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With electronic (e)-liquids containing cannabis components easily available, many anecdotal examples of cannabis vaping using electronic cigarette devices have been reported. For electronic cigarette cannabis vaping, there are potential risks of secondary indoor air pollution from vapers. However, quantitative and accurate prediction of the inhalation and dermal exposure of a passive smoker in the same room is difficult to achieve due to the ethical constraints on subject experiments. The numerical method, i.e., in silico method, is a powerful tool to complement these experiments with real humans. In this study, we adopted a computer-simulated person that has been validated from multiple perspectives for prediction accuracy. We then conducted an in silico study to elucidate secondary indoor air pollution and passive smoking associated with cannabis vaping using an electronic cigarette device in an indoor environment. The aerosols exhaled by a cannabis vaper were confirmed to be a secondary emission source in an indoor environment; non-smokers were exposed to these aerosols via respiratory and dermal pathways. Tetrahydrocannabinol was used as a model chemical compound for the exposure study. Its uptake by the non-smoker through inhalation and dermal exposure under a worst-case scenario was estimated to be 5.9% and 2.6% of the exhaled quantity from an e-cigarette cannabis user, respectively.
Kazuki Kuga; Kazuhide Ito; Wenhao Chen; Ping Wang; Jeff Fowles; Kazukiyo Kumagai. Secondary indoor air pollution and passive smoking associated with cannabis smoking using electric cigarette device–demonstrative in silico study. PLOS Computational Biology 2021, 17, e1009004 .
AMA StyleKazuki Kuga, Kazuhide Ito, Wenhao Chen, Ping Wang, Jeff Fowles, Kazukiyo Kumagai. Secondary indoor air pollution and passive smoking associated with cannabis smoking using electric cigarette device–demonstrative in silico study. PLOS Computational Biology. 2021; 17 (5):e1009004.
Chicago/Turabian StyleKazuki Kuga; Kazuhide Ito; Wenhao Chen; Ping Wang; Jeff Fowles; Kazukiyo Kumagai. 2021. "Secondary indoor air pollution and passive smoking associated with cannabis smoking using electric cigarette device–demonstrative in silico study." PLOS Computational Biology 17, no. 5: e1009004.
Many people spend most of their time in an indoor environment. A positive relationship exists between indoor environmental quality and the health, wellbeing, and productivity of occupants in buildings. The indoor environment is affected by pollutants, such as gases and particles. Pollutants can be removed from the indoor environment in various ways. Air-cleaning devices are commonly marketed as benefiting the removal of air pollutants and, consequently, improving indoor air quality. Depending on the type of cleaning technology, air cleaners may generate undesired and toxic byproducts. Different air filtration technologies, such as electrostatic precipitators (ESPs) have been introduced to the market. The ESP has been used in buildings because it can remove particles while only causing low pressure drops. Moreover, ESPs can be either in-duct or standalone units. This review aims to provide an overview of ESP use, methods for testing this product, the performance of existing ESPs concerning removing pollutants and their byproducts, and the existing market for ESPs.
Alireza Afshari; Lars Ekberg; Luboš Forejt; Jinhan Mo; Siamak Rahimi; Jeffrey Siegel; Wenhao Chen; Pawel Wargocki; Sultan Zurami; Jianshun Zhang. Electrostatic Precipitators as an Indoor Air Cleaner—A Literature Review. Sustainability 2020, 12, 8774 .
AMA StyleAlireza Afshari, Lars Ekberg, Luboš Forejt, Jinhan Mo, Siamak Rahimi, Jeffrey Siegel, Wenhao Chen, Pawel Wargocki, Sultan Zurami, Jianshun Zhang. Electrostatic Precipitators as an Indoor Air Cleaner—A Literature Review. Sustainability. 2020; 12 (21):8774.
Chicago/Turabian StyleAlireza Afshari; Lars Ekberg; Luboš Forejt; Jinhan Mo; Siamak Rahimi; Jeffrey Siegel; Wenhao Chen; Pawel Wargocki; Sultan Zurami; Jianshun Zhang. 2020. "Electrostatic Precipitators as an Indoor Air Cleaner—A Literature Review." Sustainability 12, no. 21: 8774.
Kathleen R. Attfield; Wenhao Chen; Kristin J. Cummings; Peyton Jacob; Donal F. O’Shea; Jeff Wagner; Ping Wang; Jefferson Fowles. Potential of Ethenone (Ketene) to Contribute to Electronic Cigarette, or Vaping, Product Use–associated Lung Injury. American Journal of Respiratory and Critical Care Medicine 2020, 202, 1187 -1189.
AMA StyleKathleen R. Attfield, Wenhao Chen, Kristin J. Cummings, Peyton Jacob, Donal F. O’Shea, Jeff Wagner, Ping Wang, Jefferson Fowles. Potential of Ethenone (Ketene) to Contribute to Electronic Cigarette, or Vaping, Product Use–associated Lung Injury. American Journal of Respiratory and Critical Care Medicine. 2020; 202 (8):1187-1189.
Chicago/Turabian StyleKathleen R. Attfield; Wenhao Chen; Kristin J. Cummings; Peyton Jacob; Donal F. O’Shea; Jeff Wagner; Ping Wang; Jefferson Fowles. 2020. "Potential of Ethenone (Ketene) to Contribute to Electronic Cigarette, or Vaping, Product Use–associated Lung Injury." American Journal of Respiratory and Critical Care Medicine 202, no. 8: 1187-1189.
Emissions of formaldehyde from building materials and furniture can cause adverse health effects. Traditional models generally only consider emissions as a physical process that can be characterized by three key parameters: the initial emittable concentration, the diffusion coefficient and the partition coefficient. However, the physical-based model causes discrepancy in predicting long-term formaldehyde emissions for the cases where chemical reaction (i.e., hydrolysis) occurs over time. In this study, an improved mechanism-based model was developed by combining the chemical reaction process with a physical mass transfer process to more accurately predict the long-term emission behaviors. The chamber testing data of formaldehyde emissions from exposed edges and seams of a laminate flooring product made with composite wood core for about 1.5 year was used to validate the model. Results indicate that the mechanism-based model characterizes well the long-term formaldehyde emissions from the tested material. Predictions of different models further demonstrate the advantages of this improved model compared with the physical model or with empirical models. This study is the first attempt to check the feasibility of including the chemical reaction term in emission modeling and to quantitatively explore the importance of its contribution to long-term formaldehyde emissions, which includes most of the indoor emissions from materials and furniture.
Zhangcan He; Jianyin Xiong; Kazukiyo Kumagai; Wenhao Chen. An improved mechanism-based model for predicting the long-term formaldehyde emissions from composite wood products with exposed edges and seams. Environment International 2019, 132, 105086 .
AMA StyleZhangcan He, Jianyin Xiong, Kazukiyo Kumagai, Wenhao Chen. An improved mechanism-based model for predicting the long-term formaldehyde emissions from composite wood products with exposed edges and seams. Environment International. 2019; 132 ():105086.
Chicago/Turabian StyleZhangcan He; Jianyin Xiong; Kazukiyo Kumagai; Wenhao Chen. 2019. "An improved mechanism-based model for predicting the long-term formaldehyde emissions from composite wood products with exposed edges and seams." Environment International 132, no. : 105086.
Dampness and mold in buildings are linked to multiple adverse health effects. The principal factor allowing microbial growth in a material is the water activity (aw), the amount of metabolically available water. To assess the practicality of a portable “aw sensor” that estimates aw by measuring equilibrium relative humidity (ERH) at a surface, we measured the time required, starting at typical room RH, to reach a stable ERH reading on gypsum board at an elevated aw supportive of microbial growth. To estimate aw with commonly used moisture meters, we compared multiple meters (two types: pinless or 2-pin) to each other and to the portable aw sensor, for several gypsum board configurations, at multiple targeted ERH conditions. The aw sensor response was too slow for practical use. Across board configurations (i.e., single or double layers, unpainted or painted, and moisture-resistant), relationships between moisture meter readings and estimated aw differed, as expected, between adsorbing and desorbing conditions. Some pinless meters showed inadequate sensitivity to low moisture conditions. Unexpected irregularities in responses were seen, especially on painted board. We provide estimated ranges of moisture meter readings, for each meter and board configuration, corresponding with selected aw values potentially supportive of microbial growth. One or 2 m showed most promise for use in estimating critical aw values, although with substantial caveats. The irregularities observed may limit the potential for estimating aw from moisture meter readings in real world applications, even with prior collection of the data needed across different meters, conditions, and building materials.
Rachel I. Adams; Wenhao Chen; Kazukiyo Kumagai; Janet M. Macher; Mark J. Mendell. Relating measured moisture of gypsum board to estimated water activity using moisture meters. Building and Environment 2018, 147, 284 -298.
AMA StyleRachel I. Adams, Wenhao Chen, Kazukiyo Kumagai, Janet M. Macher, Mark J. Mendell. Relating measured moisture of gypsum board to estimated water activity using moisture meters. Building and Environment. 2018; 147 ():284-298.
Chicago/Turabian StyleRachel I. Adams; Wenhao Chen; Kazukiyo Kumagai; Janet M. Macher; Mark J. Mendell. 2018. "Relating measured moisture of gypsum board to estimated water activity using moisture meters." Building and Environment 147, no. : 284-298.
Concern about high formaldehyde emission from specific models of laminate flooring (LF) products has recently drawn wide public attention in the U.S. This raises questions about how to best test emissions of LF products and how to make appropriate model assumptions when conducting relevant lifetime exposure and risk assessments. This paper presents a preliminary study focused on these questions. Formaldehyde emissions were measured in 20-L environmental chambers for 6 months for two LF products made with low- and high-emitting composite wood core. Tests were conducted for specimens with and without exposed seams (“click-joints” at the sides and ends of each flooring plank) and perimeter cut edges. Results demonstrate that exposed seams and cut edges can contribute significantly to overall emissions, especially for the product with a high-emitting core, and this effect could last long after flooring installation. Testing with no exposed seams and perimeter cut edges might allow a finished flooring product with a high-emitting core and high emissions after installation to meet low-emitting labelling criteria inappropriately.
Wenhao Chen; Mark Mendell; Na Li; Kazukiyo Kumagai. Formaldehyde emissions from seams and cut edges of laminate flooring: Implications for emission testing protocols and exposure estimation. Building and Environment 2018, 143, 652 -660.
AMA StyleWenhao Chen, Mark Mendell, Na Li, Kazukiyo Kumagai. Formaldehyde emissions from seams and cut edges of laminate flooring: Implications for emission testing protocols and exposure estimation. Building and Environment. 2018; 143 ():652-660.
Chicago/Turabian StyleWenhao Chen; Mark Mendell; Na Li; Kazukiyo Kumagai. 2018. "Formaldehyde emissions from seams and cut edges of laminate flooring: Implications for emission testing protocols and exposure estimation." Building and Environment 143, no. : 652-660.
To determine the effect of applied power settings, coil wetness conditions, and e-liquid compositions on the coil heating temperature for e-cigarettes with a “top-coil” clearomizer, and to make associations of coil conditions with emission of toxic carbonyl compounds by combining results herein with the literature. The coil temperature of a second generation e-cigarette was measured at various applied power levels, coil conditions, and e-liquid compositions, including (1) measurements by thermocouple at three e-liquid fill levels (dry, wet-through-wick, and full-wet), three coil resistances (low, standard, and high), and four voltage settings (3–6 V) for multiple coils using propylene glycol (PG) as a test liquid; (2) measurements by thermocouple at additional degrees of coil wetness for a high resistance coil using PG; and (3) measurements by both thermocouple and infrared (IR) camera for high resistance coils using PG alone and a 1:1 (wt/wt) mixture of PG and glycerol (PG/GL). For single point thermocouple measurements with PG, coil temperatures ranged from 322 ‒ 1008°C, 145 ‒ 334°C, and 110 ‒ 185°C under dry, wet-through-wick, and full-wet conditions, respectively, for the total of 13 replaceable coil heads. For conditions measured with both a thermocouple and an IR camera, all thermocouple measurements were between the minimum and maximum across-coil IR camera measurements and equal to 74% ‒ 115% of the across-coil mean, depending on test conditions. The IR camera showed details of the non-uniform temperature distribution across heating coils. The large temperature variations under wet-through-wick conditions may explain the large variations in formaldehyde formation rate reported in the literature for such “top-coil” clearomizers. This study established a simple and straight-forward protocol to systematically measure e-cigarette coil heating temperature under dry, wet-through-wick, and full-wet conditions. In addition to applied power, the composition of e-liquid, and the devices’ ability to efficiently deliver e-liquid to the heating coil are important product design factors effecting coil operating temperature. Precautionary temperature checks on e-cigarettes under manufacturer-recommended normal use conditions may help to reduce the health risks from exposure to toxic carbonyl emissions associated with coil overheating.
Wenhao Chen; Ping Wang; Kazuhide Ito; Jeff Fowles; Dennis Shusterman; Peter A. Jaques; Kazukiyo Kumagai. Measurement of heating coil temperature for e-cigarettes with a “top-coil” clearomizer. PLOS ONE 2018, 13, e0195925 .
AMA StyleWenhao Chen, Ping Wang, Kazuhide Ito, Jeff Fowles, Dennis Shusterman, Peter A. Jaques, Kazukiyo Kumagai. Measurement of heating coil temperature for e-cigarettes with a “top-coil” clearomizer. PLOS ONE. 2018; 13 (4):e0195925.
Chicago/Turabian StyleWenhao Chen; Ping Wang; Kazuhide Ito; Jeff Fowles; Dennis Shusterman; Peter A. Jaques; Kazukiyo Kumagai. 2018. "Measurement of heating coil temperature for e-cigarettes with a “top-coil” clearomizer." PLOS ONE 13, no. 4: e0195925.
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.
Kazuki Kuga; Kazuhide Ito; Sung-Jun Yoo; Wenhao Chen; Ping Wang; Jiawen Liao; Jeff Fowles; Dennis Shusterman; Kazukiyo Kumagai. First- and second-hand smoke dispersion analysis from e-cigarettes using a computer-simulated person with a respiratory tract model. Indoor and Built Environment 2017, 27, 898 -916.
AMA StyleKazuki Kuga, Kazuhide Ito, Sung-Jun Yoo, Wenhao Chen, Ping Wang, Jiawen Liao, Jeff Fowles, Dennis Shusterman, Kazukiyo Kumagai. First- and second-hand smoke dispersion analysis from e-cigarettes using a computer-simulated person with a respiratory tract model. Indoor and Built Environment. 2017; 27 (7):898-916.
Chicago/Turabian StyleKazuki Kuga; Kazuhide Ito; Sung-Jun Yoo; Wenhao Chen; Ping Wang; Jiawen Liao; Jeff Fowles; Dennis Shusterman; Kazukiyo Kumagai. 2017. "First- and second-hand smoke dispersion analysis from e-cigarettes using a computer-simulated person with a respiratory tract model." Indoor and Built Environment 27, no. 7: 898-916.
Wenhao Chen; Andrew K. Persily; Alfred T. Hodgson; Francis J. Offermann; Dustin G Poppendieck; Kazukiyo Kumagai. Area-specific airflow rates for evaluating the impacts of VOC emissions in U.S. single-family homes. Building and Environment 2014, 71, 204 -211.
AMA StyleWenhao Chen, Andrew K. Persily, Alfred T. Hodgson, Francis J. Offermann, Dustin G Poppendieck, Kazukiyo Kumagai. Area-specific airflow rates for evaluating the impacts of VOC emissions in U.S. single-family homes. Building and Environment. 2014; 71 ():204-211.
Chicago/Turabian StyleWenhao Chen; Andrew K. Persily; Alfred T. Hodgson; Francis J. Offermann; Dustin G Poppendieck; Kazukiyo Kumagai. 2014. "Area-specific airflow rates for evaluating the impacts of VOC emissions in U.S. single-family homes." Building and Environment 71, no. : 204-211.
Formaldehyde emissions from fiberglass and polyester filters used in building heating, ventilation, and air conditioning (HVAC) systems were measured in bench-scale tests using 10 and 17 cm2 coupons over 24 to 720 h periods. Experiments were performed at room temperature and four different relative humidity settings (20, 50, 65, and 80% RH). Two different air flow velocities across the filters were explored: 0.013 and 0.5 m/s. Fiberglass filters emitted between 20 and 1000 times more formaldehyde than polyester filters under similar RH and airflow conditions. Emissions increased markedly with increasing humidity, up to 10 mg/h-m2 at 80% RH. Formaldehyde emissions from fiberglass filters coated with tackifiers (impaction oils) were lower than those from uncoated fiberglass media, suggesting that hydrolysis of other polymeric constituents of the filter matrix, such as adhesives or binders was likely the main formaldehyde source. These laboratory results were further validated by performing a small field study in an unoccupied office. At 80% RH, indoor formaldehyde concentrations increased by 48–64%, from 9–12 μg/m3 to 12–20 μg/m3, when synthetic filters were replaced with fiberglass filtration media in the HVAC units. Better understanding of the reaction mechanisms and assessing their overall contributions to indoor formaldehyde levels will allow for efficient control of this pollution source.
Meera Sidheswaran; Wenhao Chen; Agatha Chang; Robert Miller; Sebastian Cohn; Douglas Sullivan; William J. Fisk; Kazukiyo Kumagai; Hugo Destaillats. Formaldehyde Emissions from Ventilation Filters Under Different Relative Humidity Conditions. Environmental Science & Technology 2013, 47, 5336 -5343.
AMA StyleMeera Sidheswaran, Wenhao Chen, Agatha Chang, Robert Miller, Sebastian Cohn, Douglas Sullivan, William J. Fisk, Kazukiyo Kumagai, Hugo Destaillats. Formaldehyde Emissions from Ventilation Filters Under Different Relative Humidity Conditions. Environmental Science & Technology. 2013; 47 (10):5336-5343.
Chicago/Turabian StyleMeera Sidheswaran; Wenhao Chen; Agatha Chang; Robert Miller; Sebastian Cohn; Douglas Sullivan; William J. Fisk; Kazukiyo Kumagai; Hugo Destaillats. 2013. "Formaldehyde Emissions from Ventilation Filters Under Different Relative Humidity Conditions." Environmental Science & Technology 47, no. 10: 5336-5343.