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A novel methodology was presented for determining the representative effective density of aerosols of a given size distribution, using a lab-made two-stage low-pressure impactor and an aerosol electrometer. Electrical currents upstream (Imeasured, up) and downstream (Imeasured, down) of the 2nd stage of the impactor were measured using a corona charger and the aerosol electrometer. In addition, the electrical currents upstream (Icalculated, up) and downstream (Icalculated, down) of the 2nd stage of the impactor were calculated using the aerosol charging theory. Then, the difference between the ratio of Imeasured,down to Imeasured,up and the ratio of Icalculated,down to Icalculated,up was iterated with varying the presumed effective density until the difference was smaller than 0.001. The methodology was validated using poly-disperse sodium chloride (NaCl) particles. The effective densities of ambient aerosols were then obtained from indoor and outdoor environments and compared with those calculated from a relation between mobility (scanning mobility particle sizer (SMPS) measurement) and aerodynamic (electrical low-pressure impactor (ELPI) measurement) diameters. Compared to the effective densities obtained with SMPS and ELPI measurements, the effective densities obtained using the methodology introduced in this paper differed within 10 % deviation, depending on measurement location. After an averaged effective density for given size distribution is obtained at a measurement location, the number-based size distribution can be easily converted to mass-based size distribution using the representative effective density.

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Accurately locating deposited particles on the impaction plate of an inertial impactor is crucial for mineralogical and geochemical analysis. Since traditional methods relying on filter analysis are costly and time-consuming, this study delves into the numerical examination of the impact of nozzle-converging length (NCL) on the collection efficiency and depositional arrangements of various fine aerosol particles. Three distinct nozzle-converging lengths (NCL = 3, 7, and 13 mm) were simulated and rigorously compared for their performance in particle collection within an eight-nozzle inertial impactor PM 2.5 . Comprehensive analysis reveals that varying NCL does not significantly impact the collection efficiency of any investigated particle, with variations within 12% across all sizes in this study. Moreover, while NCL adjustments influence the settling ratio of primary depositions, these effects remain under 35% for all different-sized and shaped particles studied in this article. Furthermore, after examining 120 cases and averaging the collection efficiency for particles of a constant aerodynamic diameter, our findings indicate that the efficiency variations across the three distinct geometries remain under 5%. Consequently, we conclude that the head design of this impactor is independent from NCL. Notably, shorter NCLs result in denser particle accumulation near the nozzle outlet on the impaction plate, with this effect more pronounced for coarser particles. In summary, this research provides valuable insights into the role of nozzle-converging length in aerosol particle collection efficiency and deposition patterns, offering crucial guidance for particle classification and sampling methodologies eliminating the need for filter analysis.

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Tunnel boring machines (TBMs) are used to excavate tunnels in a manner where the rock is constantly penetrated with rotating cutter heads. Fine particles of the rock minerals are thereby generated. Workers on and in the vicinity of the TBM are exposed to particulate matter (PM) consisting of bedrock minerals including α-quartz. Exposure to respirable α-quartz remains a concern because of the respiratory diseases associated with this exposure. The particle size distribution of PM and α-quartz is of special importance because of its influence on adverse health effects, monitoring and control strategies as well as accurate quantification of α-quartz concentrations. The major aim of our study was therefore to investigate the particle size distribution of airborne PM and α-quartz generated during tunnel excavation using TBMs in an area dominated by gneiss, a metamorphic type of rock. Sioutas cascade impactors were used to collect personal samples on 3 separate days. The impactor fractionates the dust in 5 size fractions, from 10 µm down to below 0.25 µm. The filters were weighted, and the α-quartz concentrations were quantified using X-ray diffraction (XRD) analysis and the NIOSH 7500 method on the 5 size fractions. Other minerals were determined using Rietveld refinement XRD analysis. The size and elemental composition of individual particles were investigated by scanning electron microscopy. The majority of PM mass was collected on the first 3 stages (aerodynamic diameter = 10 to 0.5 µm) of the Sioutas cascade impactor. No observable differences were found for the size distribution of the collected PM and α-quartz for the 3 sampling days nor the various work tasks. However, the α-quartz proportion varied for the 3 sampling days demonstrating a dependence on geology. The collected α-quartz consisted of more particles with sizes below 1 µm than the calibration material, which most likely affected the accuracy of the measured respirable α-quartz concentrations. This potential systematic error is important to keep in mind when analyzing α-quartz from occupational samples. Knowledge of the particle size distribution is also important for control measures, which should target particle sizes that efficiently capture the respirable α-quartz concentration.

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Andrographolide is a plant-based compound that showed promising activity against lung cancer. However, the compound's poor water solubility and low bioavailability limit its oral administration. Inhaled drug delivery of andrographolide is highly favourable as it delivers active ingredients directly into the affected lungs. In the current study, we compared in vitro aerosol performance, anti-cancer activity and storages stability of two (2) inhalable andrographolide formulations. Formulation 1 was prepared using precipitation and spray drying techniques, while Formulation 2 was prepared via direct spray drying technique. Drug morphology and physicochemical properties were confirmed using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. In vitro aerosol dispersion profile was evaluated using the next-generation impactor (NGI). Formulation 1 consisted of elongated crystals while Formulation 2 was made up of amorphous spherical particles. Both formulations had an inhalable fraction (<5 µm) of more than 40 %, making them suitable for pulmonary drug delivery. The formulations also showed an IC25 of less than 100 µg/mL against the human lung carcinoma cells (A549). Formulation 1 and 2 was stable in a vacuum condition at 30 °C for up to 6 and 3 months, respectively. Novel inhalable andrographolide dry powders were successfully produced with a good aerosol profile, potent anti-cancer activity and adequate storage stability, which deserve further in vivo investigations.

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Spinal cord injury (SCI) is a devastating clinical condition that affects millions of people worldwide. SCI primarily affects males in younger age groups. It is characterized by a complex of neurological dysfunctions that can lead to permanent disability. We describe an adapted technique for SCI, i.e., a contusion model of SCI, in this chapter. This model is widely used to study the pathology of SCI and test potential therapies. The experimental contusion is performed by using a compression device, which allows the creation of a reproducible injury animal model through the definition of specific injury parameters. A detailed methodology has been developed and described here that utilizes a stereotactic frame and impactor to produce reproducible injuries.

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Ultraviolet germicidal irradiation (UVGI) and ozone disinfection are crucial methods for mitigating the airborne transmission of pathogenic microorganisms in high-risk settings, particularly with the emergence of respiratory viral pathogens such as SARS-CoV-2 and avian influenza viruses. This study quantitatively investigates the influence of UVGI and ozone on the viability ofE. coliin bioaerosols, with a particular focus on howE. coliviability depends on the size of the bioaerosols, a critical factor that determines deposition patterns within the human respiratory system and the evolution of bioaerosols in indoor environments. This study used a controlled small-scale laboratory chamber whereE. colisuspensions were aerosolized and subjected to varying levels of UVGI and ozone levels throughout the exposure time (2-6 s). The normalized viability ofE. coliwas found to be significantly reduced by UVGI (60-240µW s cm-2) as the exposure time increased from 2 to 6 s, and the most substantial reduction ofE. colinormalized viability was observed when UVGI and ozone (65-131 ppb) were used in combination. We also found that UVGI reduced the normalized viability ofE. coliin bioaerosols more significantly with smaller sizes (0.25-0.5µm) than with larger sizes (0.5-2.5µm). However, when combining UVGI and ozone, the normalized viability was higher for smaller particle sizes than for the larger ones. The findings provide insights into the development of effective UVGI disinfection engineering methods to control the spread of pathogenic microorganisms in high-risk environments. By understanding the influence of the viability of microorganisms in various bioaerosol sizes, we can optimize UVGI and ozone techniques to reduce the potential risk of airborne transmission of pathogens.

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Background: The pressure drop at any cascade impactor stage is related to the open area of nozzles at that stage. Pressure drop measurement therefore can potentially test whether the nozzles of a given stage are within the range specified for continued use for testing of inhalable drug products. Previous such efforts, however, have been hindered by the measurement precision required for making a pass/fail decision about these used impactors. In this study, we articulate the error analysis for a pressure drop measurement system managed with a critical flow venturi (CFV) and show that the resultant uncertainty in the effective diameter of used Next Generation Impactor (NGI) and Andersen-type impactor stages is generally small compared to the specification range. This result enables the user to make a pass/fail decision regarding suitability for continued use. Methods: We develop the equations governing the relationship between stage pressure drop and the effective diameter of each stage of a used impactor. These equations show that pressure drop measurements can indicate only the change (if any) in the effective diameter between a previous measurement and the current measurement. Propagation-of-error principles therefore show that the uncertainty of both measurements affects the resulting uncertainty. Results: The test uncertainty ratio (analytical power) of a CFV-managed pressure drop measurement system exceeds six for all but stage one of the NGI and for stages -1 and -2 of the Andersen-type impactor. The stage-one nozzle of the NGI is readily qualified with a Class X pin. Conclusions: The CFV-managed flow system described in Part I is sufficiently precise to enable a decision to be made about whether used impactor nozzles are suitable for continued use for testing of registered inhalable drug products. Examination of the industrial viability of the technology will require long-term testing in real-world settings with comparison to optical inspection methods.

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Background: Cascade impactors are essential for measuring the aerodynamic particle size distribution delivered by metered dose, dry powder, and similar inhalable drug products. For quality control of used impactors, periodic optical inspection of the nozzles of each impactor stage (stage mensuration) is currently the only method sufficiently precise to test whether used impactors are suitable for continued use, in accord with pharmacopeial standards. Here, we demonstrate a new method for quality control of used impactors. The method combines stage-wise pressure-drop measurement with a critical flow venturi (CFV) for air flow management. This technique avoids the unacceptably large uncertainty in conventional air flow rate measurements and instead relies on pressure and temperature measurement upstream of the CFV. These measurements can be made precisely with affordable equipment. Methods: We placed a toroidally shaped CFV downstream of a Next Generation Impactor™** (NGI) and precisely measured the stagnation pressure (±0.02%) and temperature (±0.03%) upstream of this CFV at impactor inlet flow rates close to 60 L/min. Pressure-drop measurements (±0.25%) at stages 3-7 and the micro-orifice collector were made with capacitive diaphragm transducers and with a special lid to the NGI that allowed pneumatic connection to the interstage passageways before and after each impactor stage. Results: The measured pressure drop values matched, to fractional percentage precision, those predicted by the incompressible flow theory through the nozzles and the compressible flow theory through the CFV. Conclusions: Practical equipment has been assembled that measures, to fractional percentage precision, the pressure drop through impactor nozzles at precisely managed flow conditions. The experimental results support the relevant flow principles. The results, thereby, support the use of this method for quantifying whether used impactor stages are suitable for continued use in the testing of registered inhalable drug products, in accord with pharmacopeial standards.

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Background: At present, basic scientific research on pancreatic trauma is rare due to the lack of ideal animal models and modeling equipment for pancreatic trauma. Therefore, we intend to develop a multifunctional impact system with simple operation, diverse impact and accurate measurement and to establish a rat pancreatic trauma model based on injury area control by using the system. Methods: The impactor was designed based on the convenience of the impact energy acquisition, the diversity of the impact operation, and the precision of the impact strength parameter measurement by the team. The efficacy and stability/repeatability of the impactor were preliminarily evaluated. An impact head with different impact areas (3 cm2 and 6 cm2) of the impactor was used to squeeze the rat pancreas in the abdomen to form different injury areas under a pressure of 400 kPa. The efficacy features of this trauma model were evaluated by detecting the outcomes of pathology and biochemistry at 24 h after injury in the two groups. Furthermore, these changes were also evaluated at 6 h, 24 h, 48 h and 72 h after injury in the 3 cm2 trauma group. Result: Multifunctional impactors were successfully explored. The impact force was continuously adjustable with a range of 0-200 kg. The compression and extrusion stress ranges were continuously adjustable from 0 to 100 kg. System adjustment verified that the impactor had fine efficacy (P < 0.05) and stability/repeatability (P > 0.05). Compared with the control group, rats in the pancreatic trauma group with different injury areas exhibited obvious injuries (P < 0.05), and compared with the 3 cm2 trauma group, the 6 cm2 trauma group exhibited the more severe injury (P < 0.05). After modeling, the injury characteristics at different time points showed stable differences(P < 0.05). Conclusions: A rat pancreatic trauma model based on injury area control was successfully established using the impactor developed in this study. This model is simple, effective, controllable, and suitable for animal experimental research on pancreatic trauma.

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Objective: The main objective of this study is to design a custom-made weight-drop impactor device to produce a consistent spinal cord contusion model in rats in order to examine the efficacy of potential therapies for post-traumatic spinal cord injuries (SCIs). Methods: Adult female Sprague-Dawley rats (n = 24, 11 weeks old) were randomly divided equally into two groups: sham and injured. The consistent injury pattern was produced by a 10 g stainless steel rod dropped from a height of 30 mm to cause (0.75 mm) intended displacement to the dorsal surface of spinal cord. The neurological functional outcomes were assessed at different time intervals using the following standardized neurobehavioral tests: Basso, Beattie, and Bresnahan (BBB) scores, BBB open-field locomotion test, Louisville Swim Scale (LSS), and CatWalk gait analysis system. Results: Hind limb functional parameters between the two groups using BBB scores and LSS were significantly different (p < 0.05). There were significant differences (p < 0.05) between the SCI group and the sham group for the hind limb functional parameters using the CatWalk gait analysis. Conclusion: We developed an inexpensive custom-made SCI device that yields a precise adjustment of the height and displacement of the impact relative to the spinal cord surface.

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Deck structures subjected to drop-weight low-velocity impact are critical safety elements for ships and offshore structures. Therefore, the aim of the present study is to propose experimental research on dynamic responses of deck structures composed of stiffened plates subjected to drop-weight impact of a wedge impactor. The first step was to fabricate a conventional stiffened plate specimen and a strengthened stiffened plate specimen, as well as a drop-weight impact tower. Then, drop-weight impact tests were carried out. Test results show that local deformation and fracture occurred in the impact area. A sharp wedge impactor caused premature fracture, even under relative low impact energy; the permanent lateral deformation of the stiffened plate was reduced by 20-26% by the strengthening effect of a strengthening stiffer; residual stress and the stress concentration of the cross-joint caused by welding may cause undesired brittle fracture. The present investigation provides useful insight for improving the crashworthiness design of the deck structure of ships and offshore structures.

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The device or the formulation? Which one governs drug dispersibility from the inhaler? To address this question, three budesonide-containing reservoir DPIs: Novopulmon Novolizer®, Giona Easyhaler® and DuoResp Spiromax®, were analyzed using the Next Generation Impactor, NGI. Thereafter, the devices were carefully opened, emptied, and formulations were switched between devices. Finally, three 'prototype' formulations with carriers of different particle size were produced and tested in the Novolizer and Easyhaler devices. Among the DPI products, the two devices which have a flow path with a cyclone-type geometry, i.e., the Novolizer and the Spiromax, yielded a fine particle fraction, FPF, above 40%. The Easyhaler, which has a straight mouthpiece outlet, produced an FPF of 18%. When the Novopulmon and the DuoResp formulations were assayed in the Easyhaler device, poor fine particle fractions were obtained. To the contrary, the Giona formulation produced a high FPF when tested in the Novolizer device. The results clearly show that the device is the dominating factor to dispersibility for the investigated products. Along the same lines, all three 'prototype' formulations produced high fine particle fractions in the Novolizer device, with the formulation with the largest carrier giving the best performance. Tested in the Easyhaler device, the prototype formulations produced low fine particle fractions, but interestingly, the formulation with the smallest carrier particle size yielded the highest FPF. It can be concluded that there is a link between inhaler design and the effect of carrier particle size, where larger carriers provide better dispersion in cyclone-type devices while smaller carriers seem to be more beneficial for inhalers which has a straight flow path for the powder formulation.

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Hypervelocity impact in the universe can be generated by a three-stage gas gun. Achieving the desirable planarity of the flyer enlarges the experimentally effective area of the flyer under the hypervelocity condition. The multidimensional graded density impactor (MDGDI) enhances the planarity of the flyer. In this investigation, a one-dimensional Lagrange elastoplastic hydrodynamic method and a Euler grid finite difference method were used to examine the relationship between the structure of graded density impactors (GDIs) and the planarity of flyers. MDGDIs lead to a deviation of the stress wave produced by the one-dimensional graded density impactor (1DGDI), which offsets the stress disturbance effect, changes the velocity at each particle, and enhances the planarity of flyers. The proportion of flat areas of the flyer increases from 52.70% to 95.71% by adopting MDGDIs. The proportion of flat areas is linear with the wave impedance of the high-impedance layer for 1DGDIs and the wave impedance near the barrel of the high-impedance layer for MDGDIs. This investigation guides the design of GDIs and expands the application of gas gun technology in the field of hypervelocity impact.

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Background: Measurement of aerodynamic particle size distribution, a clinically relevant in vitro attribute of inhalable drug products, involves multistage cascade impactors and is tedious and expensive. A leading candidate for a quicker method is the reduced NGI™ (rNGI). This method involves placing glass fiber filters on top of the nozzles of a chosen NGI stage, selected often to collect all particles with an aerodynamic diameter smaller than approximately five microns. These filters contribute additional flow resistance that can alter the flow rate start-up curve, potentially affecting the size distribution and mass of the drug product dispensed by passive dry powder inhalers (DPIs). The magnitude of these additional flow resistance measurements is currently unreported in the literature. Materials and Methods: We placed glass fiber filters on top of the stage 3 nozzles of an NGI, along with the necessary support screen and hold-down ring. We measured the pressure drop across NGI stage 3 with the assistance of a delta P lid and a high-precision pressure transducer. With each filter material type and multiple individual filters, we gathered eight replicates at flow rates of 30, 45, and 60 L/min. Results: The filters typically doubled the total pressure drop through the NGI. For example, at a flow rate of 60 L/min, the Whatman 934-AH filters introduced a pressure drop of about 9800 Pa at stage 3, reducing the absolute pressure exiting the NGI to about 23 kPa below ambient, compared with a typical value of 10 kPa for the NGI alone at this flow rate. Conclusions: The pressure drop across typical filters is approximately equal to that through the NGI alone and therefore will affect the flow start-up rate intrinsic to compendial testing of passive DPIs. This change in start-up rate could cause differences between results of the rNGI configuration and those of the full NGI and will increase the required vacuum pump capacity.

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Multiple sources must be consulted to determine the most appropriate procedures for the laboratory-based performance evaluation of aqueous oral inhaled products (OIPs) for the primary measures, dose uniformity/delivery, and aerodynamic particle (droplet) size distribution (APSD). These sources have been developed at different times, mainly in Europe and North America, during the past 25 years by diverse organizations, including pharmacopeial chapter/monograph development committees, regulatory agencies, and national and international standards bodies. As a result, there is a lack of consistency across all the recommendations, with the potential to cause confusion to those developing performance test methods. We have reviewed key methodological aspects of source guidance documents identified by a survey of the pertinent literature and evaluated the underlying evidence supporting their recommendations for the evaluation of these performance measures. We have also subsequently developed a consistent series of solutions to guide those faced with the various associated challenges when developing OIP performance testing methods for oral aqueous inhaled products.

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Respiratory tract infections (RTIs) are reported to be the leading cause of death worldwide. Delivery of liposomal antibiotic nano-systems via the inhalation route has drawn significant interest in RTIs treatment as it can directly target the site of infection and reduces the risk of systemic exposure and side effects. Moreover, this formulation system can improve pharmacokinetics and biodistribution and enhance the activity against intracellular pathogens. Microfluidics is an innovative manufacturing technology that can produce nanomedicines in a homogenous and scalable way. The objective of this study was to evaluate the antibiofilm efficacy of two liposomal ciprofloxacin formulations with different vesicle sizes manufactured by using a 3D-printed microfluidic chip. Each formulation was characterised in terms of size, polydispersity index, charge and encapsulation. Moreover, the aerosolisation characteristics of the liposomal formulations were investigated and compared with free ciprofloxacin solution using laser diffraction and cascade impaction methods. The in vitro drug release was tested using the dialysis bag method. Furthermore, the drug transport and drug release studies were conducted using the alveolar epithelial H441 cell line integrated next-generation impactor in vitro model. Finally, the biofilm eradication efficacy was evaluated using a dual-chamber microfluidic in vitro model. Results showed that both liposomal-loaded ciprofloxacin formulations and free ciprofloxacin solution had comparable aerosolisation characteristics and biofilm-killing efficacy. The liposomal ciprofloxacin formulation of smaller vesicle size showed significantly slower drug release in the dialysis bag technique compared to the free ciprofloxacin solution. Interestingly, liposomal ciprofloxacin formulations successfully controlled the release of the drug in the epithelial cell model and showed different drug transport profiles on H441 cell lines compared to the free ciprofloxacin solution, supporting the potential for inhaled liposomal ciprofloxacin to provide a promising treatment for respiratory infections.

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Atmospheric particulate pollution poses a great danger to the environment and human health, and there is a strong need to develop equipment for collecting and separating particulate matter of different particle sizes to study the effects of particulate matter on human health. A virtual impactor is a particle separation device based on the principle of inertial separation which provides scientific guidance for identifying the composition characteristics of particles. Much existing virtual impactor research focuses on the design of structural dimensions with little exploration of the effect of fluid properties on performance. In this paper, a microfluidic chip with a cutoff diameter of 1.85 µm was designed based on computational fluid dynamics and numerically simulated via finite element analysis to analyze important parameters such as inlet flow rate, splitting ratio and fluid properties. By numerical simulation of the split ratio, we found that the obtained collection efficiency curves could not be combined into one characteristic curve by the Stk0.5 scaling method. We therefore propose a modified Stokes number equation for predicting the cutoff diameter at different splitting ratios. The collection efficiency curves of different fluids as microfluidic chip media were plotted, and the results show that the cut particle size was reduced from 2.5 µm to 1.85 µm after replacing conventional fluid air with CO2 formed by dry ice sublimation. This is a decrease of approximately 26%, which is superior to other existing methods for reducing the cutoff diameter.

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BACKGROUND: SARS-CoV-2 in exhaled aerosols is considered an important contributor to the spread of COVID-19. However, characterizing the size distribution of virus-containing aerosol particles has been challenging as high concentrations of SARS-CoV-2 in exhaled air is mainly present close to symptom onset. We present a case study of a person with COVID-19 who was able to participate in extensive measurements of exhaled aerosols already on the day of symptom onset and then for the following three days. METHODS: Aerosol collection was performed using an eight-stage impactor while the subject was breathing, talking and singing, for 30 min each, once every day. In addition, nasopharyngeal samples, saliva samples, room air samples and information on symptom manifestations were collected every day. Samples were analyzed by RT-qPCR for detection of SARS-CoV-2 RNA. RESULTS: SARS-CoV-2 RNA was detected in seven of the eight particle size fractions, from 0.34 to >8.1 µm, with the highest concentrations found in 0.94-2.8 µm particles. The concentration of SARS-CoV-2 RNA was highest on the day of symptom onset, and declined for each day thereafter. CONCLUSION: Our data showed that 90% of the exhaled SARS-CoV-2 RNA was found in aerosol particles <4.5 µm, indicating the importance of small particles for the transmission of COVID-19 close to symptom onset. These results are important for our understanding of airborne transmission, for developing accurate models and for selecting appropriate mitigation strategies.

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This study presents the development and evaluation of a high flow rate gelatin cascade impactor (GCI) to collect different PM particle sizes on water-soluble gelatin substrates. The GCI operates at a flow rate of 100 lpm, and consists of two impaction stages, followed by a filter holder to separate particles in the following diameter ranges: >2.5 µm, 0.2-2.5 µm, and <0.2 µm. Laboratory characterization of the GCI performance was conducted using monodisperse polystyrene latex (PSL) particles as well as polydisperse ammonium sulfate, sodium chloride, and ammonium nitrate aerosols to obtain the particle collection efficiency curves for both impaction stages. In addition to the laboratory characterization, we performed concurrent field experiments to collect PM2.5 employing both GCI equipped with gelatin filter and personal cascade impactor sampler (PCIS) equipped with PTFE filter for further toxicological analysis using macrophage-based reactive oxygen species (ROS) and dithiothreitol consumption (DTT) assays. Our results showed that the experimentally determined cut-point diameters for the first and second impaction stages were 2.4 µm and 0.21 µm, respectively, which agreed with the theoretical predictions. Although the GCI has been developed primarily to collect particles on gelatin filters, the use of a different type of substrate (i.e., quartz) led to similar particle separation characteristics. The findings of the field tests demonstrated the advantage of using the GCI in toxicological studies due to its ability to collect considerable PM-toxic constituents, as corroborated by the DTT and ROS values for the GCI-collected particles which were 26.44 nmoles/min/mg PM and 8813.2 µg Zymosan Units/mg PM, respectively. These redox activity values were more than twice those of particles collected concurrently on PTFE filter using the PCIS. This high-flow-rate impactor can collect considerable amounts of size-fractionated PM on water-soluble filters (i.e., gelatin), which can completely dissolve in water allowing for the extraction of soluble and insoluble PM species for further toxicological analysis.

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Bacterial filtration efficiency is the main characteristic of medical face masks effectivity and quality. The testing method is given by European and US, respectively, standard. The method is based on the analysis of biological aerosol with the bacterium Staphylococcus aureus in Andersen cascade impactor. The Andersen impactor contains six stages simulating the different parts of the respiratory tract, from the upper part with the larger droplets to the lungs with the small aerosol particles of the submicron size. The particles are separated depending on the size and sediment on agar medium in Petri dishes filled in the impactor. The use of the glass Petri dishes is recommended for the Andersen impactor, but the most of laboratories prefer the disposable plastic dishes, actually. The evaluation of the use of plastic dishes in Andersen impactor for the determination of the bacterial filtration efficiency of the medical face masks is the aim of this study.

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