Far-UVC efficiently inactivates an airborne pathogen in a room-sized chamber

Abstract Many infectious diseases, including COVID-19, are transmitted by airborne pathogens. There is a need for effective environmental control measures which, ideally, are not reliant on human behaviour. One potential solution is Far-UVC which can efficiently inactivate pathogens, such as coronaviruses and influenza, in air. When appropriately filtered, and because of its limited penetration, there is evidence that Far-UVC does not induce acute reactions in the skin or eyes, nor delayed effects such as skin cancer. While there is laboratory evidence for far-UVC efficacy, there is limited evidence in full-sized rooms. In the first study of its type, we show that Far-UVC deployed in a room-sized chamber effectively inactivates aerosolised Staphylococcus aureus. At a room ventilation rate of 3 air changes per hour (ACH), with 5 filtered sources the steady-state pathogen load was reduced by 92.1% providing an additional 35 equivalent air changes (eACH). This reduction was achieved using Far-UVC intensities consistent with current regulatory limits. Far-UVC is likely to be more effective against common airborne viruses, including SARS-CoV-2, and should thus be an effective and “hands-off” technology to reduce airborne disease transmission. The findings provide room-scale data to support the design and development of safe and effective Far-UVC systems.

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Beyond well-mixed: a simple probabilistic model of airborne disease transmission in indoor spaces

10.1101/2021.12.05.21267319 ◽

2021 ◽

Author(s):

Sijian Tan ◽

Zhihang Zhang ◽

Kevin Maki ◽

Krzysztof J. Fidkowski ◽

Jesse Capecelatro

Keyword(s):

Disease Transmission ◽

Risk Model ◽

Ventilation Rate ◽

Turbulent Dispersion ◽

Balance Model ◽

Wide Range ◽

Ventilation Rates ◽

Airborne Disease ◽

Droplet Nuclei ◽

Indoor Spaces

AbstractWe develop a simple model for assessing risk of airborne disease transmission that accounts for non-uniform mixing in indoor spaces and is compatible with existing epidemiological models. A database containing 174 high-resolution simulations of airflow in classrooms, lecture halls, and buses is generated and used to quantify the spatial distribution of expiratory droplet nuclei for a wide range of ventilation rates, exposure times, and room configurations. Imperfect mixing due to obstructions, buoyancy, and turbulent dispersion results in concentration fields with significant variance. The spatial non-uniformity is found to be accurately described by a shifted lognormal distribution. A well-mixed mass balance model is used to predict the mean, and the standard deviation is parameterized based on ventilation rate and room geometry. When employed in a dose-response function risk model, infection probability can be estimated considering spatial heterogeneity that contributes to both short- and long-range transmission.

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A Computational Framework for Transmission Risk Assessment of Aerosolized Particles in Classrooms

10.21203/rs.3.rs-902643/v1 ◽

2021 ◽

Author(s):

Kendrick Tan ◽

Boshun Gao ◽

Cheng-Hau Yang ◽

Emily Johnson ◽

Ming-Chen Hsu ◽

...

Keyword(s):

Risk Assessment ◽

Disease Transmission ◽

Ventilation Rate ◽

Mitigation Strategies ◽

Transmission Risk ◽

Computational Framework ◽

Seating Arrangement ◽

K 12 ◽

Education Administrators ◽

Airborne Disease

Abstract The ongoing COVID-19 pandemic has rendered confined spaces as high-risk areas. There is an increasing push to resume in-person activities, for instance, teaching in K-12 and university settings. It becomes important to evaluate the risk of airborne disease transmission while accounting for the physical presence of humans, furniture, and electronic equipment, as well as ventilation. Here, we present a computational framework based on detailed flow physics simulations that allows straightforward evaluation of various seating and operating scenarios to identify risk factors and assess the effectiveness of various mitigation strategies. These scenarios include seating arrangement changes, presence/absence of computer screens, ventilation rate changes, and presence/absence of mask-wearing. This approach democratizes risk assessment by automating a key bottleneck in simulation-based analysis--creating an adequately refined mesh around multiple complex geometries. Not surprisingly, we find that wearing masks (with at least 74% inward protection efficiency) significantly reduced transmission risk against unmasked and infected individuals. The availability of such an analysis approach will allow education administrators, government officials (courthouses, police stations), and hospital administrators to make informed decisions on seating arrangements and operating procedures.

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Water Quality in the Priority Watercourses of Hong Kong in Respect of Various Environmental Control Measures

Water Science & Technology ◽

10.2166/wst.1991.0404 ◽

1991 ◽

Vol 23 (1-3) ◽

pp. 85-91 ◽

Cited By ~ 1

Author(s):

Ho Kin-chung

Keyword(s):

Water Quality ◽

Hong Kong ◽

Environmental Control ◽

Control Measures ◽

Livestock Waste ◽

Water Control ◽

Control Zone ◽

Town Development ◽

Control Scheme ◽

Term Monitoring

The water quality in the 12 priority watercourses of Hong Kong was appraised in respect of the various environmental control measures being undertaken. It was noted that water quality in Lam Tsuen River had been significantly improved since 1983. This is attributed to recent resumption of unsewered lands for town development, training of river basin to increase flow, and declaration of the catchment as a “Water Control Zone” under the Water Pollution Control Ordinance. In contrast with the other heavily polluted watercourses to which little abatement measures were implemented, the water qualities of Shing Mun River and Tuen Mun River were slightly upgraded because of the efforts to rectify unauthorized industrial discharges back to foul sewer and provision of interceptors and sewers to villages. The 10 year Livestock Waste Control Scheme enforced on 24 June 1989 was found in parallel with BOD and suspended solids decrease in watercourses. To assess its effectiveness, however, a longer term monitoring is required to get a conclusive result.

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Transmission of SARS-CoV-2 in Different Districts of a County in Istanbul, March to September 2020

Asia Pacific Journal of Public Health ◽

10.1177/10105395211009008 ◽

2021 ◽

pp. 101053952110090

Author(s):

Hüseyin Bilgin ◽

Ahmet Topuzoğlu ◽

Volkan Korten

Keyword(s):

Public Transportation ◽

Disease Transmission ◽

Geographical Information Systems ◽

Geographical Information ◽

Chain Reaction ◽

Heat Map ◽

Large Populations ◽

Polymerase Chain ◽

Education Tool ◽

Airborne Viruses

Epidemics caused by airborne viruses in cities with large populations create a big problem as in the current COVID-19 pandemic. Cramped lifestyle, busy workplaces, crowded public transportation, and higher household member counts are responsible for the transmission of the disease. In Turkey, Istanbul has taken the lead in the number of cases since the beginning of the epidemic. The excess population density is the major cause for disease transmission. It is essential to monitor the contaminated regions with geographical information systems on city maps. Outbreak maps visualize and help analyze the patterns of transmission and serve as a communication and education tool. A dynamic heat map video of SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) polymerase chain reaction positive cases in a county of Istanbul was generated. The heat map visualizes how the epidemic spread to all the districts and the cumulative cases increased in one county of Istanbul with real attack rates.

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Splatters and Aerosols Contamination in Dental Aerosol Generating Procedures

Applied Sciences ◽

10.3390/app11041914 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1914

Author(s):

Pingping Han ◽

Honghui Li ◽

Laurence J. Walsh ◽

Sašo Ivanovski

Keyword(s):

Particle Size ◽

Disease Transmission ◽

High Speed ◽

Low Speed ◽

Dental Procedures ◽

Dental Equipment ◽

Produce Contamination ◽

Fluorescein Dye ◽

Filter Papers ◽

Airborne Disease

Dental aerosol-generating procedures produce a large amount of splatters and aerosols that create a major concern for airborne disease transmission, such as COVID-19. This study established a method to visualise splatter and aerosol contamination by common dental instrumentation, namely ultrasonic scaling, air-water spray, high-speed and low-speed handpieces. Mock dental procedures were performed on a mannequin model, containing teeth in a typodont and a phantom head, using irrigation water containing fluorescein dye as a tracer. Filter papers were placed in 10 different locations to collect splatters and aerosols, at distances ranging from 20 to 120 cm from the source. All four types of dental equipment produced contamination from splatters and aerosols. At 120 cm away from the source, the high-speed handpiece generated the greatest amount and size (656 ± 551 μm) of splatter particles, while the triplex syringe generated the largest amount of aerosols (particle size: 1.73 ± 2.23 μm). Of note, the low-speed handpiece produced the least amount and size (260 ± 142 μm) of splatter particles and the least amount of aerosols (particle size: 4.47 ± 5.92 μm) at 120 cm. All four dental AGPs produce contamination from droplets and aerosols, with different patterns of distribution. This simple model provides a method to test various preventive strategies to reduce risks from splatter and aerosols.

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Extended Lifetime of Respiratory Droplets in a Turbulent Vapor Puff and Its Implications on Airborne Disease Transmission

Physical Review Letters ◽

10.1103/physrevlett.126.034502 ◽

2021 ◽

Vol 126 (3) ◽

Cited By ~ 2

Author(s):

Kai Leong Chong ◽

Chong Shen Ng ◽

Naoki Hori ◽

Rui Yang ◽

Roberto Verzicco ◽

...

Keyword(s):

Disease Transmission ◽

Airborne Disease ◽

Respiratory Droplets

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Overview: The allergic reaction and site-based therapy

Otolaryngology ◽

10.1177/019459989210700602.2 ◽

1992 ◽

Vol 107 (6_part_2) ◽

pp. 828-830 ◽

Cited By ~ 2

Author(s):

Richard L. Mabry

Keyword(s):

Allergic Reaction ◽

Environmental Control ◽

Allergic Patient ◽

Control Measures ◽

Rational Approach ◽

Upper Respiratory Tract ◽

Mediators Of Inflammation ◽

Care Approach ◽

Step Care ◽

Step Care Approach

The successful management of upper respiratory tract allergy is based on a triad of interdependent approaches that, with rare exceptions, must all be considered in every allergic patient. They consist of allergen avoidance with environmental control measures, pharmacotherapy with use of a step-care approach, and immunotherapy. Environmental control measures should be used to prevent events that trigger and sustain the condition. Once started, the allergic reaction includes the release of mediators of inflammation that produce well-known symptoms of allergic rhinitis. Treatment should consist of a step-wise, rational approach that includes site-based therapy with one or more drugs acting at different sites. The drugs used are antihistamines, decongestants, cromolyn sodium, and corticosteroids. Immunotherapy should be considered at any step, because it offers the only curative approach.

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