Size-resolved aerosol at a Coastal Great Lakes Site: Impacts of new particle formation and lake spray.

The quantification of aerosol size distributions is crucial for understanding the climate and health impacts of aerosols, validating models, and identifying aerosol sources. This work provides one of the first continuous measurements of aerosol size distribution from 1.02 to 8671 nm near the shore of Lake Michigan. The data were collected during the Lake Michigan Ozone Study (LMOS 2017), a comprehensive air quality measurement campaign in May and June 2017. The time-resolved (2-min) size distribution are reported herein alongside meteorology, remotely sensed data, gravimetric filters, and gas-phase variables. Mean concentrations of key aerosol parameters include PM2.5 (6.4 µg m-3), number from 1 to 3 nm (1.80x104 cm-3) and number greater than 3 nm (8x103 cm-3). During the field campaign, approximately half of days showed daytime ultrafine burst events, characterized by particle growth from sub 10 nm to 25-100 nm. A specific investigation of ultrafine lake spray aerosol was conducted due to enhanced ultrafine particles in onshore flows coupled with sustained wave breaking conditions during the campaign. Upon closer examination, the relationships between the size distribution, wind direction, wind speed, and wave height did not qualitatively support ultrafine particle production from lake spray aerosol; statistical analysis of particle number and wind speed also failed to show a relationship. The alternative hypothesis of enhanced ultrafine particles in onshore flow originating mainly from new particle formation activity is supported by multiple lines of evidence.

Enhanced saccharide enrichment in sea spray aerosols by coupling surface-active fatty acids.

The chemical composition of aerosols plays a significant role in aerosol-cloud interactions and, although saccharides make up their largest organic mass fraction, the current process model for understanding sea spray aerosol (SSA) composition struggles to replicate the enrichment of saccharides that has been observed. Here, we simulated the generation of SSA and quantified the enrichment of two soluble saccharides (glucose and trehalose) in SSA with a homemade sea spray aerosol generator. The results of the generation experiments demonstrated that both saccharides, especially trehalose, can promote the generation of SSA, whereas surface-active fatty acids primarily inhibit SSA production due to fewer bubble bursts caused by a large amount of foam accumulation. A significant decrease in surface tension of seawater with the addition of fatty acids was observed, while only a minor decrease was observed for seawater with the addition of only saccharide. Enrichment factors (EFs) of saccharides measured using high performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD) revealed no enrichment of glucose in submicron SSA, while trehalose showed a slight enrichment. In the presence of surface-active fatty acids on the seawater surface, a significant increase in the enrichment of saccharides in SSA was observed, with glucose and trehalose showing EF of approximately 27-fold and 58-fold, respectively. Besides, this enrichment was accompanied by the accumulation of calcium and magnesium ions. The results presented here suggest that the coupling interaction mechanism of soluble saccharides and surface-active fatty acids on the ocean surface contributes to the enrichment of soluble saccharides in SSA.

Bacterial and Chemical Evidence of Coastal Water Pollution from the Tijuana River in Sea Spray Aerosol.

Roughly half of the human population lives near the coast, and coastal water pollution (CWP) is widespread. Coastal waters along Tijuana, Mexico, and Imperial Beach (IB), USA, are frequently polluted by millions of gallons of untreated sewage and stormwater runoff. Entering coastal waters causes over 100 million global annual illnesses, but CWP has the potential to reach many more people on land via transfer in sea spray aerosol (SSA). Using 16S rRNA gene amplicon sequencing, we found sewage-associated bacteria in the polluted Tijuana River flowing into coastal waters and returning to land in marine aerosol. Tentative chemical identification from non-targeted tandem mass spectrometry identified anthropogenic compounds as chemical indicators of aerosolized CWP, but they were ubiquitous and present at highest concentrations in continental aerosol. Bacteria were better tracers of airborne CWP, and 40 tracer bacteria comprised up to 76% of the bacteria community in IB air. These findings confirm that CWP transfers in SSA and exposes many people along the coast. Climate change may exacerbate CWP with more extreme storms, and our findings call for minimizing CWP and investigating the health effects of airborne exposure.

Droplet nuclei are generated during colonoscopy and are decreased by the use of carbon dioxide and water immersion technique.

OBJECTIVES: The COVID-19 pandemic has raised concerns on whether colonoscopies (CS) carry a transmission risk. The aim was to determine whether CS are aerosol-generating procedures. METHODS: This was a prospective observational trial including all patients undergoing CS at the Prince of Wales Hospital from 1 June to 31 July 2020. Three particle counters were placed 10 cm from each patient's anus and near the mouth of endoscopists and nurses. The particle counter recorded the number of particles of size 0.3, 0.5, 0.7, 1, 5, and 10 µm. Patient demographics, seniority of endoscopists, use of CO2 and water immersion technique, and air particle count (particles/cubic foot, dCF) were recorded. Multilevel modeling was used to test all the hypotheses with a post-hoc analysis. RESULTS: A total of 117 patients were recruited. During CS, the level of 5 µm and 10 µm were significantly higher than the baseline period (P = 0.002). Procedures performed by trainees had a higher level of aerosols when compared to specialists (0.3 µm, P < 0.001; 0.5 µm and 0.7 µm, P < 0.001). The use of CO2 and water immersion techniques had significantly lower aerosols generated when compared to air (CO2 : 0.3, 0.5, and 0.7 µm: P < 0.001; water immersion: 0.3 µm: P = 0.048; 0.7 µm: P = 0.03). There were no significant increases in any particle sizes during the procedure at the endoscopists' and nurses' mouth. However, 8/117 (6.83%) particle count tracings showed a simultaneous surge of all particle sizes at the patient's anus and endoscopists' and nurses' level during rectal extubation. CONCLUSION: Colonoscopy generates droplet nuclei especially during rectal extubation. The use of CO2 and water immersion techniques may mitigate these risks.

Characterization of aerosolized particles in effluents from carbon fibre composites incorporating nanomaterials during simultaneous fire and impact.

This work investigates the aerosols emitted from carbon fibre-reinforced epoxy composites (CFC) incorporating nanomaterials (nanoclays and nanotubes), subjected to simultaneous fire and impact, representing an aeroplane or automotive crash. Simultaneous fire and impact tests were performed using a previously described bespoke testing methodology with the capability to collect particles released from the front/back faces of the impacted composites plus the effluents. In this work the methodology has been further developed by connecting the Dekati Low Pressure Impactor (DLPI) and Mini Particle Sampler (MPS) sampling system in the extraction chimney. The aerosols emitted have been characterized using various devices devoted to the analysis of aerosols. The influence of the nanoadditives in the matrix on the number concentration and the size distribution of airborne particles produced, was studied with a cascade impactor in the 5 nm-10 µm range. The morphology of the separated soot fractions was examined by SEM. The measurement of aerodynamic size of particles that can deposit in human respiratory tract indicate that 75% of the soot and particles released from CFC could deposit in the lungs reaching the bronchi region at a minimum. There was however, a minimal difference between the number particle concentrations or particle-size mass distribution of particles from CFC and CFC containing nanoadditives. Moreover, no fibres were found in the effluents.

Constraining the Effect of Surfactants on the Hygroscopic Growth of Model Sea Spray Aerosol Particles.

The cloud condensation nuclei activation of sea spray aerosol (SSA) is tightly linked to the hygroscopic properties of these particles and is defined by their physical and chemical properties. While hygroscopic sea salt in SSA strongly influences particle water uptake, the marine-derived components that make up the organic fraction of SSA constitute a complex mixture, and their effect on hygroscopic growth is unknown. To constrain the effect of organic compounds and specifically surface-active compounds that adsorb on particle interfaces, particle hygroscopic growth studies were performed on laboratory-generated model sea salt/sugar particles. For sea salt/glucose particles, ionic surfactants facilitated water uptake at low relative humidity (RH), increasing the particle growth factor (GF) by up to 7.61%, and caused a reduction in the deliquescence relative humidity (DRH), while nonionic surfactants had a minimal effect. Replacing glucose with polysaccharide laminarin in sea salt/sugar/surfactant particles caused a reduction in GF at low RHs and minimized the effect of ionic surfactants on the DRH. At RHs above the DRH, the addition of anionic or nonionic surfactants caused a decrease in GF for both sea salt/glucose and sea salt/laminarin particles. The addition of cationic surfactants, however, did not have a dampening effect on water uptake of sea salt/sugar particles and even showed a GF increase of up to 3.7% at 90% RH. An increase in the complexity of the sugar dampens the water uptake for particles containing nonionic surfactants but increases the water uptake for cationic surfactants. The cloud activation potential for 100 nm particles analyzed in this study is higher for ionic surfactants and decreases with an increase in surfactant molecular size when particle interfacial tension is considered. The surfactant effect on the hygroscopic growth and cloud activation potential of the particles containing sea salt/sugar is dependent on the surfactant ionicity and molecular size, the particle size and interfacial tension, and the interactions between inorganic salt and organic species under different RH conditions.

Anthropogenic and Biogenic Contributions to the Organic Composition of Coastal Submicron Sea Spray Aerosol.

The organic composition of coastal sea spray aerosol is important for both atmospheric chemistry and public health but remains poorly characterized. Coastal waters contain an organic material derived from both anthropogenic processes, such as wastewater discharge, and biological processes, including biological blooms. Here, we probe the chemical composition of the organic fraction of sea spray aerosol over the course of the 2019 SeaSCAPE mesocosm experiment, in which a phytoplankton bloom was facilitated in natural coastal water from La Jolla, California. We apply untargeted two-dimensional gas chromatography to characterize submicron nascent sea spray aerosol samples, reporting ∼750 unique organic species traced over a 19 day phytoplankton bloom experiment. Categorization and quantitative compositional analysis reveal three major findings. First, anthropogenic species made up 30% of total submicron nascent sea spray aerosol organic mass under the pre-bloom condition. Second, biological activity drove large changes within the aerosolized carbon pool, decreasing the anthropogenic mass fraction by 89% and increasing the biogenic and biologically transformed fraction by a factor of 5.6. Third, biogenic marine organics are underrepresented in mass spectral databases in comparison to marine organic pollutants, with more than twice as much biogenic aerosol mass attributable to unlisted compounds.

Prevention of submicron aerosolized particle dispersion: evaluation of an aerosol box using a pediatric simulation model.

Background and Aim: The SplashGuard CG (SG) is a barrier enclosure developed to protect healthcare workers from SARS-CoV-2 transmission during aerosol-generating procedures. Our objective was to evaluate the protection provided by the SG against aerosolized particles (AP), using a pediatric simulation model of spontaneous ventilation (SV) and noninvasive ventilation (NIV). Methods: An aerosol generator was connected to the airways of a pediatric high-fidelity manikin with a breathing simulator. AP concentrations were measured both in SV and NIV in the following conditions: with and without SG, inside and outside the SG, with and without suction applied to the device. Results: In the SV simulated setting, AP peaks were lower with SG: 0.1 × 105 particles/L compared to without: 1.6 × 105, only when the ports were closed and suction applied. In the NIV simulated setting, AP peaks outside the SG were lower than without SG (20.5 × 105 particles/L), whatever the situation, without suction (14.4 × 105particles/L), with suction and ports open or closed: 10.3 and 0.7 × 105 particles/L. In SV and NIV simulated settings, the AP peaks measured within the SG were much higher than the AP peaks measured without SG, even when suction was applied to the device. Conclusions: The SG seems to decrease peak AP exposure in the 2 ventilation contexts, but only with closed port and suction in SV. However, high concentrations of AP remain inside even with suction and SG should be used cautiously.

Preventing spread of aerosolized infectious particles during medical procedures: A lab-based analysis of an inexpensive plastic enclosure.

Severe viral respiratory diseases, such as SARS-CoV-2, are transmitted through aerosol particles produced by coughing, talking, and breathing. Medical procedures including tracheal intubation, extubation, dental work, and any procedure involving close contact with a patient's airways can increase exposure to infectious aerosol particles. This presents a significant risk for viral exposure of nearby healthcare workers during and following patient care. Previous studies have examined the effectiveness of plastic enclosures for trapping aerosol particles and protecting health-care workers. However, many of these enclosures are expensive or are burdensome for healthcare workers to work with. In this study, a low-cost plastic enclosure was designed to reduce aerosol spread and viral transmission during medical procedures, while also alleviating issues found in the design and use of other medical enclosures to contain aerosols. This enclosure is fabricated from clear polycarbonate for maximum visibility. A large single-side cutout provides health care providers with ease of access to the patient with a separate cutout for equipment access. A survey of medical providers in a local hospital network demonstrated their approval of the enclosure's ease of use and design. The enclosure with appropriate plastic covers reduced total escaped particle number concentrations (diameter > 0.01 µm) by over 93% at 8 cm away from all openings. Concentration decay experiments indicated that the enclosure without active suction should be left on the patient for 15-20 minutes following a tracheal manipulation to allow sufficient time for >90% of aerosol particles to settle upon interior surfaces. This decreases to 5 minutes when 30 LPM suction is applied. This enclosure is an inexpensive, easily implemented additional layer of protection that can be used to help contain infectious or otherwise potentially hazardous aerosol particles while providing access into the enclosure.

Optimization and Scale Up of Spray Dried CPZEN-45 Aerosol Powders for Inhaled Tuberculosis Treatment.

PURPOSE: Tuberculosis (TB) remains one of the most serious diseases caused by a single organism. Multiple (MDR) and extensively (XDR) drug resistant disease poses a threat to global health and requires new drugs and/or innovative approaches to treatment. A number of drugs have been proposed as inhaled therapy for TB, frequently prepared by spray drying. CPZEN-45 is a novel anti-tubercular drug that has poor oral bioavailability but has shown promise when administered via inhalation. METHODS: Excipient-free CPZEN-45 HCl has been spray dried into a powder with physicochemical characteristics, aerodynamic particle size distribution, and delivered dose suitable for consideration as an inhaled product. RESULTS: The mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) of the powder delivered using a RS01 inhaler were 2.62 ± 0.04 µm and 1.76 ± 0.09, respectively. Additionally, the powder was physically and chemically stable after storage at ambient conditions for >1.5 years with particle size similar to freshly manufactured product. Overages in spray dried powder were recycled the powder and resprayed into drug product likewise resulting in negligible change in quality thus allowing for further preclinical characterization as necessary. CPZEN-45 was scaled up using pilot-scale manufacturing equipment where the density of the powder was increased to facilitate larger delivered doses without affecting the aerodynamic performance properties. CONCLUSION: The spray dried powders were suitable for pharmacokinetics, efficacy and preclinical toxicology studies. The final method of manufacture may be used directly for CGMP particle manufacture to support IND and Phase I clinical trials and beyond.

Enrichment of short-chain organic acids transferred to submicron sea spray aerosols.

Organic acids, considered to be a substantial component of the marine carbon cycle, can enter the atmosphere through sea spray aerosol (SSA) and further affect the climate. Despite their importance, the distribution and mixing state of organic acids in SSA over the marine boundary layer are poorly understood and therefore need more investigation. Here, we have used ion chromatography (IC) in anion mode to measure short-chain organic acids concentrations in SSA collected throughout a custom-made SSA simulation chamber. The enrichment behavior and morphology of monocarboxylic acids (MAs, C1-8) and dicarboxylic acids (DAs) in submicron SSA were studied in seawater. We found that with MAs addition, the number concentration and mass concentration of SSA particles decreased gradually for C5-8 MAs, whereas they weakly varied with DAs addition due to the fact that carboxyl groups at both ends of DAs increased the surface tension of seawater. Moreover, the target compounds in submicron SSA displayed a surface activity-dependent enrichment behavior, where seawater with stronger surface activity, such as that containing MAs with >5 carbons, was more enriched in SSA in comparison to seawater with weaker surface activity. MAs with chain length <5 carbons were slightly enriched in SSA, whereas the enrichment factor (EF) of C5-8 MAs further increased with increasing chain length. These findings are of utmost importance in further understanding and quantifying the contribution of organic matter to SSA, which is crucial for assessing the atmosphere feedback of the marine carbon cycle. MAIN FINDING OF THE WORK: Surface tension of seawater is the key factor affecting the enrichment of short-chain organic acids in SSA.

Visualizing endoscopy-generated aerosols with laser light scattering (with videos).

BACKGROUND AND AIMS: Upper GI endoscopy is speculated to be an aerosol-generating procedure (AGP). Robust evidence exists for aerosol transmission of severe acute respiratory syndrome coronavirus 2. The quality of data available confirming aerosol generation during GI endoscopy is limited. We aimed to objectively demonstrate that GI endoscopy is an AGP and illustrate the mechanism by which the greatest risk for aerosolization of droplets during endoscopy may occur. METHODS: Aerosolized droplets generated during insertion and withdrawal of an endoscope and with passage of various tools through the endoscopic working channel using 2 experimental apparatuses modeling an upper GI tract (ie, a fluid-filled tube and a lamb esophagus) were qualitatively assessed by laser light scattering. RESULTS: Insertion and withdrawal of the upper endoscope into the upper GI tract models generated numerous aerosolized particles. A large number of brightly scattering particles were observed at the site of insertion and withdrawal of the endoscope. Passage of a cytology brush, biopsy forceps, and hemostatic clip through the working endoscope channel also generated aerosolized particles but in fewer numbers. There was no significant variation in quantity or brightness of droplets generated on testing different biopsy valve cap models or when suctioning fluid with an open versus closed biopsy valve cap. These results were reproducible over several trials. CONCLUSIONS: We illustrate in an objective manner that upper GI endoscopy is an AGP. These findings may have implications for transmission of infectious airborne pathogens outside of severe acute respiratory syndrome coronavirus 2 and can help to inform guidance on appropriate personal protective equipment use and other measures for transmission risk mitigation during GI endoscopy.

Cleaner air is adding to global warming.

Satellites capture fall in light-blocking pollution.

Isotopic Insights into Organic Composition Differences between Supermicron and Submicron Sea Spray Aerosol.

To elucidate the seawater biological and physicochemical factors driving differences in organic composition between supermicron and submicron sea spray aerosol (SSAsuper and SSAsub), carbon isotopic composition (δ13C) measurements were performed on size-segregated, nascent SSA collected during a phytoplankton bloom mesocosm experiment. The δ13C measurements indicate that SSAsuper contains a mixture of particulate and dissolved organic material in the bulk seawater. After phytoplankton growth, a greater amount of freshly produced carbon was observed in SSAsuper with the proportional contribution being modulated by bacterial activity, emphasizing the importance of the microbial loop in controlling the organic composition of SSAsuper. Conversely, SSAsub exhibited no apparent relationship with biological activity but tracked closely with surface tension measurements probing the topmost ∼0.2-1.5 µm of the sea surface microlayer. This probing depth is similar to a bubble's film thickness at the ocean surface, suggesting that SSAsub organic composition may be influenced by the presence of surfactants at the air-sea interface that are transferred into SSAsub by bubble bursting. Our findings illustrate the substantial impact of seawater dynamics on the pronounced organic compositional differences between SSAsuper and SSAsub and demonstrate that these two SSA populations should be considered separately when assessing their contribution to marine aerosols and climate.

The dynamics of SARS-CoV-2 infectivity with changes in aerosol microenvironment.

Understanding the factors that influence the airborne survival of viruses such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in aerosols is important for identifying routes of transmission and the value of various mitigation strategies for preventing transmission. We present measurements of the stability of SARS-CoV-2 in aerosol droplets (∼5 to 10 µm equilibrated radius) over timescales spanning 5 s to 20 min using an instrument to probe survival in a small population of droplets (typically 5 to 10) containing ∼1 virus/droplet. Measurements of airborne infectivity change are coupled with a detailed physicochemical analysis of the airborne droplets containing the virus. A decrease in infectivity to ∼10% of the starting value was observable for SARS-CoV-2 over 20 min, with a large proportion of the loss occurring within the first 5 min after aerosolization. The initial rate of infectivity loss was found to correlate with physical transformation of the equilibrating droplet; salts within the droplets crystallize at relative humidities (RHs) below 50%, leading to a near-instant loss of infectivity in 50 to 60% of the virus. However, at 90% RH, the droplet remains homogenous and aqueous, and the viral stability is sustained for the first 2 min, beyond which it decays to only 10% remaining infectious after 10 min. The loss of infectivity at high RH is consistent with an elevation in the pH of the droplets, caused by volatilization of CO2 from bicarbonate buffer within the droplet. Four different variants of SARS-CoV-2 were compared and found to have a similar degree of airborne stability at both high and low RH.

Sea spray aerosols intervening phospholipids ozonolysis at the air-water interface.

With more than half of the world's population lives along the coast and in its vicinity, the sea spray aerosols (SSAs) with respect to respiratory system impact has attracted increasing attention. In this paper, ozonolysis of model lung phospholipids intervened by salt cations in SSAs at air-water interface was investigated using acoustic levitation-nano-electrospray ionization-mass spectrometry (AL-nano-ESI-MS). The cation species facilitated the interfacial ozonolysis of phospholipids, and this increased ozonolysis showed a dependence on the concentration of salt cations. The charge number and ion radius of salt cations were also investigated, and the times of increased efficiency for phospholipids ozonolysis at the air-water interface were higher with more charge numbers or lower ion radius. The mechanism study revealed that the electrostatic interaction between the electronegative headgroup of phospholipids and the cations disturbed the packing of phospholipids, and resulted in oleyl chains more vulnerable with ozone. Finally, aerosolization of the salt-dominated artificial seawater and real seawater revealed a significant increase on ozonolysis of phospholipid intervened by salt cations. These results reveal SSAs intervening phospholipids interfacial reaction at the molecule level, which will be beneficial to gain the knowledge of the negative health effect concerning the components involved in SSAs.

Identifying behavior of long-distance virus transmission and mitigation performance from a COVID-19 outbreak of a daycare center.

During the last two years, hundreds of millions of people in the world have been infected with SARS-CoV-2 due to recurrent waves and closed spaces. Daycare centers are critical infrastructures that cannot be replaced, even during the COVID-19 period. However, the existing settings in daycare centers may pose risks of inevitable close contact between teachers and children, as well as fomite and airborne transmission during care hours. Therefore, reinforced mitigation strategies have been applied in daycare centers to reduce potential indoor virus transfer in many countries. However, numerous outbreaks of COVID-19 have been reported in daycare centers. Therefore, in this study, researchers focused on the risk and behavior of long-distance virus transmission based on the detected viruses on air purifier filter sampling in a daycare center outbreak in Korea. Various experiments of possible situations were conducted in nursing rooms based on field interviews. The experiments monitored the long-distance transmission behavior of aerosol-sized particles and visualized particle behavior at the daycare center. The results of this study revealed that long-distance virus transmission is possible under the current settings in the daycare center, and flush-out can be an important countermeasure with reinforced ventilation methods to prevent potential airborne spread in the daycare center. The results of air purifiers represented that air purifiers should be properly installed and operated in the daycare center to prevent airborne virus spread by airflow during occupied hours. The findings of this study will contribute to the understanding of airborne virus risk and the development of customized virus measures for daycare centers.

Leaching material from Antarctic seaweeds and penguin guano affects cloud-relevant aerosol production.

Within the Southern Ocean, the greatest warming is occurring on the Antarctic Peninsula (AP) where clear cryospheric and biological consequences are being observed. Antarctic coastal systems harbour a high diversity of marine and terrestrial ecosystems heavily influenced by Antarctic seaweeds (benthonic macroalgae) and bird colonies (mainly penguins). Primary sea spray aerosols (SSA) formed by the outburst of bubbles via the sea-surface microlayer depend on the organic composition of the sea water surface. In order to gain insight into the influence of ocean biology and biogeochemistry on atmospheric aerosol, we performed in situ laboratory aerosol bubble chamber experiments to study the effect of different leachates of biogenic material - obtained from common Antarctic seaweeds as well as penguin guano - on primary SSA. The addition of different leachate materials on a seawater sample showed a dichotomous effect depending on the leachate material added - either suppressing (up to 52%) or enhancing (22-88%) aerosol particle production. We found high ice nucleating particle number concentrations resulting from addition of guano leachate material. Given the evolution of upper marine polar coastal ecosystems in the AP, further studies on ocean-atmosphere coupling are needed in order to represent the currently poorly understood climate feedback processes.

Novel Negative Pressure Procedural Tent Reduces Aerosolized Particles in a Simulated Prehospital Setting.

BACKGROUND/OBJECTIVE: The coronavirus disease 2019 (COVID-19) pandemic has challenged the ability of Emergency Medical Services (EMS) providers to maintain personal safety during the treatment and transport of patients potentially infected. Increased rates of COVID-19 infection in EMS providers after patient care exposure, and notably after performing aerosol-generating procedures (AGPs), have been reported. With an already strained workforce seeing rising call volumes and increased risk for AGP-requiring patient presentations, development of novel devices for the protection of EMS providers is of great importance.Based on the concept of a negative pressure room, the AerosolVE BioDome is designed to encapsulate the patient and contain aerosolized infectious particles produced during AGPs, making the cabin of an EMS vehicle safer for providers. The objective of this study was to determine the efficacy and safety of the tent in mitigating simulated infectious particle spread in varied EMS transport platforms during AGP utilization. METHODS: Fifteen healthy volunteers were enrolled and distributed amongst three EMS vehicles: a ground ambulance, an aeromedical-configured helicopter, and an aeromedical-configured jet. Sodium chloride particles were used to simulate infectious particles and particle counts were obtained in numerous locations close to the tent and around the patient compartment. Counts near the tent were compared to ambient air with and without use of AGPs (non-rebreather mask, continuous positive airway pressure [CPAP] mask, and high-flow nasal cannula [HFNC]). RESULTS: For all transport platforms, with the tent fan off, the particle generator alone, and with all AGPs produced particle counts inside the tent significantly higher than ambient particle counts (P <.0001). With the tent fan powered on, particle counts near the tent, where EMS providers are expected to be located, showed no significant elevation compared to baseline ambient particle counts during the use of the particle generator alone or with use of any of the AGPs across all transport platforms. CONCLUSION: Development of devices to improve safety for EMS providers to allow for use of all available therapies to treat patients while reducing risk of communicable respiratory disease transmission is of paramount importance. The AerosolVE BioDome demonstrated efficacy in creating a negative pressure environment and workspace around the patient and provided significant filtration of simulated respiratory droplets, thus making the confined space of transport vehicles potentially safer for EMS personnel.

Droplet nuclei caustic formations in exhaled vortex rings.

Vortex ring (VR) structures occur in light or hoarse cough configurations. These instances consist of short impulses of exhaled air resulting to a self-contained structure that can travel large distances. The present study is the first implementation of the second order Fully Lagrangian Approach (FLA) for three-dimensional realistic flow-fields obtained by means of Computational Fluid Dynamics (CFD) and provides a method to calculate the occurrence and the intensity of caustic formations. The carrier phase flow field is resolved by means of second order accurate Direct Numerical Simulation (DNS) based on a Finite Difference approach for the momentum equations, while a spectral approach is followed for the Poisson equation using Fast Fourier Transform (FFT). The effect of the undulations of the carrier phase velocity due to large scale vortical structures and turbulence is investigated. The evaluation of the higher order derivatives needed by the second order FLA is achieved by pre-fabricated least squares second order interpolations in three dimensions. This method allows for the simulation of the clustering of droplets and droplet nuclei exhaled in ambient air in conditions akin to light cough. Given the ambiguous conditions of vortex-ring formation during cough instances, three different exhale (injection) parameters n are assumed, i.e. under-developed ([Formula: see text]), ideal ([Formula: see text]) and over-developed ([Formula: see text]) vortex rings. The formation of clusters results in the spatial variance of the airborne viral load. This un-mixing of exhumed aerosols is related to the formation of localised high viral load distributions that can be linked to super-spreading events.