simulated residential fire scene conditions. Even though the "number" dosage of arsenic in the limited ventilation living room fire was similar to the "number" dosage of chromium in the living room, particle mass and surface area dosages simulated in the limited living room were 90–200 fold higher than that in the ventilated living room. These were also confirmed when comparing the dosimetry in the living room and the kitchen. This phenomenon implied that particles with larger size were the dominant factors in mass and surface area dosages. Firefighters should not remove the self-contained breathing apparatus (SCBA) during fire suppression and overhaul operations, especially in smoldering fires with limited ventilation. [ABSTRACT FROM AUTHOR]

Transport characteristics of TVOC in cockpits of commercial airliners have not been carefully studied relative to passenger cabins, and VOC emissions are currently not well regulated by the standards (e.g. ASHRAE, FAA, etc.). This study numerically performed a comprehensive assessment of cockpit environment using the developed all-in-one model, for the first time, integrating a full-scale A320 cockpit model and detailed manikins with 3D-rebuilt nasal cavity models. A generalised total volatile organic compound (TVOC) was selected as one representative gaseous contaminant and two representative emission scenarios in the cabin environment (aged and new aircraft) were analysed. Potential risky regions of the nasal system after inhaling the given contaminants were further evaluated. The outcomes demonstrated that windshield inlets were the key determinant of yielding the strong local vortex in the pilot's near field, which could potentially promote the contaminant lock-up. For aged aircraft, the average contaminant concentration in the pilots' breathing zone was nearly half of that in a brand-new aircraft, while TVOC concentrations were significantly higher in the human upper respiratory system than those detected in the breathing zones for both cases, particularly for vestibule, olfactory, sinus and nasopharynx regions. Olfactory regions were the most affected region in two cases, with an approximately 20% increase in the case of brand-new aircraft compared to an aged one. This study enlightened a novel pathway to assess indoor environment, from tracing the pollutants from the release source to ultimately quantifying the contaminant distribution characteristics in human upper respiratory system. [Display omitted] • Cockpit environment is analysed with manikin model including CT-rebuilt nasal cavity. • TVOC transport characteristics in aged and brand-new aircraft are investigated. • TVOC inhalation characteristics in pilots' upper respiratory systems are quantified. • TVOC concentration is 132%–171% higher in nasal cavity than those in breathing zone. • Olfactory region is the most affected region of inhaled TVOC. [ABSTRACT FROM AUTHOR]

Abstract: CFD computations of particle flows in a human nasal cavity were conducted, using two types of inlet velocity profiles at the nostril openings respectively. One type is the widely used uniform inlet velocity profile while the other is a realistic inlet velocity profile extracted from the external environment that is influenced by facial features. The latter type of inlet velocity profiles were obtained through CFD computations of indoor gas-particle flows around a human head geometry containing detailed facial features in an enclosed space. Comparisons were made between the predicted results of airflow field, particle tracks and particle deposition efficiency in the nasal cavity. It was revealed that although the effects of facial features exist only in a small region (10–20 mm) in front of the face, they lead to complicated, and non-uniform velocity profiles at the nostril openings. This discrepancy leads to different predictions of airflow fields and local particle deposition efficiency in the nasal cavity, especially in the anterior regions such as the vestibule and nasal valve. The results may further lead to discrepant health-risk assessments associated with particle inhalation. Therefore, for CFD simulations of particle deposition in the nasal cavity, the inlet velocity profiles induced by facial features are important for more realistic results. [Copyright &y& Elsevier]

Laboratory animals have historically performed a vital function in evaluating health effects of human exposure to ambient particulate matter (PM). Due to the complexity of particle-laden flows and airway interactions that involve multiple species, in-depth knowledge of airflow and particle transport in both the non-human primate surrogates and human airways is still lacking. To advance the understanding in this field, this paper presents a numerical study that investigated the airflow and particle deposition characteristics of inhaled PMs in monkey and human nasal airways. Anatomically accurate macaca fuscata monkey and human nasal cavity models were reconstructed from CT images, micron particles with diameters less than 10 μm were included to conduct in silico exposure studies. Resultant particle deposition patterns were quantified by deposition enhancement factor (DEF) and deposition intensity (DI) along the airways to provide profound understanding of the similarities and differences in particle inhalation exposure characteristics across species. Anatomy comparison showed that the convoluted nasal passage of the monkey airway possessed higher level of complexity in terms of the surface-area-to-volume ratio compared to the two human nasal models, which could lead to higher evaluated nasal exposure to airborne particulate matter. Similar airflow patterns were observed from streamlines and wall shear stress distributions in all three nasal cavities of two species, with bulk air concentrated mainly in the middle and inferior meatuses in the nasal chambers. Despite the evidenced inter-subject deposition variations presented in all considered nasal cavity models, strong and similar micron particle deposition preferences with comparable DEF and DI levels were observed along the floor region of middle and inferior meatuses for both species. The methods and research findings presented in this work represent critical, initial steps towards establishing high-fidelity qualitative and quantitative linkages between the two species that enable more effective laboratory data extrapolations, improve study design, and facilitate validations of in vitro techniques currently being developed as part of international efforts to reduce or replace the use of animals in toxicity assessments for aerosol exposures. • Higher level of surface-area-to-volume ratio was found in the monkey nasal airway compared to the two human models. • Similar airflow patterns were observed in all three nasal cavities of two species. • Similar micron particle deposition preferences were found along the floor of middle and inferior meatuses for both species. • This work shows critical, initial steps towards establishing high-fidelity extropolation approach between the two species. [ABSTRACT FROM AUTHOR]

Understanding the transport and deposition of fibers in the respiratory airway is of great significance for the exposure assessment to non-spherical contaminants. Due to its complexity, few computational studies physically resolved the fibers' coupled translational and rotational motion in investigating fiber transport behaviors in the 3D human nasal airways. Additional studies are needed to fully understand the role of the fiber lengths in nasal deposition and the practical benchmarking of fiber characterization to its spherical equivalency. This study investigated the transport and deposition of fibrous particles in the human nasal cavity, resolving the coupled translational and rotational motion to fill the gap. For the first time, a detailed single fiber trajectory in the 3D nasal chamber, accounting for the coupled translational and rotational movement, was visually presented. The subtle effects of fiber deposition due to fiber lengths, rotation, and interaction with the local flow stream, were revealed and analyzed. Furthermore, the study identified the relationship between microfiber deposition and fiber lengths in the human nasal cavity. In particular, nasal deposition of the fibrous and spherical particles with the same impaction parameter or aerodynamic diameter was compared and discussed. The study led to the findings that fiber lengths play different roles in affecting the transport and deposition of microfibers in the human nasal cavity. The relative deposition level between elongated fibers and the spherical particles varies depending on the impaction parameter or the aerodynamic diameter. Current findings are well supported by the literature data. • The transport and deposition of microfibers in human nasal cavity was investigated. • Effects on fiber deposition due to fiber lengths and rotation were analyzed. • Nasal deposition of the fibrous and spherical particles were compared. • Both fibers' diameter and length affect the nasal transport and deposition. • Fiber length might play different roles in three identifiable regions for deposition. [ABSTRACT FROM AUTHOR]

Abstract: The inhalation of toxic particles such as asbestos fibres through the nasal airway has been found to cause harmful damage to the respiratory system. This study made use of CFD techniques to investigate deposition of fibrous particles in a human nasal cavity. A 3D computational model was created from CT scans which provided the framework to study the flow and deposition of fibres at a constant flow rate of 7.5L/min. The effects of the fibres’ elongated shape, density and size were incorporated into empirical drag correlations and the fibre trajectories were recorded through a Lagrangian tracking scheme. In general, good agreement was found in the right cavity and an overprediction in the left cavity. The major cause of deposition differences was in the geometrical variations between subjects as well as the left and right cavities. The dominant mechanism of deposition was by inertial impaction, with a majority of the particles depositing in the anterior region. It was found that asbestos had a very low deposition, , and was independent of fibre length. In comparison, the carbon fibre exhibited increases in deposition as the fibre length increased. A parameter which represents the mass per unit length was used to equate the for different fibre lengths. [Copyright &y& Elsevier]