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Kulmala I, Taipale A, Sanmark E, Lastovets N, Sormunen P, Nuorti P, Saari S, Luoto A, Säämänen A. Estimated relative potential for airborne SARS-CoV-2 transmission in a day care centre. Heliyon 2024; 10:e30724. [PMID: 38756615 PMCID: PMC11096945 DOI: 10.1016/j.heliyon.2024.e30724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Revised: 05/01/2024] [Accepted: 05/02/2024] [Indexed: 05/18/2024] Open
Abstract
We estimated the hourly probability of airborne severe acute respiratory coronavirus 2 (SARS-CoV-2) transmission and further the estimated number of persons at transmission risk in a day care centre by calculating the inhaled dose for airborne pathogens based on their concentration, exposure time and activity. Information about the occupancy and activity of the rooms was collected from day care centre personnel and building characteristics were obtained from the design values. The generation rate of pathogens was calculated as a product of viral load of the respiratory fluids and the emission of the exhaled airborne particles, considering the prevalence of the disease and the activity of the individuals. A well-mixed model was used in the estimation of the concentration of pathogens in the air. The Wells-Riley model was used for infection probability. The approach presented in this study was utilised in the identification of hot spots and critical events in the day care centre. Large variation in the infection probabilities and estimated number of persons at transmission risk was observed when modelling a normal day at the centre. The estimated hourly infection probabilities between the worst hour in the worst room and the best hour in the best room varied in the ratio of 100:1. Similarly, the number of persons at transmission risk between the worst and best cases varied in the ratio 1000:1. Although there are uncertainties in the input values affecting the absolute risk estimates the model proved to be useful in ranking and identifying the hot spots and events in the building and implementing effective control measures.
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Affiliation(s)
- Ilpo Kulmala
- VTT Smart Energy and Built Environment, Visiokatu 4, PO Box 1300, FI-33101, Tampere, Finland
| | - Aimo Taipale
- VTT Smart Energy and Built Environment, Visiokatu 4, PO Box 1300, FI-33101, Tampere, Finland
| | - Enni Sanmark
- Helsinki University Hospital, Department of Otorhinolaryngology and Phoniatrics – Head and Neck Surgery, Helsinki, Finland
- University of Helsinki, Helsinki, Finland
| | - Natalia Lastovets
- Tampere University, Faculty of Built Environment, Civil Engineering Unit, Korkeakoulunkatu 5D, FI-33720, Tampere, Finland
| | - Piia Sormunen
- Tampere University, Faculty of Built Environment, Civil Engineering Unit, Korkeakoulunkatu 5D, FI-33720, Tampere, Finland
| | - Pekka Nuorti
- Tampere University, Faculty of Social Sciences, Health Sciences Unit, Arvo Ylpön Katu 34, 33520, Tampere, Finland
| | - Sampo Saari
- Tampere University of Applied Sciences, Kuntokatu 3, 33520, Tampere, Finland
| | - Anni Luoto
- Granlund Oy, Malminkaari 21, 00700, Helsinki, Finland
| | - Arto Säämänen
- VTT Smart Energy and Built Environment, Visiokatu 4, PO Box 1300, FI-33101, Tampere, Finland
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Goray M, Taylor D, Bibbo E, Fantinato C, Fonneløp AE, Gill P, van Oorschot RAH. Emerging use of air eDNA and its application to forensic investigations - A review. Electrophoresis 2024; 45:916-932. [PMID: 38419135 DOI: 10.1002/elps.202300228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Revised: 12/17/2023] [Accepted: 02/19/2024] [Indexed: 03/02/2024]
Abstract
Biological material is routinely collected at crime scenes and from exhibits and is a key type of evidence during criminal investigations. Improvements in DNA technologies allow collection and profiling of trace samples, comprised of few cells, significantly expanding the types of exhibits targeted for DNA analysis to include touched surfaces. However, success rates from trace and touch DNA samples tend to be poorer compared to other biological materials such as blood. Simultaneously, there have been recent advances in the utility of environmental DNA collection (eDNA) in identification and tracking of different biological organisms and species from bacteria to naked mole rats in different environments, including, soil, ice, snow, air and aquatic. This paper examines the emerging methods and research into eDNA collection, with a special emphasis on the potential forensic applications of human DNA collection from air including challenges and further studies required to progress implementation.
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Affiliation(s)
- Mariya Goray
- College of Science and Engineering, Flinders University, Adelaide, South Australia, Australia
| | - Duncan Taylor
- College of Science and Engineering, Flinders University, Adelaide, South Australia, Australia
- Forensic Science SA, Adelaide, South Australia, Australia
| | - Emily Bibbo
- College of Science and Engineering, Flinders University, Adelaide, South Australia, Australia
| | - Chiara Fantinato
- Forensic Genetics Research Group, Department of Forensic Sciences, Oslo University Hospital, Oslo, Norway
- Department of Forensic Medicine, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Ane Elida Fonneløp
- Forensic Genetics Research Group, Department of Forensic Sciences, Oslo University Hospital, Oslo, Norway
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Oslo, Norway
| | - Peter Gill
- Forensic Genetics Research Group, Department of Forensic Sciences, Oslo University Hospital, Oslo, Norway
- Department of Forensic Medicine, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Roland A H van Oorschot
- Victoria Police Forensic Services Department, Office of Chief Forensic Scientist, Macleod, Victoria, Australia
- School of Agriculture, Biomedicine and Environment, La Trobe University, Bundoora, Victoria, Australia
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Wolkoff P. Indoor air humidity revisited: Impact on acute symptoms, work productivity, and risk of influenza and COVID-19 infection. Int J Hyg Environ Health 2024; 256:114313. [PMID: 38154254 DOI: 10.1016/j.ijheh.2023.114313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2023] [Revised: 10/30/2023] [Accepted: 12/18/2023] [Indexed: 12/30/2023]
Abstract
Recent epidemiological and experimental findings reconfirm that low indoor air humidity (dry air) increases the prevalence of acute eye and airway symptoms in offices, result in lower mucociliary clearance in the airways, less efficient immune defense, and deteriorate the work productivity. New epidemiological and experimental research also support that the environmental conditions for the risk of infection of influenza and COVID-19 virus is lowest in the Goldilocks zone of 40-60% relative humidity (RH) by decrease of the airways' susceptibility, which can be elevated by particle exposure. Furthermore, low RH increases the generation of infectious virus laden aerosols exhaled from infected people. In general, elevation of the indoor air humidity from dry air increases the health of the airways concomitantly with lower viability of infectious virus. Thus, the negative effects of ventilation with dry outdoor air (low absolute air humidity) should be assessed according to 1) weakened health and functionality of the airways, 2) increased viability and possible increased transmissibility of infectious virus, and 3) evaporation of virus containing droplets to dry out to droplet nuclei (also possible at high room temperature), which increases their floating time in the indoor air. The removal of acid-containing ambient aerosols from the indoor air by filtration increases pH, viability of infectious viruses, and the risk of infection, which synergistically may further increase by particle exposure. Thus, the dilution of indoor air pollutants and virus aerosols by dry outdoor air ventilation should be assessed and compared with the beneficial health effects by control of the center zone of 40-60% RH, an essential factor for optimal functionality of the airways, and with the additional positive impact on acute symptoms, work productivity, and reduced risk of infection.
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Affiliation(s)
- Peder Wolkoff
- National Research Centre for the Working Environment, Denmark.
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Berlanga FA, Gomez P, Esteban A, Liu L, Nielsen PV. Three dimensional analysis of the exhalation flow in the proximity of the mouth. Heliyon 2024; 10:e26283. [PMID: 38434078 PMCID: PMC10906307 DOI: 10.1016/j.heliyon.2024.e26283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 02/02/2024] [Accepted: 02/09/2024] [Indexed: 03/05/2024] Open
Abstract
The human exhalation flow is characterized in this work from the three-dimensional velocimetry results obtained by using the stereo particle image velocimetry (SPIV) measurement technique on the flow emitted from a realistic airway model. For this purpose, the transient exhalation flow through the mouth of a person performing two different breaths corresponding to two metabolic rates, standing relaxed (SR) and walking active (WA), is emulated and studied. To reproduce the flow realistically, a detailed three-dimensional model obtained from computed tomography measurements on real subjects is used. To cope with the variability of the experimental data, a subsequent analysis of the results is performed using the TR-PIV (time resolved particle image velocimetry) technique. Exhalation produces a transient jet that becomes a puff when flow emission ends. Three-dimensional vector fields of the jet velocity are obtained in five equally spaced transverse planes up to a distance of Image 1 from the mouth at equally spaced time instants Image 2 which will be referred to as phases (φ), from the beginning to the end of exhalation. The time evolution during exhalation of the jet area of influence, the velocity field and the jet air entrainment have been characterized for each of the jet cross sections. The importance of the use of realistic airway models for the study of this type of flow and the influence of the metabolic rate on its development are also analyzed. The results obtained contribute to the characterization of the human exhalation as a pathway of the transmission of pathogens such as SARS-CoV-2 virus.
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Affiliation(s)
- F A Berlanga
- Dept. de Mecánica, ETSII, Universidad Nacional de Educación a Distancia (UNED), E-28040, Madrid, Spain
| | - P Gomez
- Dept. de Mecánica, ETSII, Universidad Nacional de Educación a Distancia (UNED), E-28040, Madrid, Spain
| | - A Esteban
- Dept. de Mecánica, ETSII, Universidad Nacional de Educación a Distancia (UNED), E-28040, Madrid, Spain
| | - L Liu
- Dept. of Building Science and Technology, School of Architecture, Tsinghua University, Haidian District, Beijing, China
| | - P V Nielsen
- Dept. of the Built Environment, Aalborg Universitet, Thomas Manns Vej 23 9220 Aalborg Øst, Denmark
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Schijven JF, van Veen T, Delmaar C, Kos J, Vermeulen L, Roosien R, Verhoeven F, Schipper M, Peerlings B, Duizer E, Derei J, Lammen W, Bartels O, van der Ven H, Maas R, de Roda Husman AM. Quantitative Microbial Risk Assessment of Contracting COVID-19 Derived from Measured and Simulated Aerosol Particle Transmission in Aircraft Cabins. ENVIRONMENTAL HEALTH PERSPECTIVES 2023; 131:87011. [PMID: 37589660 PMCID: PMC10434022 DOI: 10.1289/ehp11495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 07/13/2023] [Accepted: 07/13/2023] [Indexed: 08/18/2023]
Abstract
BACKGROUND SARS-CoV-2 can be effectively transmitted between individuals located in close proximity to each other for extended durations. Aircraft provide such conditions. Although high attack rates during flights were reported, little was known about the risk levels of aerosol transmission of SARS-CoV-2 in aircraft cabins. OBJECTIVES The major objective was to estimate the risk of contracting COVID-19 from transmission of aerosol particles in aircraft cabins. METHODS In two single-aisle and one twin-aisle aircraft, dispersion of generated aerosol particles over a seven-row economy class cabin section was measured under cruise and taxi conditions and simulated with a computational fluid dynamic model under cruise conditions. Using the aerosol particle dispersion data, a quantitative microbial risk assessment was conducted for scenarios with an asymptomatic infectious person expelling aerosol particles by breathing and speaking. Effects of flight conditions were evaluated using generalized additive mixed models. RESULTS Aerosol particle concentration decreased with increasing distance from the infectious person, and this decrease varied with direction. On a typical flight with an average shedder, estimated mean risk of contracting COVID-19 ranged from 1.3 × 10 - 3 to 9.0 × 10 - 2 . Risk increased to 7.7 × 10 - 2 with a super shedder (< 3 % of cases) on a long flight. Risks increased with increasing flight duration: 2-23 cruise flights of typical duration and 2-10 flights of longer duration resulted in at least 1 case of COVID-19 due to onboard aerosol transmission by one average shedder, and in the case of one super shedder, at least 1 case in 1-3 flights of typical duration cruise and 1 flight of longer duration. DISCUSSION Our findings indicate that the risk of contracting COVID-19 by aerosol transmission in an aircraft cabin is low, but it will not be zero. Testing before boarding may help reduce the chance of a (super)shedder boarding an aircraft and mask use further reduces aerosol transmission in the aircraft cabin. https://doi.org/10.1289/EHP11495.
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Affiliation(s)
- Jack F. Schijven
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, the Netherlands
- Department of Earth Sciences, Utrecht University, Utrecht, the Netherlands
| | - Theo van Veen
- Royal Netherlands Aerospace Centre, Amsterdam, the Netherlands
| | - Christiaan Delmaar
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, the Netherlands
| | - Johan Kos
- Royal Netherlands Aerospace Centre, Amsterdam, the Netherlands
| | - Lucie Vermeulen
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, the Netherlands
| | - Rui Roosien
- Royal Netherlands Aerospace Centre, Amsterdam, the Netherlands
| | | | - Maarten Schipper
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, the Netherlands
| | - Bram Peerlings
- Royal Netherlands Aerospace Centre, Amsterdam, the Netherlands
| | - Erwin Duizer
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, the Netherlands
| | - Jonathan Derei
- Royal Netherlands Aerospace Centre, Amsterdam, the Netherlands
| | - Wim Lammen
- Royal Netherlands Aerospace Centre, Amsterdam, the Netherlands
| | - Onno Bartels
- Royal Netherlands Aerospace Centre, Amsterdam, the Netherlands
| | | | - Robert Maas
- Royal Netherlands Aerospace Centre, Amsterdam, the Netherlands
| | - Ana Maria de Roda Husman
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, the Netherlands
- Institute for Risk Assessment Sciences, Utrecht University, Utrecht, the Netherlands
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Martínez-Espinosa E, Carvajal-Mariscal I. Virus-laden droplet nuclei in vortical structures associated with recirculation zones in indoor environments: A possible airborne transmission of SARS-CoV-2. ENVIRONMENTAL ADVANCES 2023; 12:100376. [PMID: 37193349 PMCID: PMC10163794 DOI: 10.1016/j.envadv.2023.100376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Accepted: 05/03/2023] [Indexed: 05/18/2023]
Abstract
Droplet nuclei dispersion patterns in indoor environments are reviewed from a physics view to explore the possibility of airborne transmission of SARS-CoV-2. This review analyzes works on particle dispersion patterns and their concentration in vortical structures in different indoor environments. Numerical simulations and experiments reveal the formation of the buildings' recirculation zones and vortex flow regions by flow separation, airflow interaction around objects, internal dispersion of airflow, or thermal plume. These vortical structures showed high particle concentration because particles are trapped for long periods. Then a hypothesis is proposed to explain why some medical studies detect the presence of SARS-CoV-2 and others do not detect the virus. The hypothesis proposes that airborne transmission is possible if virus-laden droplet nuclei are trapped in vortical structures associated with recirculation zones. This hypothesis is reinforced by a numerical study in a restaurant that presented possible evidence of airborne transmission by a large recirculating air zone. Furthermore, a medical study in a hospital is discussed from a physical view for identifying the formation of recirculation zones and their relation with positive tests for viruses. The observations show air sampling site located in this vortical structure is positive for the SARS-CoV-2 RNA. Therefore, the formation of vortical structures associated with recirculation zones should be avoided to minimize the possibility of airborne transmission. This work tries to understand the complex phenomenon of airborne transmission as a way in the prevention of transmission of infectious diseases.
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Affiliation(s)
- E Martínez-Espinosa
- Industrial and Environmental Processes Department, Instituto de Ingeniería, UNAM, Ciudad Universitaria, Mexico City 04510, México
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Chang L, Chong WT, Yau YH, Cui T, Wang XR, Pei F, Liu YQ, Pan S. An investigation of the PM 2.5 concentrations and cumulative inhaled dose during subway commutes in Changchun, China. INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCE AND TECHNOLOGY : IJEST 2023:1-14. [PMID: 37360559 PMCID: PMC10208554 DOI: 10.1007/s13762-023-04994-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 04/13/2023] [Accepted: 05/08/2023] [Indexed: 06/28/2023]
Abstract
Air quality in subway systems is crucial as it affects the health of passengers and staff. Although most tests of PM2.5 concentrations in subway stations have taken place in public areas, PM2.5 is less understood in workplaces. Few studies have estimated the cumulative inhaled dose of passengers based on real-time changes in PM2.5 concentrations as they commute. To clarify the above issues, this study first measured PM2.5 concentrations in four subway stations in Changchun, China, where measuring points included five workrooms. Then, passengers' exposure to PM2.5 during the whole subway commute (20-30 min) was measured and segmented inhalation was calculated. The results showed that PM2.5 concentration in public places ranged from 50 to 180 μg/m3, and was strongly correlated with outdoors. While the PM2.5 average concentration in workplaces was 60 µg/m3, and it was less affected by outdoor PM2.5 concentration. Passenger's cumulative inhalations in single commuting were about 42 μg and 100 μg when the outdoor PM2.5 concentrations were 20-30 μg/m3 and 120-180 μg/m3, respectively. The PM2.5 inhalation in carriages accounted for the largest proportion of the entire commuting, about 25-40%, because of the longer exposure time and higher PM2.5 concentrations. It is recommended to improve the tightness of the carriage and filter the fresh air to improve the air quality inside. The average daily PM2.5 inhaled by staff was 513.53 μg, which was 5-12 times higher than that of passengers. Installing air purification devices in workplaces and reminding staff to take personal protection can positively protect their health.
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Affiliation(s)
- L. Chang
- Department of Mechanical Engineering, Faculty of Engineering, Universiti Malaya, 50603 Kuala Lumpur, Malaysia
| | - W. T. Chong
- Department of Mechanical Engineering, Faculty of Engineering, Universiti Malaya, 50603 Kuala Lumpur, Malaysia
- Centre for Energy Sciences, Universiti Malaya, 50603 Kuala Lumpur, Malaysia
| | - Y. H. Yau
- Department of Mechanical Engineering, Faculty of Engineering, Universiti Malaya, 50603 Kuala Lumpur, Malaysia
- UM-JAF Laboratory, Department of Mechanical Engineering, Faculty of Engineering, Universiti Malaya, 50603 Kuala Lumpur, Malaysia
| | - T. Cui
- Department of Building Environment and Energy Engineering, School of Civil Engineering, Chang’an University, Xi’an, 710061 China
| | - X. R. Wang
- Mechanical Engineering College, Tianjin University of Commerce, Tianjin, 300134 China
| | - F. Pei
- Department of Mechanical Engineering, Faculty of Engineering, Universiti Malaya, 50603 Kuala Lumpur, Malaysia
| | - Y. Q. Liu
- Department of Mechanical Engineering, Faculty of Engineering, Universiti Malaya, 50603 Kuala Lumpur, Malaysia
| | - S. Pan
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, 100124 China
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Butler MJ, Sloof D, Peters C, Conway Morris A, Gouliouris T, Thaxter R, Keevil VL, Beggs CB. Impact of supplementary air filtration on aerosols and particulate matter in a UK hospital ward: a case study. J Hosp Infect 2023; 135:81-89. [PMID: 36842537 PMCID: PMC9957342 DOI: 10.1016/j.jhin.2023.02.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 02/15/2023] [Accepted: 02/16/2023] [Indexed: 02/28/2023]
Abstract
BACKGROUND Aerosol spread of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a major problem in hospitals, leading to an increase in supplementary high-efficiency particulate air filtration aimed at reducing nosocomial transmission. This article reports a natural experiment that occurred when an air cleaning unit (ACU) on a medicine for older people ward was switched off accidentally while being commissioned. AIM To assess aerosol transport within the ward and determine whether the ACU reduced airborne particulate matter (PM) levels. METHODS An ACU was placed in a ward comprising two six-bedded bays plus three single-bed isolation rooms which had previously experienced several outbreaks of coronavirus disease 2019. During commissioning, real-time measurements of key indoor air quality parameters (PM1-10, CO2, temperature and humidity) were collected from multiple sensors over 2 days. During this period, the ACU was switched off accidentally for approximately 7 h, allowing the impact of the intervention on PM to be assessed. FINDINGS The ACU reduced the PM counts considerably (e.g. PM1 65.5-78.2%) throughout the ward (P<0.001 all sizes), with positive correlation found for all PM fractions and CO2 (r=0.343-0.817; all P<0.001). PM counts rose/fell simultaneously when the ACU was off, with correlation of PM signals from multiple locations (e.g. r=0.343-0.868; all P<0.001) for particulates <1 μm). CONCLUSION Aerosols migrated rapidly between the various ward subcompartments, suggesting that social distancing alone cannot prevent nosocomial transmission of SARS-CoV-2 as this fails to mitigate longer-range (>2 m) transmission. The ACU reduced PM levels considerably throughout the ward space, indicating its potential as an effective intervention to reduce the risk posed by infectious airborne particles.
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Affiliation(s)
- M J Butler
- Department of Medicine for the Elderly, Cambridge University Hospitals, Cambridge, UK
| | - D Sloof
- AirPurity UK, Ltd, Cambridge, UK
| | - C Peters
- Department of Microbiology, NHS Greater Glasgow and Clyde, Glasgow, UK
| | - A Conway Morris
- John V Farman Intensive Care Unit, Cambridge University Hospitals, Cambridge, UK; Division of Immunology, Department of Pathology, University of Cambridge, Cambridge, UK; Department of Medicine, University of Cambridge, Cambridge, UK
| | - T Gouliouris
- Department of Medicine, University of Cambridge, Cambridge, UK
| | - R Thaxter
- Infection Prevention and Control, Cambridge University Hospitals, Cambridge, UK
| | - V L Keevil
- Department of Medicine for the Elderly, Cambridge University Hospitals, Cambridge, UK; Department of Medicine, University of Cambridge, Cambridge, UK
| | - C B Beggs
- Department of Medicine for the Elderly, Cambridge University Hospitals, Cambridge, UK; Carnegie School of Sport, Leeds Beckett University, Leeds, UK.
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Clements N, Arvelo I, Arnold P, Heredia NJ, Hodges UW, Deresinski S, Cook PW, Hamilton KA. Informing Building Strategies to Reduce Infectious Aerosol Transmission Risk by Integrating DNA Aerosol Tracers with Quantitative Microbial Risk Assessment. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:5771-5781. [PMID: 37000413 DOI: 10.1021/acs.est.2c08131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Using aerosol-based tracers to estimate risk of infectious aerosol transmission aids in the design of buildings with adequate protection against aerosol transmissible pathogens, such as SARS-CoV-2 and influenza. We propose a method for scaling a SARS-CoV-2 bulk aerosol quantitative microbial risk assessment (QMRA) model for impulse emissions, coughing or sneezing, with aerosolized synthetic DNA tracer concentration measurements. With point-of-emission ratios describing relationships between tracer and respiratory aerosol emission characteristics (i.e., volume and RNA or DNA concentrations) and accounting for aerosolized pathogen loss of infectivity over time, we scale the inhaled pathogen dose and risk of infection with time-integrated tracer concentrations measured with a filter sampler. This tracer-scaled QMRA model is evaluated through scenario testing, comparing the impact of ventilation, occupancy, masking, and layering interventions on infection risk. We apply the tracer-scaled QMRA model to measurement data from an ambulatory care room to estimate the risk reduction resulting from HEPA air cleaner operation. Using DNA tracer measurements to scale a bulk aerosol QMRA model is a relatively simple method of estimating risk in buildings and can be applied to understand the impact of risk mitigation efforts.
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Affiliation(s)
- Nicholas Clements
- Paul M. Rady Department of Mechanical Engineering, University of Colorado at Boulder, Boulder, Colorado 80309, United States
| | - Ilan Arvelo
- SafeTraces, Inc., Pleasanton, California 94588, United States
| | - Phil Arnold
- SafeTraces, Inc., Pleasanton, California 94588, United States
| | | | - Ulrike W Hodges
- SafeTraces, Inc., Pleasanton, California 94588, United States
| | - Stan Deresinski
- Stanford University School of Medicine, Stanford, California 94305, United States
| | - Peter W Cook
- Independent researcher, Atlanta, Georgia 30333, United States
| | - Kerry A Hamilton
- School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, Arizona 85281, United States
- The Biodesign Institute Center for Environmental Health Engineering, Arizona State University, Tempe, Arizona 85281, United States
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10
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Wang Y, Wei J, Gao CX, Jin T, Liu L. Tracing the origin of large respiratory droplets by their deposition characteristics inside the respiratory tract during speech. BUILDING SIMULATION 2023; 16:781-794. [PMID: 37101943 PMCID: PMC10009356 DOI: 10.1007/s12273-022-0982-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2022] [Revised: 12/12/2022] [Accepted: 12/22/2022] [Indexed: 05/28/2023]
Abstract
Origin of differently sized respiratory droplets is fundamental for clarifying their viral loads and the sequential transmission mechanism of SARS-CoV-2 in indoor environments. Transient talking activities characterized by low (0.2 L/s), medium (0.9 L/s), and high (1.6 L/s) airflow rates of monosyllabic and successive syllabic vocalizations were investigated by computational fluid dynamics (CFD) simulations based on a real human airway model. SST k-ω model was chosen to predict the airflow field, and the discrete phase model (DPM) was used to calculate the trajectories of droplets within the respiratory tract. The results showed that flow field in the respiratory tract during speech is characterized by a significant laryngeal jet, and bronchi, larynx, and pharynx-larynx junction were main deposition sites for droplets released from the lower respiratory tract or around the vocal cords, and among which, over 90% of droplets over 5 µm released from vocal cords deposited at the larynx and pharynx-larynx junction. Generally, droplets' deposition fraction increased with their size, and the maximum size of droplets that were able to escape into external environment decreased with the airflow rate. This threshold size for droplets released from the vocal folds was 10-20 µm, while that for droplets released from the bronchi was 5-20 µm under various airflow rates. Besides, successive syllables pronounced at low airflow rates promoted the escape of small droplets, but do not significantly affect the droplet threshold diameter. This study indicates that droplets larger than 20 µm may entirely originate from the oral cavity, where viral loads are lower; it provides a reference for evaluating the relative importance of large-droplet spray and airborne transmission route of COVID-19 and other respiratory infections.
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Affiliation(s)
- Yihan Wang
- Institute of Refrigeration and Cryogenics, Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, Zhejiang University, Hangzhou, 310000 China
| | - Jianjian Wei
- Institute of Refrigeration and Cryogenics, Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, Zhejiang University, Hangzhou, 310000 China
| | - Caroline X. Gao
- Public Health and Preventive Medicine, Monash University, Melbourne, VIC 3004 Australia
| | - Tao Jin
- Institute of Refrigeration and Cryogenics, Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, Zhejiang University, Hangzhou, 310000 China
| | - Li Liu
- Department of Building Science, Tsinghua University, Beijing, 100084 China
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11
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Bahramian A. Influence of indoor environmental conditions on airborne transmission and lifetime of sneeze droplets in a confined space: a way to reduce COVID-19 spread. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023; 30:44067-44085. [PMID: 36680724 PMCID: PMC9867553 DOI: 10.1007/s11356-023-25421-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 01/16/2023] [Indexed: 06/17/2023]
Abstract
Effects of indoor temperature (T∞) and relative humidity (RH∞) on the airborne transmission of sneeze droplets in a confined space were studied over the T∞ range of 15-30 °C and RH∞ of 22-62%. In addition, a theoretical evaporation model was used to estimate the droplet lifetime based on experimental data. The results showed that the body mass index (BMI) of the participants played an important role in the sneezing jet velocity, while the impact of the BMI and gender of participants was insignificant on the size distribution of droplets. At a critical relative humidity RH∞,crit of 46%, the sneezing jet velocity and droplet lifetime were roughly independent of T∞. At RH∞ < RH∞,crit, the sneezing jet velocity decreased by increasing T∞ from 15 to 30 °C, while its trend was reversed at RH∞ > RH∞,crit. The maximum spreading distance of aerosols increased by decreasing the RH∞ and increasing T∞, while the droplet lifetime increased by decreasing T∞ at RH∞ > RH∞,crit. The mean diameter of aerosolized droplets was less affected by T∞ than the large droplets at RH∞ < RH∞,crit, while the mean diameter and number fraction of aerosols were more influenced by RH∞ than the T∞ in the range of 46% ≤ RH∞ ≤ 62%. In summary, this study suggests suitable indoor environmental conditions by considering the transmission rate and lifetime of respiratory droplets to reduce the spread of COVID-19.
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Affiliation(s)
- Alireza Bahramian
- Department of Chemical Engineering, Hamedan University of Technology, P.O. Box, Hamedan, 65155, Iran.
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12
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Tandjaoui-Lambiotte Y, Lomont A, Moenne-Locoz P, Seytre D, Zahar JR. Spread of viruses, which measures are the most apt to control COVID-19? Infect Dis Now 2023; 53:104637. [PMID: 36526247 PMCID: PMC9746078 DOI: 10.1016/j.idnow.2022.12.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 11/22/2022] [Accepted: 12/06/2022] [Indexed: 12/15/2022]
Abstract
The persistent debate about the modes of transmission of SARS-CoV2 and preventive measures has illustrated the limits of our knowledge regarding the measures to be implemented in the face of viral risk. Past and present (pandemic-related) scientific data underline the complexity of the phenomenon and its variability over time. Several factors contribute to the risk of transmission, starting with incidence in the general population (i.e., colonization pressure) and herd immunity. Other major factors include intensity of symptoms, interactions with the reservoir (proximity and duration of contact), the specific characteristics of the virus(es) involved, and a number of unpredictable elements (humidity, temperature, ventilation…). In this review, we will emphasize the difficulty of "standardizing" the situations that might explain the discrepancies found in the literature. We will show that the airborne route remains the main mode of transmission. Regarding preventive measures of prevention, while vaccination remains the cornerstone of the fight against viral outbreaks, we will remind the reader that wearing a mask is the main barrier measure and that the choice of type of mask depends on the risk situations. Finally, we believe that the recent pandemic should induce us in the future to modify our recommendations by adapting our measures in hospitals, not to the pathogen concerned, which is currently the case, but rather to the type of at-risk situation.
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Affiliation(s)
- Y Tandjaoui-Lambiotte
- Service de Pneumologie-Infectiologie, CH Saint Denis, 2 rue Dr. Delafontaine, 93200, France
| | - A Lomont
- Unité de Prévention du Risque Infectieux, Service de microbiologie clinique, GHU Paris Seine Saint-Denis, Université Sorbonne Paris Nord, France
| | - P Moenne-Locoz
- Unité de Prévention du Risque Infectieux, Service de microbiologie clinique, GHU Paris Seine Saint-Denis, Université Sorbonne Paris Nord, France
| | - D Seytre
- Unité de Prévention du Risque Infectieux, Service de microbiologie clinique, GHU Paris Seine Saint-Denis, Université Sorbonne Paris Nord, France
| | - J R Zahar
- Unité de Prévention du Risque Infectieux, Service de microbiologie clinique, GHU Paris Seine Saint-Denis, Université Sorbonne Paris Nord, France.
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13
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Norvihoho LK, Yin J, Zhou ZF, Han J, Chen B, Fan LH, Lichtfouse E. Mechanisms controlling the transport and evaporation of human exhaled respiratory droplets containing the severe acute respiratory syndrome coronavirus: a review. ENVIRONMENTAL CHEMISTRY LETTERS 2023; 21:1701-1727. [PMID: 36846189 PMCID: PMC9944801 DOI: 10.1007/s10311-023-01579-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Accepted: 02/13/2023] [Indexed: 05/24/2023]
Abstract
Transmission of the coronavirus disease 2019 is still ongoing despite mass vaccination, lockdowns, and other drastic measures to control the pandemic. This is due partly to our lack of understanding on the multiphase flow mechanics that control droplet transport and viral transmission dynamics. Various models of droplet evaporation have been reported, yet there is still limited knowledge about the influence of physicochemical parameters on the transport of respiratory droplets carrying the severe acute respiratory syndrome coronavirus 2. Here we review the effects of initial droplet size, environmental conditions, virus mutation, and non-volatile components on droplet evaporation and dispersion, and on virus stability. We present experimental and computational methods to analyze droplet transport, and factors controlling transport and evaporation. Methods include thermal manikins, flow techniques, aerosol-generating techniques, nucleic acid-based assays, antibody-based assays, polymerase chain reaction, loop-mediated isothermal amplification, field-effect transistor-based assay, and discrete and gas-phase modeling. Controlling factors include environmental conditions, turbulence, ventilation, ambient temperature, relative humidity, droplet size distribution, non-volatile components, evaporation and mutation. Current results show that medium-sized droplets, e.g., 50 µm, are sensitive to relative humidity. Medium-sized droplets experience delayed evaporation at high relative humidity, and increase airborne lifetime and travel distance. By contrast, at low relative humidity, medium-sized droplets quickly shrink to droplet nuclei and follow the cough jet. Virus inactivation within a few hours generally occurs at temperatures above 40 °C, and the presence of viral particles in aerosols impedes droplet evaporation.
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Affiliation(s)
- Leslie Kojo Norvihoho
- State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an, 710049 Shaanxi People’s Republic of China
| | - Jing Yin
- State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an, 710049 Shaanxi People’s Republic of China
| | - Zhi-Fu Zhou
- State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an, 710049 Shaanxi People’s Republic of China
| | - Jie Han
- School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, Xi’an, 710049 Shaanxi People’s Republic of China
| | - Bin Chen
- State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an, 710049 Shaanxi People’s Republic of China
| | - Li-Hong Fan
- The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, 710061 Shaanxi People’s Republic of China
| | - Eric Lichtfouse
- State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an, 710049 Shaanxi People’s Republic of China
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14
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Strydom D, le Roux JD, Craig IK. State estimation for nonlinear state-space transmission models of tuberculosis. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2023; 43:339-357. [PMID: 35165919 DOI: 10.1111/risa.13901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Given the high prevalence of tuberculosis (TB) and the mortality rate associated with the disease, numerous models, such as the Gammaitoni and Nucci (GN) model, were developed to model the risk of transmission. These models typically rely on a quanta generation rate as a measurement of infectivity. Since the quanta generation rate cannot be measured directly, the unique contribution of this work is to develop state estimators to estimate the quanta generation rate from available measurements. To estimate the quanta generation rate, the GN model is adapted into an augmented single-room GN model and a simplified two-room GN model. Both models are shown to be observable, i.e., it is theoretically possible to estimate the quanta generation rate given available measurements. Kalman filters are used to estimate the quanta generation rate. First, a continuous-time extended Kalman filter is used for both adapted models using a simulation and measurement sampling rate of 60 s. Accurate quanta generate rate estimates are achieved in both cases. A more realistic scenario is also considered with a measurement sampling rate of one day. For these estimates, a hybrid extended Kalman filter (HEKF) is used. Accurate quanta generation rate estimates are achieved for the more realistic scenario. Future work could potentially use the HEKFs, the adapted models, and real-time measurements in a control system feedback loop to reduce the transmission of TB in confined spaces such as hospitals.
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Affiliation(s)
- Duayne Strydom
- Department of Electrical, Electronic and Computer Engineering, University of Pretoria, South Africa
| | - Johan Derik le Roux
- Department of Electrical, Electronic and Computer Engineering, University of Pretoria, South Africa
| | - Ian Keith Craig
- Department of Electrical, Electronic and Computer Engineering, University of Pretoria, South Africa
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15
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Nishandar SR, He Y, Princevac M, Edwards RD. Fate of Exhaled Droplets From Breathing and Coughing in Supermarket Checkouts and Passenger Cars. ENVIRONMENTAL HEALTH INSIGHTS 2023; 17:11786302221148274. [PMID: 36644342 PMCID: PMC9834932 DOI: 10.1177/11786302221148274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 12/12/2022] [Indexed: 06/17/2023]
Abstract
The global pandemic of COVID-19 has highlighted the importance of understanding the role that exhaled droplets play in virus transmission in community settings. Computational Fluid Dynamics (CFD) enables systematic examination of roles the exhaled droplets play in the spread of SARS-CoV-2 in indoor environments. This analysis uses published exhaled droplet size distributions combined with terminal aerosol droplet size based on measured peak concentrations for SARS-CoV-2 RNA in aerosols to simulate exhaled droplet dispersion, evaporation, and deposition in a supermarket checkout area and rideshare car where close proximity with other individuals is common. Using air inlet velocity of 2 m/s in the passenger car and ASHRAE recommendations for ventilation and comfort in the supermarket, simulations demonstrate that exhaled droplets <20 μm that contain the majority of viral RNA evaporated leaving residual droplet nuclei that remain aerosolized in the air. Subsequently ~ 70% of these droplet nuclei deposited in the supermarket and the car with the reminder vented from the space. The maximum surface deposition of droplet nuclei/m2 for speaking and coughing were 2 and 819, 18 and 1387 for supermarket and car respectively. Approximately 15% of the total exhaled droplets (aerodynamic diameters 20-700 µm) were deposited on surfaces in close proximity to the individual. Due to the non-linear distribution of viral RNA across droplet sizes, however, these larger exhaled droplets that deposit on surfaces have low viral content. Maximum surface deposition of viral RNA was 70 and 1.7 × 103 virions/m2 for speaking and 2.3 × 104 and 9.3 × 104 virions/m2 for coughing in the supermarket and car respectively while the initial airborne concentration of viral RNA was 7 × 106 copies per ml. Integrating the droplet size distributions with viral load distributions, this study helps explain the apparent importance of inhalation exposures compared to surface contact observed in the pandemic.
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Affiliation(s)
- Sanika Ravindra Nishandar
- Department of Mechanical Engineering,
Bourns College of Engineering, University of California, Riverside, CA, USA
| | - Yucheng He
- Department of Mechanical Engineering,
Bourns College of Engineering, University of California, Riverside, CA, USA
| | - Marko Princevac
- Department of Mechanical Engineering,
Bourns College of Engineering, University of California, Riverside, CA, USA
| | - Rufus D Edwards
- Department of Epidemiology, Program in
Public Health, University of California Irvine, CA, USA
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16
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Argyropoulos CD, Skoulou V, Efthimiou G, Michopoulos AK. Airborne transmission of biological agents within the indoor built environment: a multidisciplinary review. AIR QUALITY, ATMOSPHERE, & HEALTH 2022; 16:477-533. [PMID: 36467894 PMCID: PMC9703444 DOI: 10.1007/s11869-022-01286-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 11/17/2022] [Indexed: 06/17/2023]
Abstract
The nature and airborne dispersion of the underestimated biological agents, monitoring, analysis and transmission among the human occupants into building environment is a major challenge of today. Those agents play a crucial role in ensuring comfortable, healthy and risk-free conditions into indoor working and leaving spaces. It is known that ventilation systems influence strongly the transmission of indoor air pollutants, with scarce information although to have been reported for biological agents until 2019. The biological agents' source release and the trajectory of airborne transmission are both important in terms of optimising the design of the heating, ventilation and air conditioning systems of the future. In addition, modelling via computational fluid dynamics (CFD) will become a more valuable tool in foreseeing risks and tackle hazards when pollutants and biological agents released into closed spaces. Promising results on the prediction of their dispersion routes and concentration levels, as well as the selection of the appropriate ventilation strategy, provide crucial information on risk minimisation of the airborne transmission among humans. Under this context, the present multidisciplinary review considers four interrelated aspects of the dispersion of biological agents in closed spaces, (a) the nature and airborne transmission route of the examined agents, (b) the biological origin and health effects of the major microbial pathogens on the human respiratory system, (c) the role of heating, ventilation and air-conditioning systems in the airborne transmission and (d) the associated computer modelling approaches. This adopted methodology allows the discussion of the existing findings, on-going research, identification of the main research gaps and future directions from a multidisciplinary point of view which will be helpful for substantial innovations in the field.
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Affiliation(s)
| | - Vasiliki Skoulou
- B3 Challenge Group, Chemical Engineering, School of Engineering, University of Hull, Cottingham Road, Hull, HU6 7RX UK
| | - Georgios Efthimiou
- Centre for Biomedicine, Hull York Medical School, University of Hull, Cottingham Road, Hull, HU6 7RX UK
| | - Apostolos K. Michopoulos
- Energy & Environmental Design of Buildings Research Laboratory, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus
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17
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Avni O, Dagan Y. Dispersion of free-falling saliva droplets by two-dimensional vortical flows. THEORETICAL AND COMPUTATIONAL FLUID DYNAMICS 2022; 36:993-1011. [PMID: 36373071 PMCID: PMC9638496 DOI: 10.1007/s00162-022-00633-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Accepted: 10/07/2022] [Indexed: 06/16/2023]
Abstract
ABSTRACT The dispersion of respiratory saliva droplets by indoor wake structures may enhance the transmission of various infectious diseases, as the wake spreads virus-laden droplets across the room. Thus, this study analyzes the interaction between vortical wake structures and exhaled multi-component saliva droplets. A self-propelling analytically described dipolar vortex is chosen as a model wake flow, passing through a cloud of micron-sized evaporating saliva droplets. The droplets' spatial location, velocity, diameter, and temperature are traced, coupled to their local flow field. For the first time, the wake structure decay is incorporated and analyzed, which is proved essential for accurately predicting the settling distances of the dispersed droplets. The model also considers the nonvolatile saliva components, adequately capturing the essence of droplet-aerosol transition and predicting the equilibrium diameter of the residual aerosols. Our analytic model reveals non-intuitive interactions between wake flows, droplet relaxation time, gravity, and transport phenomena. We reveal that given the right conditions, a virus-laden saliva droplet might translate to distances two orders of magnitude larger than the carrier-flow characteristic size. Moreover, accounting for the nonvolatile contents inside the droplet may lead to fundamentally different dispersion and settling behavior compared to non-evaporating particles or pure water droplets. Ergo, we suggest that the implementation of more complex evaporation models might be critical in high-fidelity simulations aspiring to assess the spread of airborne respiratory droplets.
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Affiliation(s)
- Orr Avni
- Faculty of Aerospace Engineering, Technion - Israel Institute of Technology, 320003 Haifa, Israel
| | - Yuval Dagan
- Faculty of Aerospace Engineering, Technion - Israel Institute of Technology, 320003 Haifa, Israel
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18
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Assessment of COVID-19 aerosol transmission in a university campus food environment using a numerical method. GEOSCIENCE FRONTIERS 2022; 13:101353. [PMID: 37521137 PMCID: PMC8780192 DOI: 10.1016/j.gsf.2022.101353] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 11/30/2021] [Accepted: 01/20/2022] [Indexed: 05/30/2023]
Abstract
With the prevalence of COVID-19, the phenomenon of viruses spreading through aerosols has become a focus of attention. Diners in university dining halls have a high risk of exposure to respiratory droplets from others without the protection of face masks, which greatly increases the risk of COVID-19 transmission. Therefore, the transmission mechanism of respiratory droplets in extremely crowded dining environments should be investigated. In this study, a numerical simulation of coughing at dining tables under two conditions was performed, namely the presence and absence of protective partitions, and the evaporation and condensation of aerosol droplets in the air were examined. By using the numerical method, we analyzed and verified the isolation effect of dining table partitions in the propagation of aerosol droplets. The effect of changes in room temperature on the diffusion of coughed aerosols when partitions were present was analyzed. We demonstrated how respiratory droplets spread through coughing and how these droplets affect others. Finally, we proposed a design for a dining table partition that minimizes the transmission of COVID-19.
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19
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Keetels GH, Godderis L, van de Wiel BJH. Associative evidence for the potential of humidification as a non-pharmaceutical intervention for influenza and SARS-CoV-2 transmission. JOURNAL OF EXPOSURE SCIENCE & ENVIRONMENTAL EPIDEMIOLOGY 2022; 32:720-726. [PMID: 36104526 PMCID: PMC9472723 DOI: 10.1038/s41370-022-00472-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 08/30/2022] [Accepted: 08/30/2022] [Indexed: 06/15/2023]
Abstract
BACKGROUND Both influenza and SARS-CoV-2 viruses show a strong seasonal spreading in temperate regions. Several studies indicated that changes in indoor humidity could be one of the key factors explaining this. OBJECTIVE The purpose of this study is to quantify the association between relevant epidemiological metrics and humidity in both influenza and SARS-CoV-2 epidemic periods. METHODS The atmospheric dew point temperature serves as a proxy for indoor relative humidity. This study considered the weekly mortality rate in the Netherlands between 1995 and 2019 to determine the correlation between the dew point and the spread of influenza. During influenza epidemic periods in the Netherlands, governmental restrictions were absent; therefore, there is no need to control this confounder. During the SARS-CoV-2 pandemic, governmental restrictions strongly varied over time. To control this effect, periods with a relatively constant governmental intervention level were selected to analyze the reproduction rate. We also examine SARS-CoV-2 deaths in the nursing home setting, where health policy and social factors were less variable. Viral transmissibility was measured by computing the ratio between the estimated daily number of infectious persons in the Netherlands and the lagged mortality figures in the nursing homes. RESULTS For both influenza and SARS-CoV-2, a significant correlation was found between the dew point temperature and the aforementioned epidemiological metrics. The findings are consistent with the anticipated mechanisms related to droplet evaporation, stability of virus in the indoor environment, and impairment of the natural defenses of the respiratory tract in dry air. SIGNIFICANCE This information is helpful to understand the seasonal pattern of respiratory viruses and motivate further study to what extent it is possible to alter the seasonal pattern by actively intervening in the adverse role of low humidity during fall and winter in temperate regions. IMPACT A solid understanding and quantification of the role of humidity on the transmission of respiratory viruses is imperative for epidemiological modeling and the installation of non-pharmaceutical interventions. The results of this study indicate that improving the indoor humidity by humidifiers could be a promising technology for reducing the spread of both influenza and SARS-CoV-2 during winter and fall in the temperate zone. The identification of this potential should be seen as a strong motivation to invest in further prospective testing of this non-pharmaceutical intervention.
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Affiliation(s)
- G H Keetels
- Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Mekelweg 2, 2628 CD, Delft, The Netherlands.
| | - L Godderis
- Centre for Environment and Health, Department of Public Health and Primary Care, KU Leuven (University of Leuven), Kapucijnenvoer 35, 3000, Leuven, Belgium
- IDEWE, External Service for Prevention and Protection at Work, Heverlee, Belgium
| | - B J H van de Wiel
- Faculty of Civil Engineering and Geosciences, Delft University of Technology, Stevinweg 1, 2628 CN, Delft, The Netherlands
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20
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Ultrahigh sensitive and selective detection of single nucleotide polymorphism using peptide nucleic acid and ribonuclease H assembled DNA amplification (PRADA). Anal Chim Acta 2022; 1233:340423. [DOI: 10.1016/j.aca.2022.340423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 09/06/2022] [Accepted: 09/19/2022] [Indexed: 11/22/2022]
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21
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Morawska L, Buonanno G, Mikszewski A, Stabile L. The physics of respiratory particle generation, fate in the air, and inhalation. NATURE REVIEWS. PHYSICS 2022; 4:723-734. [PMID: 36065441 PMCID: PMC9430019 DOI: 10.1038/s42254-022-00506-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 08/03/2022] [Indexed: 05/31/2023]
Abstract
Given that breathing is one of the most fundamental physiological functions, there is an urgent need to broaden our understanding of the fluid dynamics that governs it. There would be many benefits from doing so, including a better assessment of respiratory health, a basis for more precise delivery of pharmaceutical drugs for treatment, and the understanding and potential minimization of respiratory infection transmission. We review the physics of particle generation in the respiratory tract, the fate of these particles in the air on exhalation and the physics of particle inhalation. The main focus is on evidence from experimental studies. We conclude that although there is qualitative understanding of the generation of particles in the respiratory tract, a basic quantitative knowledge of the characteristics of the particles emitted during respiratory activities and their fate after emission, and a theoretical understanding of particle deposition during inhalation, nevertheless the general understanding of the entire process is rudimentary, and many open questions remain.
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Affiliation(s)
- Lidia Morawska
- Queensland University of Technology, International Laboratory for Air Quality & Health (ILAQH), Brisbane, Queensland Australia
- Global Centre for Clean Air Research, Department of Civil and Environmental Engineering, University of Surrey, Guildford, UK
| | - Giorgio Buonanno
- Queensland University of Technology, International Laboratory for Air Quality & Health (ILAQH), Brisbane, Queensland Australia
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, Italy
| | - Alex Mikszewski
- Queensland University of Technology, International Laboratory for Air Quality & Health (ILAQH), Brisbane, Queensland Australia
| | - Luca Stabile
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, Italy
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22
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Li S, Li Z, Dong Y, Shi T, Zhou S, Chen Y, Wang X, Qin F. Temporal-spatial risk assessment of COVID-19 under the influence of urban spatial environmental parameters: The case of Shenyang city. BUILDING SIMULATION 2022; 16:683-699. [PMID: 35968515 PMCID: PMC9364280 DOI: 10.1007/s12273-022-0918-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Revised: 06/07/2022] [Accepted: 06/25/2022] [Indexed: 06/15/2023]
Abstract
Respiratory infection is the main route for the transmission of coronavirus pneumonia, and the results have shown that the urban spatial environment significantly influences the risk of infection. Based on the Wells-Riley model of respiratory infection probability, the study determined the human respiratory-related parameters and the effective influence range; extracted urban morphological parameters, assessed the ventilation effects of different spatial environments, and, combined with population flow monitoring data, constructed a method for assessing the risk of Covid-19 respiratory infection in urban-scale grid cells. In the empirical study in Shenyang city, a severe cold region, urban morphological parameters, population size, background wind speed, and individual behavior patterns were used to calculate the distribution characteristics of temporal and spatial concomitant risks in urban areas grids under different scenarios. The results showed that the correlation between the risk of respiratory infection in urban public spaces and the above variables was significant. The exposure time had the greatest degree of influence on the probability of respiratory infection risk among the variables. At the same time, the change in human body spacing beyond 1 m had a minor influence on the risk of infection. Among the urban morphological parameters, building height had the highest correlation with the risk of infection, while building density had the lowest correlation. The actual point distribution of the epidemic in Shenyang from March to April 2022 was used to verify the evaluation results. The overlap rate between medium or higher risk areas and actual cases was 78.55%. The planning strategies for epidemic prevention and control were proposed for the spatial differentiation characteristics of different risk elements. The research results can accurately classify the risk level of urban space and provide a scientific basis for the planning response of epidemic prevention and control and the safety of public activities.
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Affiliation(s)
- Sui Li
- School of Architecture and Planning, Shenyang Jianzhu University, Shenyang, Liaoning, 110168 China
- Institute of Ecological Urban Planning and Green Building, Shenyang Jianzhu University, Shenyang, Liaoning, 110168 China
| | - Zhe Li
- School of Architecture and Planning, Shenyang Jianzhu University, Shenyang, Liaoning, 110168 China
| | - Yixin Dong
- School of Architecture, Tianjin University, Tianjin, 300072 China
| | - Tiemao Shi
- School of Architecture and Planning, Shenyang Jianzhu University, Shenyang, Liaoning, 110168 China
- Institute of Spatial Planning and Design, Shenyang Jianzhu University, Shenyang, Liaoning, 110168 China
| | - Shiwen Zhou
- School of Architecture and Planning, Shenyang Jianzhu University, Shenyang, Liaoning, 110168 China
| | - Yumeng Chen
- School of Architecture and Planning, Shenyang Jianzhu University, Shenyang, Liaoning, 110168 China
| | - Xun Wang
- School of Science, Shenyang Jianzhu University, Shenyang, Liaoning, 110168 China
| | - Feifei Qin
- Institute of Ecological Urban Planning and Green Building, Shenyang Jianzhu University, Shenyang, Liaoning, 110168 China
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23
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Park J, Lee KS, Park H. Optimized mechanism for fast removal of infectious pathogen-laden aerosols in the negative-pressure unit. JOURNAL OF HAZARDOUS MATERIALS 2022; 435:128978. [PMID: 35472540 PMCID: PMC9020843 DOI: 10.1016/j.jhazmat.2022.128978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Revised: 04/09/2022] [Accepted: 04/18/2022] [Indexed: 05/07/2023]
Abstract
It has been frequently emphasized that highly contagious respiratory disease pathogens (such as SARS-CoV-2) are transmitted to the other hosts in the form of micro-sized aerosols (< 5 μm) in the air without physical contacts. Hospital environments such as negative-pressure unit are considered being consistently exposed to pathogens, so it is essential to quickly discharge them through the effective ventilation system. To achieve that, in the present study, we propose the optimized ventilation mechanism and design for the fastest removal of pathogen-laden aerosol using numerical simulations. We quantitatively evaluated the aerosol removal performance of various ventilation configurations (combinations of air exhaust and supply ducts), and found that the key mechanism is to form the coherent (preferentially upward) airflow structure to surround the respiratory flow containing the aerosol cluster. We believe that the present findings will play a critical role in developing the high-efficiency negative-pressure facility irrespective of its size and environments.
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Affiliation(s)
- Jooyeon Park
- Department of Mechanical Engineering, Seoul National University, Seoul 08826, South Korea
| | - Kwang Suk Lee
- Department of Urology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 06273, South Korea
| | - Hyungmin Park
- Department of Mechanical Engineering, Seoul National University, Seoul 08826, South Korea; Institute of Advanced Machines and Design, Seoul National University, Seoul 08826, South Korea.
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Multi-objective performance assessment of HVAC systems and physical barriers on COVID-19 infection transmission in a high-speed train. JOURNAL OF BUILDING ENGINEERING 2022; 53:104544. [PMCID: PMC9022448 DOI: 10.1016/j.jobe.2022.104544] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Revised: 04/11/2022] [Accepted: 04/17/2022] [Indexed: 06/16/2023]
Abstract
A computational fluid dynamics (CFD) simulation was performed to model and study the transmission risk associated with cough-related SARS-CoV-2 droplets in a real-world high-speed train (HST). In this study, the evaporating of the droplets was considered. Simulation data were post-processed to assess the fraction of the particles deposited on each passenger's face and body, suspended in air, and escaped from exhausts. Firstly, the effects of temperature, relative humidity, ventilation rate, injection source, exhausts' location and capacity, and adding the physical barriers on evaporation and transport of respiratory droplets are investigated in long distance HST. The results demonstrate that overall, 6–43% of the particles were suspended in the cabin after 2.7 min, depending on conditions, and 3–58% of the particles were removed from the cabin in the same duration. Use of physical barriers and high ventilation rate is therefore recommended for both personal and social protection. We found more exhaust capacity and medium relative humidity to be effective in reducing the particles' transmission potential across all studied scenarios. The results indicate that reducing ventilation rate and exhaust capacity, increased aerosols shelf time and dispersion throughout the cabin.
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25
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Saied AA. Should not airborne transmission be ignored in the 2022 monkeypox outbreak? Int J Surg 2022; 104:106762. [PMID: 35798203 PMCID: PMC9534014 DOI: 10.1016/j.ijsu.2022.106762] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Accepted: 07/02/2022] [Indexed: 11/02/2022]
Affiliation(s)
- AbdulRahman A Saied
- National Food Safety Authority (NFSA), Aswan Branch, Aswan, 81511, Egypt; Ministry of Tourism and Antiquities, Aswan Office, Aswan, 81511, Egypt.
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26
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Li Y, Wu C, Cao G, Guan D, Zhan C. Transmission characteristics of respiratory droplets aerosol in indoor environment: an experimental study. INTERNATIONAL JOURNAL OF ENVIRONMENTAL HEALTH RESEARCH 2022; 32:1768-1779. [PMID: 33825604 DOI: 10.1080/09603123.2021.1910629] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 03/25/2021] [Indexed: 06/12/2023]
Abstract
Transmission of droplets has been recognized as an important form of infection for the respiratory diseases. This study investigated the distribution of human respiratory droplets and assessed the effects of air change rate and generated velocity on droplet transmission using an active agent in an enclosed chamber (46 m3). Results revealed that the higher the air change rate was, the fewer viable droplets were detected in the range of <3.3 μm with ventilation; an increased air change rate can increase the attenuation of droplet aerosol. Without ventilation, the viable droplet size was observed to mainly distribute greater than 3.3 μm, which occupied up 87.5% of the total number. When the generated velocity was increased to 20 m/s, 29.38% of the viable droplets were detected at the position of 2.0 m. The findings are excepted to be useful for developing the technology of reducing droplet propagation and providing data verification for simulation research.
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Affiliation(s)
- Yanju Li
- School of Energy and Safety Engineering, Tianjin Chengjian University, Tianjin, China
| | - Chunbin Wu
- School of Energy and Safety Engineering, Tianjin Chengjian University, Tianjin, China
| | - Guoqing Cao
- Institute of Building Environment and Energy, China Academy of Building Research, Beijing, China
| | - Dexing Guan
- School of Energy and Safety Engineering, Tianjin Chengjian University, Tianjin, China
| | - Chaoguo Zhan
- School of Environmental Science and Safety Engineering, Tianjin University of Technology, Tianjin, China
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27
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Ge H, Zhao P, Choi S, Deng T, Feng Y, Cui X. Effects of face shield on an emitter during a cough process: A large-eddy simulation study. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 831:154856. [PMID: 35358516 DOI: 10.1016/j.scitotenv.2022.154856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Revised: 03/03/2022] [Accepted: 03/23/2022] [Indexed: 06/14/2023]
Abstract
Face shield is a common personal protection equipment for pandemic. In the present work, three-dimensional computational fluid dynamic (CFD) method is used to simulate a cough jet from an emitter who wears a face shield. A realistic manikin model with a simplified mouth cavity is employed. A large eddy simulation with a dynamic structure subgrid scale model is applied to model the turbulence. An Eulerian-Lagrangian approach is adopted to model the two-phase flows, with which the droplets are represented by a cloud of particles. The droplet breakup, evaporation, dispersion, drag force, and wall impingement are considered in this model. An inlet velocity profile that is based on a variable mouth opening area is considered. Special attentions have been put the vortex structure and droplet re-distribution induced by the face shield. It is found that the multiple vortices are formed when the cough jet impinges on the face shield. Some droplets move backward and others move downward after the impinging. It is also found that a small modification of the face shield significantly modifies the flow field and droplet distribution. We conclude that face shield significantly reduces the risk factor in the front of the emitter, meanwhile the risk factor in the back of the emitter increases. When the receiver standing in front of the emitter is shorter than the emitter, the risk is still very high. More attentions should be paid on the design of the face field, clothes cleaning and floor cleaning of the emitters with face shields. Based on the predicted droplet trajectory, a conceptual model for droplet flux is proposed for the scenario with the face shield.
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Affiliation(s)
- Haiwen Ge
- Department of Mechanical Engineering, Texas Tech University, Lubbock, TX, USA
| | - Peng Zhao
- Department of Mechanical, Aerospace & Biomedical Engineering, UT Space Institute, University of Tennessee, Knoxville, TN, USA
| | - Sanghun Choi
- School of Mechanical Engineering, Kyungpook National University, Daegu, Republic of Korea
| | - Teng Deng
- School of Aerospace Engineering, Huazhong University of Science and Technology, Wuhan, China
| | - Yaning Feng
- School of Aerospace Engineering, Huazhong University of Science and Technology, Wuhan, China
| | - Xinguang Cui
- School of Aerospace Engineering, Huazhong University of Science and Technology, Wuhan, China.
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28
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Luo Q, Ou C, Hang J, Luo Z, Yang H, Yang X, Zhang X, Li Y, Fan X. Role of pathogen-laden expiratory droplet dispersion and natural ventilation explaining a COVID-19 outbreak in a coach bus. BUILDING AND ENVIRONMENT 2022; 220:109160. [PMID: 35615259 PMCID: PMC9122785 DOI: 10.1016/j.buildenv.2022.109160] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 04/28/2022] [Accepted: 04/30/2022] [Indexed: 05/30/2023]
Abstract
The influencing mechanism of droplet transmissions inside crowded and poorly ventilated buses on infection risks of respiratory diseases is still unclear. Based on experiments of one-infecting-seven COVID-19 outbreak with an index patient at bus rear, we conducted CFD simulations to investigate integrated effects of initial droplet diameters(tracer gas, 5 μm, 50 μm and 100 μm), natural air change rates per hour(ACH = 0.62, 2.27 and 5.66 h-1 related to bus speeds) and relative humidity(RH = 35% and 95%) on pathogen-laden droplet dispersion and infection risks. Outdoor pressure difference around bus surfaces introduces natural ventilation airflow entering from bus-rear skylight and leaving from the front one. When ACH = 0.62 h-1(idling state), the 30-min-exposure infection risk(TIR) of tracer gas is 15.3%(bus rear) - 11.1%(bus front), and decreases to 3.1%(bus rear)-1.3%(bus front) under ACH = 5.66 h-1(high bus speed).The TIR of large droplets(i.e., 100 μm/50 μm) is almost independent of ACH, with a peak value(∼3.1%) near the index patient, because over 99.5%/97.0% of droplets deposit locally due to gravity. Moreover, 5 μm droplets can disperse further with the increasing ventilation. However, TIR for 5 μm droplets at ACH = 5.66 h-1 stays relatively small for rear passengers(maximum 0.4%), and is even smaller in the bus middle and front(<0.1%). This study verifies that differing from general rooms, most 5 μm droplets deposit on the route through the long-and-narrow bus space with large-area surfaces(L∼11.4 m). Therefore, tracer gas can only simulate fine droplet with little deposition but cannot replace 5-100 μm droplet dispersion in coach buses.
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Affiliation(s)
- Qiqi Luo
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
- Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai, 519000, China
| | - Cuiyun Ou
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
- Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai, 519000, China
| | - Jian Hang
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
- Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai, 519000, China
| | - Zhiwen Luo
- School of the Built Environment, University of Reading, Reading, UK
| | - Hongyu Yang
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
- Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai, 519000, China
| | - Xia Yang
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
- Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai, 519000, China
| | - Xuelin Zhang
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
- Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai, 519000, China
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China
| | - Xiaodan Fan
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
- Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai, 519000, China
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29
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Ahlawat A, Mishra SK, Herrmann H, Rajeev P, Gupta T, Goel V, Sun Y, Wiedensohler A. Impact of Chemical Properties of Human Respiratory Droplets and Aerosol Particles on Airborne Viruses' Viability and Indoor Transmission. Viruses 2022; 14:v14071497. [PMID: 35891477 PMCID: PMC9318922 DOI: 10.3390/v14071497] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 07/01/2022] [Accepted: 07/01/2022] [Indexed: 02/04/2023] Open
Abstract
The airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been identified as a potential pandemic challenge, especially in poorly ventilated indoor environments, such as certain hospitals, schools, public buildings, and transports. The impacts of meteorological parameters (temperature and humidity) and physical property (droplet size) on the airborne transmission of coronavirus in indoor settings have been previously investigated. However, the impacts of chemical properties of viral droplets and aerosol particles (i.e., chemical composition and acidity (pH)) on viability and indoor transmission of coronavirus remain largely unknown. Recent studies suggest high organic content (proteins) in viral droplets and aerosol particles supports prolonged survival of the virus by forming a glassy gel-type structure that restricts the virus inactivation process under low relative humidity (RH). In addition, the virus survival was found at neutral pH, and inactivation was observed to be best at low (<5) and high pH (>10) values (enveloped bacteriophage Phi6). Due to limited available information, this article illustrates an urgent need to research the impact of chemical properties of exhaled viral particles on virus viability. This will improve our fundamental understanding of indoor viral airborne transmission mechanisms.
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Affiliation(s)
- Ajit Ahlawat
- Leibniz Institute for Tropospheric Research, 04318 Leipzig, Germany; (H.H.); (A.W.)
- Correspondence:
| | | | - Hartmut Herrmann
- Leibniz Institute for Tropospheric Research, 04318 Leipzig, Germany; (H.H.); (A.W.)
| | - Pradhi Rajeev
- Department of Civil Engineering, Indian Institute of Technology (IIT), Kanpur 208016, India; (P.R.); (T.G.)
| | - Tarun Gupta
- Department of Civil Engineering, Indian Institute of Technology (IIT), Kanpur 208016, India; (P.R.); (T.G.)
| | - Vikas Goel
- School of Interdisciplinary Research, Indian Institute of Technology (IIT), Delhi 110016, India;
| | - Yele Sun
- LAPC, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100017, China;
| | - Alfred Wiedensohler
- Leibniz Institute for Tropospheric Research, 04318 Leipzig, Germany; (H.H.); (A.W.)
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30
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Wang Y, Liu Z, Liu H, Wu M, He J, Cao G. Droplet aerosols transportation and deposition for three respiratory behaviors in a typical negative pressure isolation ward. BUILDING AND ENVIRONMENT 2022; 219:109247. [PMID: 35669356 PMCID: PMC9159814 DOI: 10.1016/j.buildenv.2022.109247] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Revised: 05/22/2022] [Accepted: 05/26/2022] [Indexed: 05/28/2023]
Abstract
Negative pressure isolation wards could provide safety for health care workers (HCWs) and patients infected with SARS-CoV-2. However, respiratory behavior releases aerosols containing pathogens, resulting in a potential risk of infection for HCWs. In this study, the spatiotemporal distribution of droplet aerosols in a typical negative pressure isolation ward was investigated using a full-scale experiment. In this experiment, artificial saliva was used to simulate the breathing behavior, which can reflect the effect of evaporation on droplet aerosols. Moreover, numerical simulations were used to compare the transport of droplet aerosols released by the three respiratory behaviors (breathing, speaking, and coughing). The results showed that droplet aerosols generated by coughing and speaking can be removed and deposited more quickly. Because reduction in the suspension proportion per unit time was much higher than that in the case of breathing. Under the air supply inlets, there was significant aerosol deposition on the floor, while the breathing area possessed higher aerosol concentrations. The risk of aerosol resuspension and potential infection increased significantly when HCWs moved frequently to these areas. Finally, more than 20% of the droplet aerosols escaped from the ward when the number of suspended aerosols in the aerosol space was 1%.
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Affiliation(s)
- Yongxin Wang
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei, 071003, PR China
| | - Zhijian Liu
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei, 071003, PR China
| | - Haiyang Liu
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei, 071003, PR China
| | - Minnan Wu
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei, 071003, PR China
| | - Junzhou He
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei, 071003, PR China
| | - Guoqing Cao
- Institute of Building Environment and Energy, China Academy of Building Research, Beijing, 100013, PR China
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31
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Faleiros DE, van den Bos W, Botto L, Scarano F. TU Delft COVID-app: A tool to democratize CFD simulations for SARS-CoV-2 infection risk analysis. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 826:154143. [PMID: 35227716 PMCID: PMC8875768 DOI: 10.1016/j.scitotenv.2022.154143] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 02/20/2022] [Accepted: 02/21/2022] [Indexed: 05/05/2023]
Abstract
This work describes a modelling approach to SARS-CoV-2 dispersion based on experiments. The main goal is the development of an application integrated in Ansys Fluent to enable computational fluid dynamics (CFD) users to set up, in a relatively short time, complex simulations of virion-laden droplet dispersion for calculating the probability of SARS-CoV-2 infection in real life scenarios. The software application, referred to as TU Delft COVID-app, includes the modelling of human expiratory activities, unsteady and turbulent convection, droplet evaporation and thermal coupling. Data describing human expiratory activities have been obtained from selected studies involving measurements of the expelled droplets and the air flow during coughing, sneezing and breathing. Particle Image Velocimetry (PIV) measurements of the transient air flow expelled by a person while reciting a speech have been conducted with and without a surgical mask. The instantaneous velocity fields from PIV are used to determine the velocity flow rates used in the numerical simulations, while the average velocity fields are used for validation. Furthermore, the effect of surgical masks and N95 respirators on particle filtration and the probability of SARS-CoV-2 infection from a dose-response model have also been implemented in the application. Finally, the work includes a case-study of SARS-CoV-2 infection risk analysis during a conversation across a dining/meeting table that demonstrates the capability of the newly developed application.
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Affiliation(s)
- David Engler Faleiros
- Faculty of Mechanical, Maritime and Materials Engineering (3mE), TU Delft, the Netherlands
| | - Wouter van den Bos
- Faculty of Mechanical, Maritime and Materials Engineering (3mE), TU Delft, the Netherlands; SDC Verifier, the Netherlands.
| | - Lorenzo Botto
- Faculty of Mechanical, Maritime and Materials Engineering (3mE), TU Delft, the Netherlands
| | - Fulvio Scarano
- Faculty of Aerospace Engineering, TU Delft, the Netherlands
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32
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Liu F, Qian H. Uncertainty analysis of facemasks in mitigating SARS-CoV-2 transmission. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 303:119167. [PMID: 35307493 PMCID: PMC8926848 DOI: 10.1016/j.envpol.2022.119167] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 02/14/2022] [Accepted: 03/14/2022] [Indexed: 05/09/2023]
Abstract
In the context of global spread of coronavirus disease 2019 (COVID-19) caused by a novel coronavirus (SARS-CoV-2), there is a controversial issue on whether the use of facemasks is promising to control or mitigate the COVID-19 transmission. This study modeled the SARS-CoV-2 transmission process and analyzed the ability of surgical mask and N95 in reducing the infection risk with Sobol's analysis. Two documented outbreaks of COVID-19 with no involvers wearing face masks were reviewed in a restaurant in Guangzhou (China) and a choir rehearsal in Mount Vernon (USA), suggesting that the proposed model can be well validated when airborne transmission is assumed to dominate the virus transmission indoors. Subsequently, the uncertainty analysis of the protection efficiency of N95 and surgical mask were conducted with Monte Carlo simulations, with three main findings: (1) the uncertainty in infection risk is primarily apportioned by respiratory activities, virus dynamics, environment factors and individual exposures; (2) wearing masks can effectively reduce the SARS-CoV-2 infection risk to an acceptable level (< 10-3) by at least two orders of magnitude; (3) faceseal leakage can reduce protection efficiency by approximately 4% when the infector is speaking or coughing, and by approximately 28% when the infector is sneezing. This work indicates the effectiveness of non-pharmaceutical interventions during the pandemic, and implies the importance of the synergistic studies of medicine, environment, social policies and strategies, etc., on reducing hazards and risks of the pandemic.
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Affiliation(s)
- Fan Liu
- School of Energy and Environment, Southeast University, Nanjing, China; School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai, China
| | - Hua Qian
- School of Energy and Environment, Southeast University, Nanjing, China; Engineering Research Center for Building Energy Environments & Equipments, Ministry of Education, China.
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33
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Wang L, Lin T, Da Costa H, Zhu S, Stockman T, Kumar A, Weaver J, Spede M, Milton DK, Hertzberg J, Toohey DW, Vance ME, Miller SL, Srebric J. Characterization of aerosol plumes from singing and playing wind instruments associated with the risk of airborne virus transmission. INDOOR AIR 2022; 32:e13064. [PMID: 35762243 PMCID: PMC9328346 DOI: 10.1111/ina.13064] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 04/25/2022] [Accepted: 05/23/2022] [Indexed: 06/15/2023]
Abstract
The exhalation of aerosols during musical performances or rehearsals posed a risk of airborne virus transmission in the COVID-19 pandemic. Previous research studied aerosol plumes by only focusing on one risk factor, either the source strength or convective transport capability. Furthermore, the source strength was characterized by the aerosol concentration and ignored the airflow rate needed for risk analysis in actual musical performances. This study characterizes aerosol plumes that account for both the source strength and convective transport capability by conducting experiments with 18 human subjects. The source strength was characterized by the source aerosol emission rate, defined as the source aerosol concentration multiplied by the source airflow rate (brass 383 particle/s, singing 408 particle/s, and woodwind 480 particle/s). The convective transport capability was characterized by the plume influence distance, defined as the sum of the horizontal jet length and horizontal instrument length (brass 0.6 m, singing 0.6 m and woodwind 0.8 m). Results indicate that woodwind instruments produced the highest risk with approximately 20% higher source aerosol emission rates and 30% higher plume influence distances compared with the average of the same risk indicators for singing and brass instruments. Interestingly, the clarinet performance produced moderate source aerosol concentrations at the instrument's bell, but had the highest source aerosol emission rates due to high source airflow rates. Flute performance generated plumes with the lowest source aerosol emission rates but the highest plume influence distances due to the highest source airflow rate. Notably, these comprehensive results show that the source airflow is a critical component of the risk of airborne disease transmission. The effectiveness of masking and bell covering in reducing aerosol transmission is due to the mitigation of both source aerosol concentrations and plume influence distances. This study also found a musician who generated approximately five times more source aerosol concentrations than those of the other musicians who played the same instrument. Despite voice and brass instruments producing measurably lower average risk, it is possible to have an individual musician produce aerosol plumes with high source strength, resulting in enhanced transmission risk; however, our sample size was too small to make generalizable conclusions regarding the broad musician population.
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Affiliation(s)
- Lingzhe Wang
- Department of Mechanical EngineeringUniversity of MarylandCollege ParkMarylandUSA
| | - Tong Lin
- Department of Mechanical EngineeringUniversity of MarylandCollege ParkMarylandUSA
| | - Hevander Da Costa
- Department of Mechanical EngineeringUniversity of MarylandCollege ParkMarylandUSA
| | - Shengwei Zhu
- Department of Mechanical EngineeringUniversity of MarylandCollege ParkMarylandUSA
| | - Tehya Stockman
- Department of Civil, Environmental, and Architectural EngineeringUniversity of Colorado BoulderBoulderColoradoUSA
| | - Abhishek Kumar
- Department of Mechanical EngineeringUniversity of Colorado BoulderBoulderColoradoUSA
| | - James Weaver
- National Federation of State High School AssociationsIndianapolisIndianaUSA
| | - Mark Spede
- Department of Performing ArtsClemson UniversityClemsonSouth CarolinaUSA
| | - Donald K. Milton
- Maryland Institute for Applied Environmental Health, School of Public HealthUniversity of MarylandCollege ParkMarylandUSA
| | - Jean Hertzberg
- Department of Mechanical EngineeringUniversity of Colorado BoulderBoulderColoradoUSA
| | - Darin W. Toohey
- Department of Atmospheric and Oceanic SciencesUniversity of Colorado BoulderBoulderColoradoUSA
| | - Marina E. Vance
- Department of Mechanical EngineeringUniversity of Colorado BoulderBoulderColoradoUSA
| | - Shelly L. Miller
- Department of Mechanical EngineeringUniversity of Colorado BoulderBoulderColoradoUSA
| | - Jelena Srebric
- Department of Mechanical EngineeringUniversity of MarylandCollege ParkMarylandUSA
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34
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Wang CT, Xu JC, Chan KC, Lee HH, Tso CY, Lin CSK, Chao CYH, Fu SC. Infection control measures for public transportation derived from the flow dynamics of obstructed cough jet. JOURNAL OF AEROSOL SCIENCE 2022; 163:105995. [PMID: 35382445 PMCID: PMC8971108 DOI: 10.1016/j.jaerosci.2022.105995] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/06/2022] [Revised: 03/21/2022] [Accepted: 03/21/2022] [Indexed: 06/14/2023]
Abstract
During the COVID-19 pandemic, WHO and CDC suggest people stay 1 m and 1.8 m away from others, respectively. Keeping social distance can avoid close contact and mitigate infection spread. Many researchers suspect that suggested distances are not enough because aerosols can spread up to 7-8 m away. Despite the debate on social distance, these social distances rely on unobstructed respiratory activities such as coughing and sneezing. Differently, in this work, we focused on the most common but less studied aerosol spread from an obstructed cough. The flow dynamics of a cough jet blocked by the backrest and gasper jet in a cabin environment was characterized by the particle image velocimetry (PIV) technique. It was proved that the backrest and the gasper jet can prevent the front passenger from droplet spray in public transportation where maintaining social distance was difficult. A model was developed to describe the cough jet trajectory due to the gasper jet, which matched well with PIV results. It was found that buoyancy and inside droplets almost do not affect the short-range cough jet trajectory. Infection control measures were suggested for public transportation, including using backrest/gasper jet, installing localized exhaust, and surface cleaning of the backrest.
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Affiliation(s)
- C T Wang
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
- Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Hong Kong, China
| | - J C Xu
- Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Hong Kong, China
| | - K C Chan
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
| | - H H Lee
- Department of Energy and Environment, City University of Hong Kong, Hong Kong, China
| | - C Y Tso
- Department of Energy and Environment, City University of Hong Kong, Hong Kong, China
| | - Carol S K Lin
- Department of Energy and Environment, City University of Hong Kong, Hong Kong, China
| | - Christopher Y H Chao
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
- Department of Building Environment and Energy Engineering & Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - S C Fu
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
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35
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Droplets Transmission Mechanism in a Commercial Wide-Body Aircraft Cabin. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12104889] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
COVID-19 is a respiratory infectious disease that spreads readily between people, and an urgent issue of passengers’ exposure risk assessment in commercial aircraft has been raised because an aircraft cabin as a confined space may carry and transmit the disease worldwide. In this study, the droplets transmission process under different ventilation systems in a twin-aisle wide-body aircraft was studied using CFD simulations and the infection risk of passengers was assessed by the improved Wells–Riley model. Numerical results found that the transmission mechanism of droplets in the aircraft cabin was different depending on the type of ventilation systems and the location of the infectious source. Annular airflow could effectively enhance the ability of droplets transmission, while direct airflow, represented by displacement ventilation, could significantly inhibit droplets transmission. Accordingly, a new type of ventilation system was proposed based on the concept that the overall space is organized by annular airflow and the local area is direct airflow. Compared with sidewall mixing ventilation system, the infection risk of the new ventilation system presented in this study is reduced by 27%.
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36
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Modeling and Predicting Pulmonary Tuberculosis Incidence and Its Association with Air Pollution and Meteorological Factors Using an ARIMAX Model: An Ecological Study in Ningbo of China. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:ijerph19095385. [PMID: 35564780 PMCID: PMC9105987 DOI: 10.3390/ijerph19095385] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Revised: 04/23/2022] [Accepted: 04/25/2022] [Indexed: 11/24/2022]
Abstract
The autoregressive integrated moving average with exogenous regressors (ARIMAX) modeling studies of pulmonary tuberculosis (PTB) are still rare. This study aims to explore whether incorporating air pollution and meteorological factors can improve the performance of a time series model in predicting PTB. We collected the monthly incidence of PTB, records of six air pollutants and six meteorological factors in Ningbo of China from January 2015 to December 2019. Then, we constructed the ARIMA, univariate ARIMAX, and multivariate ARIMAX models. The ARIMAX model incorporated ambient factors, while the ARIMA model did not. After prewhitening, the cross-correlation analysis showed that PTB incidence was related to air pollution and meteorological factors with a lag effect. Air pollution and meteorological factors also had a correlation. We found that the multivariate ARIMAX model incorporating both the ozone with 0-month lag and the atmospheric pressure with 11-month lag had the best performance for predicting the incidence of PTB in 2019, with the lowest fitted mean absolute percentage error (MAPE) of 2.9097% and test MAPE of 9.2643%. However, ARIMAX has limited improvement in prediction accuracy compared with the ARIMA model. Our study also suggests the role of protecting the environment and reducing pollutants in controlling PTB and other infectious diseases.
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37
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Handiso TB, Jifar MS, Nuriye Hagisso S. Coronavirus’s (SARS-CoV-2) airborne transmission. SAGE Open Med 2022; 10:20503121221094185. [PMID: 35492889 PMCID: PMC9047781 DOI: 10.1177/20503121221094185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 03/19/2022] [Indexed: 01/08/2023] Open
Abstract
This scientific review of mode of transmission of COVID-19 is to aid
scientific community in generating hypothesis. The inadequate evidence
on SARS-CoV-2 transmission has hindered the development of effective
prevention strategy and resulted in continues pandemic of the
COVID-19. Therefore, in this review, existing evidence is discussed,
hypothesis is generated regarding COVID-19 mode of transmission, and
recommendations are forwarded based on existing body of knowledge.
Thus, two meters (2 m) physical distance is not completely safe even
for large droplets and wearing a face mask is a key in the prevention
of SARS-CoV-2 in public areas and confined space and public need to be
vaccinated.
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38
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Stiti M, Castanet G, Corber A, Alden M, Berrocal E. Transition from saliva droplets to solid aerosols in the context of COVID-19 spreading. ENVIRONMENTAL RESEARCH 2022; 204:112072. [PMID: 34562485 PMCID: PMC8459388 DOI: 10.1016/j.envres.2021.112072] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 08/11/2021] [Accepted: 09/11/2021] [Indexed: 05/27/2023]
Abstract
To control the evolution of a pandemic such as COVID-19, knowing the conditions under which the pathogen is being transmitted represents a critical issue, especially when implementing protection strategies such as social distancing and wearing face masks. For viruses and bacteria that spread via airborne and/or droplet pathways, this requires understanding how saliva droplets evolve over time after their expulsion by speaking or coughing. Within this context, the transition from saliva droplets to solid residues, due to water evaporation, is studied here both experimentally, considering the saliva from 5 men and 5 women, and via numerical modeling to accurately predict the dynamics of this process. The model assumes saliva to be a binary water/salt mixture and is validated against experimental results using saliva droplets that are suspended in an ultrasound levitator. We demonstrate that droplets with an initial diameter smaller than 21 μm will produce a solid residue that would be considered an aerosol of <5 μm diameter in less than 2 s (for any relative humidity less than 80% and/or any temperature greater than 20°C). Finally, the model developed here accounts for the influence of the saliva composition, relative humidity and ambient temperature on droplet drying. Thus, the travel distance prior to becoming a solid residue can be deduced. We found that saliva droplets of initial size below 80 μm, which corresponds to the vast majority of speech and cough droplets, will become solid residues prior to touching the ground when expelled from a height of 160 cm.
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Affiliation(s)
- Mehdi Stiti
- Division of Combustion Physics, Department of Physics, Lund University, Lund, Sweden.
| | | | - Andrew Corber
- Aerospace Research Centre, National Research Council of Canada, Ottawa, Canada
| | - Marcus Alden
- Division of Combustion Physics, Department of Physics, Lund University, Lund, Sweden
| | - Edouard Berrocal
- Division of Combustion Physics, Department of Physics, Lund University, Lund, Sweden.
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39
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Zhang K, Fang W, Lv C, Feng XQ. Evaporation of liquid nanofilms: A minireview. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2022; 34:021302. [PMID: 35342277 PMCID: PMC8939525 DOI: 10.1063/5.0082191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 01/24/2022] [Indexed: 06/14/2023]
Abstract
Evaporation of virus-loaded droplets and liquid nanofilms plays a significant role in the pandemic of COVID-19. The evaporation mechanism of liquid nanofilms has attracted much attention in recent decades. In this minireview, we first introduce the relationship between the evaporation process of liquid nanofilms and the pandemic of COVID-19. Then, we briefly provide the frontiers of liquid droplet/nanofilm evaporation on solid surfaces. In addition, we discuss the potential application of machine learning in liquid nanofilm evaporation studies, which is expected to be helpful to build up a more accurate molecular model and to investigate the evaporation mechanism of liquid nanofilms on solid surfaces.
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40
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A missing layer in COVID-19 studies: Transmission of enveloped viruses in mucus-rich droplets. INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER 2022; 131:105746. [PMCID: PMC8576065 DOI: 10.1016/j.icheatmasstransfer.2021.105746] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 11/03/2021] [Indexed: 02/13/2024]
Abstract
Here we evaluate the influence of mucus layers on the evaporation time and transport of enveloped viruses, including SARS-CoV-2. Enveloped viruses must remain moist to be fully infective. Yet, the Wells model based on water droplets divides respiratory droplets into either quickly evaporated aerosolized particles termed droplet nuclei (<10 s) or liquid droplets that fall to the nearest surface, leaving no physical mechanism for airborne transmission of fully infective enveloped viruses over large distances (greater than a few meters). Yet, the role of mucus layers on evaporation times has not been considered even though the formation of mucus shells around liquid cores of respiratory droplets has been shown experimentally. Here we show that mucus shells increase the drying time by orders of magnitude so that enveloped virions may remain well hydrated and, thus, fully infective at substantial distances. This provides a mechanism by which infective enveloped virus particles can transmit as aerosols within buildings and between buildings over extended distances. This analysis is important because public health agencies typically follow the Wells model to establish health policies including social/physical distancing guidelines.
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41
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Investigation on the evaporation and dispersion of human respiratory droplets with COVID-19 virus. INTERNATIONAL JOURNAL OF MULTIPHASE FLOW 2022; 147. [PMCID: PMC8603237 DOI: 10.1016/j.ijmultiphaseflow.2021.103904] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
On March 11, 2020, COVID-19 was declared as a pandemic by World Health Organization (WHO). Effective prevention is indispensable for defeating the ongoing COVID-19 pandemic. The evaporation and diffusion characteristics of the droplet in the air are the critical factors for the virus transmission by droplets. To better understand transmission routes of COVID-19 through respiratory droplets, a new evaporation and dispersion model for respiratory droplets is proposed to estimate droplet lifetime and the size of spreading zone in air. The importance of respiratory activities and environmental factors on the transmission of respiratory viruses are further discussed. The predictive results demonstrate initial particle size, ambient temperature and relative humidity all have significant effect on the survival time and infection distance of respiratory droplets. Decreasing droplet initial size always shortens the lifetime and the transmission distance of respiratory droplets. The 100 μm droplets expelled by talking or coughing can be carried more than 2 m away. Increasing ambient temperature and decreasing ambient humidity can effectively reduce the lifetime and propagation distance of respiratory droplets, thus reducing the risk of viral infection. These findings could contribute to developing effective prevention measures for controlling infectious disease transmission via droplets.
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42
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Fatima S, Ahlawat A, Mishra SK, Maheshwari M, Soni VK. Variations and Source Apportionment of PM2.5 and PM10 Before and During COVID-19 Lockdown Phases in Delhi, India. MAPAN 2022. [PMCID: PMC8785379 DOI: 10.1007/s12647-021-00506-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Major cities across the globe including megacity Delhi have experienced considerable lower levels of air pollutants including particulate matter (PM) during COVID-19 lockdown. This study explores pre-lockdown and during lockdown air quality changes in PM2.5, PM10, PM2.5/PM10 ratio along with meteorological effects. Selected sites with different pollution signatures in Delhi including Alipur (residential), Okhla (industrial) and Pusa Road (traffic) have experienced mean (S.D.) PM2.5 as 87.56(± 54.06), 124.45(± 73.49) and 62.14(± 58.64) µg/m3 and PM10 as 163.01(± 77.37), 217.71(± 93.94) and 135.15(± 77.90) µg/m3 before lockdown (BL), while for Lockdown 1 (L1), PM2.5 concentrations decreased drastically as 39.26(± 16.31), 38.01(± 15.16) and 31.03(± 12.79) µg/m3 and for PM10 as 100.76(± 43.71), 79.47(± 30.97) and 66.53(± 22.78) µg/m3, respectively, with gradual increase in both pollutants during successive lockdown phase—Lockdown 2, Lockdown 3, Lockdown 4 and Unlock phase 1. The percentage (%) decrease in PM2.5 (69.46%) and PM10 (63.49%) during lockdown was found well correlated with people mobility (Google and Apple mobility reports), as outdoor activities showed 70–80% decrease in L1 from BL phase. Source apportionment studies suggested both local and regional pollution contribution in Delhi. Comparison of PM2.5 and PM10 concentrations for the year 2020 with that of 2018 and 2019 and study on diurnal variations of PM2.5 and PM10 have been discussed.
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Affiliation(s)
- Sadaf Fatima
- CSIR-National Physical Laboratory, New Delhi, 110012 India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh 201002 India
| | - Ajit Ahlawat
- Leibniz Institute for Tropospheric Research (TROPOS), Permoserstraße, 04318 Leipzig, Germany
| | - Sumit Kumar Mishra
- CSIR-National Physical Laboratory, New Delhi, 110012 India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh 201002 India
| | | | - Vijay Kumar Soni
- India Meteorological Department, Ministry of Earth Sciences, New Delhi, 110003 India
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43
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Davis G, Li K, Thankam FG, Wilson DR, Agrawal DK. Ocular transmissibility of COVID-19: possibilities and perspectives. Mol Cell Biochem 2022; 477:849-864. [PMID: 35066705 PMCID: PMC8783769 DOI: 10.1007/s11010-021-04336-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Accepted: 12/15/2021] [Indexed: 12/12/2022]
Abstract
Since the initial outbreak of coronavirus disease 2019 (COVID-19), extensive research has emerged from across the globe to understand the pathophysiology of this novel coronavirus. Transmission of this virus is a subject of particular interest as researchers work to understand which protective and preventative measures are most effective. Despite the well understood model of aerosol-respiratory mediated transmission, the exact mechanism underlying the inoculation, infection and spread of COVID-19 is currently unknown. Given anatomical positioning and near constant exposure to aerosolized pathogens, the eye may be a possible gateway for COVID-19 infection. This critical review explores the possibility of an ocular-systemic or ocular-nasal-pulmonic pathway of COVID-19 infection and includes novel insights into the possible immunological mechanisms leading to cytokine surge.
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Affiliation(s)
- Gavin Davis
- Department of Translational Research, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, 309 E. Second Street, Pomona, CA, 91766, USA
| | - Kin Li
- Department of Translational Research, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, 309 E. Second Street, Pomona, CA, 91766, USA
| | - Finosh G Thankam
- Department of Translational Research, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, 309 E. Second Street, Pomona, CA, 91766, USA
| | - Daniel R Wilson
- Department of Translational Research, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, 309 E. Second Street, Pomona, CA, 91766, USA
| | - Devendra K Agrawal
- Department of Translational Research, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, 309 E. Second Street, Pomona, CA, 91766, USA.
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44
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Nazaroff WW. Indoor aerosol science aspects of SARS-CoV-2 transmission. INDOOR AIR 2022; 32:e12970. [PMID: 34873752 DOI: 10.1111/ina.12970] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 11/17/2021] [Accepted: 11/26/2021] [Indexed: 05/04/2023]
Abstract
Knowledge about person-to-person transmission of SARS-CoV-2 is reviewed, emphasizing three components: emission of virus-containing particles and drops from infectious persons; transport and fate of such emissions indoors; and inhalation of viral particles by susceptible persons. Emissions are usefully clustered into three groups: small particles (diameter 0.1-5 µm), large particles (5-100 µm), and ballistic drops (>100 µm). Speaking generates particles and drops across the size spectrum. Small particles are removed from indoor air at room scale by ventilation, filtration, and deposition; large particles mainly deposit onto indoor surfaces. Proximate exposure enhancements are associated with large particles with contributions from ballistic drops. Masking and social distancing are effective in mitigating transmission from proximate exposures. At room scale, masking, ventilation, and filtration can contribute to limit exposures. Important information gaps prevent a quantitative reconciliation of the high overall global spread of COVID-19 with known transmission pathways. Available information supports several findings with moderate-to-high confidence: transmission occurs predominantly indoors; inhalation of airborne particles (up to 50 µm in diameter) contributes substantially to viral spread; transmission occurs in near proximity and at room scale; speaking is a major source of airborne SARS-CoV-2 virus; and emissions can occur without strong illness symptoms.
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Affiliation(s)
- William W Nazaroff
- Department of Civil and Environmental Engineering, University of California, Berkeley, California, USA
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45
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Yang H, Balakuntala MV, Quiñones JJ, Kaur U, Moser AE, Doosttalab A, Esquivel-Puentes A, Purwar T, Castillo L, Ma X, Zhang LT, Voyles RM. Occupant-centric robotic air filtration and planning for classrooms for Safer school reopening amid respiratory pandemics. ROBOTICS AND AUTONOMOUS SYSTEMS 2022; 147:103919. [PMID: 34703078 PMCID: PMC8530773 DOI: 10.1016/j.robot.2021.103919] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 07/17/2021] [Accepted: 10/15/2021] [Indexed: 06/13/2023]
Abstract
Coexisting with the current COVID-19 pandemic is a global reality that comes with unique challenges impacting daily interactions, business, and facility maintenance. A monumental challenge accompanied is continuous and effective disinfection of shared spaces, such as office/school buildings, elevators, classrooms, and cafeterias. Although ultraviolet light and chemical sprays are routines for indoor disinfection, they irritate humans, hence can only be used when the facility is unoccupied. Stationary air filtration systems, while being irritation-free and commonly available, fail to protect all occupants due to limitations in air circulation and diffusion. Hence, we present a novel collaborative robot (cobot) disinfection system equipped with a Bernoulli Air Filtration Module, with a design that minimizes disturbance to the surrounding airflow and maneuverability among occupants for maximum coverage. The influence of robotic air filtration on dosage at neighbors of a coughing source is analyzed with derivations from a Computational Fluid Dynamics (CFD) simulation. Based on the analysis, the novel occupant-centric online rerouting algorithm decides the path of the robot. The rerouting ensures effective air filtration that minimizes the risk of occupants under their detected layout. The proposed system was tested on a 2 × 3 seating grid (empty seats allowed) in a classroom, and the worst-case dosage for all occupants was chosen as the metric. The system reduced the worst-case dosage among all occupants by 26% and 19% compared to a stationary air filtration system with the same flow rate, and a robotic air filtration system that traverses all the seats but without occupant-centric planning of its path, respectively. Hence, we validated the effectiveness of the proposed robotic air filtration system.
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Affiliation(s)
- Haoguang Yang
- Polytechnic Institute, Purdue University, United States of America
| | | | - Jhon J Quiñones
- School of Mechanical Engineering, Purdue University, United States of America
| | - Upinder Kaur
- Polytechnic Institute, Purdue University, United States of America
| | - Abigayle E Moser
- School of Mechanical Engineering, Purdue University, United States of America
- Department of Aerospace Engineering, Iowa State University, United States of America
| | - Ali Doosttalab
- School of Mechanical Engineering, Purdue University, United States of America
| | | | - Tanya Purwar
- School of Mechanical Engineering, Purdue University, United States of America
| | - Luciano Castillo
- School of Mechanical Engineering, Purdue University, United States of America
| | - Xin Ma
- Polytechnic Institute, Purdue University, United States of America
| | - Lucy T Zhang
- Mechanical Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, United States of America
| | - Richard M Voyles
- Polytechnic Institute, Purdue University, United States of America
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46
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Li Y, Cheng P, Jia W. Poor ventilation worsens short-range airborne transmission of respiratory infection. INDOOR AIR 2022; 32:e12946. [PMID: 34704625 PMCID: PMC8652937 DOI: 10.1111/ina.12946] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2020] [Revised: 08/31/2021] [Accepted: 10/12/2021] [Indexed: 05/20/2023]
Abstract
To explain the observed phenomenon that most SARS-CoV-2 transmission occurs indoors whereas its outdoor transmission is rare, a simple macroscopic aerosol balance model is developed to link short- and long-range airborne transmission. The model considers the involvement of exhaled droplets with initial diameter ≤50 µm in the short-range airborne route, whereas only a fraction of these droplets with an initial diameter within 15 µm or equivalently a final diameter within 5 µm considered in the long-range airborne route. One surprising finding is that the room ventilation rate significantly affects the short-range airborne route, in contrast to traditional belief. When the ventilation rate in a room is insufficient, the airborne infection risks due to both short- and long-range transmission are high. A ventilation rate of 10 L/s per person provides a similar concentration vs distance decay profile to that in outdoor settings, which provides additional justification for the widely adopted ventilation standard of 10 L/s per person. The newly obtained data do not support the basic assumption in the existing ventilation standard ASHRAE 62.1 (2019) that the required people outdoor air rate is constant if the standard is used directly for respiratory infection control. Instead, it is necessary to increase the ventilation rate when the physical distance between people is less than approximately 2 m.
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Affiliation(s)
- Yuguo Li
- Department of Mechanical EngineeringThe University of Hong KongHong Kong SARChina
| | - Pan Cheng
- Department of Mechanical EngineeringThe University of Hong KongHong Kong SARChina
| | - Wei Jia
- Department of Mechanical EngineeringThe University of Hong KongHong Kong SARChina
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47
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Coyle JP, Derk RC, Lindsley WG, Blachere FM, Boots T, Lemons AR, Martin SB, Mead KR, Fotta SA, Reynolds JS, McKinney WG, Sinsel EW, Beezhold DH, Noti JD. Efficacy of Ventilation, HEPA Air Cleaners, Universal Masking, and Physical Distancing for Reducing Exposure to Simulated Exhaled Aerosols in a Meeting Room. Viruses 2021; 13:2536. [PMID: 34960804 PMCID: PMC8707272 DOI: 10.3390/v13122536] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 12/07/2021] [Accepted: 12/14/2021] [Indexed: 12/12/2022] Open
Abstract
There is strong evidence associating the indoor environment with transmission of SARS-CoV-2, the virus that causes COVID-19. SARS-CoV-2 can spread by exposure to droplets and very fine aerosol particles from respiratory fluids that are released by infected persons. Layered mitigation strategies, including but not limited to maintaining physical distancing, adequate ventilation, universal masking, avoiding overcrowding, and vaccination, have shown to be effective in reducing the spread of SARS-CoV-2 within the indoor environment. Here, we examine the effect of mitigation strategies on reducing the risk of exposure to simulated respiratory aerosol particles within a classroom-style meeting room. To quantify exposure of uninfected individuals (Recipients), surrogate respiratory aerosol particles were generated by a breathing simulator with a headform (Source) that mimicked breath exhalations. Recipients, represented by three breathing simulators with manikin headforms, were placed in a meeting room and affixed with optical particle counters to measure 0.3-3 µm aerosol particles. Universal masking of all breathing simulators with a 3-ply cotton mask reduced aerosol exposure by 50% or more compared to scenarios with simulators unmasked. While evaluating the effect of Source placement, Recipients had the highest exposure at 0.9 m in a face-to-face orientation. Ventilation reduced exposure by approximately 5% per unit increase in air change per hour (ACH), irrespective of whether increases in ACH were by the HVAC system or portable HEPA air cleaners. The results demonstrate that mitigation strategies, such as universal masking and increasing ventilation, reduce personal exposure to respiratory aerosols within a meeting room. While universal masking remains a key component of a layered mitigation strategy of exposure reduction, increasing ventilation via system HVAC or portable HEPA air cleaners further reduces exposure.
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Affiliation(s)
- Jayme P. Coyle
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, WV 26505, USA; (J.P.C.); (R.C.D.); (F.M.B.); (T.B.); (A.R.L.); (J.S.R.); (W.G.M.); (E.W.S.); (D.H.B.); (J.D.N.)
| | - Raymond C. Derk
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, WV 26505, USA; (J.P.C.); (R.C.D.); (F.M.B.); (T.B.); (A.R.L.); (J.S.R.); (W.G.M.); (E.W.S.); (D.H.B.); (J.D.N.)
| | - William G. Lindsley
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, WV 26505, USA; (J.P.C.); (R.C.D.); (F.M.B.); (T.B.); (A.R.L.); (J.S.R.); (W.G.M.); (E.W.S.); (D.H.B.); (J.D.N.)
| | - Francoise M. Blachere
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, WV 26505, USA; (J.P.C.); (R.C.D.); (F.M.B.); (T.B.); (A.R.L.); (J.S.R.); (W.G.M.); (E.W.S.); (D.H.B.); (J.D.N.)
| | - Theresa Boots
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, WV 26505, USA; (J.P.C.); (R.C.D.); (F.M.B.); (T.B.); (A.R.L.); (J.S.R.); (W.G.M.); (E.W.S.); (D.H.B.); (J.D.N.)
| | - Angela R. Lemons
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, WV 26505, USA; (J.P.C.); (R.C.D.); (F.M.B.); (T.B.); (A.R.L.); (J.S.R.); (W.G.M.); (E.W.S.); (D.H.B.); (J.D.N.)
| | - Stephen B. Martin
- Respiratory Health Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, WV 26505, USA;
| | - Kenneth R. Mead
- Division of Field Studies and Engineering, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Cincinnati, OH 45226, USA;
| | - Steven A. Fotta
- Facilities Management Office, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, WV 26505, USA;
| | - Jeffrey S. Reynolds
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, WV 26505, USA; (J.P.C.); (R.C.D.); (F.M.B.); (T.B.); (A.R.L.); (J.S.R.); (W.G.M.); (E.W.S.); (D.H.B.); (J.D.N.)
| | - Walter G. McKinney
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, WV 26505, USA; (J.P.C.); (R.C.D.); (F.M.B.); (T.B.); (A.R.L.); (J.S.R.); (W.G.M.); (E.W.S.); (D.H.B.); (J.D.N.)
| | - Erik W. Sinsel
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, WV 26505, USA; (J.P.C.); (R.C.D.); (F.M.B.); (T.B.); (A.R.L.); (J.S.R.); (W.G.M.); (E.W.S.); (D.H.B.); (J.D.N.)
| | - Donald H. Beezhold
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, WV 26505, USA; (J.P.C.); (R.C.D.); (F.M.B.); (T.B.); (A.R.L.); (J.S.R.); (W.G.M.); (E.W.S.); (D.H.B.); (J.D.N.)
| | - John D. Noti
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, WV 26505, USA; (J.P.C.); (R.C.D.); (F.M.B.); (T.B.); (A.R.L.); (J.S.R.); (W.G.M.); (E.W.S.); (D.H.B.); (J.D.N.)
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48
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Muthusamy J, Haq S, Akhtar S, Alzoubi MA, Shamim T, Alvarado J. Implication of coughing dynamics on safe social distancing in an indoor environment-A numerical perspective. BUILDING AND ENVIRONMENT 2021; 206:108280. [PMID: 34493895 PMCID: PMC8413013 DOI: 10.1016/j.buildenv.2021.108280] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 08/17/2021] [Accepted: 08/18/2021] [Indexed: 05/30/2023]
Abstract
Coughing is a primary symptomatic pathway of respiratory or air-borne disease transmission, including COVID-19. Several parameters such as cougher's age, gender, and posture affect particle dispersion indoors. This study numerically investigates the transient cough evolution, contamination range, particle reach probability, and deposition fraction for different age groups of males and females in standing and sitting postures in a ventilated room. The efficacy of a cloth mask has also been studied with and without the influence of air ventilation. Validated Computational Fluid Dynamics methodology has been implemented to model complex physics such as turbulent buoyant cloud, particle-air interaction, particle collision/breakup, and droplet evaporation. Our results show that overall, the contamination range is slightly lower for females due to lower cough velocities and particle counts. Moreover, a significant fraction of particles crosses the two meters social distancing guideline threshold with an unhindered cough. Besides, wearing a cloth mask reduces the average contamination range by approximately two-third of the distance compared to coughing without the mask. However, aerosolized particles reach longer streamwise distances and drift for extended durations beyond thirty seconds. This study can be used to improve the heating, ventilation, and air conditioning recommendations and distancing guidelines in indoor settings.
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Affiliation(s)
- Jayaveera Muthusamy
- Department of Mechanical Engineering, Texas A&M University, College Station, TX, USA
| | - Syed Haq
- Department of Mechanical Engineering, Texas A&M University, College Station, TX, USA
| | - Saad Akhtar
- Department of Mining and Materials Engineering, McGill University, Montreal, QC, Canada
| | - Mahmoud A Alzoubi
- Department of Mechanical Engineering, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Tariq Shamim
- Department of Mechanical Engineering, Northern Illinois University, DeKalb, IL, USA
| | - Jorge Alvarado
- Department of Engineering Technology and Industrial Distribution, Texas A&M University, College Station, TX, USA
- Department of Mechanical Engineering, Texas A&M University, College Station, TX, USA
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Jarvis MC. Drying of virus-containing particles: modelling effects of droplet origin and composition. JOURNAL OF ENVIRONMENTAL HEALTH SCIENCE & ENGINEERING 2021; 19:1987-1996. [PMID: 34754455 PMCID: PMC8569499 DOI: 10.1007/s40201-021-00750-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 10/17/2021] [Indexed: 05/13/2023]
Abstract
BACKGROUND AND PURPOSE Virus-containing aerosol droplets emitted by breathing, speech or coughing dry rapidly to equilibrium with ambient relative humidity (RH), increasing in solute concentration with effects on virus survival and decreasing in diameter with effects on sedimentation and respiratory uptake. The aim of this paper is to model the effect of ionic and macromolecular solutes on droplet drying and solute concentration. METHODS Deliquescence-efflorescence concepts and Kohler theory were used to simulate the evolution of solute concentrations and water activity in respiratory droplets, starting from efflorescence data on mixed NaCl/KCl aerosols and osmotic pressure data on respiratory macromolecules. RESULTS In NaCl/KCl solutions total salt concentrations were shown to reach 10-13 M at the efflorescence RH of 40-55%, depending on the K:Na ratio. Dependence on K:Na ratio implies that the evaporation curves differ between aerosols derived from saliva and from airway surfaces. The direct effect of liquid droplet size through the Kelvin term was shown to be smaller and restricted to the evolution of breath emissions. Modelling the effect of proteins and glycoproteins showed that salts determine drying equilibria down to the efflorescence RH, and macromolecules at lower RH. CONCLUSION Differences in solute composition between airway surfaces and saliva are predicted to lead to different drying behaviour of droplets emitted by breathing, speech and coughing. These differences may influence the inactivation of viruses.
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Affiliation(s)
- Michael C. Jarvis
- School of Chemistry, Glasgow University, Glasgow, Scotland G12 8QQ UK
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Influence of ambient conditions on evaporation and transport of respiratory droplets in indoor environment. INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER 2021; 129. [PMCID: PMC8577817 DOI: 10.1016/j.icheatmasstransfer.2021.105750] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Respiratory droplets are playing a significant role in the transmission of any flu type disease as well as SARS-Cov-2 virus. The presence of pathogens affects the evaporation of the liquid droplets along with ambient temperature and relative humidity (rh). Complete evaporation of droplets leads to the formation of aerosol or droplet nuclei which remain suspended in the air for a longer period of time and get spread over larger distances increasing the risk of disease transmission. In present work, a droplet evaporation model has been formulated considering the droplet as a salt solution and the formation of crystals has been taken into account which will be analogous to the aerosol formation. After the establishment of the evaporation model, the trajectories of the droplets are investigated considering a turbulent round jet model during exhalation. Aerosols are found to be spreading over distances of 8 to 9 m which is quite alarming. Large droplets get converted to smaller ones but the viral loading of the large droplets is much higher than the smaller as viral loading is proportional to initial size. This is highlighted by the viral load contour and the mean diameter line contour for a half-height window. Different weather conditions are investigated to observe the evaporation of droplets and the formation of aerosols in order to qualitatively analyse the risks associated with each city in specific weather conditions. Hot and dry conditions are most favourable to aerosol formation.
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