Small Aerosol Research Articles

Technical note: Impact of face covering on aerosol transport patterns during coughing and sneezing

COVID-19 is spread via different routes, including virus-laden airborne particles generated by human respiratory activities. In addition to large droplets, coughing and sneezing produce a lot of small aerosol particles. While face coverings are believed to reduce the aerosol transmission, information about their outward effectiveness is limited. Here, we determined the aerosol concentration patterns around a coughing and sneezing manikin and established spatial zones representing specific elevations of the aerosol concentration relative to the background. Real-time measurements of sub-micrometer aerosol particles were performed in the vicinity of the manikin. The tests were carried out without any face covering and with three different types of face covers: a safety faceshield, low-efficiency facemask and high-efficiency surgical mask. With no face covering, the simulated coughing and sneezing created a powerful forward-propagating fine aerosol flow. At 6 ft forward from the manikin head, the aerosol concentration was still 20-fold above the background. Adding a face covering reconfigured the forward-directed aerosol transmission pattern. The tested face coverings were found capable of mitigating the risk of coronavirus transmission; their effectiveness is dependent on the protective device. The outward leakage associated with a specific face covering was shown to be a major determinant of the exposure level for a person standing or seating next to or behind the coughing or sneezing “spreader” in a bus/train/aircraft/auditorium setting. Along with reports recently published in the literature, the study findings help assess the infectious dose and ultimately health risk for persons located within a 6-ft radius around the “spreader.”

Modern Development and Production of a New Live Attenuated Bacterial Vaccine, SCHU S4 ΔclpB, to Prevent Tularemia

Inhalation of small numbers of Francisella tularensis subspecies tularensis (Ftt) in the form of small particle aerosols causes severe morbidity and mortality in people and many animal species. For this reason, Ftt was developed into a bona fide biological weapon by the USA, by the former USSR, and their respective allies during the previous century. Although such weapons were never deployed, the 9/11 attack quickly followed by the Amerithrax attack led the U.S. government to seek novel countermeasures against a select group of pathogens, including Ftt. Between 2005–2009, we pursued a novel live vaccine against Ftt by deleting putative virulence genes from a fully virulent strain of the pathogen, SCHU S4. These mutants were screened in a mouse model, in which the vaccine candidates were first administered intradermally (ID) to determine their degree of attenuation. Subsequently, mice that survived a high dose ID inoculation were challenged by aerosol or intranasally (IN) with virulent strains of Ftt. We used the current unlicensed live vaccine strain (LVS), first discovered over 70 years ago, as a comparator in the same model. After screening 60 mutants, we found only one, SCHU S4 ΔclpB, that outperformed LVS in the mouse ID vaccination-respiratory-challenge model. Currently, SCHU S4 ΔclpB has been manufactured under current good manufacturing practice conditions, and tested for safety and efficacy in mice, rats, and macaques. The steps necessary for advancing SCHU S4 ΔclpB to this late stage of development are detailed herein. These include developing a body of data supporting the attenuation of SCHU S4 ΔclpB to a degree sufficient for removal from the U.S. Select Agent list and for human use; optimizing SCHU S4 ΔclpB vaccine production, scale up, and long-term storage; and developing appropriate quality control testing approaches.

Droplet-catching gel for disease control

Gels made from cosmetic ingredients could trap respiratory droplets and aerosols, say scientists at Northwestern University ( Chem 2021, DOI: 10.1016/j.chempr.2021.05.017 ). Jiaxing Huang and his team hope the gels could be put on walls, windows, cloth, and plexiglass barriers to make buildings healthier and stop the spread of infections. Small respiratory droplets and aerosols that bacteria and viruses use to hop from person to person are surprisingly “bouncy,” Huang says, so protections like the plexiglass shields that have become widespread during the COVID-19 pandemic can actually end up keeping aerosols in the air between a person and the barrier. Huang’s team decided that physically trapping or destroying the aerosols could be better than just blocking them. The group eventually settled on poly(acrylamide- co -dialkyl dimethyl ammonium dichloride), a transparent gel found in cosmetics and hair conditioners, as its main component. The researchers added the gel to surfaces, at which

Contrasting fates of terrestrial organic carbon pools in marginal sea sediments

Burial of terrestrial organic carbon (OCterr) in marginal sea sediments is a key component of the carbon cycle, exerting long-term influence on atmospheric CO2 and climate. Assessment of the burial efficiency of OCterr is of key importance, yet remains poorly constrained due to current gaps in our knowledge of mechanistic controls, including the influence of organic matter composition and age on the fate of OCterr in marine sediments. We measured bulk characteristics (δ13C and Δ14C of OC; mineral surface area, SA; grain size; n = 98 samples) and biomarker carbon isotopic compositions (fatty acid δ13C and Δ14C; n = 11) of a suite of surface sediment samples from the Bohai Sea and Yellow Sea (BS-YS). Combining with published results, bulk OC (n = 234) and biomarker (n = 19) carbon isotopic data are used to examine spatial variability in the sources and ages of OCterr in this shallow marginal sea system. Biomarker carbon isotopic values are used to constrain endmember values, and a dual carbon isotope mixing model was applied to all bulk samples to develop a spatially explicit assessment of contributions of different pools of OCterr. Although highly spatially variable, pre-aged OC (OCpre-aged) and fossil OC (OCfossil) when combined (i.e., “non-modern OC”) on average accounted for 51 ± 10% of the OC in BS-YS surface sediments. This was equivalent to the proportion of OCterr (ave., 51 ± 14%) estimated from a δ13COC binary mixing model, suggesting OCterr in the mixed layer of BS-YS sediments is predominantly composed of millennial-aged OC. The burial potential of pool-specific OCterr was then evaluated through comparison of corresponding mineral SA-normalized loadings of surface sediments with those of Yellow River suspended particulate matter. Both the regression slope and the arithmetic mean value approaches reveal high burial potential for all terrestrial OC pools delivered by Yellow River, which is attributed to the aged and refractory nature of OC exported from the Yellow River. However, differing relationships of pool-specific OCterr loadings between BS-YS and Yellow River sediments imply contrasting fates. In particular, we find that the burial potential of OCpre-aged is consistently greater than that of OCfossil. This surprising observation suggests either enhanced degradation of OCfossil during lateral transport (possibly as a consequence of different mineral associations and hydrodynamic sorting effects), or additional sources for OCpre-aged, such as from small rivers or aerosol deposition. Overall, OC age, mineralogical composition and hydrological settings contribute to the complex patterns of OC residing in northern China marginal sea surface sediments. This novel molecular-isotopic approach reveals significant spatial variability in proportions, contents and burial potential among terrestrial OC pools, and underlines the importance of considering organic matter age and composition in understanding and constraining the fate of OCterr in marine sedimentary environments.

Breathing, speaking, coughing or sneezing: What drives transmission of SARS-CoV-2?

The SARS‐CoV‐2 virus is highly contagious, as demonstrated by numerous well‐documented superspreading events. The infection commonly starts in the upper respiratory tract (URT) but can migrate to the lower respiratory tract (LRT) and other organs, often with severe consequences. Whereas LRT infection can lead to shedding of virus via breath and cough droplets, URT infection enables shedding via abundant speech droplets. Their viral load can be high in carriers with mild or no symptoms, an observation linked to the abundance of SARS‐CoV‐2‐susceptible cells in the oral cavity epithelium. Expelled droplets rapidly lose water through evaporation, with the smaller ones transforming into long‐lived aerosol. Although the largest speech droplets can carry more virions, they are few in number, fall to the ground rapidly and therefore play a relatively minor role in transmission. Of more concern is small speech aerosol, which can descend deep into the LRT and cause severe disease. However, since their total volume is small, the amount of virus they carry is low. Nevertheless, in closed environments with inadequate ventilation, they can accumulate, which elevates the risk of direct LRT infection. Of most concern is the large fraction of speech aerosol that is intermediate‐sized because it remains suspended in air for minutes and can be transported over considerable distances by convective air currents. The abundance of this speech‐generated aerosol, combined with its high viral load in pre‐ and asymptomatic individuals, strongly implicates airborne transmission of SARS‐CoV‐2 through speech as the primary contributor to its rapid spread.

SARS CoV-2 aerosol: How far it can travel to the lower airways?

The recent outbreak of the SARS CoV-2 virus has had a significant effect on human respiratory health around the world. The contagious disease infected a large proportion of the world population, resulting in long-term health issues and an excessive mortality rate. The SARS CoV-2 virus can spread as small aerosols and enters the respiratory systems through the oral (nose or mouth) airway. The SARS CoV-2 particle transport to the mouth–throat and upper airways is analyzed by the available literature. Due to the tiny size, the virus can travel to the terminal airways of the respiratory system and form a severe health hazard. There is a gap in the understanding of the SARS CoV-2 particle transport to the terminal airways. The present study investigated the SARS CoV-2 virus particle transport and deposition to the terminal airways in a complex 17-generation lung model. This first-ever study demonstrates how far SARS CoV-2 particles can travel in the respiratory system. ANSYS Fluent solver was used to simulate the virus particle transport during sleep and light and heavy activity conditions. Numerical results demonstrate that a higher percentage of the virus particles are trapped at the upper airways when sleeping and in a light activity condition. More virus particles have lung contact in the right lung than the left lung. A comprehensive lobe specific deposition and deposition concentration study was performed. The results of this study provide a precise knowledge of the SARs CoV-2 particle transport to the lower branches and could help the lung health risk assessment system.

What is the real risk of COVID transmission during oxygenation?

Recently, I was called up to the intensive care unit (ICU) to intubate a hypoxic patient with coronavirus disease (COVID). Walking into the patient's room, I noted lots of people in personal protective equipment (PPE), most of whom I knew to be fully vaccinated. The patient was, indeed, hypoxic on high flow nasal cannula (HFNC). Could we put him on bi-level positive airway pressure (BiPAP) for better pre-oxygenation before rapid sequence intubation (RSI)? Nope. Hospital policy prevented the use of BiPAP (but not HFNC) on COVID patients. So, we had to accept sub-optimal pre-oxygenation because of a policy understandably designed to protect staff but that was not in the patient's best interest. Experiences like this really beg several important clinical questions: what is the risk associated with different approaches to oxygenation and how well does the PPE we wear work? Fortunately, 2 recent papers in JACEP Open address these questions. They give us additional data to help better understand our actual risk when treating patients with COVID. Emily Pearce and her colleagues at the University of New Mexico report on an experiment in which they estimate the exposure from different approaches to oxygen administration (aerosol generation with various approaches to oxygenation in healthy volunteers in the emergency department [ED]).1 They had 8 healthy volunteers, including the researchers themselves, breath normally in a positive pressure ED exam room while receiving oxygen from 3 devices: HFNC, non-rebreather mask (NRB), and continuous positive airway pressure (CPAP). The HFNC was tested at 15, 30, and 60 L/min flow. They used a spectrometer to measure both large and small droplet aerosols. Finally, they placed a procedural mask over the HFNC and NRB to evaluate the impact of the common approach of mask-over-oxygen device. Ultimately, they demonstrated that higher flow oxygen led to higher aerosol generation, and CPAP was actually associated with lower aerosol generation. Masks were helpful for reduction of small particulates but not with larger ones, at least not statistically with only 8 subjects. These findings help us understand that CPAP is actually relatively low risk, certainly less than HFNC, and placing a mask over the devices may help lower exposure risk. So, we now have more information about aerosol generation, but what about the extent to which PPE protects us against infection? Dr. Darren Braude and colleagues looked at this with a pragmatic approach. In their paper “Safety of air medical transport of patients with COVID-19 by personnel using routine personal protective equipment” they used an 8-base regional air medical consortium to describe the rate of infection among transport personnel after flying patients with COVID.2 They included only patients with known or suspected COVID and then describe oxygen therapy. Most patients were receiving some form of oxygen, but only 30% were intubated. Among 108 transport staff, the overall rate of COVID infection was under 2%. This is consisted with other descriptions of PPE effectiveness among EMS personnel.3 Taken together, these 2 papers provide additional information we can use to guide our approach to caring for COVID patients with respiratory distress while still protecting ourselves and our colleagues. It appears that CPAP is a relatively low risk approach to respiratory support, certainly it looks like a lower risk than HFNC or NRB. In addition, we have additional reassurance that the PPE we are using provides substantial protection against infection.

Respirators, face masks, and their risk reductions via multiple transmission routes for first responders within an ambulance

First responders may have high SARS-CoV-2 infection risks due to working with potentially infected patients in enclosed spaces. The study objective was to estimate infection risks per transport for first responders and quantify how first responder use of N95 respirators and patient use of cloth masks can reduce these risks. A model was developed for two Scenarios: an ambulance transport with a patient actively emitting a virus in small aerosols that could lead to airborne transmission (Scenario 1) and a subsequent transport with the same respirator or mask use conditions, an uninfected patient; and remaining airborne SARS-CoV-2 and contaminated surfaces due to aerosol deposition from the previous transport (Scenario 2). A compartmental Monte Carlo simulation model was used to estimate the dispersion and deposition of SARS-CoV-2 and subsequent infection risks for first responders, accounting for variability and uncertainty in input parameters (i.e., transport duration, transfer efficiencies, SARS-CoV-2 emission rates from infected patients, etc.). Infection risk distributions and changes in concentration on hands and surfaces over time were estimated across sub-Scenarios of first responder respirator use and patient cloth mask use. For Scenario 1, predicted mean infection risks were reduced by 69%, 48%, and 85% from a baseline risk (no respirators or face masks used) of 2.9 × 10−2 ± 3.4 × 10−2 when simulated first responders wore respirators, the patient wore a cloth mask, and when first responders and the patient wore respirators or a cloth mask, respectively. For Scenario 2, infection risk reductions for these same Scenarios were 69%, 50%, and 85%, respectively (baseline risk of 7.2 × 10−3 ± 1.0 × 10−2). While aerosol transmission routes contributed more to viral dose in Scenario 1, our simulations demonstrate the ability of face masks worn by patients to additionally reduce surface transmission by reducing viral deposition on surfaces. Based on these simulations, we recommend the patient wear a face mask and first responders wear respirators, when possible, and disinfection should prioritize high use equipment.

A simple HEPA filtering facepiece

Shortages of efficient filtering facepiece respirators leave the public vulnerable to transmission of infectious diseases in small particle aerosols. This study demonstrates that a high-filtration-efficiency facepiece capable of filtering out >95% of 0.05μm particles while being worn can be simply produced with available materials.

Aerosol radiative forcings induced by substantial changes in anthropogenic emissions in China from 2008 to 2016

Abstract. Anthropogenic emissions in China play an important role in altering the global radiation budget. Over the past decade, the strong clean-air policies in China have resulted in substantial reductions of anthropogenic emissions of sulfur dioxide (SO2) and primary particulate matter, and air quality in China has consequently improved. However, the resultant aerosol radiative forcings have been poorly understood. In this study, we used an advanced global climate model integrated with the latest localized emission inventory to quantify the aerosol radiative forcings by the changes of anthropogenic emissions in China between 2008 and 2016. By comparing with multiple observation datasets, our simulations reproduced the considerable reductions of sulfate and black carbon (BC) mass loadings reasonably well over eastern China (the key region subject to stringent emission controls) during the period and accordingly showed a clear decline in both aerosol optical depth and absorption aerosol optical depth. The results revealed a regional annual mean positive direct radiative forcing (DRF) of +0.29 W m−2 at the top of the atmosphere (TOA) due to the reduction of SO2 emissions. This positive aerosol radiative forcing was comprised of diminished sulfate scattering (+0.58 W m−2), enhanced nitrate radiative effects (−0.29 W m−2), and could be completely offset by the concurrent reduction of BC emissions that induced a negative BC DRF of −0.33 W m−2. Despite the small net aerosol DRF (−0.05 W m−2) at the TOA, aerosol–radiation interactions could explain the surface brightening in China over the past decade. The overall reductions in aerosol burdens and associated optical effects mainly from BC and sulfate enhanced the regional annual mean downward solar radiation flux at the surface by +1.0 W m−2 between 2008 and 2016. The enhancement was in general agreement with a long-term observational record of surface energy fluxes in China. We also estimated that aerosol effects on cloud radiative forcings may have played a dominant role in the net aerosol radiative forcings at the TOA in China and over the northern Pacific Ocean during the study period. This study will facilitate more informed assessment of climate responses to projected emissions in the future as well as to sudden changes in human activities (e.g., the COVID-19 lockdown).

Comparison of the performance of aerosol sampling devices for measuring infectious SARS-CoV-2 aerosols

To assess the risk of aerosol transmission of SARS-CoV-2, measurements of the airborne viral concentrations in proximity to infected individuals, the persistence of the virus in aerosols, and the dose of the virus needed to cause infection following inhalation are required. For studies aimed at quantifying these parameters, an aerosol sampling device needs to be employed. A number of recent studies have reported the detection of both genetic material and infectious SARS-CoV-2 virus in air samples collected in clinical settings. Previous studies have demonstrated that the efficiency of different samplers for collection and preservation of the infectivity of microorganisms can vary as a function of the specific microorganism. In the present study, the performance of eight common low-flow aerosol sampling devices were compared for their ability to collect and preserve the infectivity of airborne SARS-CoV-2 contained in small particle aerosols. The influence of sampling duration on recovery of infectious virus was also evaluated. Similar concentrations of infectious SARS-CoV-2 were measured in aerosols for the majority of the samplers tested, with the exception of the midget impingers, which measured significantly lower concentrations of SARS-CoV-2. Additionally, in three of the four impingers tested, additional clean airflow through the device following collection of infectious virus resulted in a decrease of the infectious concentration of virus over time, suggesting that virus was being inactivated and these devices may not be suitable for sampling for long durations. Further, RNA copies in the samples over time did not correspond with the losses of infectious SARS-CoV-2 observed in the impingers samples. These data can be utilized to inform interpretation of current studies on the SARS-CoV-2 viral loads in air samples, as well as inform sampling device selection in future studies.

Aerosol characteristics from earth observation systems: A comprehensive investigation over South Asia (2000–2019)

The present study summarizes two decades (2000–2019) of climatology and trends in aerosol loading and optical properties using a high spatial resolution data obtained from NASA's MODIS MAIAC and MISR aerosol products supplemented by moderate resolution aerosol data from OMI sensor over South Asia (SA). MISR AOD showed good agreement against AERONET AOD with 68.68% of the retrievals falling within the expected error and high Pearson's correlation coefficient (R = 0.83). The 20 years geometric mean of MAIAC and MISR AOD revealed higher loading of aerosols over the Indo-Gangetic Plain (IGP) and Eastern coast of India by 30% to 44% compared to the mean AOD over the entire SA. The highest mean AOD under cloud-free conditions was noted during monsoon season, followed by pre-monsoon, post-monsoon, and winter. The high contribution of coarse-mode AOD (cAOD) mainly from natural aerosol emission and small-mode AOD (sAOD) from local anthropogenic emissions are the main driver to high AOD in monsoon and pre-monsoon seasons. Besides, the presence of high humidity during the monsoon season favors the hygroscopic growth of the particles and leads to higher AOD values over SA. The high spatial resolutions of MODIS/MAIAC and MISR aerosol products enabled the identification of previously unobserved aerosol hotspots over Bihar, West Bengal, and the eastern Indian coastal state of Odisha, which is mainly dominated by small aerosol particles. The contributions of smaller aerosol particles to the total aerosol loading were found to be higher during post-monsoon and winter over most states in India, Nepal, and Bangladesh. In contrast, the contribution of coarser particles was higher over Pakistan during pre-monsoon and monsoon seasons. Smaller particles were predominantly retrieved over the Indian states dominated by mining industries, including Jharkhand and Odisha. A typical dominance of absorbing carbonaceous aerosols was also noted over the northwestern region of IGP during post-monsoon, which otherwise was mainly affected by mixed dust aerosols and carbonaceous aerosols in pre-monsoon and monsoon seasons. A statistically significant positive temporal trend in AOD was observed for the whole study period, over most of the SA region, which was influenced by the increase in small particles over India and Bangladesh. Urban/industrial weakly absorbing aerosols were found to be the main contributor to a similarly positive trend over Central India and East coast Indian states. Overall, recent advancements in high spatial resolution satellite-based aerosol optical properties showed good potential to identify the aerosol hotspots and constrain aerosol types across a highly polluted SA region.

Practical approach to prevent COVID-19 infection at breast cancer screening

BackgroundThe novel coronavirus disease 2019 (COVID-19) undermines the benefits of cancer screening. To date, no study has identified specific infection control methods. We aimed to provide practical methods for COVID-19 risk reduction during breast cancer screening mammography (MMG) by examining an overview of potential contamination routes of aerosols and possible risks for patients and health care providers.MethodsComputational fluid dynamics (CFD) simulations were conducted for airflow and aerosol dispersion in a 3D virtual model of a mobile MMG laboratory room. This model was constructed based on the actual mobile screening MMG bus ‘Cosmos’ in the Chiba Foundation for Health Promotion & Disease Prevention. Examiner and patient geometries were obtained by scanning an actual human using a 3D Scanner. Contamination of the room was evaluated by counting the numbers of suspended and deposited aerosols.ResultsWe applied the CFD simulation model to the exhalation of small or large aerosols from a patient and examiner in the MMG laboratory. Only 14.5% and 54.5% of large and small aerosols, respectively, were discharged out of the room with two doors open. In contrast, the proportion of large and small aerosols discharged out of the room increased to 96.6% and 97.9%, respectively, with the addition of forced gentle wind by the blower fan. This simulation was verified by a mist aerosol experiment conducted in the mobile MMG laboratory.ConclusionAdding forced ventilation to a MMG laboratory with two doors open may enable risk reduction dramatically. This could be applied to other clinical situations.

Experimental Investigation of Aerosol and CO2 Dispersion for Evaluation of COVID-19 Infection Risk in a Concert Hall.

The dispersion of small aerosols in a concert hall is experimentally studied for estimating the risk of infection with SARS-CoV-2 during a concert. A mannequin was modified to emit an air stream containing aerosols and CO2. The aerosols have a size distribution with a peak diameter close to 0.3 µm and a horizontal initial particle velocity () of 2.4 m/s. The CO2-concentration (c) emitted simultaneously is 7500 ppm. It is investigated, if the spatial dissipation of aerosols and CO2 can be correlated. This would allow the use of technically easier CO2 measurements to monitor compliance with aerosol concentration limits. Both aerosol and CO2 concentrations are mapped by different sensors placed around the mannequin. As a result, no significant enrichment of aerosols and CO2 was obtained outside a radius of 1.5 m when the fresh air ventilation in the concert hall has a steady vertical flow with a velocity of and the installed ventilation system was operating at an air change rate per hour (ACH) of 3, corresponding to an air exchange rate of 51,000 m3/h. A Pearson correlation coefficient of 0.77 was obtained for CO2 and aerosol concentrations measured simultaneously at different positions within the concert hall.

SARS-CoV and SARS-CoV-2 are transmitted through the air between ferrets over more than one meter distance

SARS-CoV-2 emerged in late 2019 and caused a pandemic, whereas the closely related SARS-CoV was contained rapidly in 2003. Here, an experimental set-up is used to study transmission of SARS-CoV and SARS-CoV-2 through the air between ferrets over more than a meter distance. Both viruses cause a robust productive respiratory tract infection resulting in transmission of SARS-CoV-2 to two of four indirect recipient ferrets and SARS-CoV to all four. A control pandemic A/H1N1 influenza virus also transmits efficiently. Serological assays confirm all virus transmission events. Although the experiments do not discriminate between transmission via small aerosols, large droplets and fomites, these results demonstrate that SARS-CoV and SARS-CoV-2 can remain infectious while traveling through the air. Efficient virus transmission between ferrets is in agreement with frequent SARS-CoV-2 outbreaks in mink farms. Although the evidence for virus transmission via the air between humans under natural conditions is absent or weak for SARS-CoV and SARS-CoV-2, ferrets may represent a sensitive model to study interventions aimed at preventing virus transmission.

Aerosol generation with various approaches to oxygenation in healthy volunteers in the emergency department.

ObjectivesHealth care workers experience an uncertain risk of aerosol exposure during patient oxygenation. To improve our understanding of these risks, we sought to measure aerosol production during various approaches to oxygenation in healthy volunteers in an emergency department.MethodsThis was a prospective study conducted in an empty patient room in an academic ED. The room was 10 ft. long x 10 ft. wide x 9 ft. tall (total volume 900 ft3) with positive pressure airflow (1 complete turnover of air every 10 minutes). Five oxygenation conditions were used: humidified high‐flow nasal cannula (HFNC) at 3 flow rates [15, 30, and 60 liters per minute (LPM)], non‐rebreather mask (NRB) at 1 flow rate (15 LPM), and closed‐circuit continuous positive airway pressure (CPAP) using the ED ventilator; in all cases a simple procedural mask was used. The NRB and HFNC at 30 LPM maneuvers were also repeated without the procedural mask, and CPAP was applied both with and without a filter. Each subject then sequentially underwent 8 total oxygenation conditions, always in the same order. Each oxygenation condition was performed with the participant on a standard ED bed. Particles were measured by laser aerosol spectrometer, with the detector sampling port positioned directly over the center of the bed, 0.35 meters away and at a 45‐degree angle from the subject's mouth. Each approach to oxygenation was performed for 10 minutes, followed by a 20‐minute room washout (≈ 2 complete room air turnovers). Particle counts were summated for 2 size ranges (150–300 nm and 0.5–2.0 μm) and compared before, during, and after each of the 8 oxygenation conditions.ResultsEight adult subjects were enrolled (mean age 42 years, body mass index 25). All subjects completed 8 oxygenation procedures (64 total). Mean particle counts per minute across all oxygenation procedures was 379 ± 112 (mean ± SD) for smaller aerosols (150–300 nm) and 9.3 ± 4.6 for larger aerosols (0.5–2.0 μm). HFNC exhibited a flow‐dependent increase in particulate matter (PM) generation—at 60 LPM, HFNC had a substantial generation of small (55% increase) and large particles (70% increase) compared to 15 LPM. CPAP was associated with lowered small and large particle generation (≈ 10–15% below baseline for both sizes of PM). A patient mask limited particle generation with the NRB, where it was associated with a reduction in small and large particulates (average 40% and 20% lower, respectively).ConclusionAmong 3 standard oxygenation procedures, higher flow rates generally were associated with greater production of both small and large aerosols. A patient mask lowered aerosol counts in the NRB only. Protocol development for oxygenation application should consider these factors to increase health care worker safety.

Does polyacrylamide-based adjuvant actually reduce primary drift of airborne pesticides?

Atmospheric drift of pesticides sprayed outside treated fields may pose serious environmental and health concerns. Chemical adjuvants, among other techniques, reduce drift by modifying the physicochemical properties of the pesticide solution, which presumably produces larger droplets upon spraying that are less prone to drift. Previous studies, that have addressed the effect of adjuvants on drift reduction, mainly rely on measurements of droplet sedimentation while ignoring the presence of pesticides in the forms of small aerosols and vapor. Such forms are expected to be highly susceptible to atmospheric drift that may pose human health risk via inhalation exposure.The present study examines the effect of a polymer-based adjuvant on airborne-pesticide drift using active air sampling in two field campaigns. Surprisingly, these measurements indicate higher primary drift (PD) of airborne pesticides in the presence of adjuvant in the spraying solution. The results are further supported by comparing measured drifts to those calculated using a modified Gaussian puff dispersion model, which enabled to evaluate the impact of varying meteorological conditions during the field experiments. In addition, the adjuvant effect on droplet size distribution generated by common nozzles, was tested in a wind tunnel. The resulting size-distributions demonstrated that while the addition of adjuvant resulted in a desired shift of the volumetric distribution towards larger droplets, it also led to a significant increase in the number concentration of fine droplets. Such trends can explain how the addition of polymeric adjuvant can yield both, a reduction in sedimenting drift outside treated areas and an increase in airborne PD intensity, as observed in the present study. This study demonstrates the complex effect of chemical adjuvants and the urgent need to further explore and understand their environmental impact.

Airborne aerosol olfactory deposition contributes to anosmia in COVID-19.

Olfactory dysfunction (OD) affects a majority of COVID-19 patients, is atypical in duration and recovery, and is associated with focal opacification and inflammation of the olfactory epithelium. Given recent increased emphasis on airborne transmission of SARS-CoV-2, the purpose of the present study was to experimentally characterize aerosol dispersion within olfactory epithelium (OE) and respiratory epithelium (RE) in human subjects, to determine if small (sub 5μm) airborne aerosols selectively deposit in the OE. Healthy adult volunteers inhaled fluorescein-labeled nebulized 0.5-5μm airborne aerosol or atomized larger aerosolized droplets (30-100μm). Particulate deposition in the OE and RE was assessed by blue-light filter modified rigid endoscopic evaluation with subsequent image randomization, processing and quantification by a blinded reviewer. 0.5-5μm airborne aerosol deposition, as assessed by fluorescence gray value, was significantly higher in the OE than the RE bilaterally, with minimal to no deposition observed in the RE (maximum fluorescence: OE 19.5(IQR 22.5), RE 1(IQR 3.2), p<0.001; average fluorescence: OE 2.3(IQR 4.5), RE 0.1(IQR 0.2), p<0.01). Conversely, larger 30-100μm aerosolized droplet deposition was significantly greater in the RE than the OE (maximum fluorescence: OE 13(IQR 14.3), RE 38(IQR 45.5), p<0.01; average fluorescence: OE 1.9(IQR 2.1), RE 5.9(IQR 5.9), p<0.01). Our data experimentally confirm that despite bypassing the majority of the upper airway, small-sized (0.5-5μm) airborne aerosols differentially deposit in significant concentrations within the olfactory epithelium. This provides a compelling aerodynamic mechanism to explain atypical OD in COVID-19.

Influence of aerodynamic particle size on botulinum neurotoxin potency in mice

Objective For many agents, the aerodynamic particle size can affect both the virulence and disease course in animal models. Botulinum neurotoxins (BoNTs), which are widely known as potential bioterrorism agents, have been shown to be toxic via multiple routes of exposure, including small particle inhalation (1–3 µm MMAD). However, the impact of larger particle sizes on the potency of BoNT has not been previously reported. In this study, we compared the potency of BoNT in small and large particle aerosols. Materials and methods Outbred mice (ICR (CD-1®)) were exposed to BoNT-containing aerosols with differing mass median aerodynamic diameters (MMADs) of 1.1, 4.9, and 7.6 microns. The effects of bioaerosol sampler and inhalation exposure modality were studied. Results and discussion Collecting aerosolized BoNT onto gelatin filters or into liquid impingers resulted in equivalent estimates of aerosol concentration. Nose-only and whole-body inhalation exposure resulted in nearly identical estimates of the median lethal dose (LD50). The LD50 for inhaled BoNT increased approximately 50-fold when the median aerodynamic particle size was increased from 1.1 to 4.9 µm, from 139 (95% CI: 111–185) to 7324 (95% CI: 4287–10 891) mouse intraperitoneal median lethal doses (MIPLD50). These results demonstrate the importance of aerodynamic particle size and regional deposition patterns with regards to BoNT inhalational toxicity. Conclusions These data will be useful for medical countermeasure development, as well as biodefense preparedness modeling by demonstrating that the estimates of dose and toxicity of an inhaled aerosol containing BoNT can be significantly affected by a range of factors.

COVID-19 Implication by Physical Interaction of Artificial fog on Respiratory Aerosols

Background: Artificial fog consists of small liquid aerosols suspended in air which reduce visibility and reflect light. Artificial fog is used in the film, television, and live entertainment industries to enhance lighting, as a visual effect, and to create a specific sense of mood or atmosphere. Objective: This study investigated the suspension time for liquid respiratory aerosols spiked with tagged deoxyribonucleic acid (DNA) tracers in the presence and absence of glycerin- or glycol-containing artificial fogs. Methods: Liquid respiratory aerosols with tagged DNA tracers were sprayed into a closed environment without and with glycerin- or glycol-containing artificial fog, with air samples taken at regular intervals to determine the decay of tagged DNA tracer over time. The study treatments included Control (no fog), Glycerin Low (~3 mg/m3 ), Glycerin High (~15 mg/m3 ), Glycol Low (~5 mg/m3 ), and Glycol High (~40 mg/m3 ). Results: All artificial fog treatments had lower mean log reduction curves compared to the Control treatment. The differences in mean log reduction for artificial fog treatments vs. control treatments were all statistically significant (p&lt;0.001), except for Glycerin Low treatment (p=0.087). The differences in mean log reduction between treatments using glycerin fog (p=0.129) and glycol fog (p=0.209) were not statistically significant. Conclusion: Artificial fog use does not increase suspension time of liquid respiratory aerosols, and therefore does not appear to increase the risk of airborne transmission of diseases from liquid respiratory aerosols, such as COVID-19. The suspension time of aerosols in glycol-containing artificial fog decreased more than glycerin-containing fog. In practice, the additional reduction in suspension time provided by the physical interaction of liquid respiratory aerosols with artificial fog does not suggest any practical benefit for using artificial fog as a control measure.