Airborne Concentrations Research Articles

Aerosol mass and size-resolved metal content in urban Bangkok, Thailand

Inhalable particulate matter (PM) is a health concern, and people living in large cities such as Bangkok are exposed to high concentrations. This exposure has been linked to respiratory and cardiac diseases and cancers of the lung and brain. Throughout 2018, PM was measured in northern Bangkok near a toll road (13.87°N, 100.58°E) covering all three seasons (cool, hot and rainy). PM10 was measured in 24- and 72-h samples. On selected dates aerodynamic size and mass distribution were measured as 3-day samples from a fixed 5th floor inlet. Particle number concentration was measured from the 5th floor inlet and in roadside survey measurements. There was a large fraction of particle number concentration in the sub-micron range, which showed the greatest variability compared with larger fractions. Metals associated with combustion sources were most found on the smaller size fraction of particles, which may have implications for associated adverse health outcomes because of the likely location of aerosol deposition in the distal airways of the lung. PM10 samples varied between 30 and 100 μg m−3, with highest concentrations in the cool season. The largest metal fractions present in the PM10 measurements were calcium, iron and magnesium during the hot season with average airborne concentrations of 13.2, 3.6 and 2.0 μg m−3, respectively. Copper, zinc, arsenic, selenium, molybdenum, cadmium, antimony and lead had large non-crustal sources. Principal component analysis (PCA) identified likely sources of the metals as crustal minerals, tailpipe exhaust and non-combustion traffic. A health risk analysis showed a higher risk of both carcinogenic and non-carcinogenic health effects in the drier seasons than the wet season due to ingestion of nickel, arsenic, cadmium and lead.Graphical abstract

Environmental Factors Shaping the Diversity and Spatial-Temporal Distribution of Indoor and Outdoor Culturable Airborne Fungal Communities in Tianjin University Campus, Tianjin, China.

Airborne fungi have significant influence on air quality and may pose adverse effects on human health due to their allergenic and pathogenic effect. We carried out a 1-year survey on the airborne fungal diversity and concentration of indoor and outdoor environments, within the Tianjin University campus. Airborne fungi were sampled using an HAS-100B air sampler. Isolated fungal strains were identified based on morphological and molecular analysis. A total of 641 fungal strains belonging to 173 species and 74 genera were identified in this study. The dominant fungal genera were Cladosporium (29.49%), Alternaria (25.9%), and Epicoccum (6.24%), while the most frequently occurring species were A. alternata (15.44%), C. cladosporioides (11.86%), and E. nigrum (5.77%). The mean fungal concentration at different sites ranged from 0 to 420 CFU/m3, which is lower than the permissive standard level. There was a seasonal variation in the airborne fungal community, while temperature and relative humidity were positively correlated with the fungal concentration and diversity at almost all the sites. Higher fungal diversity was recorded in peak period of human traffic at the two canteens, whereas the two dormitories showed higher fungal diversity in off-peak period. Our study provides the first report on the diversity and concentration of airborne fungal species within different Tianjin University campus environments and clarifies the role played by environmental factors on the analyzed fungal community. Our results may represent valuable information for air quality monitoring and microbial pollution control in densely populated human living environments.

Uncertainty quantification of atmospheric transport and dispersion modelling using ensembles for CTBT verification applications

Airborne concentrations of specific radioactive xenon isotopes (referred to as “radioxenon”) are monitored globally as part of the verification regime of the Comprehensive Nuclear-Test-Ban Treaty, as these could be the signatures of a nuclear explosion. However, civilian nuclear facilities emit a regulated amount of radioxenon that can interfere with the very sensitive monitoring network. One approach to deal with this civilian background of radioxenon for Treaty verification purposes, is to explicitly simulate the expected radioxenon concentration from civilian sources at monitoring stations using atmospheric transport modelling. However, atmospheric transport modelling is prone to uncertainty, and the absence of an uncertainty quantification can limit its use for detection screening. In this paper, several ensembles are assessed that could provide an atmospheric transport modelling uncertainty quantification. These ensembles are validated with radioxenon observations, and recommendations are given for atmospheric transport modelling uncertainty quantification. Finally, the added value of an ensemble for detection screening is illustrated.

Evaluation of two surface sampling methods for the detection of Bacillus atrophaeus aerosolized in a test chamber

In response to the airborne release of biothreat agents, surface sampling is often used to provide information on bioaerosol dispersal and deposition, to identify biocontaminant sources, and determine the effectiveness of decontamination. The objective of this project was to use aerosolization and deposition of dry spores to evaluate the efficiency of the cellulose sponge wipe and 37-mm cassette micro vacuum surface sampling methods for the collection of microorganisms from two contaminated surfaces, metal and concrete. Aerosolization trials were performed in a room-sized test chamber with known airborne concentrations of Bacillus atrophaeus spores serving as a surrogate for a bioterrorism agent. Following each aerosolization trial, the chamber heating, ventilation, air conditioning (HVAC) system was turned off to allow airborne spores to settle onto the test materials. Surface sampling was conducted and culture analysis was used to determine the concentration of B. atrophaeus on the surfaces. Results were compared with reference samples to determine the collection efficiency of the sampling methods. The sponge wipe sampling method was significantly more effective than the vacuum method for the collection of B. atrophaeus from both metal and concrete surfaces (P < 0.001). The collection efficiency of the sponge wipe method was 39.5% for metal and 26.5% for concrete, while the collection efficiency of the vacuum method was 7.6% for metal and 9.3% for concrete. The results of this study provided data on the collection efficiencies of two surface sampling methods for detection and enumeration of biocontaminants and can aid in selection of sampling methods.

A Review of Road Traffic-Derived Non-Exhaust Particles: Emissions, Physicochemical Characteristics, Health Risks, and Mitigation Measures.

Implementation of regulatory standards has reduced exhaust emissions of particulate matter from road traffic substantially in the developed world. However, nonexhaust particle emissions arising from the wear of brakes, tires, and the road surface, together with the resuspension of road dust, are unregulated and exceed exhaust emissions in many jurisdictions. While knowledge of the sources of nonexhaust particles is fairly good, source-specific measurements of airborne concentrations are few, and studies of the toxicology and epidemiology do not give a clear picture of the health risk posed. This paper reviews the current state of knowledge, with a strong focus on health-related research, highlighting areas where further research is an essential prerequisite for developing focused policy responses to nonexhaust particles.

Multi-route exposure sampling of quaternary ammonium compounds and ethanol surface disinfectants in a K-8 school.

The frequency of surface disinfectant use has increased over the last several years in public settings such as schools, especially during the COVID-19 pandemic. Although these products are important for infection control and prevention, their increased use may intensify the exposure to both persons applying the disinfection product as well as bystanders. Safety assessments have demonstrated that these products, when used as intended, are considered safe for use and effective; however, point-of-contact effects (such as respiratory or dermal irritation) may still occur. Additionally, relative exposures may vary significantly due to the wide variation in disinfectant formulation and application methods. Quantitative estimations of exposures to two commonly used active ingredients, quaternary ammonium compounds (QACs) and ethanol, are not well characterized during product use and application scenarios. To assess the potential for health risks attributable to increased use in classroom settings, as well as to quantitatively evaluate the potential exposure to both ethanol and QACs, student and adult bystander surface and air measurements were collected in a K-8 school setting in Ohio, United States, over a three-day period. Direct-reading instruments were utilized to collect real-time air samples that characterized mass fraction concentrations following the use of the QAC- and ethanol-based disinfectants. Furthermore, surface and air sampling of microbial species were conducted to establish the overall bioburden and effectiveness of each disinfectant to inform the comparative risk and health effect impacts from the tested products use scenario. Both tested products were approximately equally effective at reducing bioburdens on desk surfaces. In some classrooms, concentrations of QAC congeners were significantly increased on desk surfaces following the application of the disinfectant spray; however, the magnitude of the change in concentration was small. Ethanol was not measured on surfaces due to its volatility. Airborne concentrations increased immediately following spray of each disinfectant product but rapidly returned to baseline. Each of the QAC congeners listed in the product safety data sheets were detected and measurable on desk surfaces; however, air concentrations were generally below the limit of detection. The 15-min time-weighted averages (TWAs) of both QACs and ethanol in the air were below respective health effects benchmarks, and therefore, the negative impact on health outcomes is considered to be minimal from short-term, repeated use of ethanol- or QAC-based spray products in a school setting when the products are used as directed.

Temporal and spatial patterns of airborne pollen dispersal in six salt marsh halophytes

Pollination is a key process in the life cycle of most plant species, but very little is known about airborne pollen dispersal in salt marsh anemophilous halophytes. We analyzed the temporal and spatial dynamics of airborne pollen dispersal, using portable volumetric pollen traps, for six anemophilous Chenopodiaceae halophytic species in tidal salt marshes. In addition, we studied the effects of air temperature and wind speed on airborne pollen dispersal. Our study shows high levels of temporal and spatial constraint on airborne pollen dispersal. We recorded the lowest airborne pollen concentrations at air temperatures lower than 22 °C and wind speeds higher than 6 m s−1. These environmental conditions set up a narrow temporal pollination window during morning hours. We also recorded severe spatial limitation for pollen dispersal in three of the six halophytes studied, which presented airborne pollen concentrations that were 9 to 53 times smaller only 5 m away from source populations than within those populations. These results show that even related species colonizing the same ecosystem may show contrasted airborne pollen spatial dispersal dynamics that depend on several environmental factors. This should be taken into account for estimates of vegetation composition based on pollen production in aerobiological and paleopalinological studies. The restricted airborne pollen dispersal recorded would promote geitonogamy and limit interpopulation genetic exchange to the dispersal of their hydrochorous fruits.

Estimation of Aerosol Concentrations of Oil Dispersants COREXIT™ EC9527A and EC9500A during the Deepwater Horizon Oil Spill Response and Clean-up Operations.

The April 2010 Deepwater Horizon drilling unit explosion at the Macondo oil well resulted in the release of approximately 779 million l of oil into the Gulf of Mexico. As part of the response effort to break up oil slicks on the water's surface, 6.81 million l of chemical dispersants COREXIT™ EC9500A and COREXIT™ EC9527A were applied by plane or vessel or injected near the seabed. The GuLF Long-term Follow-up Study is investigating possible adverse health effects of workers involved in the oil spill response and clean-up (OSRC). In this paper, we describe potential dispersant-related air concentrations generated from aerial spraying of dispersants to provide insight as to what concentrations OSRC workers may have been exposed under worst-case conditions. Personal exposure measurement data were not collected. Modeling, therefore, was conducted to estimate airborne concentrations of total aerosol to COREXIT™ EC9527A and EC9500A. Using the AgDISP model, we estimated air concentrations to dispersant total aerosols, defined as all components of the dispersant including active ingredients, surfactants, and water, resulting from aerial and vessel applications, as average 1-h and 2-min concentrations. For comparison, 1-h air concentrations associated with aerial spraying were estimated using another model, AERMOD. At 152 m horizontal to the flight path, average 1-h total aerosol concentrations associated with aerial applications were estimated to be as high as 49.3 µg m-3 (9527A) and 45.4 µg m-3 (9500A), and both decreased with increased distance from the flight line. The estimates for spraying 9500A from vessels indicated that total aerosol concentrations were potentially as high as 0.33 µg m-3 at 10 m from the nozzles. These results suggest that personal exposures to dispersant aerosols were negligible.

Efficacy of N-acetyl aspartyl glutamic acid versus fluorometholone for treating allergic conjunctivitis in an environmental exposure chamber.

BackgroundTopical mast cell stabilizers were previously shown to treat the signs and symptoms of seasonal and perennial allergic conjunctivitis safely and effectively in active and placebo‐controlled trials. However, mast cell stabilizers have not been compared to topical corticosteroids for efficacy. We tested the non‐inferiority of a topical mast cell stabilizer, N‐acetyl aspartyl glutamic acid (4.9%, NAAGA), compared to fluorometholone (0.1%, FM) during controlled exposures to the airborne birch pollen allergen, Bet v 1, in an environmental exposure chamber (EEC).MethodsThis randomized, cross‐over, investigator‐blinded study included 24 patients with a history of birch pollen allergic conjunctivitis. Patients were randomized to 5 days of treatment with NAAGA, then FM (n = 12) or FM, then NAAGA (n = 12). After each treatment, patients were exposed to a fixed airborne concentration of Bet v 1 in ALYATEC EEC. The primary endpoint was the amount of allergen required to trigger a conjunctival response (Abelson score ≥5). Groups were compared with a linear model for cross‐over studies. Non‐inferiority was assumed, when the lower bound of the risk ratio confidence interval (CI) was >0.5.ResultsAt screening, the mean time‐to‐conjunctival response was 72.5 ± 35.9 min. NAAGA and FM extended the response time to 114.8 ± 55.0 and 116.6 ± 51.5 min respectively. The mean amounts of allergen required to trigger a conjunctival response were 1.165 ng after NAAGA and 1.193 ng after FM treatment. The risk ratio for the conjunctival response was 0.977 (95% CI: 0.812; 1.174), which indicated non‐inferiority. Adverse events occurred less frequently with NAAGA (29.2%) than with FM (58.3%).ConclusionIn patients with allergic conjunctivitis to birch pollen, NAAGA was non‐inferior to FM in exposures to airborne Bet v 1. The EEC was a good model for simulating real‐life airborne allergen exposure and for demonstrating the efficacy and safety of eye drops for treating allergic conjunctivitis.Trial registrationNot registered.

Seasonal variation of airborne phthalates in classroom and dormitory, and its exposure assessment in college students

Phthalates are widely used as plasticizers in various products. However, only few studies have focused on its pollution in university dormitories and classrooms. In this study, we measured the airborne concentrations of phthalates in the dormitories and classrooms of a university in Beijing, China. We analyzed the pollution characteristics and possible sources of phthalates, used Monte Carlo simulation to estimate phthalate intake via inhalation and dermal absorption through direct air-through-skin pathways, and explored the seasonal variations in airborne phthalate concentrations and exposure levels. Di (2-methoxyethyl) phthalate and di-n-butyl phthalate were predominantly observed in the classroom and dormitory. Three possible phthalate sources existed in the classroom and dormitory. The airborne concentrations of high-molecular-weight phthalates were significantly higher in winter than those during spring and autumn. The room’s orientation weakly affected the indoor airborne phthalate concentrations. More surface sinks in female dormitories significantly affected the concentration of airborne phthalates, which is worthy of a comprehensive study. Low-molecular-weight phthalates in the dormitory significantly differed between urban and suburban areas. The influences of orientation, dormitory type, and geographic location on indoor phthalate concentrations are related to the seasons. The total daily intake of phthalates in dormitories was greater than that in classrooms. The daily intake of phthalates via dermal absorption was greater than that via inhalation, and was the highest during winter.

Innate and Adaptive Immunity in Workers of the Main Occupations Exposed to Fine Particulate Matter in Potassium Chloride Production

Background: Workplace air pollution with fine particulate matter in industrial premises contributes to imbalance of nonspecific and specific immunity factors, increasing the risk of developing premorbid conditions in workers. Objective: To study the features of phagocytic activity and subpopulation T-lymphocytes composition in workers engaged in the potassium chloride production. Material and methods: The study was conducted in 2019–2022 within the Research Program of the Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing on hygiene problems, Clause 2.2.18 “Development of approaches to early diagnosis of production-related diseases using genomic and postgenomic analysis technologies in workers associated with harmful factors of working conditions”, R&amp;D No. 121081900044-4. The observation group consisted of 54 workers of the main occupations exposed, inter alia, to fine respirable particulate matter in potassium chloride production. The comparison group included 67 individuals having no occupational exposure to industrial hazards. We evaluated the phagocytic activity of peripheral blood leukocytes and determined the level of CD25+ and CD95+ differentiation cluster expression on T-lymphocytes by flow cytometry. Results: We measured high airborne concentrations of fine particles at workplaces of mill, centrifuge and filter operators, granulation and drying workers that were 6.6 and 7 times higher than those of PM2.5 and PM10 in the working environment of the administrative staff, respectively. We also observed that the ability of neutrophils to absorb and digest foreign particles was 20 % lower in the workers of the observation group (p = 0.047), while the proportions of CD25+ and CD95+ lymphocytes in them were 30 % and 60 % lower than those in the comparison group, respectively (p = 0.001–0.046). Conclusion: We established the effect of fine particulate matter as a priority workplace air pollutant on innate and adaptive immunity in workers of the main occupations in the potassium chloride production facility. Parameters of innate (phagocytic number) and adaptive (CD25+ and CD95+ lymphocytes) immunity are recommended for use in early diagnosis of immune dysfunction and the development of occupational diseases in workers with inhalation exposure to fine particles.

Occupational Exposure of Hairdressers to Airborne Hazardous Chemicals: A Scoping Review.

Introduction: Exposure to hazardous chemicals released during hairdressing activities from hair care products puts hairdressers at risk of adverse health effects. Safety assessments of hair products are mainly focused on consumers, but exposure for professional hairdressers might be substantially higher. Objective: To identify and assess available research data on inhalation exposures of professional hairdressers. Methods: A systematic search of studies between 1 January 2000 and 30 April 2021 was performed in Medline, Embase, Web of Science and in Cochrane registry, toxicological dossiers of the Scientific Committee on Consumer Safety (SCCS) of the European Commission as well as the German MAK Commission. Studies reporting quantitative data on airborne concentrations of chemicals in the hairdresser’s workplace were considered. The outcome was an airborne concentration of chemicals in the working environment, which was compared, when possible, with current occupational exposure limits (OEL) or guidance levels. Results: In total, 23 studies performed in 14 countries were included. The average number of hairdressing salons per study was 22 (range 1–62). Chemicals most frequently measured were formaldehyde (n = 8), ammonia (n = 5), total volatile organic compounds (TVOC) (n = 5), and toluene (n = 4). More than fifty other chemicals were measured in one to three studies, including various aromatic and aliphatic organic solvents, hydrogen peroxide, persulfate, and particulate matter. Most studies reported environmental air concentrations, while personal exposure was measured only in seven studies. The measured air concentrations of formaldehyde, ammonia, and TVOC exceeded OEL or guidance values in some studies. There was large variability in measuring conditions and reported air concentrations differed strongly within and between studies. Conclusion: Hairdressers are exposed to a wide spectrum of hazardous chemicals, often simultaneously. Airborne concentrations of pollutants depend on salon characteristics such as ventilation and the number of customers but also on used products that are often country- or client-specific. For exposure to formaldehyde, ammonia, and TVOC exceeding OELs or guidance values for indoor air was observed. Therefore, occupational exposure should be taken into account by safety regulations for hair care products.

Formal methods of selecting monitoring locations and control levels

It is necessary to determine locations in a cleanroom where airborne concentrations of particles and microbe-carrying particles (MCPs) should be monitored. It is also necessary to determine the concentrations of airborne contamination that should not be exceeded during manufacturing operations, ie. the alert and action control levels. Both these requirements can be ascertained by simple and informal means. However, should a formal approach be required, the monitoring locations can be determined by a risk assessment, and the control levels by a statistical method. Key Words: Monitoring, airborne particles, control levels, pharmaceutical, cleanrooms

Detection and identification of potentially infectious gastrointestinal and respiratory viruses at workplaces of wastewater treatment plants with viability qPCR/RT-qPCR

This study aimed to qualitatively and quantitatively assess the prevalence of the most common respiratory and gastrointestinal viruses in the air, surface swab, and influent/effluent samples collected in wastewater treatment plants (WWTPs). Application of qPCR/RT-qPCR (quantitative polymerase chain reaction/reverse-transcription quantitative polymerase chain reaction) assays combined with PMA (propidium monoazide) dye pretreatment allowed detecting the potentially infectious and disintegrated viral particles in collected samples. In the air at workplaces in WWTPs, the most frequent isolation with the highest concentrations (reaching up to 103 gc/m3 of potentially infectious intact viral particles) were observed in case of adenoviruses (AdVs) and rotaviruses (RoVs), followed by noroviruses (NoVs). Viruses were significantly more often detected in the air samples collected with Coriolis μ impinger, than with MAS-100NT impactor. The temperature negatively (Spearman correlation: –1 < R < 0; p < 0.05), while RH (relative humidity) positively (0 < R < 1; p < 0.05) affected airborne concentrations of potentially infectious viral particles. In turn, the predominant viruses on studied surfaces were RoVs and noroviruses GII (NoV GII) with concentrations of potentially infectious virions up to 104 gc/100 cm2. In the cases of SARS-CoV-2 and presumptive SARS-CoV-2 or other coronaviruses, their concentrations reached up to 103 gc/100 cm2. The contamination level of steel surfaces in WWTPs was similar to this on plastic ones. This study revealed that the qualitative and quantitative characteristics of respiratory and gastrointestinal viruses at workplaces in WWTPs is important for proper exposure assessment and needs to be included in risk management in occupational environment with high abundance of microbial pollutants derived from wastewater.

Aerial Survey Robotics in Extreme Environments: Mapping Volcanic CO2 Emissions With Flocking UAVs

We present methods for autonomous collaborative surveying of volcanic CO2 emissions using aerial robots. CO2 is a useful predictor of volcanic eruptions and an influential greenhouse gas. However, current CO2 mapping methods are hazardous and inefficient, as a result, only a small fraction of CO2 emitting volcanoes have been surveyed. We develop algorithms and a platform to measure volcanic CO2 emissions. The Dragonfly Unpiloted Aerial Vehicle (UAV) platform is capable of long-duration CO2 collection flights in harsh environments. We implement two survey algorithms on teams of Dragonfly robots and demonstrate that they effectively map gas emissions and locate the highest gas concentrations. Our experiments culminate in a successful field test of collaborative rasterization and gradient descent algorithms in a challenging real-world environment at the edge of the Valles Caldera supervolcano. Both algorithms treat multiple flocking UAVs as a distributed flexible instrument. Simultaneous sensing in multiple UAVs gives scientists greater confidence in estimates of gas concentrations and the locations of sources of those emissions. These methods are also applicable to a range of other airborne concentration mapping tasks, such as pipeline leak detection and contaminant localization.

Fabrication of electrospun membranes for air sampling applications: A statistical optimization approach

Introduction: The applicability of Nanofiber (NF) membranes in air sampling of pollutants for the purpose of determining the airborne concentration has received little attention around the world. The present study aims to optimize the fabrication of NF membrane for the of air sampling application.&#x0D; Materials and methods: The polyvinyl chloride NF membranes were fabricated using needle-based solution electrospinning technique. The experimental design was prepared by Design-Expert v7.0 and data analysis was done by Central Composite Design (CCD) base on Response Surface Methodology (RSM) technique. The ability of the fabricated membranes in air sampling applications was performed by sampling of airborne crystalline silica by them using the National Institute for Occupational Safety and Health (NIOSH7602) method and then comparing with the commercial PVC membranes.&#x0D; Results: The fabricated NF membranes had a mean porosity of 31.60% compared to a porosity of 25.1% in the case of commercial Polyvinyl Chloride (PVC) membranes. The electrospun NF membranes had mean pressure drop of 194.23 Pa, which is lower than the 204 Pa pressure drop of commercial PVC filters. The mean concentration of silica sampled by the electrospun NF membrane was 0.14 mg/m3 while this was 0.03 mg/m3 for commercial PVC membrane. The difference concentration of crystalline silica sampled by NF and commercial PVC membranes had the strongest relationship with the electrospinning solution concentration (r=-0.785, p&gt;0.05).&#x0D; Conclusion: The NF membrane has high performance in sampling the crystalline silica dust from the air stream compared to commercial PVC membranes.

Predicting airborne pollutant concentrations and events in a commercial building using low-cost pollutant sensors and machine learning: A case study

Prediction of indoor airborne pollutant concentrations can enable a smart indoor air quality control strategy that potentially reduces building energy use and improves occupant comfort. In service of this overarching goal, this work pursues four objectives: 1) Determine which low-cost airborne pollutant sensors are useful for prediction of indoor air quality variables of interest, investigating whether a few commercially available sensors held value for making such predictions. 2) Investigate which algorithms are most useful for making these predictions. 3) Develop an understanding of how far into the future we can conceivably predict indoor concentrations based on low-cost airborne pollutant signals. 4) Investigate methods for predicting elevated concentration events from historical data. Four different methods (Rolling Average, Random Forest, Gradient Boosting, and Long-Short Term Memory) for predicting eight indoor pollutant concentrations (carbon dioxide, nitrogen dioxide, ozone, PM 1, PM 2.5, PM 10, formaldehyde, total volatile organic compounds) are compared for their ability to predict future sensor signals in a single commercial building in California. Long-Short Term Memory was consistently the best method for predicting indoor pollutants, though the best combinations of input variables differed depending on pollutant of interest. To predict elevated concentration events, results show that indirect classification through a regression prediction that was then compared to a threshold performed marginally better than a direct classification prediction for all pollutants except PM1.

Modeling and experimental study of dispersion and deposition of respiratory emissions with implications for disease transmission.

The ability to model the dispersion of pathogens in exhaled breath is important for characterizing transmission of the SARS‐CoV‐2 virus and other respiratory pathogens. A Computational Fluid Dynamics (CFD) model of droplet and aerosol emission during exhalations has been developed and for the first time compared directly with experimental data for the dispersion of respiratory and oral bacteria from ten subjects coughing, speaking, and singing in a small unventilated room. The modeled exhalations consist of a warm, humid, gaseous carrier flow and droplets represented by a discrete Lagrangian particle phase which incorporates saliva composition. The simulations and experiments both showed greater deposition of bacteria within 1 m of the subject, and the potential for a substantial number of bacteria to remain airborne, with no clear difference in airborne concentration of small bioaerosols (<10 μm diameter) between 1 and 2 m. The agreement between the model and the experimental data for bacterial deposition directly in front of the subjects was encouraging given the uncertainties in model input parameters and the inherent variability within and between subjects. The ability to predict airborne microbial dispersion and deposition gives confidence in the ability to model the consequences of an exhalation and hence the airborne transmission of respiratory pathogens such as SARS‐CoV‐2.

Link between SARS-CoV-2 emissions and airborne concentrations: Closing the gap in understanding

The airborne transmission of SARS-CoV-2 remains surprisingly controversial; indeed, health and regulatory authorities still require direct proof of this mode of transmission. To close this gap, we measured the viral load of SARS-CoV-2 of an infected subject in a hospital room (through an oral and nasopharyngeal swab), as well as the airborne SARS-CoV-2 concentration in the room resulting from the person breathing and speaking. Moreover, we simulated the same scenarios to estimate the concentration of RNA copies in the air through a novel theoretical approach and conducted a comparative analysis between experimental and theoretical results. Results showed that for an infected subject's viral load ranging between 2.4 × 106 and 5.5 × 106 RNA copies mL-1, the corresponding airborne SARS-CoV-2 concentration was below the minimum detection threshold when the person was breathing, and 16.1 (expanded uncertainty of 32.8) RNA copies m-3 when speaking. The application of the predictive approach provided concentrations metrologically compatible with the available experimental data (i.e. for speaking activity). Thus, the study presented significant evidence to close the gap in understanding airborne transmission, given that the airborne SARS-CoV-2 concentration was shown to be directly related to the SARS-CoV-2 emitted. Moreover, the theoretical analysis was shown to be able to quantitatively link the airborne concentration to the emission.

Measurement of Airborne Radioactivity in the Inpatient Room after Administering [177Lu]Lu-PSMA-617 to Humans

[177Lu]Lu-PSMA-617 is a radioisotope used in nuclear medicine. It is necessary to take appropriate measures to limit its exposure and ensures its airborne concentrations do not exceed legally permitted levels. Therefore, the purpose of this study was to measure the airborne radioactivity concentration in the inpatient room after administering [177Lu]Lu-PSMA-617 to humans. Three males with advanced prostate-specific membrane antigen (PSMA)-positive metastatic castration resistant prostate cancer were intravenously administered [177Lu]Lu-PSMA-617 (7.4 GBq ± 10%) in an inpatient room, and the airborne radioactivity concentrations were measured at two locations in the room (in the center of the room and at the bedside) using a filter collection method. After administration of [177Lu]Lu-PSMA-617, the airborne radioactivity concentrations measured were below the limit of detection (1.1 × 10-6 Bq/cm3 or 9.5 × 10-7 Bq/cm3) in all three humans, and all concentrations were consistently below the standard value of 1/10,000 of 2 × 10-2 Bq/cm3, the legal airborne concentration limit of 177Lu. The results of this study confirmed that the airborne concentration of [177Lu]Lu-PSMA-617 after administration to humans was below the legally permitted level.