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1.
BMJ ; 375: n3050, 2021 12 16.
Article in English | MEDLINE | ID: covidwho-1583147
2.
Viruses ; 13(12)2021 12 17.
Article in English | MEDLINE | ID: covidwho-1580426

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.


Subject(s)
Air Pollution, Indoor/prevention & control , Inhalation Exposure/prevention & control , Masks , Physical Distancing , Ventilation , Air Conditioning , COVID-19/prevention & control , Humans , SARS-CoV-2/isolation & purification
3.
Environ Sci Pollut Res Int ; 28(29): 39322-39332, 2021 Aug.
Article in English | MEDLINE | ID: covidwho-1549509

ABSTRACT

The objective of this study is to understand the effect of indoor air stability on personal exposure to infectious contaminant in the breathing zone. Numerical simulations are carried out in a test chamber with a source of infectious contaminant and a manikin (Manikin A). To give a good visual illustration of the breathing zone, the contaminant source is visualized by the mouth of another manikin. Manikin A is regarded as a vulnerable individual to infectious contaminant. Exposure index and exposure intensity are used as indicators of the exposure level in the breathing zone. The results show that in the stable condition, the infectious contaminant proceeds straightly towards the breathing zone of the vulnerable individual, leading to a relatively high exposure level. In the unstable condition, the indoor air experiences a strong mixing due to the heat exchange between the hot bottom air and the cool top air, so the infectious contaminant disperses effectively from the breathing zone. The unstable air can greatly reduce personal exposure to the infectious contaminant in the breathing zone. This study demonstrates the importance of indoor air stability on personal exposure in the indoor environment and provides a new direction for future study of personal exposure reduction in the indoor environment.


Subject(s)
Air Pollution, Indoor , Ventilation , Air Movements , Air Pollution, Indoor/analysis , Manikins
4.
Ind Health ; 59(5): 318-324, 2021 Oct 05.
Article in English | MEDLINE | ID: covidwho-1547178

ABSTRACT

COVID-19 is around the world. We attempt to apply three-step method in ISO/IEC Guide 51: 2014 to COVID-19 infection control in the workplace. The results show that the COVID-19 infection control measures include the eradication of the virus, the destruction of infectivity, the detoxification and weakening and the elimination of opportunities for infection as "Inherently Safe Design Measures", the avoidance of contact as "Safeguarding and Complementary Protective Measures" and the reduction of contact and the avoidance of seriousness as "Information for Use". Among these specific measures, the New Normal, especially in the manufacturing industries, would be "telecommuting" and "unmanned workplaces", which are part of the elimination of opportunities for infection, and "changes in flow lines" and "changes in airflow", which are part of the avoidance of contact. Where "telecommuting" and "unmanned workplaces" are feasible, they should be implemented as much as possible, and where they are not, attempts should be made to minimize human-to-human contact by "changes in flow lines". In addition, in the area of "changes in airflow", there are high expectations for future research on how to establish a ventilation design for COVID-19, in which but also the source would be workers themselves, not only combustible gases and toxic gases.


Subject(s)
COVID-19/epidemiology , COVID-19/prevention & control , Infection Control/organization & administration , Occupational Health/standards , Workplace/organization & administration , Global Health , Humans , Infection Control/standards , Manufacturing and Industrial Facilities/standards , SARS-CoV-2 , Teleworking , Ventilation/standards , Workplace/standards
5.
BMC Infect Dis ; 21(1): 1193, 2021 Nov 26.
Article in English | MEDLINE | ID: covidwho-1538062

ABSTRACT

BACKGROUND: Effective vaccines are now available for SARS-CoV-2 in the 2nd year of the COVID-19 pandemic, but there remains significant uncertainty surrounding the necessary vaccination rate to safely lift occupancy controls in public buildings and return to pre-pandemic norms. The aim of this paper is to estimate setting-specific vaccination thresholds for SARS-CoV-2 to prevent sustained community transmission using classical principles of airborne contagion modeling. We calculated the airborne infection risk in three settings, a classroom, prison cell block, and restaurant, at typical ventilation rates, and then the expected number of infections resulting from this risk at varying percentages of occupant immunity. RESULTS: We estimate the setting-specific immunity threshold for control of wild-type SARS-CoV-2 to range from a low of 40% for a mechanically ventilation classroom to a high of 85% for a naturally ventilated restaurant. CONCLUSIONS: If vaccination rates are limited to a theoretical minimum of approximately two-thirds of the population, enhanced ventilation above minimum standards for acceptable air quality is needed to reduce the frequency and severity of SARS-CoV-2 superspreading events in high-risk indoor environments.


Subject(s)
Air Pollution, Indoor , COVID-19 , Humans , Pandemics , SARS-CoV-2 , Vaccination , Ventilation
7.
Eur Rev Med Pharmacol Sci ; 25(21): 6745-6766, 2021 11.
Article in English | MEDLINE | ID: covidwho-1524863

ABSTRACT

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that has created the current pandemic, has caused a worldwide worry. Different countries have since enforced varying levels of lockdowns and guidelines for their populations to follow in a serious effort to mitigate the spread. Up until recently, the majority of these regulations and policies were established on the assumption that the dominant routes of transmission of this virus are through droplets and fomite contact. However, there is now a substantial amount of research pointing towards the strong possibility that SARS-CoV-2 can spread through airborne means. The World Health Organization (WHO) and the Center for Disease Control and Prevention (CDC) have recently recognized this, which poses the question of whether our collective methods of lessening transmission risk and keeping people safe have been sufficient. This paper is a comprehensive review of the evidence on SARS-CoV-2 being an airborne disease, through different epidemiological, experimental, and animal-model based published research. Studies opposing this evidence have also been discussed. The majority of these studies are favoring the high plausibility of SARS-CoV-2 aerosol transmission, and therefore the many implications of aerosol transmission have been discussed in this paper to suggest effective mitigation and control strategies.


Subject(s)
Aerosols , COVID-19/transmission , SARS-CoV-2/physiology , Animals , COVID-19/epidemiology , COVID-19/prevention & control , COVID-19/virology , Cricetinae , Disease Models, Animal , Equipment and Supplies, Hospital/virology , Feces/virology , Humans , Masks , Pandemics , Particulate Matter , RNA, Viral/metabolism , SARS-CoV-2/genetics , SARS-CoV-2/isolation & purification , Ventilation/standards , Virus Inactivation
8.
PLoS One ; 16(11): e0257549, 2021.
Article in English | MEDLINE | ID: covidwho-1511814

ABSTRACT

Particulate generation occurs during exercise-induced exhalation, and research on this topic is scarce. Moreover, infection-control measures are inadequately implemented to avoid particulate generation. A laminar airflow ventilation system (LFVS) was developed to remove respiratory droplets released during treadmill exercise. This study aimed to investigate the relationship between the number of aerosols during training on a treadmill and exercise intensity and to elucidate the effect of the LFVS on aerosol removal during anaerobic exercise. In this single-center observational study, the exercise tests were performed on a treadmill at Running Science Lab in Japan on 20 healthy subjects (age: 29±12 years, men: 80%). The subjects had a broad spectrum of aerobic capacities and fitness levels, including athletes, and had no comorbidities. All of them received no medication. The exercise intensity was increased by 1-km/h increments until the heart rate reached 85% of the expected maximum rate and then maintained for 10 min. The first 10 subjects were analyzed to examine whether exercise increased the concentration of airborne particulates in the exhaled air. For the remaining 10 subjects, the LFVS was activated during constant-load exercise to compare the number of respiratory droplets before and after LFVS use. During exercise, a steady amount of particulates before the lactate threshold (LT) was followed by a significant and gradual increase in respiratory droplets after the LT, particularly during anaerobic exercise. Furthermore, respiratory droplets ≥0.3 µm significantly decreased after using LFVS (2120800±759700 vs. 560 ± 170, p<0.001). The amount of respiratory droplets significantly increased after LT. The LFVS enabled a significant decrease in respiratory droplets during anaerobic exercise in healthy subjects. This study's findings will aid in exercising safely during this pandemic.


Subject(s)
Air Conditioning/methods , COVID-19/prevention & control , Exercise/physiology , Particulate Matter/chemistry , Adult , Aerosols/chemistry , Air Filters , Anaerobic Threshold/physiology , COVID-19/metabolism , Exercise Test/methods , Exhalation/physiology , Female , Heart Rate/physiology , Humans , Japan , Lactic Acid/metabolism , Male , Oxygen Consumption/physiology , Respiration , Respiratory System/physiopathology , Running/physiology , SARS-CoV-2/pathogenicity , Ventilation/methods
10.
Sensors (Basel) ; 21(21)2021 Oct 30.
Article in English | MEDLINE | ID: covidwho-1488704

ABSTRACT

Since students and teachers spend much of their time in educational buildings, it is critical to provide good levels of indoor environmental quality (IEQ). The current COVID-19 pandemic has shown that maintaining a good indoor air quality level is an effective measure to control the transmission of the SARS-CoV-2 virus. This study used sensors to monitor key IEQ factors and assess several natural ventilation scenarios in a classroom of the University of Granada. Subsequently, the IEQ factors (temperature, relative humidity, CO2 concentration, acoustic environment, and air velocity) were evaluated for the selected ventilation scenarios in the occupied classroom, and the field monitoring was carried out in two different assessment periods, winter and summer. The obtained results show that the CO2 concentration levels were well below the recommended limits. However, the maintenance of the recommended thermal and acoustic IEQ factors was significantly affected by the natural ventilation strategies (temperature and relative humidity values were very close to the outside values, and the background sound pressure level was over 35 dBA during the entire assessment). The proper measurements and careful selection of the appropriate ventilation scenarios become of utmost importance to ensure that the ventilation rates required by the health authorities are achieved.


Subject(s)
Air Pollution, Indoor , COVID-19 , Air Pollution, Indoor/analysis , Environmental Monitoring , Humans , Pandemics , SARS-CoV-2 , Spain , Temperature , Ventilation
11.
Sci Total Environ ; 806(Pt 3): 151349, 2022 Feb 01.
Article in English | MEDLINE | ID: covidwho-1487964

ABSTRACT

BACKGROUND: Ventilation has emerged as an important strategy to reduce indoor aerosol transmission of coronavirus disease 2019. Indoor air carbon dioxide (CO2) concentrations are a surrogate measure of respiratory pathogen transmission risk. OBJECTIVES: To determine whether CO2 monitors are necessary and effective to improve ventilation in hospitals. METHODS: A randomized, placebo (sham)-controlled, crossover, open label trial. Between February and May 2021, we placed CO2 monitors in twelve double-bed patient rooms across two geriatric wards. Staff were instructed to open windows, increase the air exchange rate and reduce room crowding to maintain indoor air CO2 concentrations ≤800 parts per million (ppm). RESULTS: CO2 levels increased during morning care and especially in rooms housing couples (rooming-in). The median (interquartile range, IQR) time/day with CO2 concentration > 800 ppm (primary outcome) was 110 min (IQR 47-207) at baseline, 82 min (IQR 12-226.5) during sham periods, 78 min (IQR 20-154) during intervention periods and 140 min (IQR 19.5-612.5) post-intervention. The intervention period only differed significantly from the post-intervention period (P = 0.02), mainly due to an imbalance in rooming-in. Significant but small differences were observed in secondary outcomes of time/day with CO2 concentrations > 1000 ppm and daily peak CO2 concentrations during the intervention vs. baseline and vs. the post-intervention period, but not vs. sham. Staff reported cold discomfort for patients as the main barrier towards increasing ventilation. DISCUSSION: Indoor air CO2 concentrations in hospital rooms commonly peaked above recommended levels, especially during morning care and rooming-in. There are many possible barriers towards implementing CO2 monitors to improve ventilation in a real-world hospital setting. A paradigm shift in hospital infection control towards adequate ventilation is warranted. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT04770597.


Subject(s)
Air Pollution, Indoor , COVID-19 , Aged , Air Pollution, Indoor/analysis , Carbon Dioxide/analysis , Cross-Over Studies , Hospitals , Humans , SARS-CoV-2 , Ventilation
12.
PLoS Comput Biol ; 17(10): e1009474, 2021 10.
Article in English | MEDLINE | ID: covidwho-1477508

ABSTRACT

The role of heating, ventilation, and air-conditioning (HVAC) systems in the transmission of SARS-CoV-2 is unclear. To address this gap, we simulated the release of SARS-CoV-2 in a multistory office building and three social gathering settings (bar/restaurant, nightclub, wedding venue) using a well-mixed, multi-zone building model similar to those used by Wells, Riley, and others. We varied key factors of HVAC systems, such as the Air Changes Per Hour rate (ACH), Fraction of Outside Air (FOA), and Minimum Efficiency Reporting Values (MERV) to examine their effect on viral transmission, and additionally simulated the protective effects of in-unit ultraviolet light decontamination (UVC) and separate in-room air filtration. In all building types, increasing the ACH reduced simulated infections, and the effects were seen even with low aerosol emission rates. However, the benefits of increasing the fraction of outside air and filter efficiency rating were greatest when the aerosol emission rate was high. UVC filtration improved the performance of typical HVAC systems. In-room filtration in an office setting similarly reduced overall infections but worked better when placed in every room. Overall, we found little evidence that HVAC systems facilitate SARS-CoV-2 transmission; most infections in the simulated office occurred near the emission source, with some infections in individuals temporarily visiting the release zone. HVAC systems only increased infections in one scenario involving a marginal increase in airflow in a poorly ventilated space, which slightly increased the likelihood of transmission outside the release zone. We found that improving air circulation rates, increasing filter MERV rating, increasing the fraction of outside air, and applying UVC radiation and in-room filtration may reduce SARS-CoV-2 transmission indoors. However, these mitigation measures are unlikely to provide a protective benefit unless SARS-CoV-2 aerosol emission rates are high (>1,000 Plaque-forming units (PFU) / min).


Subject(s)
Air Conditioning , COVID-19/transmission , Heating , SARS-CoV-2 , Ventilation , Aerosols , Air Microbiology , Air Movements , COVID-19/prevention & control , COVID-19/virology , Computational Biology , Computer Simulation , Humans , Models, Biological , Pandemics , SARS-CoV-2/radiation effects , Social Interaction , Ultraviolet Rays , Workplace
13.
Environ Int ; 157: 106814, 2021 12.
Article in English | MEDLINE | ID: covidwho-1474520

ABSTRACT

We examined the trade-offs between in-car aerosol concentrations, ventilation and respiratory infection transmission under three ventilation settings: windows open (WO); windows closed with air-conditioning on ambient air mode (WC-AA); and windows closed with air-conditioning on recirculation (WC-RC). Forty-five runs, covering a total of 324 km distance on a 7.2-km looped route, were carried out three times a day (morning, afternoon, evening) to monitor aerosols (PM2.5; particulate matter < 2.5 µm and PNC; particle number concentration), CO2 and environmental conditions (temperature and relative humidity). Ideally, higher ventilation rates would give lower in-car pollutant concentrations due to dilution from outdoor air. However, in-car aerosol concentrations increased with ventilation (WO > WC-AA > WC-RC) due to the ingress of polluted outdoor air on urban routes. A clear trade-off, therefore, exists for the in-car air quality (icAQ) versus ventilation; for example, WC-RC showed the least aerosol concentrations (i.e. four-times lower compared with WO), but corresponded to elevated CO2 levels (i.e. five-times higher compared with WO) in 20 mins. We considered COVID-19 as an example of respiratory infection transmission. The probability of its transmission from an infected occupant in a five-seater car was estimated during different quanta generation rates (2-60.5 quanta hr-1) using the Wells-Riley model. In WO, the probability with 50%-efficient and without facemasks under normal speaking (9.4 quanta hr-1) varied only by upto 0.5%. It increased by 2-fold in WC-AA (<1.1%) and 10-fold in WC-RC (<5.2%) during a 20 mins trip. Therefore, a wise selection of ventilation settings is needed to balance in-car exposure in urban areas affected by outdoor air pollution and that by COVID-19 transmission. We also successfully developed and assessed the feasibility of using sensor units in static and dynamic environments to monitor icAQ and potentially infer COVID-19 transmission. Further research is required to develop automatic-alarm systems to help reduce both pollutant exposure and infection from respiratory COVID-19 transmission.


Subject(s)
Air Pollutants , COVID-19 , Aerosols , Air Pollutants/analysis , Automobiles , Humans , Particulate Matter/analysis , SARS-CoV-2 , Ventilation
15.
PLoS One ; 16(10): e0258382, 2021.
Article in English | MEDLINE | ID: covidwho-1463317

ABSTRACT

The COVID-19 global pandemic has caused millions of infections and deaths despite mitigation efforts that involve physical distancing, mask-wearing, avoiding indoor gatherings and increasing indoor ventilation. The purpose of this study was to compare ways to improve indoor ventilation and assess its effect on artificially generated aerosol counts. It was hypothesized that inbuilt kitchen vents would be more effective in reducing indoor aerosol counts than opening windows alone. A fixed amount of saline aerosol was dispersed in the experimental area using a nebulizer under constant temperature and a narrow range of humidity. A laser air quality monitor was used to record small particle counts every 30 minutes from baseline to 120 minutes for four different experimental groups for each combination of kitchen vents and windows. The results of the study demonstrate that aerosol counts were lowest with the kitchen exhaust vents on. This study suggests that liberal use of home exhaust systems like the kitchen vents could achieve significantly more air exchange than open windows alone and may present an effective solution to improving indoor ventilation, especially during the colder months when people tend to congregate indoors in closed spaces. There were no safety concerns involved when conducting this experiment.


Subject(s)
Air Pollution, Indoor , COVID-19 , SARS-CoV-2 , Ventilation , COVID-19/epidemiology , COVID-19/transmission , Environmental Monitoring , Humans , Particle Size
16.
AORN J ; 114(4): P4-P6, 2021 10.
Article in English | MEDLINE | ID: covidwho-1449913
19.
PLoS One ; 16(9): e0230700, 2021.
Article in English | MEDLINE | ID: covidwho-1430517

ABSTRACT

Weatherization of residential homes is a widespread procedure to retrofit older homes to improve the energy efficiency by reducing building leakage. Several studies have evaluated the effect of weatherization on indoor pollutants, such as formaldehyde, radon, and indoor particulates, but few studies have evaluated the effect of weatherization on indoor microbial exposure. Here, we monitored indoor pollutants and bacterial communities during reductions in building leakage for weatherized single-family residential homes in New York State and compared the data to non-weatherized homes. Nine weatherized and eleven non-weatherized single-family homes in Tompkins County, New York were sampled twice: before and after the weatherization procedures for case homes, and at least 3 months apart for control homes that were not weatherized. We found that weatherization efforts led to a significant increase in radon levels, a shift in indoor microbial community, and a warmer and less humid indoor environment. In addition, we found that changes in indoor airborne bacterial load after weatherization were more sensitive to shifts in season, whereas indoor radon levels were more sensitive to ventilation rates.


Subject(s)
Air Pollution, Indoor , Case-Control Studies , Environmental Exposure , Environmental Monitoring , Housing , Humans , Radon , Ventilation
20.
Sensors (Basel) ; 21(18)2021 Sep 12.
Article in English | MEDLINE | ID: covidwho-1410900

ABSTRACT

Indoor environmental conditions can significantly affect occupants' health and comfort. These conditions are especially important in educational buildings, where students, teachers and staff spend long periods of the day and are vulnerable to these factors. Recently, indoor air quality has been a focus of attention to ensure that disease transmission in these spaces is minimised. In order to increase the knowledge in this field, experimental tests have been carried out to characterise the impact of natural ventilation strategies on indoor air quality and the acoustic environment. This study has evaluated three ventilation scenarios in four different classrooms in buildings of the University of Granada, considering different window and door opening configurations. Ventilation rates were estimated using the CO2 Decay Method, and background noise recordings were made in each classroom for acoustic tests. Results show that specific natural ventilation strategies have a relevant impact that is worth considering on the background noise in indoor spaces. In this sense ventilation rates provided by the different configurations varied between 3.7 and 39.8 air changes per hour (ACH) and the acoustic tests show a background noise ranging from 43 to 54 dBA in these scenarios. Consequently, managers and teachers should take into account not only the ACH, but also other collateral impacts on the indoor environmental conditions such as the thermal comfort or the acoustic environment.


Subject(s)
Air Pollution, Indoor , Ventilation , Acoustics , Air Pollution, Indoor/analysis , Humans , Noise , Students
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