Kazuhide Ito

• Doctor of Engineering
• Professor at Kyushu University

Di(2-ethylhexyl) phthalate (DEHP) is the most pervasive phthalate in the environment and is identified as an endocrine-disrupting chemical causing dysfunction in multiple organs. This study has employed a novel computational fluid dynamics (CFD)-based pollutant transport analysis and a local-whole-body hybrid physiologically based pharmacokinetics...

In an air-conditioned multinational graduate students’ office in Japan during the winter season, we examined indoor environmental conditions, occupants’ perceptions, and their acceptance levels over five consecutive days. Indoor air quality (IAQ) acceptance peaked on the third day, coinciding with the most favourable thermal sensation vote, which w...

The intricate dynamics of odorants in the indoor environment and human respiratory system remain poorly understood. In the present study, we integrate odor sensory tests (OSTs) and computational fluid dynamics coupled with a physiologically based pharmacokinetic (CFD-PBPK) model to elucidate various aspects of odorant transport and olfaction dynami...

Coughing events are eruptive sources of virus-laden droplets/droplet nuclei. These increase the risk of infection in susceptible individuals during airborne transmission. The oral cavity functions as an exit route for exhaled droplets. Thus, its configuration contributes significantly to the metrics of exhaled droplets. In this study, two realistic...

The intricate dynamics of volatile organic compounds (VOCs) in the human respiratory system remain poorly understood. In the present study, we integrate odor sensory tests (OSTs) coupled with computational fluid dynamics and a physiologically based pharmacokinetic (CFD-PBPK) model to elucidate various aspects of the olfaction process. Safe yogurt-d...

This study numerically assessed the impact of human crowd density and outdoor wind conditions (average velocity, its profile, and direction) on the convective heat transfer and drag coefficients (hc and Cd). Five different configurations of standing computer-simulated persons (CSPs) were tested in a semi-outdoor environment. A single isolated CSP,...

This paper presents a comprehensive numerical investigation to predict the human breathing zones (BZs) in crowded semi-outdoor environments. The computational domain consisted of a nine-human block array with integrated nasal cavities subjected to the lower part of the atmospheric boundary layer. Five crowding levels, seven wind directions, and inf...

Background and Objective : Respiratory diseases caused by respiratory viruses have significantly threatened public health worldwide. This study presents a comprehensive approach to predict viral dynamics and the generation of stripped droplets within the mucus layer of the respiratory tract during coughing using a larynx-trachea-bifurcation (LTB) m...

This paper presents a comprehensive numerical investigation to predict the human breathing zones (BZs) in crowded semi-outdoor environments. The computational domain consisted of a nine-human block array with integrated nasal cavities subjected to the lower part of the atmospheric boundary layer. Five crowding levels, seven wind directions, and inf...

Infectious respiratory diseases have long been a serious public health issue, with airborne transmission via close person-to-person contact being the main infection route. Coughing episodes are an eruptive source of virus-laden droplets that increase the infection risk of susceptible individuals. In this study, the droplet generation process during...

The transport and prediction of the concentration of particles in confined spaces are crucial for human well-being; this has become particularly evident during the current worldwide pandemic. Computational fluid dynamics (CFD) has been widely used for such predictions, relying on Eulerian–Eulerian (EE) and Eulerian–Lagrangian (EL) models to study p...

Highway buses are used in a wide range of commuting services and in the tourist industry. The demand for highway bus transportation has dramatically increased in the recent post-pandemic world, and airborne transmission risks may increase alongside the demand for highway buses, owing to a higher passenger density in bus cabins. We developed a numer...

The purpose of this study was to analyze the transport dynamics of inhaled gaseous odorants in the respiratory tract and investigate the characteristics of the adsorption flux on the olfactory epithelium tissue. Following the procedure of the perceptive air quality test described in ISO 16000–28, we analyzed the adsorption flux on the olfactory epi...

The purpose of this study was to accurately predict the dynamics of SARS-CoV-2 infection–based on a 3D shell model and combining computational fluid and particle dynamics (CFPD) and host-cell dynamics–along the mucus layer of the upper airway. Assuming that a healthy person inhaled droplets coughed up by an infected individual via nasal inhalation,...

Fibrous-particle (asbestos) exposure induces lung cancer, mesothelioma, and fibrosis. Man-made vitreous fibers (MMVFs) share some similarities, and so their related health effects need to be determined. Computational fluid dynamics (CFD) was used to simulate the airflow patterns (Eulerian method) and to predict the particle behaviors (Lagrangian me...

This study focused on the impact of the reproduction of oral cavity shape on the droplets dispersion dynamics, and compared the coughing dynamics between human models with and without oral cavity by using computational fluid dyanmics (CFD) technique. In this analysis, droplets were released from mouth opening surface or from the trachea via oral ca...

The purpose of this study is to reproduce CO2 emission from a human in the chamber experiment and investigate a relationship between CO2 emission rate and indoor air environment. A “digital-twin” model of the experiments for estimation of CO2 emission rate was developed by CSP integrated with CFD technique. As a result, the inhaled CO2 level depend...

Inhalation exposure to various types of airborne particles is an important risk factor for human health. This study predicted particle transport and deposition in a realistic human airway model during breathing and observed the effects of steady-state flow and transient flow on the deposition fraction using computational fluid dynamics (CFD). To ev...

This study investigates outdoor public health by predicting the airflow fields and probabilistic size of breathing zones. Computational fluid dynamics (CFD) simulations were performed in a simplified semi-outdoor domain, utilizing a validated computer-simulated person (CSP) with an integrated nasal cavity. The simulations were conducted for eight w...

The impinging jet ventilation system (IJV) is one of the ventilation systems with high ventilation effectiveness systems, which creates temperature and contaminant stratification. The influence of exhaust opening locations on temperature and ventilation effectiveness in a room with IJV was studied using computational fluid dynamics (CFD). The heigh...

The study of fluid flow in the respiratory system facilitates advanced simulation work involving drug delivery or toxic substances-related health risk assessment. Accordingly, extensive simulation efforts have been conducted to characterize the airflow distribution in human airways using the RANS (Reynold-Averaged Navier Stokes) equation, which del...

In recent years, the plastics pollution of 5mm or less size (microplastics) in marine ecosystems has been a global issue. The presence of microplastics (microfibers) is also a major concern in indoor environments of the residetial house. Many sources of microplastics in the marine environment also exist in the indoor environment. In the modern age...

The airflow balance test to confirm the physical performance of biological safety cabinets (BSC) is standardized by JIS K 3800 in accordance with NSF/ANSI 49 in Japan. In the test, Bacillus atrophaeus spores are used as an evaluation index, which poses a few limitations, such as their dependence on the environmental conditions to be tested. The aim...

We conducted isothermal large-eddy simulations to generate the velocity and concentration distributions to investigate the air pollution transport from outside to inside of a space surrounded by urban-like block arrays. Contrary to previous study, we assumed that the pollution in the form of scalars are generated outdoors and not indoors which we p...

Natural and cross ventilation is recognized as an important measure for introducing outdoor fresh air to indoor without the use of mechanical equipment. Plenty of fruitful studies for elucidating natural and cross ventilation mechanisms have been reported adopting experimental and computational methods. Field and wind tunnel experiments could provi...

The behavior of airborne particles in the human respiratory system is closely related to local tissue dosimetry and its associated health risks. The inhalation of these particles is known to be the origin of lung diseases, such as lung cancer, chronic obstructive pulmonary disease, and cardiovascular disease. To compensate for the difficulty of exp...

Respiratory diseases, such as COVID-19 (coronavirus disease 2019) caused by SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), have posed a threat to human health. For infection control and a better understanding of the pathogenesis, this study mainly focused on elucidating the virus dynamics in the mucus layer of the human nasal cavity-...

Background and objective: Respiratory diseases caused by viruses are a major human health problem. To better control the infection and understand the pathogenesis of these diseases, this paper studied SARS-CoV-2, a novel coronavirus outbreak, as an example. Methods: Based on coupled computational fluid and particle dynamics (CFPD) and host-cell...

Background and objectives: Suspended respirable airborne particles are associated with human health risks and especially particles within the range of ultrafine (< 0.1 μm) or fine (< 2.5 μm) have a high possibility of penetrating the lung region, which is concerned to be closely related to the bronchial or alveoli tissue dosimetry. Nature complex...

Recently, health risk assessment of chemical substances has become a legal requirement, and accordingly, estimation of indoor gas concentrations and their impact on workers has taken on increasing importance. Therefore, we have developed a numerical model based on CFD (Computational Fluid Dynamics) methods to predict transient and non-uniform conce...

Background and objective: From various perspectives (e.g. inhalation exposure and drug delivery), it is important to provide insights into the behavior of inhaled particles in the human respiratory system. Although most of the experimental and numerical studies have relied on an assumption of steady inhalation, the transient breathing profile is a...

Commuter buses have a high passenger density relative to the interior cabin volume, and it is difficult to maintain a physical/social distance in terms of airborne transmission control. Therefore, it is important to quantitatively investigate the impact of ventilation and air-conditioning in the cabin on the airborne transmission risk for passenger...

A significant feature of the indoor environment is the heterogeneity of airflow and pollutant distributions, which are primarily dependent on ventilation systems. In the case of short- and high-concentration exposures to hazardous chemical pollutants, it may be necessary to precisely determine the concentration in the breathing zone or, more direct...

The issue of marine pollution caused by micro-plastics has emerged and has attracted worldwide attention. If the source of micro-plastic is routine plastic waste and products, they will be located very close to the living environment, and there is a concern about the risk of micro plastic contamination even in the residential environment. However,...

Background and Objective : Brachycephalic obstructive airway syndrome (BOAS) susceptible dogs (e.g., French bulldog), suffer health complications related to deficient breathing primarily due to anatomical airway geometry. Surgical interventions are known to provide acceptable functional and cosmetic results; however, the long-term post-surgery outc...

Keywords: Computational fluid dynamics, human lower airway, deposition mechanism, ultrafine and fine particles. 1. Introduction Inhalation of toxic airborne particles can induce adverse health effects in humans, including lung cancer, asthma, and chronic obstructive pulmonary disease. Particle deposition on the airway surface is governed by differe...

In the existing ventilation design, the ventilation rate is defined by the time‐averaged flow rate, and the fluctuating (turbulence) component is not typically considered. However, inlet turbulent conditions are also assumed to have some influence on the formation of contaminant distributions. Therefore, the influence of turbulent kinetic energy at...

Computer‐simulated persons (CSPs) with respiratory systems have been developed for microclimate analysis around the human body and inhalation exposure analysis, for detailed assessment of comfort and health risks in indoor spaces. This study examined and validated the prediction accuracy of a CSP, for precise estimation of indoor environmental qual...

A fume hood is a local ventilation system that is typically installed in a laboratory space to ensure the safety of workers from chemical exposure. A fume hood is designed to capture hazardous gas‐phase pollutants generated inside a box‐like enclosure, and the pollutant capture efficiency is regulated by the average opening surface air velocity. Ho...

Although microplastic (size ≤5 mm) pollution in marine ecosystems has received global attention, the presence of microplastics and microfibers in indoor environments is also a major concern. Compared to the available field survey data on microplastics in the ocean, such information remains limited for indoor environments. Microplastics in indoor en...

Assuming the leakage of hazardous liquid chemicals in factories and chemical plants caused by natural disasters or human error, it is important to precisely estimate exposure risk and design appropriate evacuation plans and risk‐reduction measures. The exposure risk of indoor residents to leaked chemicals may be estimated using direct measurements...

The evaluation of inhalation exposure of workers in industrial production environments is significant. Current studies on inhalation exposure in industrial workshops are quite limited and lack experimental data validation. This study established a scaled experimental cabin and performed inhalation exposure experiments. Subsequently, the validated n...

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to the worldwide spread of coronavirus disease-2019 (COVID-19) since its emergence in 2019. Virus replication and infection dynamics after its deposition on the respiratory tissues require detailed studies for infection control. This study focused primarily on SARS-CoV-2 dynamics...

In recent years, an integrated analysis of computational fluid dynamics (CFD) and computer simulation person (CSP), especially to reproduce the shape of the human body, has been conducted to estimate the interaction between the human body and its surrounding indoor environment. Meanwhile, clothing is often treated in a simplified manner, as a means...

Accurate prediction of inhaled CO2 concentration and alveolar gas exchange efficiency would improve the prediction of CO2 concentrations around the human body, which is essential for advanced ventilation design in buildings. We therefore, developed a computer‐simulated person (CSP) that included a computational fluid dynamics approach. The CSP simu...

Particles longer than 5 μm and with a length/diameter ratio >3 are defined as fibers. Asbestos or other fibers are still identified in residential environments due to the emission from asbestos‐used building materials. The respiratory system is the primary route of asbestos exposure; under a longer residence time, asbestos‐related adverse health ef...

In this study, following the procedure of the perceptive air quality test described in ISO 16000-28 and ISO 16000-30, we numerically analyzed the odorant transportation from the odorant generator to human breathing zone using acetone which is considered as a standard substance for pi-scale evaluation. For the evaluation of access to olfactory recep...

Fibrous-particle (asbestos) exposure induces lung cancer, mesothelioma, and fibrosis. Man-made vitreous fibers (MMVFs) share some similarities, and so their related health effects need to be determined. Computational fluid dynamics (CFD) was used to simulate the airflow patterns (Eulerian method) and to predict the particle behaviors (Lagrangian me...

The purpose of this study is to investigate the effect of supply air return from the HVAC system on indoor air quality. We discuss the structure of the formation mechanism in local pollutant concentration distributions using various indices on the ventilation efficiency of a local domain in 3 rooms with different layout of the exhaust outlet locati...

There have been serious hazardous liquid chemical leakage cases in factories, chemical plants, and laboratories owing to natural disasters or contingent human accidents. Regarding risk management, when high-risk liquid chemical substances are assumed to leak inside enclosed indoor spaces, reasonable prediction of transient and heterogeneous concent...

Net escape velocity (NEV) and net escape probability (NEP) are concepts that describe that scalar quantity discharged from a source in an indoor air environment is expressed by the unique velocity scales of the returning and escaping populations. Despite the conceptual description and applications of several numerical simulations, the definitions w...

The establishment of a healthy indoor environment requires the accurate evaluation of an individual’s exposure to pollutants. The concentration of indoor chemical pollutants is a representative indicator for such evaluation and is generally measured on-site. Moreover, material flow analysis (MFA), using macroscopic statistical data, is a reasonable...

A thorough understanding of the inhalation dynamics of infectious aerosols indoors and infection dynamics within the host by inhaled viruses such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) plays an important role in the assessment and control of infection risks indoors. Here, by combining computational fluid–particle dynamics (...

The breathing zone of an individual indoors is usually defined as a finite region steadily formed in front of a face. Assuming the steady formation of the breathing zone, we propose a procedure for quantitatively identifying a breathing zone formed in front of a human face in the transient condition. This assumption is reasonable considering that t...

Fume hoods are an indispensable instrument for experimental operations dealing with hazardous chemicals, wherein safety operations are strictly adherent to regulations. Within this context, few cases exist wherein the ventilation efficiency and pollutant capture efficiency inside fume hoods are precisely analyzed and quantitatively visualized. In t...

Several studies regarding indoor environmental quality assessments based on computational human models have been reported. Recently, various computer-simulated persons for computational fluid dynamics (CFD) simulations that reproduce a detailed human body geometry has been developed. However, clothing is usually treated with simplification as a res...

Fiber particles are generally defined as elongated particles with a length of more than 5 micron and a length/diameter ratio of greater than 3. Asbestos fibers, one of the representatives, have been proven to cause lung cancer, mesothelioma, and fibrosis. In recent years, because of their toxicity, asbestos fibers have been replaced by manmade vitr...

The recognition that the spread of COVID-19 is primarily through airborne transmission has brought renewed urgency to understand the spread of aerosols generated from patients. Viral-laden aerosols generated from oral coughs have been well studied; however, aerosols generated from nasal sneezing has been overlooked. This scenario arises from patien...

Ten healthy young adults slept one by one in a specially designed and constructed sleep capsule located in a climate chamber at two temperatures (24 and 28 °C) and two ventilation rates that ensured that the resulting CO2 concentrations were 800 and 1700 ppm. Subjectively rated sleep quality was reduced at 28 °C and reduced ventilation, while sleep...

We determined carbon dioxide (CO2) emission rates from sedentary subjects performing light work on tablets or smartphones in controlled chamber exposures. Five groups, each consisting of four people (four groups with two females and two males and one with three males and one female), stayed in a 22.5 m³ stainless steel chamber under different envir...

Currently, the airway reproduction process can be performed utilizing the medical images associated with a medical image post-processing software. It has been adopted that the airway structure has profound influences on the distribution of fluid flow. Therefore, this study investigated the effects of morphological simplification on airflow patterns...

Humans emit carbon dioxide (CO2) as a product of their metabolism. Its concentration in buildings is used as a marker of ventilation rate (VR) and degree of mixing of supply air, and indoor air quality (IAQ). The CO2 emission rate (CER) may be used to estimate the ventilation rate. Many studies have measured CERs from subjects who were awake but li...

Background: Brachycephalic obstructive airway syndrome (BOAS) in dogs indicates a particular set of upper airway abnormalities found in brachycephalic dogs (e.g., French bulldogs). Stenotic nares is one of the primary BOAS-related abnormalities restricting the functional breathing of affected dogs. For severe stenosis, rhinoplasty is required to in...

In factories where high-risk chemical pollutants are treated, it is essential to anticipate response measures in the event of chemical pollutant leakage to minimize adverse health effects on workers. When high-risk liquid chemical pollutants are assumed to be leaked inside enclosed spaces, it becomes crucial to predict the non-uniform concentration...