Kazuhide Ito

A Device-Independent Evaluation of Carbonyl Emissions from Heated Electronic Cigarette Solvents

Objectives To investigate how the two main electronic (e-) cigarette solvents—propylene glycol (PG) and glycerol (GL)—modulate the formation of toxic volatile carbonyl compounds under precisely controlled temperatures in the absence of nicotine and flavor additives. Methods PG, GL, PG:GL = 1:1 (wt/wt) mixture, and two commercial e-cigarette liquids were vaporized in a stainless steel, tubular reactor in flowing air ranging up to 318°C to simulate e-cigarette vaping. Aerosols were collected and analyzed to quantify the amount of volatile carbonyls produced with each of the five e-liquids. Results Significant amounts of formaldehyde and acetaldehyde were detected at reactor temperatures ≥215°C for both PG and GL. Acrolein was observed only in e-liquids containing GL when reactor temperatures exceeded 270°C. At 318°C, 2.03±0.80 μg of formaldehyde, 2.35±0.87 μg of acetaldehyde, and a trace amount of acetone were generated per milligram of PG; at the same temperature, 21.1±3.80 μg of formaldehyde, 2.40±0.99 μg of acetaldehyde, and 0.80±0.50 μg of acrolein were detected per milligram of GL. Conclusions We developed a device-independent test method to investigate carbonyl emissions from different e-cigarette liquids under precisely controlled temperatures. PG and GL were identified to be the main sources of toxic carbonyl compounds from e-cigarette use. GL produced much more formaldehyde than PG. Besides formaldehyde and acetaldehyde, measurable amounts of acrolein were also detected at ≥270°C but only when GL was present in the e-liquid. At 215°C, the estimated daily exposure to formaldehyde from e-cigarettes, exceeded United States Environmental Protection Agency (USEPA) and California Office of Environmental Health Hazard Assessment (OEHHA) acceptable limits, which emphasized the need to further examine the potential cancer and non-cancer health risks associated with e-cigarette use.

Integrated building energy-computational fluid dynamics simulation for estimating the energy-saving effect of energy recovery ventilator with CO2 demand-controlled ventilation system in office space

As ventilation is one of the critical heat loads in an office space, the ventilation rate might be optimized to develop sustainable, low-energy buildings and a healthy indoor environment. To create comprehensive and optimized indoor environmental designs, a building energy simulation (BES)-computational fluid dynamics (CFD)-integrated simulation is used to provide accurate and informative prediction of the thermal and air-quality performance in buildings, especially in the design stage. With the aim of developing an optimization procedure for the ventilation rate, this paper presents simulations that integrates BES and CFD with CO2 demand-controlled ventilation (DCV) system, and applies them to a typical office space in Japan to optimize the ventilation rate through an energy recovery ventilator (ERV). The transient system control strategy is applied to two different airflow conditions in an office: a traditional ceiling supply system and an under-floor air distribution system. Compared with the fixed outdoor air intake rate, which is referred to as constant air volume ventilation, optimized ventilation systems associated with a CO2 DCV produces energy savings of 11.6% and 24.1%, respectively. The difference in the energy saving effects of the two ventilation systems is caused by the difference in the ventilation efficiency in the occupied zone. The ventilation rate and ventilation efficiency have a significant impact on the energy penalty of an ERV. Therefore, optimizing the ventilation rate according to a CO2 DCV system with an appropriate airflow pattern could contribute to both creating and maintaining a healthy, comfortable environment, in addition to saving energy.

Toward the development of an in silico human model for indoor environmental design.

In modern society where people spend more than 90% of their time in indoor spaces, the indoor air quality (IAQ) created by buildings has the potential of greatly influencing quality of life. Because the time spent by workers/residents in indoor spaces has increased over time, the importance of IAQ issues in terms of public health is also increasing. Additionally, the quality of the indoor thermal environment also has great impact on human comfort and performance; hence, the development of a comprehensive prediction method integrating indoor air quality/thermal environment assessment and human physiological responses, is crucial for creating a healthy, comfortable, and productive indoor environment. Accordingly, the overarching objective of this study was to develop a comprehensive and universal computer simulated person (i.e., in silico human model), integrating computational fluid dynamics (CFD), to be used in indoor environmental design and quality assessment. This paper presents and discusses the development of this computer-simulated person and its application to indoor environmental design.

Prediction of convective heat transfer coefficients for the upper respiratory tracts of rat, dog, monkey, and humans

In vivo studies involving mammal surrogate models for toxicology studies have restrictions related to animal protection and ethics. Computer models, i.e., in silico models, have great potential to contribute towards essential understanding of heat and mass transfer phenomena in respiratory tracts in place of in vivo and in vitro studies. Here, we developed numerical upper airway models of a rat, a dog, a monkey, and two humans by using computed tomography data and then applied computational fluid dynamics analysis. Convective heat transfer coefficients were precisely analysed as a function of breathing airflow rate. Based on the computational fluid dynamics simulation results, the correlations between Nusselt (Nu) number and the product of the Reynolds (Re) and Prandtl (Pr) numbers were summarized. The heat transfer efficiency (order of hc and correlation of Nu and RePr) in the upper airway of the dog seems to match those of the human models. On the other hand, the results for the rat and monkey showed clear differences compared with those of human models. The identified fundamental qualities of convective heat transfer phenomena in airways for rats, dogs, monkeys, and humans, have enabled discussions about quantitative differences of heat and mass transfer efficiency between different animals/species.

Cost-effectiveness Analysis of Improved Indoor Temperature and Ventilation Conditions in School Buildings

Abstract This paper reports simulation results of the potential fiscal benefits from investment in improved indoor environmental quality in school buildings. Improving indoor environmental quality can result in substantial benefits due to improved academic performance, but it can also result in increased energy and heating, ventilation, and air-conditioning (HVAC) maintenance costs. The aim of this paper is to demonstrate the cost-effectiveness of additional indoor environmental control by HVAC and the associated benefit of improved academic performance in a limited-scale school building model. This study estimated the impact of an increased ventilation rate and an alteration of target room air temperature on energy costs and on academic performance. The annual benefit due to improved thermal conditions (room air temperature) was up to five times higher than the benefit of increased ventilation rate per person. Lifecycle cost analysis showed that the benefit (improved academic performance) resulting from better indoor temperature conditions was up to 20–40% against the increased costs (increased HVAC total cost) of a few thousand JPY per year [JPY/year/person].

Experimental and CFD Analyses Examining Ozone Distribution in Model Rooms with Laminar and Turbulent Flow Fields

Abstract The principle goal of this work was to better understand ozone distribution within rooms. Towards this end, the paper has two parts. The first describes the development of a flat plate test chamber (FPT chamber) that can be used to obtain mass accommodation coefficients (γ) for ozone that deposits on the surface of different materials. The second consists of model room experiments coupled with Computational Fluid Dynamics (CFD) analysis of the experimental scenarios to obtain ozone distribution in turbulent flow fields.

First- and second-hand smoke dispersion analysis from e-cigarettes using a computer-simulated person with a respiratory tract model

The purpose of this study was to investigate, in the human respiratory tract, the flow patterns and adsorption flux (deposition flux) distributions of volatile organic compounds (VOCs) generated by the use of electronic cigarettes (e-cigarettes) through the application of a three-dimensional computational fluid dynamics (CFD) analysis. Two types of human respiratory tract models, which give detailed respiratory tract geometries were reproduced in this study using computed tomography data, for the CFD analysis of inhalation exposure. Complicated flow patterns, nonuniform distributions of VOC concentrations, and heterogeneous adsorption flux distributions were determined within the human respiratory tract models, and individual specificity was confirmed. The CFD simulation results of adsorption flux distributions on the epithelium tissue surfaces of airways denoted the probability distributions of inhalation exposure in respiratory tracts, and high adsorption flux sites representing ‘hot spots’ were delineated for tissue doses of VOCs generated from smoking e-cigarettes. Furthermore, dispersion and diffusion of VOCs in an indoor environment due to exhalation of the vapour phase of e-cigarette emissions were analysed by using a computer-simulated person with a numerical respiratory tract model through an integrated and contiguous analysis of inhalation and exhalation modes during e-cigarette smoking.

Numerical prediction of tissue dosimetry in respiratory tract using computer simulated person integrated with physiologically based pharmacokinetic–computational fluid dynamics hybrid analysis

Indoor environmental quality, e.g. air quality and thermal environments, has a potential impact on residents in indoors. Development of a computer simulated person (CSP) for indoor computational fluid dynamics (CFD) simulation can contribute to the improvement of design and prediction method regarding the interaction between indoor air/thermal environmental factors and human responses. In this study, a CSP integrated with a virtual airway was developed and used to estimate inhalation exposure in an indoor environment. The virtual airway is a numerical respiratory tract model for CFD simulation that reproduces detailed geometry from the nasal/oral cavity to the bronchial tubes by way of the trachea. Physiologically based pharmacokinetic (PBPK)-CFD hybrid analysis is also integrated into the CSP. Through the coupled simulation of PBPK-CFD-CSP analysis, inhalation exposure under steady state conditions where formaldehyde was emitted from floor material was analysed and respiratory tissue doses and their distributions of inhaled contaminants are discussed quantitatively.

Integrated Numerical Simulation with Fungal Spore Deposition and Subsequent Fungal Growth on Bathroom Wall Surface

Fungal contaminations in indoor environment are recognized as one of the serious problem in terms of health and aesthetic impact. Large numbers of studies have shown an association between the health risk of fungal contamination. Residence in houses and fungal growth is well known to be strongly related to various indoor environmental parameters and hence the development of a comprehensive prediction method for fungal contamination is needed for healthy indoor environmental design. This research focused on the fungal growth problems in residential bathroom where the temperature and humidity can become relatively high. This paper reports the procedure and results of numerical simulations of fungal contamination. The simulation was incorporated with flow field, temperature/humidity distribution, which was used to predict fungal spore dispersion/deposition in bathroom space and subsequent non-uniform distribution of fungal growth on wall surfaces. Fungal spores transportation was analyzed by Lagrangean approach. For fungal growth phenomenon, the reaction-diffusion model that reproduces morphological colony formation of fungi was adopted. By continuously executing these numerical analyses, fungal spore deposition and subsequent fungal growth on wall surfaces was demonstrated for two targeted representative ventilation rate in normal bathroom condition.

Multi-stage downscaling procedure to analyse the impact of exposure concentration in a factory on a specific worker through computational fluid dynamics modelling:

Indoor air quality plays a significant role in human health, especially for those who spend the majority of their time indoors, as is the case of workers in the industrial field. The control of contaminants inside the occupational indoor environment becomes critically important for promoting health. In terms of Health Impact Assessment, indoor air quality inside a factory becomes an essential factor of industrial hygiene. Here, computational fluid dynamics-based indoor environmental design was applied to potentially evaluate the environmental quality in a factory and to improve industrial hygiene. In particular, this study proposes an integrated simulation procedure to predict the inhalation exposure concentration of a hazardous chemical compound (here, cyclohexanone) by using a multi-stage, one-way nesting method. This procedure connects a factory building space, a micro-climate around the human body, and a respiratory tract in the human body. This research provides quantitative and qualitative detailed information of contaminant dosing in workers. The exact inhalation dose of contaminants in the human airways can be estimated based on factory-environment conditions through this procedure. Subsequently, the average contaminant concentration in the work place and inside the human body can be calculated.