Aerosol Generation Research Articles

Analysis of aerosol generation during Er:YAG laser-assisted caries treatment: A randomized clinical trial.

Maintaining biosafety in dental practice involves the effective elimination of aerosols produced during dental treatment. To assess the quantity of aerosols and aerobic bacteria in the air during the treatment of caries. The study involved 60 patients with a total of 60 molar teeth (n = 60) in the mandible who were divided into 2 groups based on caries treatment method. Group 1 (G1, n = 30) received treatment with a conventional dental turbine (W&H Synea TA-98LC; W&H, Burmoos, Austria), while group 2 (G2, n = 30) underwent treatment with an Er:YAG (erbium-doped yttrium aluminium garnet) laser (LightWalker, Fotona, Slovenia). Measurements of aerosol particles between 0.3 Ęm and 10.0 Ęm near the operatorfs mouth were taken using the PC200 laser particle counter (Trotec GmbH, Schwerin, Germany). The number of aerobic bacteria in the air was determined using 60 Petri plates with a microbiological medium (Columbia agar with 5% sheep blood) and the sedimentation method. A control group (G3) was established to measure initial aerosol levels and initial total number of bacteria colony-forming units (CFUs) before each treatment. In G1 (dental turbine), the median value of aerosol particles was 57,021 (42,564.67,568), while in G2 (Er:YAG laser), it was significantly lower at 33,318 (28,463.35,484) (p < 0.001). The median total bacteria count per cubic meter of air in G1 (conventional dental turbine + high volume evacuator (HVE)), G2 (Er:YAG laser + HVE) and G3 (control group before caries treatment) were 734 (420.988), 158 (96.288) and 48 (32.74), respectively, with a statistically significant difference between the groups (p < 0.001). The use of Er:YAG laser during caries treatment resulted in a 41.6% reduction in aerosol amounts and a 78.5% decrease in the total bacterial count (TBC) compared to treatment with a dental turbine.

Investigation of aerosol generation through laser cleaning of various surfaces and optimization of mist & spray scavenging

To ensure the safe and effective decommissioning of the Fukushima Daiichi Nuclear Power Plant (NPP), it is crucial to investigate the behavior of radioactive aerosols generated during the laser decontamination of radiation hot spots and laser cutting of fuel debris. Understanding the generation and dispersion patterns of these aerosols is of utmost importance for the proper planning and execution of decommissioning activities. This study focuses on the performance evaluation of high-power continuous wave (CW) fiber lasers for cleaning surfaces composed of carbon steel, stainless steel, and concrete. The effective confinement and scavenging of radioactive aerosols are critical in minimizing the risk of radiation exposure during decommissioning processes. Test samples, made of carbon steel (CS), stainless steel (SS), and concrete, coated with ZrO2, CeO2, and CsI, were subjected to laser decontamination using a class-4 fiber laser within the UTARTS (University of Tokyo Aerosol Removal Test with Sprays) facility. The aerosol particles generated during the laser decontamination process were confined and captured utilizing a spray and mist system. The study proposes the utilization of a combined spray and mist technique, which has demonstrated high efficiency in scavenging aerosols generated through laser irradiation. This research contributes to the broader goal of promoting best practices and innovative solutions in the field of nuclear decommissioning, thereby safeguarding the environment and human health.

Development of a radiochemical test procedure for the separation of aerosol-borne allergens

An innovative radiochemical method has been developed to determine the filtration efficiency of HEPA filters for biological nanoparticles. The setup based on EN 1822, for flat sheet media, is up to 40 times more sensitive for a single particle than methods based on particle counting, even for low particle concentrations. To achieve such a high sensitivity the radioactive tracer technique is utilised using a solution of bovine serum albumin (BSA) labelled with radioactive iodine (131I). With the aid of an aerosol generator, this solution is nebulised into nanoparticles of a defined size, which are then passed to the test filter via a compressed air flow. On the raw and clean gas side of the test filter, the 131I is measured with two NaI(Tl) detectors. By balancing the measurement data with each other, the filter efficiency can be determined. Initially, the setup has been validated with current particle counting methods, according to EN 1822, to ensure its functionality. Subsequently, the first experiments with radiolabelled nanoparticles gave promising results, as will be shown below. Further experiments also yielded information about filter clogging and its influence on the filter efficiency.

Detection of Micrometer-Sized Virus Aerosols by Using a Real-Time Bioaerosol Monitoring System.

This study investigates a real-time handheld bioaerosol monitoring system for the detection of biological particles using UV-LED and light-induced fluorescence technology. Biological particles produce both scattering and fluorescence signals simultaneously, which can help distinguish them from general particles. The detected scattering, fluorescence, and simultaneous signals are then converted into photon signals and categorized based on predetermined criteria. A reliable biological particle generator was required to validate the performance of the system. This study explores the use of an M13 bacteriophage as a virus simulant of biological agents and employs a customized inkjet aerosol generator to produce M13 bacteriophage aerosols of a specific size by controlling the concentration of M13. We confirmed that micro-sized, narrowly dispersed M13 aerosols were efficiently generated. Additionally, we confirmed the performance of this real-time handheld bioaerosol monitoring system by detecting viruses.

Evaluation of the efficacy of hydroxyl radical (OH˙) release for disinfection of the air and surfaces in the dental clinic: an in vitro study.

Concerning about the quality of room air has increased exponentially. Specially in dental clinics where diary practice is characterized by the important generation of aerosols. An in vitro model was used in which samples were collected from the surfaces and room air of a dental clinic before and after the use of an OH˙ radical generator. A total of 1260 samples were collected for bacteriological analysis and 14 samples for the detection of SARS-CoV-2. Following OH˙ treatment, the tested surface samples showed a decrease in the number of colony forming units (CFUs) of 76.9% in TSA culture medium. The circulating room air samples in turn showed a decrease in CFUs of 66.7% in Sabouraud medium and 71.4% in Mannitol agar medium. No presence of SARS-CoV-2 was observed on the surface of the face shield. The disinfectant technology based on the use of hydroxyl radicals (OH˙) is effective in reducing the presence of moulds and yeasts and Staphylococcus in the air, and in reducing total aerobic bacteria on the tested surfaces.

Effect of surface viscoelasticity on top jet drops produced by bursting bubbles.

Jet drops resulting from bubble bursting at a liquid surface play a key role in various mass transfer processes across the interface, including sea spray aerosol generation and pathogen transmission. However, the impact of structurally compound interfaces, characterized by complex surface rheology introduced by surface-active contaminants, on the jet drop ejection still remains unclear. Here, we experimentally investigate the influence of surface viscoelasticity on the size and velocity of the top jet drops from surface bubble bursting, examining both pure protein and mixed protein-surfactant solutions. We document that for bubble bursting at a pure-protein-laden surface where surface elasticity dominates, the increase in Ec, i.e. the interfacial elastocapillary number as the ratio between the effects of interfacial elasticity and capillarity, efficiently increases the radius and decreases the velocity of the top jet drop, ultimately inhibiting the jet drop ejection. On the other hand, considering the mixed protein-surfactant solution, we show that the top jet drop radius and velocity exhibit a different variation trend with Ec, which is attributed to the additional dissipation on the capillary waves as well as the retardation and resistance on the converging flow for jet formation from surface viscoelasticity. Our work may advance the understanding of bubble bursting dynamics at contaminated liquid surfaces and shed light on the potential influence of surface viscoelasticity on the generation of bubble bursting aerosols.

Influence of atmospheric oxidation capacity on atmospheric particulate matters concentration in Lanzhou

The atmospheric oxidation capacity (AOC) reflects the removal rate of atmospheric pollutants, and this index is typically characterized by the oxidant concentration or total reaction rate. The AOC plays a crucial role in the formation of atmospheric particulate matters and serves as an important indicator for studying changes in the concentration. In this study, we analyse the characteristics of atmospheric oxidants in Lanzhou based on data in the year of 2020 and 2021 retrieved from the Atmospheric Comprehensive Observation Station in Lanzhou. Empirical equations are applied to estimate the impact of atmospheric oxidative properties secondary generation concentrations of atmospheric particulate matters with different particle sizes. The results indicate that the annual average values of Ox were 146 μg/m3 in 2020 and 139 μg/m3 in 2021. The AOC was the highest in summer and lowest in winter. The correlation coefficient between O3 and Ox was significantly higher than that between NO2 and Ox, suggesting that O3 exerted a greater impact on the AOC in Lanzhou. A low AOC (MDA8 O3 ≤ 100 μg/m3) promoted the oxidation process of VOCs and other precursors, leading to the generation of secondary aerosols and subsequent formation of secondary particles. There were negative correlations between Ox and atmospheric particulate matters, secondary inorganic components, sulfur oxidation ratio (SOR) and nitrogen oxidation ratio (NOR), indicating that excessively high levels of Ox could inhibit the conversion rate of SO2 and NO2 into their respective forms to a certain extent.

Process optimisation of alumina coatings by modification of powder characteristics in the aerosol deposition method

The aerosol deposition process, involving the impact of solid particles on a substrate at high velocities, is an attractive method for the manufacture of ceramic coatings at room temperature. For process optimisation, it is crucial to select a powder having the appropriate physical characteristics and evaluate the particle flow behaviour during the deposition process. In this study, a powder modification process using high-energy milling and spray drying to improve the applicability of precursor powders was developed and evaluated both numerically and experimentally. A modified aerosol deposition system incorporating a brush-type aerosol generator was employed to maintain the continuity of the aerosol supply and improve the stability of the particle concentration. The deposition efficiency was nearly tripled when using spray-dried granules (0.68%) instead of the as-received powders (0.26%). From tribological measurements, the strongest interfacial bonding was also confirmed for coatings prepared with alumina granules.

An Approach to Flavor Chemical Thermal Degradation Analysis.

Toxicological evaluations of flavor chemicals for use in inhalation products that utilize heat for aerosol generation are complicated because of the potential effect heat may have on the flavor chemical. The objective was to develop a thermal degradation technique to screen flavor chemicals as part of a toxicological testing program for their potential use in ENDS formulations. Based upon published data for acetaldehyde, acrolein, and glycidol from ENDS products (common thermal degradants of propylene glycol and glycerin), the pyrolizer temperature was adjusted until a similar ratio of acetaldehyde, acrolein, and glycidol was obtained from a 60/40 ratio (v/v) of glycerin/propylene glycol via GC/MS analysis. For each of 90 flavor chemicals, quantitative measurements of acetaldehyde, acrolein, and glycidol, in addition to semiquantitative non-targeted analysis tentatively identifying chemicals from thermal degradation, were obtained. Twenty flavor chemicals transferred at greater than 99% intact, another 26 transferred at greater than 95% intact, and another 15 flavor chemicals transferred at greater than 90% intact. Most flavor chemicals resulted in fewer than 10-12 tentatively identified thermal degradants. The practical approach to the thermal degradation of flavor chemicals provided useful information as part of the toxicological evaluation of flavor chemicals for potential use in ENDS formulations.

A cluster of three extrapulmonary Mycobacterium abscessus infections linked to well-maintained water-based heater-cooler devices.

Various water-based heater-cooler devices (HCDs) have been implicated in nontuberculous mycobacteria outbreaks. Ongoing rigorous surveillance for healthcare-associated M. abscessus (HA-Mab) put in place following a prior institutional outbreak of M. abscessus alerted investigators to a cluster of 3 extrapulmonary M. abscessus infections among patients who had undergone cardiothoracic surgery. Investigators convened a multidisciplinary team and launched a comprehensive investigation to identify potential sources of M. abscessus in the healthcare setting. Adherence to tap water avoidance protocols during patient care and HCD cleaning, disinfection, and maintenance practices were reviewed. Relevant environmental samples were obtained. Patient and environmental M. abscessus isolates were compared using multilocus-sequence typing and pulsed-field gel electrophoresis. Smoke testing was performed to evaluate the potential for aerosol generation and dispersion during HCD use. The entire HCD fleet was replaced to mitigate continued transmission. Clinical presentations of case patients and epidemiologic data supported intraoperative acquisition. M. abscessus was isolated from HCDs used on patients and molecular comparison with patient isolates demonstrated clonality. Smoke testing simulated aerosolization of M. abscessus from HCDs during device operation. Because the HCD fleet was replaced, no additional extrapulmonary HA-Mab infections due to the unique clone identified in this cluster have been detected. Despite adhering to HCD cleaning and disinfection strategies beyond manufacturer instructions for use, HCDs became colonized with and ultimately transmitted M. abscessus to 3 patients. Design modifications to better contain aerosols or filter exhaust during device operation are needed to prevent NTM transmission events from water-based HCDs.

Comparisons of aerosol generation across different musical instruments and loudness

Respiratory aerosols can serve as vectors for disease transmission, and aerosol emission is highly activity-dependent. COVID-19 severely impacted the performing arts due to concerns about disease spread by respiratory aerosols and droplets generated during singing and playing musical instruments. Aerosol generation from woodwind and brass performance is less understood compared to singing due to uncertainty about how the diverse range of musical instruments may impact respiratory aerosol concentrations and size distributions. Here, aerosol number and mass concentrations along with size distributions were measured for breathing, speaking, and playing four different woodwind and brass instruments by 23 professional instrumentalists. We find that a 1 dBA increase in sound pressure level corresponds to a ∼10% increase in aerosol number concentration. The aerosol size distribution is consistent with that of breathing. Differences in aerosol emission across musical instruments can be partly explained by the loudness of performance. Measuring aerosol generation from single notes or simple songs may be sufficient to characterise the aerosol emission range during actual performance, provided a range of loudnesses are accessed. These results provide insight into the factors contributing to aerosol emission during musical performance and facilitate risk assessments associated with infectious respiratory disease transmission in the performing arts.

Use of the Laser Fragmentation Method in the Extraction of LFCM from the Shelter

The Project to transform the Shelter into an environmentally safe system has achieved a significant milestone in the process of transitioning Chornobyl NPP Unit 4 to a safe environmental state. However, the program does not include the measures for long-term safe management of the nuclear stockpile at Chornobyl NPP Unit 4 that are essential. A considerable amount of fuel, approximately 200 tons, has been mixed with reactor debris and structural components, resulting in the formation of fuel-containing materials spanning hundreds of cubic meters. These fuel-containing materials are located in the lower levels of Chornobyl NPP Unit 4.&#x0D; Given the degradation and natural deterioration of fuel-containing materials leading to generation of radioactive aerosols, as well as recent changes in neutron flux density observed after the installation of the New Safe Confinement, there is an urgent need to enhance the development and implementation of appropriate technology. One promising approach is application of the dry fragmentation technology, which uses a high-power solid-state laser developed at the Fraunhofer IWS laboratory in cooperation with the Institute for Safety Problems of Nuclear Power Plants NAS of Ukraine and Plejades GmbH. This technology offers advantages such as minimizing the dynamic and static loads on local structures, efficient energy transfer (heat), and reducing dust formation.&#x0D; This article presents the main aspects of the laser fragmentation method of LFCM. The article describes the details of the controlled destruction technology of thermally stressed material, developed as a result of tests with simulated material at the Fraunhofer IWS laboratory. The work is focused on the measures required for implementing the dry fragmentation technology at the Shelter. It presents pre-conceptual approaches for retrieval and handling of fuel-containing materials located in the lower floors of Chornobyl NPP. The article outlines an approach for accessing fuel-containing materials, a strategy for their fragmentation, subsequent packaging, and safe storage within the Chornobyl NPP until final disposal. Additionally, the creation of a tool system and means of delivery are also described.

Prevention of the spread of infection during highly infectious autopsy using acraniotomy box.

In cranial autopsies, the post-mortem examination requires the use of a saw for the removal of the skull cap. In these procedures, sawing of bone becomes a critical source of infectious aerosols which spread instantaneously in the immediate environment, generating liquid aerosols including droplets of cerebrospinal fluid and blood, and leading to exposure of all autopsy personnel. In high-risk cases like prion disease, tuberculosis, severe acute respiratory syndrome (SARS), COVID-19, etc. where the skull would require sawing, the prime concern is the saw operator's exposure to these pathogens. Therefore, the author suggests the use of an ingenious ergonomic semi-circular craniotomy box during skull cap and brain removal in the autopsy procedure to successfully prevent the contamination of the entire autopsy hall. A transparent acrylic plastic box has been customized, which is semi-circular in shape having three walls, one semi-circular dome without a floor, a front wall with adjustable zipper closure, and a hind wall with circular holes with sleeves made of 5-layer fabrics. The dome contains one outlet for a vacuum suction pipe on the side, two holes on each side of the dome with non-woven fabric arms for the saw operator, and assistants' arms for performing skull opening procedures. The use of this box allowed the author to prevent and limit the spread of the generation of infectious aerosols in the autopsy hall as the bone dust collected in the vacuum ensures the safety of autopsy surgeons.

Aerosolized Cyanobacterial Harmful Algal Bloom Toxins: Microcystin Congeners Quantified in the Atmosphere.

Cyanobacterial harmful algal blooms (cHABs) have the potential to adversely affect public health through the production of toxins such as microcystins, which consist of numerous molecularly distinct congeners. Microcystins have been observed in the atmosphere after emission from freshwater lakes, but little is known about the health effects of inhaling microcystins and the factors contributing to microcystin aerosolization. This study quantified total microcystin concentrations in water and aerosol samples collected around Grand Lake St. Marys (GLSM), Ohio. Microcystin concentrations in water samples collected on the same day ranged from 13 to 23 μg/L, dominated by the d-Asp3-MC-RR congener. In particulate matter <2.5 μm (PM2.5), microcystin concentrations up to 156 pg/m3 were detected; the microcystins were composed primarily of d-Asp3-MC-RR, with additional congeners (d-Asp3-MC-HtyR and d-Asp3-MC-LR) observed in a sample collected prior to a storm event. The PM size fraction containing the highest aerosolized MC concentration ranged from 0.44 to 2.5 μm. Analysis of total bacteria by qPCR targeting 16S rDNA revealed concentrations up to 9.4 × 104 gc/m3 in aerosol samples (≤3 μm), while a marker specific to cyanobacteria was not detected in any aerosol samples. Concentrations of aerosolized microcystins varied even when concentrations in water were relatively constant, demonstrating the importance of meteorological conditions (wind speed and direction) and aerosol generation mechanism(s) (wave breaking, spillway, and aeration systems) when evaluating inhalation exposure to microcystins and subsequent impacts on human health.

Analysis method for aerosol deposition behavior under sodium spray fire

Sodium spray fire is a significant containment-related safety concern in sodium-cooled fast reactors (SFR). In a highly-energetic accident such as a core disruptive accident (CDA), the sodium spray fire not only poses a threat to containment integrity but also causes the generation and release of sodium aerosol source terms with strong radioactivity and chemical hazards. In our method, the sodium aerosol generation model, log-normal size distribution model, agglomeration models, and deposition models were applied. In particular, different turbulent energy dissipation rates were considered in the agglomeration models according to the different thermal-hydraulic states of containment and confinement, and the simplified Crump model and Beresnev models have been selected to describe the gravity-diffusion and the thermophoresis deposition behavior respectively, due to the specific conditions of sodium spray fires. Simulation studies have been divided into two categories based on a potential design concept: HTCA, AB5, and AB6 experiments were introduced to describe the drastic thermodynamic state variations caused by spray fires in the confinement, while ATF and AB7 experiments characterized a relatively stable environment similar to the containment. From the simulation results, the analysis method can be considered reasonable with respect to experimental values. Moreover, calculations have been performed for a hypothetical sodium spray fire caused by a rotator plug failure case in a paper-based European SFR.

A Technical Feasibility of Aqueous Aerosol Generation Based on the Flashing Jet: Impact of Surfactant, Electrolyte, and Drug Concentration

AbstractThis study aimed to investigate the atomization mechanism of a flashing jet (FJ), focusing on the potential factors that influence the atomization performance of the device. Those factors include surfactant, electrolyte, and drug concentration. In this work, Tween 80, sodium chloride (NaCl), and salbutamol sulfate (SBS) were used for the study. The aerosol's mass median aerodynamic diameter (MMAD) was investigated for analysis. The drug delivery ability of the FJ prototype was compared with the Pari nebulizer. Our data suggested that the MMAD of aerosol decreased as the concentration of Tween 80 increased, but the critical micelle concentration point was not influenced. Upon adding NaCl to pure water, with the increase of NaCl concentration, the MMAD of aerosol initially decreased significantly and then increased, reaching the lowest point when 0.05% NaCl was used. A higher concentration of SBS was beneficial for the atomization performance. When the SBS concentration was 5 mg/mL, the MMAD values of the FJ prototype and Pari nebulizer were 2.28 ± 0.15 and 1.03 ± 0.21 μm, respectively, and the fine particle dose (%TDD) of the FJ prototype and Pari nebulizer was 50.99 ± 5.88 and 53.51 ± 4.58%, respectively. Interestingly, the concentration of SBS has no effect on the residual dosage level of the FJ prototype, indicating that it can be applied in atomizing high-concentration solutions. In summary, surfactant, electrolyte, and drug concentration played an important role in the atomization performance of the FJ prototype and these ingredients are also crucial factors that should be considered in future formulation studies.

Impairment of Endothelial Function by Aerosol From Marijuana Leaf Vaporizers.

Marijuana leaf vaporizers, which heat plant material and sublimate Δ-9-tetrahydrocannabinol without combustion, are popular alternatives to smoking cannabis that are generally perceived to be less harmful. We have shown that smoke from tobacco and marijuana, as well as aerosol from e-cigarettes and heated tobacco products, impair vascular endothelial function in rats measured as arterial flow-mediated dilation (FMD). We exposed 8 rats per group to aerosol generated by 2 vaporizer systems (Volcano and handheld Yocan) using marijuana with varying Δ-9-tetrahydrocannabinol levels, in a single pulsatile exposure session of 2 s/min over 5 minutes, and measured changes in FMD. To model secondhand exposure, we exposed rats for 1 minute to diluted aerosol approximating release of uninhaled Volcano aerosol into typical residential rooms. Exposure to aerosol from marijuana with and without cannabinoids impaired FMD by ≈50%. FMD was similarly impaired by aerosols from Yocan (237 °C), and from Volcano at both its standard temperature (185 °C) and the minimum sublimation temperature of Δ-9-tetrahydrocannabinol (157 °C), although the low-temperature aerosol condition did not effectively deliver Δ-9-tetrahydrocannabinol to the circulation. Modeled secondhand exposure based on diluted Volcano aerosol also impaired FMD. FMD was not affected in rats exposed to clean air or water vapor passed through the Volcano system. Acute direct exposure and modeled secondhand exposure to marijuana leaf vaporizer aerosol, regardless of cannabinoid concentration or aerosol generation temperature, impair endothelial function in rats comparably to marijuana smoke. Our findings indicate that use of leaf vaporizers is unlikely to reduce the vascular risk burden of smoking marijuana.

Influence of talking behavior of infected patients and the associated exposure risk in a ventilated negative-pressure ward

Negative-pressure isolation ward is a primary choice in preventing the spread of outbreaks and safeguarding patient recovery. Inside the ward, patients with respiratory diseases generate virus-carrying bioaerosols through breathing and talking, posing a very high risk of infection to healthcare workers. In this paper, we used numerical simulation to compare the effects of different respiratory behaviors, such as normal breathing, prolonged talking, short talking, and alternating talking, on the spatial and temporal distribution of aerosols in a ward, and to study the risk of infection for healthcare workers. It was found that a short period of time in which a patient talked in a ward increased aerosol concentrations by four orders of magnitude compared to normal breathing. In the ward with the ventilation of up-supply, or the one with side-supply, the impacts of aerosol generation from talking accounted for 62.4% and 42.6% of the total time, respectively. The overall infection risk in wards designed with side-supply ventilation was lower. Patient talking time changes did not affect high-risk areas. However, when healthcare worker and patient talked alternately, the aerosol impact time was slightly extended. In addition, the aerosols produced by talking were mainly deposited on the beds and floors, leading to higher exposure risk for healthcare workers during direct contact with beds. It is hoped that the results of this study can be used as the data basis for the study of aerosol pollution control strategies in medical scenarios, and provide useful suggestions for reducing the risk of infection.

Molecular-scale investigation on the composition, sources and secondary generation of organic aerosols in polluted central China

Molecular analyses help to better understand the overall picture of characteristics, meteorological effects, sources, and secondary transformations of organic aerosols (OA). A two-year observation campaign was conducted in polluted central China during 2019–2021, and 130 compounds of molecular OA (quantified organic compounds, QOCs) were quantified. The average concentration of QOCs was 1971 ng/m3, showing the highest normalized QOCs in PM2.5 (31 ng/μg) compared to others. Among the QOCs, the polar category contributed 84%, with the dominated abundant fatty acids observed. The enhanced acid ratios of malonic/succinic and octadecanoic/oleic in summer indicated higher aerosol age, significantly promoted by temperature. Three benzenetricarboxylic acids, mostly from secondary formation, also exhibited quite high concentrations in summer. The noticeable presence of carcinogenic polycyclic aromatic hydrocarbons (PAHs) (45% of ∑28PAHs) highlighted severe health risks associated with human exposure, particularly in winter (56 ng/m3, approximately 7 times that in summer). According to the random forest model assessments, meteorological conditions in summer were most conducive to eliminating pollutants, while that in winter contributed 19% of QOC concentration. The Positive Matrix Factorization analysis revealed that anthropogenic secondary organic aerosols (ASOA) and biogenic SOA (BSOA) jointly accounted for 32% of QOCs, followed by biomass burning (20%), coal combustion (17%), vehicle emissions (16%), and cooking (15%). ASOA was positively correlated with O3 (r = 0.58) and aerosol acidity facilitated ASOA production at 40% < relative humidity <80%. On polluted days, BSOA increased as NO2 and PM2.5 increased, contributing to worsened aerosol pollution. In spring and summer, gas-phase oxidation contributed more saturated dicarboxylic acids (52 and 55%), while aqueous-phase conversion predominated in autumn and winter (59 and 66%). This study provides new information on particulate molecular organic compounds as well as the secondary transformation, which is of great significance for formulating the prevention and control measures of aerosol pollution.

Quantifying Ventilation Design, Room Layout, and Occupant Activity Parameters during Aerosol-Generating Medical Procedures in Hospitals

The risk of airborne disease transmission in hospital rooms during aerosol-generating medical procedures is known to be influenced by the size of the room, air ventilation rate, input-to-output flow ratio, vent surface area, and vent location. However, quantitative recommendations for each ventilation design parameter are scarce. Moreover, room layout and occupant activity parameters, such as furniture locations and healthcare worker movement, are often omitted from studies on airborne disease transmission in hospital settings. As a result, the development of policies and technologies aimed at mitigating airborne disease transmission in hospitals has been limited. To address this shortfall, this study is aimed at first characterizing existing ventilation, room layout, and occupancy parameters in hospital rooms where aerosol generation medical procedures (AGMPs) occur and then testing the hypotheses that ventilation, room layout, and occupancy parameters vary significantly between hospital rooms and, in some cases, with time. Information on AGMPs was collected via a survey circulated to healthcare workers within British Columbia’s Interior Health Authority (IHA), while hospital room and ventilation system information was collected by reviewing drawing packages of 37 IHA hospital rooms. The survey results indicate that AGMPs commonly occur in trauma, ICU, or general ward rooms with positive or negative pressure ventilation systems. Statistical tests, with room type (trauma, ICU, or general), room pressure (positive or negative), and/or time as independent variables, show that variables relating to ventilation (number of supply vents, supply and exhaust vent location, ventilation rate, and supply and exhaust area) and room layout (congestion score, room volume, light area, and number of lights) vary with room type but not with room pressure. Occupant activity variables (number of workers, number of moving workers, and speed score) also vary with room type, although to differing extent with room pressure and time. The survey and drawing review data presented in this study can help guide systematic comparisons of mitigative technologies as well as parametric investigations on how room layout, ventilation, and operational parameters influence airborne disease spread. This is a crucial first step in achieving quantitative and clinically relevant recommendations for mitigating airborne disease transmission in healthcare settings.