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Background: Bacillus Calmette-Guerin (BCG) is a vaccine used to protect against tuberculosis primarily in infants to stop early infection in areas of the world where the disease is endemic. Normally administered as a percutaneous injection, BCG is a live significantly attenuated bacteria that is now being investigated for its potential within an inhalable vaccine formulation. This study investigates the feasibility and performance of two jet and two vibrating mesh nebulizers aerosolizing BCG and the resulting particle characteristics and residual viability of the bacteria postaerosolization. Methods: A jet nebulizer (Collison), outfitted either with a 3- or 6-jet head, was compared with two clinical nebulizers, the vibrating mesh Omron MicroAir and Aerogen Solo devices. Particle characteristics, including aerodynamic particle sizing, was performed on all devices within a common aerosol chamber configuration and comparable BCG innocula concentrations. Integrated aerosol samples were collected for each generator and assayed for bacterial viability using conventional microbiological technique. Results: A batch lot of BCG (Danish) was grown to titer and used in all generator assessments. Aerosol particles within the respirable range were generated from all nebulizers at four different concentrations of BCG. The jet nebulizers produced a uniformly smaller particle size than the vibrating mesh devices, although particle concentrations by mass were similar across all devices tested with the exception of the Aerogen Solo, which resulted in a low concentration of BCG aerosols. Conclusions: The resulting measured viable BCG aerosol concentration fraction produced by each device approximated one another; however, a measurable decrease of efficiency and overall viability reduction in the jet nebulizer was observed in higher BCG inoculum starting concentrations, whereas the vibrating mesh nebulizer returned a remarkably stable viable aerosol fraction irrespective of inoculum concentration.

Atmospheric nanoparticles (PM0.1 µm) are a major cause of environmental problems and also affect health risk. To control and reduce these problems, sources identification of atmospheric particulates is necessary. Combustion of bituminous coal and biomass including rubber wood, palm kernel, palm fiber, rice stubble, rice straw, maize residue, sugarcane leaves and sugarcane bagasse, which are considered as sources of air quality problems in many countries, was performed. Emissions of particle-bound chemical components including organic carbon (OC), elemental carbon (EC), water-soluble ions (NH

A thorough understanding of chemical composition, particle pH, and pollutant emissions is essential to address the climate and human health effects of atmospheric particles. In this study, we used a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and Scanning Mobility Particle Sizer (SMPS) to characterize the composition of submicron particles. Moreover, we applied the ISORROPIA-II model to analyze the particle acidity effect on the compositional characterization of submicron particles from December 22, 2016 to January 7, 2017 in Albany, New York, USA. The results indicated that aerosols with mobility diameter from SMPS in the range 200–400 nm were the main contributors to the mass during the measurement period. The dominance of organics (47%) and sulfate (16%) was similar to previous observations in the eastern United States in Winter 2015, while the fraction of nitrate (23%) was much higher. Moreover, nitrate could easily form at colder temperatures and lower RH levels even when there were more acidic particle periods during the measurement period in Albany. The ISORROPIA-II model indicated that there were more acidic particles, which was estimated using pH values. Lower temperature conditions tended to favor nitrate formation. The nitrate concentration exceeded that of sulfate in the measurement period, even though the SO2 and NOx emissions were similar. The organics in submicron particles were strongly influenced by the local emissions in winter. However, the inorganic compounds in submicron particles could be derived from regional transport as their pollution sources originated from different directions. This may help strategize emission reductions in the future.

Hypothesis: While the lack of efficient tools yielding controllable uniform saturation ratios (S) has delayed basic experimental heterogeneous nucleation studies, common diffusive condensation particle counters (DCPCs) could fill this gap if their S-variation were minimized by increasing the proportion of sheath gas (σ) surrounding a central core of purified clusters. Analysis: We measure the activation probability P of Tetraheptylammonium Bromide cluster cations (THA-Br)n-1THA+ in Kanomax’s fast CPC while controlling S through the saturator and condenser temperatures (Ts, Tc), varying σ, and changing the size (n) of purified salt clusters via high resolution mobility selection. Findings: Experimental curves P(Ts,n) obtained in 1-butanol/air at fixed Tc (13 °C) and variable n and Ts (3 ≤ n ≤ 16; 30 ≤ Ts ≤ 40 °C) rise sharply versus both n and Ts. Their steepness increases five-fold with increasing σ to about σ = 75%, with little effect thereafter. Measurements changing S would yield size distributions of unknown aerosols at fairly high resolution. Comparing P(Ts,n) data with predictions from capillary theory suggests that basic heterogeneous nucleation measurements can be carried out, but instrument improvements are still needed.

Crop residue open burning is an important emission source of ambient particles in China. This study analyzed the particle emission characteristics of crop residue open burning through combustion experiments with a novel open combustion simulation device using three typical crop straws in north China (corn, wheat, and rice). Particle samples size ranging from 0.006–9.890 µm were collected by an Electrical Low Pressure Impactor plus, a high size-resolution instrument capable of dividing particles into 14 size stages. The size distributions of organic carbon (OC), elemental carbon (EC), water-soluble ions, and elements were analyzed, and source chemical profiles were constructed for PM0.1, PM1, PM2.5, and PM10. The number concentration of particles was concentrated in the Aiken nuclei mode (0.006–0.054 µm), accounting for 75% of the total number, whereas the mass concentration was concentrated in the accumulation mode (0.054–0.949 µm), accounting for 85.43% of the mass loading. OC, EC, Cl−, and K(include total K and water-soluble K) were the major chemical components of the particles, whose mass percentage distributions differed from those of other components. These five main components exhibited a bell-shaped size distribution in the 0.006–9.890 µm range, whereas the other components exhibited a U-shaped distribution. Among the chemical profiles for PM0.1–PM10, OC was the most important component at 10–30%, followed by EC at 2%–8%. The proportions of K+, Cl−, and K varied substantially in different experimental groups, ranging from 0–15%, and K+ and Cl− were significantly correlated (r = 0.878, α = 0.000).

In the current pandemic context of COVID-19, people wear different types of masks, particularly in their workplace, to limit the spread of the virus. Depending on their activity and work environment, employees are required to wear community face coverings, cloth masks with a transparent windows, surgical masks, reusable masks, or respirators. The objective of this study was to evaluate the efficiency as source control of these masks, i.e., when worn to protect the environment from the spread of particles emitted by the wearer. An experimental test bench including a dummy head and a breathing simulator associated with a DEHS droplet generator emitting 1 or 3 µm particles in the exhaled stream is used. Source control efficiency is calculated from the total flux of particles emitted in the test section without and with a mask. Seventeen models of masks are tested. Three breathing rate conditions were studied: from rest to heavy breathing, with average rates of 13, 27, and 45 L/min. Source control efficiencies vary from one mask to another. Among community face coverings (seven models) the values ranged from 15.6 to 33.8% for a medium intensity breath. The efficiencies of surgical masks (three models) ranged from 17.4 to 28.3% for the same breathing cycle. The community face coverings and the disposable surgical masks present equivalent values of source control efficiency, respectively, 25.9 and 24.1% at 1 µm and 31.5 and 23.2% at 3 µm. The respirators show higher source control efficiency than the other types of masks (76.7% at 1 µm and 82.5% at 3 µm). The statistical analysis of the data shows no effect of the breathing flow rate and an interaction effect between mask type and particle size. No differences in source control were found for the two particle sizes or the different experimental breathing rates for the respirators and the surgical masks. But the community face coverings and the cloth masks with transparent window present a source control efficiency which increases with the particle size. Varying levels of efficiency were measured with higher source control for respirators than for other types of masks. In the context of a respiratory protection programme, they can provide an effective barrier to the spread of the virus. But these results show also that no mask can stop all the particles emitted by its wearer. Regardless of the type of mask, other barrier measures (ventilation, social distancing, and hygiene) are then necessary.

For over 25 years, transmission electron microscopy (TEM) has provided a method for the study of aerosol particles with sizes from below the optical diffraction limit to several microns, resolving the particles as well as smaller features. The wide use of this technique to study aerosol particles has contributed important insights about environmental aerosol particle samples and model atmospheric systems. TEM produces an image that is a 2D projection of aerosol particles that have been impacted onto grids and, through associated techniques and spectroscopies, can contribute additional information such as the determination of elemental composition, crystal structure, and 3D particle structures. Soot, mineral dust, and organic/inorganic particles have all been analyzed using TEM and spectroscopic techniques. TEM, however, has limitations that are important to understand when interpreting data including the ability of the electron beam to damage and thereby change the structure and shape of particles, especially in the case of particles composed of organic compounds and salts. In this paper, we concentrate on the breadth of studies that have used TEM as the primary analysis technique. Another focus is on common issues with TEM and cryogenic-TEM. Insights for new users on best practices for fragile particles, that is, particles that are easily susceptible to damage from the electron beam, with this technique are discussed. Tips for readers on interpreting and evaluating the quality and accuracy of TEM data in the literature are also provided and explained.

Incidental ultrafine particles (UFPs) constitute a key pollutant in industrial workplaces. However, characterizing their chemical properties for exposure and toxicity assessments still remains a challenge. In this work, the performance of an aerosol concentrator (Versatile Aerosol Concentration Enrichment System, VACES) was assessed to simultaneously sample UFPs on filter substrates (for chemical analysis) and as liquid suspensions (for toxicity assessment), in a high UFP concentration scenario. An industrial case study was selected where metal-containing UFPs were emitted during thermal spraying of ceramic coatings. Results evidenced the comparability of the VACES system with online monitors in terms of UFP particle mass (for concentrations up to 95 µg UFP/m3) and between filters and liquid suspensions, in terms of particle composition (for concentrations up to 1000 µg/m3). This supports the applicability of this tool for UFP collection in view of chemical and toxicological characterization for incidental UFPs. In the industrial setting evaluated, results showed that the spraying temperature was a driver of fractionation of metals between UF (, This work was funded by SIINN ERA-NET (project id: 16), the Spanish MINECO (PCIN-2015-173-C02-01) and the French agency (Region Hauts de France). The Spanish Ministry of Science and Innovation (Project CEX2018-000794-S; Severo Ochoa) and the Generalitat de Catalunya (project number: AGAUR 2017 SGR41) provided support for the indirect costs for the Institute of Environmental Assessment and Water Research (IDAEA-CSIC). We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).

Airborne nanoparticles are frequently released in occupied spaces due to episodic indoor source activities. Once generated, nanoparticles undergo aerosol transformation processes such as coagulation and deposition. These aerosol processes lead to changes in particle concentration and size distribution over time and accordingly affect human exposure to nanoparticles. The present study establishes a framework for an indoor particle dynamic model that can predict time- and size-dependent particle concentrations after episodic indoor emission events. The model was evaluated with six experimental data sets obtained from previous measurement studies in the literature. The indoor particle dynamic model quantified the relative contributions of three particle loss mechanisms (i.e., coagulation, deposition, and ventilation) to the total reduction in number concentration. The results show that particle coagulation and indoor surface deposition are two dominant processes responsible for temporal changes in particle size and concentration following indoor emission events. The first-order equivalent coagulation loss rate notably varies with indoor emission source and accounts for up to 59% of the total particle loss for burning a candle, 42% for broiling a fish, and 10% for burning incense. The results reveal that while the coagulation loss rate changes markedly with the particle concentration and source type, the deposition loss rate is more dependent on particle size. Compared to coagulation and deposition, the effect of ventilation is marginal for most of the nanoparticle emission events indoors; however, ventilation loss becomes pronounced with the decrease of particle concentration below 5 × 104 cm-3, especially for particles larger than 100 nm in aerodynamic diameter.

Particle size characterization for active pharmaceutical ingredients (APIs) in nasal spray suspension products presents unique challenges because both the API and excipient particles are present in the final dosage form. Currently, an established method is lacking because traditional particle sizing technologies do not distinguish the chemical identity of the particles. In this study, a non-destructive, ingredient-specific particle sizing method was developed for characterization of mometasone furoate (MF) nasal spray suspensions using Morphology Directed Raman Spectroscopy (MDRS). A five-step method development procedure was used in this study: sample preparation, particle imaging and morphology analysis, particle Raman measurements and classification, morphology filter selection, and minimum number of particles determination. Wet dispersion sample preparation method was selected to ensure that the particles were measured in their original suspended state. A training set containing over 10,000 randomly-selected particles, including both the API and excipient particles, was used to gain a comprehensive understanding of particle size, shape, and chemical ID for the nasal spray suspension. Morphology and Raman measurements were performed on each particle in the training set. The measurement results suggested that the aspect ratio and intensity mean filter combination was an appropriate morphology filter setting to selectively target API particles and exclude most of excipient particles. With further optimization of the morphology filter cutoff values and determination of minimal number of particles to be measured, the total measurement time was reduced from 90 hours to 8 hours. The morphologically screening strategy ultimately allowed us to create a time-efficient practical API-specific particle size distribution (PSD) methods for nasal spray suspensions. This study shows that MDRS is a fit for purpose analytical technique for determining ingredient-specific PSDs of the pharmaceutical formulation studied in this work.

The severe outbreak of respiratory coronavirus disease 2019 has increased the significant demand of respiratory mask and its use become ubiquitous worldwide to control this unprecedented respiratory pandemic. The performance of a respiratory mask depends on the efficiency of the filter layer which is mostly made of polypropylene melt blown non-woven (PP-MB-NW). So far, very limited characterization data are available for the PPE-MB-NW in terms to achieve desired particulate filtration efficiency (PFE) against 0.3 µm size, which are imperative in order to facilitate the right selection of PP-MB-NW fabric for the development of mask. In present study, eight different kinds of PP-MB-NW fabrics (Sample A–H) of varied structural morphology are chosen. The different PP-MB-NW were characterized for its pore size and distribution by mercury porosimeter and BET surface area analyzer was explored first time to understand the importance of blind pore in PFE. The PP-MB-NW samples were characterized using scanning electron microscopy so as to know the surface morphology. The filtration efficiency, pressure drop and breathing resistance of various PP-MB-NW fabric samples are investigated in single and double layers combination against the particle size of 0.3, 0.5 and 1 µm. The samples which are having low pore dia, high solid fraction volume, and low air permeability has high filtration efficiency (> 90%) against 0.3 µm particle with high pressure drop (16.3–21.3 mm WC) and breathing resistance (1.42–1.92 mbar) when compared to rest of the samples. This study will pave the way for the judicial selection of right kind of filter layer i.e., PP-MB-NW fabric for the development of mask and it will be greatly helpful in manufacturing of mask in this present pandemic with desired PFE indicating considerable promise for defense against respiratory pandemic.

Ultrafine particles (UFPs) dominate the particle number population in the urban atmosphere and revealing their chemical composition is important. The thermal desorption chemical ionization mass spectrometer (TDCIMS) can semi-continuously measure UFP composition at the molecular level. We modified a TDCIMS and deployed it in urban Beijing. Radioactive materials in the TDCIMS for aerosol charging and chemical ionization were replaced by soft X-ray ionizers so that it can be operated in countries with tight regulations on radioactive materials. Protonated N-methyl-2-pyrrolidone ions were used as the positive reagent ion, which selectively detects ammonia and low-molecular weight-aliphatic amines and amides vaporized from the particle phase. With superoxide as the negative reagent ion, a wide range of inorganic and organic compounds were observed, including nitrate, sulfate, aliphatic acids with carbon numbers up to 18, and highly oxygenated CHO, CHON, and CHOS compounds. The latter two can be attributed to parent ions or the decomposition products of organonitrates and organosulfates/organosulfonates, respectively. Components from both primary emissions and secondary formation of UFPs were identified. Compared to the UFPs measured at forest and marine sites, those in urban Beijing contain more nitrogen-containing and sulfur-containing compounds. These observations illustrate unique features of the UFPs in this polluted urban environment and provide insights into their origins.

Purpose: Computational Fluid Dynamics (CFD) simulations are performed to investigate the impact of adding a grid to a two-inlet dry powder inhaler (DPI). The purpose of the paper is to show the importance of the correct choice of closure model and modeling approach, as well as to perform validation against particle dispersion data obtained from in-vitro studies and flow velocity data obtained from particle image velocimetry (PIV) experiments. Methods: CFD simulations are performed using the Ansys Fluent 2020R1 software package. Two RANS turbulence models (realisable $k - \epsilon$ and $k - \omega$ SST) and the Stress Blended Eddy Simulation (SBES) models are considered. Lagrangian particle tracking for both carrier and fine particles is also performed. Results: Excellent comparison with the PIV data is found for the SBES approach and the particle tracking data are consistent with the dispersion results, given the simplicity of the assumptions made. Conclusions: This work shows the importance of selecting the correct turbulence modelling approach and boundary conditions to obtain good agreement with PIV data for the flow-field exiting the device. With this validated, the model can be used with much higher confidence to explore the fluid and particle dynamics within the device., Comment: Accepted in Pharmaceutical Research (2021)

Phase separation is an important microscopic phenomenon in aerosol particles and reflects the surface properties of particles and the aging degree of organic components. However, few data are available to directly reveal phase separation in ambient aerosol particles, although there are abundant data from laboratory experiments. In this study, different state-of-the-art microscopic technologies were used to study the phase separation of organic matter (OM) and inorganic salts in individual particles collected from different atmospheric environments, with one type of surrogate particles prepared in the laboratory. We found that most of the collected particles with an equivalent sphere diameter of >100 nm have a secondary inorganic aerosol core with OM coating in the continental atmosphere. In addition, secondary inorganic aerosol and OM phase separation are more frequent in rural particles than suburban particles, suggesting that particle aging enhances the phase separation. Our results show that the phase separation is a frequent phenomenon that forms organic coatings on inorganic particles of individual particles (>100 nm), and their number abundances depend on the particle size and OM aging degree. The resulting morphology shows that OM is an important particle surface in the atmosphere, which influences gas partitioning, optical and hygroscopic properties, and cloud condensation nuclei formation activities.

Human emissions of fluorescent aerosol particles (FAPs) can influence the biological burden of indoor air. Yet, quantification of FAP emissions from human beings remains limited, along with a poor understanding of the underlying emission mechanisms. To reduce the knowledge gap, we characterized human emissions of size-segregated FAPs (1-10 μm) and total particles in a climate chamber with low-background particle levels. We probed the influence of several personal factors (clothing coverage and age) and environmental parameters (level of ozone, air temperature, and relative humidity) on particle emissions from human volunteers. A material-balance model showed that the mean emission rate ranged 5.3-16 × 106 fluorescent particles per person-h (0.30-1.2 mg per person-h), with a dominant size mode within 3-5 μm. Volunteers wearing long-sleeve shirts and pants produced 40% more FAPs relative to those wearing t-shirts and shorts. Particle emissions varied across the age groups: seniors (average age 70.5 years) generated 50% fewer FAPs compared to young adults (25.0 years) and teenagers (13.8 years). While we did not observe a measurable influence of ozone (0 vs 40 ppb) on human FAP emissions, there was a strong influence of relative humidity (34 vs 62%), with FAP emissions decreasing by 30-60% at higher humidity.

The reliable characterization of particle size distribution and nicotine delivery emitted by electronic cigarettes (ECs) is a critical issue in their design. Indeed, a better understanding of how nicotine is delivered as an aerosol with an appropriate aerodynamic size is a necessary step toward obtaining a well-designed nicotine transfer from the respiratory tract to the bloodstream to better satisfy craving and improve smoking cessation rates. To study these two factors, recent models of EC devices and a dedicated vaping machine were used to generate aerosols under various experimental conditions, including varying the EC power level using two different types of atomizers. The aerodynamic particle sizing of the resulting aerosol was performed using a cascade impactor. The nicotine concentration in the refill liquid and the aerosol droplet was quantified by liquid chromatography coupled with a photodiode array. The vaporization process and the physical and chemical properties of the EC aerosol were very similar at 15 watts (W) and 25 W using the low-power atomizer but quite distinct at 50 W using the high-power atomizer, as follows: (1) the mass median aerodynamic diameters ranged from 1.06 to 1.19 µm (µm) for low power and from 2.33 to 2.46 µm for high power; (2) the nicotine concentrations of aerosol droplets were approximately 11 mg per milliliter (mg/mL) for low power and 17 mg/mL for high power; and (3) the aerosol droplet particle phase of the total nicotine mass emitted by EC was 60% for low power and 95% for high power. The results indicate that varying the correlated factors (1) the power level and (2) the design of atomizer (including the type of coil and the value of resistance used) affects the particle-size distribution and the airborne nicotine portioning between the particle phase and the gas phase in equilibrium with the airborne droplets.

To investigate the secondary formation and pollution sources of atmospheric particles in urban Beijing, PM2.5 and its chemical components were collected and determined by URG-9000D ambient ion monitor (AIM) from March 2016 to January 2017. Among water-soluble ions (WSIs), NO3-, SO42- and NH4+ (SNA) had the largest proportion (77.8%) with the total concentration of 23.8 μg/m3. Moreover, as fine particle pollution worsened, the NO3-, SO42- and NH4+ concentrations increased basically, which revealed that secondary aerosols were the main cause of particle pollution in Beijing. Furthermore, the particle neutralization ratio (1.1), the ammonia to sulfate molar ratio (3.4) and the nitrate to sulfate molar ratio (2.2) showed that secondary aerosols are under ammonium-rich conditions with the main chemical forms of NH4NO3 and (NH4)2SO4, and vehicle emission could be the main anthropogenic source of secondary aerosols in Beijing. Source analysis further indicated that secondary aerosols, solid fuel combustion, dust and marine aerosol were the principal pollution sources of PM2.5, accounting for about 46.1%, 22.4% and 13.0%, respectively, and Inner Mongolia and Hebei Provinces could be considered as the main potential sources of PM2.5 in urban Beijing. In addition, secondary formation process was closely related with gaseous precursor emission amounts (SO2, NO2, NH3 and HONO), atmospheric ozone concentration (O3), meteorological conditions (temperature and relative humidity) and particle components. Sensitive analysis of the thermodynamic equilibrium model (ISORROPIA II) revealed that controlling total nitrate (TN) is the effective measure to mitigate fine particle pollution in Beijing.

“Surgical smoke” is an airborne by-product of electrosurgery comprised of vapour and suspended particles. Although concerns exist that exposure may be harmful, there is a poor understanding of the smoke in terms of particle size, morphology, composition and biological viability. Notably, it is not known how the biological tissue source and cutting method influence the smoke. The objective of this study was to develop a collection method for airborne by-product from surgical cutting. This would enable comprehensive analyses of the particulate burden, composition and biological viability. The method was applied to compare the electrosurgical smoke generated (in the absence of any evacuation mechanism) with the aerosolized/airborne by-products generated by ultrasonic and high-speed cutting, from bone and liver tissue cutting. We report a wide range of particle sizes (0.93–806.31 μm for bone, 0.05–1040.43 μm for liver) with 50% of the particles being

Semi-volatile organic compounds (SVOCs), partitioned between particulates and vapours of an aerosol, require special attention. The toxicological effects caused by the inhalation of such aerosols may depend on the concentration and in which phase the organic compounds are found. A personal denuder-gas–particle separation aerosol sampler was developed to provide information about the partitioning of aerosols from organic compounds. The sampler was tested in a series of controlled laboratory experiments, which confirmed the capability and accuracy of the sampler to measure gas–particle mixtures. An average difference of 14.8 ± 4.8% was found between sampler and reference laboratory instruments. The obtained results showed that our sampler enables a more accurate measurement of the SVOC aerosols’ gas–particle fractionation, compared with that of conventional samplers.

Aerosol plays an important role in a broad range of scientific disciplines, such as atmospheric chemistry and physics, fuel combustion, and human health. Current particle sizing instruments are usually bulky, complicated, and expensive, while the portable ones cannot provide sufficient measurement channels to describe the particle size distribution accurately. To address this challenge, we propose an optical sensing method to analyze the particle size distribution of aerosols based on the light scattering intensity field (LSIF). The LSIF is a set of scattering lights in all directions around the particles, which contains the scattering light signals in different observing angles. Then, the particle size distribution of the aerosol samples is retrieved by the Tikhonov regularization algorithm. A portable and low-cost aerosol sizing prototype sensor is designed to image part of the LSIF signals, where the LSIF is collected by a parabolic reflector and projected on the image sensor as an image with telecentric lenses. According to the experimental result of di-ethyl-hexyl-sebacate aerosol test, the relative measurement error of LSIF can be controlled to ±10%. With an integrated and cost-effective design, this particle sizing sensor shows great potential for routine field measurements outside of the laboratory.

In this work, we deployed a single particle aerosol mass spectrometer (SPAMS) at a suburban coastal site in Hong Kong from February 04 to April 17, 2013 to study individual oxalate particles and a monitor for aerosols and gases in ambient air (MARGA) to track the bulk oxalate concentrations in particle matter smaller than 2.5 μm in diameter (PM

The Sinkiang Uygur Autonomous Region is located in western China and the centre of the Asian–European continent, which frequently suffers from sandstorm disasters and haze weathers. A 1-year measurement campaign in two selected points in Shihezi and Urumqi of Sinkiang was conducted to characterise the effects of particle matters and factors on particle extinction under different weather conditions. Results showed that the average concentration of PM1–2.5 was 19.83, 9.230, 28.93 and 122.4 μg/m3 in Shihezi and 67.25, 16.80, 59.19 and 324.0 μg/m3 in Urumqi for spring, summer, autumn and winter, respectively. PM5–10 concentrations can reach up to 500.0 and 160.0 μg/m3 during polluted weather conditions in Shihezi and Urumqi, respectively. PM5–10 also accounted for the largest fraction in Shihezi and Urumqi for all types of weather, reaching up to 40.0% under dusty weather conditions. PM1–2.5 significantly increased during winter possibly due to the increased demand for heating compared with non-heating periods. PM0.5–1 is possibly produced from motor vehicle exhaust. Particle size is concluded to be the dominant factor for particle extinction capability under fine weather based on calculations of aerosol optical properties. The refractive index for a particle with a diameter of 100 μm (3.10–3.11i) is substantially larger than that with a diameter of 0.5000 μm (1.600–0.07000i), but the extinction capability of the latter is 1.30 times that of the former. Comparatively, when the mass concentration of coarse particles is over 17.0 times that of the fine particles, and then mass concentration becomes the dominant factor. Therefore, visibility is negatively correlated to particle mass variations during dust storms and hazy days but not for fine days. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.

Physicochemical properties between colloidal engineered nanomaterials (ENMs) and aerosols released from consumer spray products were characterized. A dynamic light scattering (DLS), transmission electron microscopy (TEM), and inductively coupled plasma mass spectrometer (ICP-MS) were used to evaluate the suspended ENMs in the products. Direct-reading instruments, TEM, and ICP-MS were used to characterize the properties of aerosolized ENMs. The aerosolized organic compounds with ENMs were assumed to be vaporized for a short time after spraying. The median diameter of ENMs in product solutions measured by DLS was about 200-350 nm, while individual particle was confirmed from 3 to 50 nm by TEM. The size of aerosolized ENMs was ranged from 7 to 44 nm, and their aggregates were about 100-1000 nm in near distance. Some inorganic substances including raw nanomaterials were also found in the aerosol. The particles released from the propellant sprays were identified in far distance, while they were not found in far distance when pump sprays were used. The number concentration from the propellant sprays increased up to 6000 particles/cm3 /g at near distance and dispersed to far distance, while the most of droplets emitted from pump sprays were settled down near sprayer's location. We found other metals besides labeled ENMs are included in each product and the characteristics of the particles are different when they are sprayed.

While nanoparticulate drugs for deep lung delivery hold promise for particular disease treatments, their size-related physical instability and tendency of being exhaled during breathing remain major challenges to their inhaled formulation development. Here we report a viable method for converting drug nanosuspensions into inhalable, stable and redispersible nano-agglomerates through combined in-situ thermal gelation and spray drying. Itraconazole (ITZ) nanosuspensions were prepared by flash nanoprecipitation, and co-spray dried with two different grades of the gel-forming polymer, methylcellulose (MC M20 and MC M450) as protectants. MC M20 was found superior in protecting ITZ nanoparticles against thermal stress (through nanoparticle entrapment within its gel network structure) during spray drying. In terms of redispersibility, an Sf/Si ratio (i.e., ratio of nanoparticle sizes after and before spray drying) of unity (1.02 ± 0.03), reflecting full particle size preservation, was achieved by optimizing the suspending medium content and spray drying parameters. Formulation components, nanosuspension concentration and spray drying parameters all showed a significant impact on the aerosol performance of the resulting agglomerates, but an absence of defined trends or correlations. Overall, the MC-protected nano-agglomerates displayed excellent in-vitro aerosol performance with fine particle fractions higher than 50% and mass median aerodynamic diameters within the 2-3 µm range, which are ideal for deep lung delivery.

Background: Many substances used in inhalation research are water soluble and can be administered as nebulized solutions. Typical examples are therapeutic, small-molecular agents, or macromolecules. Another category is a number of water-soluble agents used for airway diagnostics or disease modeling. Mesh nebulizers have facilitated well-controlled liquid aerosol exposures. Meanwhile, a benchtop inhalation platform, PreciseInhale, was developed for providing small-scale, well-controlled aerosol exposures in preclinical configurations. The purpose of the current research was to adapt the Aerogen mesh nebulizer to work within the PreciseInhale system for both cell culture and rodent exposures. Methods: The wet aerosols produced with the Aerogen Pro nebulizer were dried out in an aerosol holding chamber by supplying dry carrier air, which was provided by passing the incoming ambient air through a column with silica gel. The nebulizer was installed in an aerosol holding chamber between an upstream flow-rate pneumotach and a downstream aerosol monitor. By pulsing, the nebulizer output was reduced to 1%-10% of continuous operation to better match the exposure ventilation requirements. Additional drying was obtained by mantling the holding chamber with dried paper. Results and Conclusions: The nebulizer output was reduced to 3-30 μL/min and dried out before reaching the in vitro or in vivo exposure modules. Using solute concentrations in the range of 0.5%-2% (w/w), dried aerosols were produced with a mass median aerodynamic diameter of 1.5-2.0 μm, compared to the 4-5 μm droplets emitted by the nebulizer. Controlling the Aerogen nebulizer under a reduced output scheme within the PreciseInhale platform gave two major advantages: (i) by reducing aerosol output to better match exposure flow rates of single rodents, increased airway deposition yields were obtained in a range of 1%-10% relative to the nebulized amount of test substance and (ii) shrinking aerosol particle sizes through drying improved the peripheral lung deposition of test aerosols.

Aerosol particle number (PNC) and mass concentrations (PMC) were studied in 11 primary schools during the 2017–2018 school years (from September to May) in Vilnius, Lithuania, with the aim to evaluate the main aerosol pollution sources and its levels. Expeditious information on the total aerosol particle concentration over the full range of sizes (from 0.01 to > 1 μm) was estimated using a condensation particle counter (CPC). Particle number and mass concentrations in the size range of 0.3–10 μm were measured and estimated using an optical particle sizer (OPS). The use of aerosol particle size spectra (OPS) in school lodgements facilitated the identification of the main sources of indoor air pollution. The main sources responsible for the elevated levels of indoor PN and PM aerosol concentrations were determined: local canteens in the absence of ventilation (particle concentrations up to 97,500 part/cm3 (CPC)), the school-grader activity during the lesson breaks (275–586 μg/m3), soft furniture and carpets in the classrooms and corridors (~ 200 μg/m3), and in some cases (city center) elevated outdoor aerosol pollution levels (16800–18,170 part/cm3). Elevated aerosol pollution levels were also due to the occasional sources: construction works during lessons (200–1000 μg/m3), scraping the exterior walls of buildings near schools (up to 1600 μg/m3), and the use of petrol-powered trimmers during cutting of green plantings (22500–66,400 part/cm3 (CPC)).

Characteristic particle size, fluorescence intensity, and fluorescence spectra are important features to detect and categorize bioaerosols. A prototype size-resolved single-particle fluorescence spectrometer (S2FS) was developed to simultaneously measure aerodynamic diameters and fluorescence spectra. Emission spectra are dispersed in 512 channels from 370 to 610 nm, where a major portion of biological fluorescence emission occurs. The S2FS consists of an aerodynamic particle sizer and a fluorescence spectrometer with a 355 nm laser excitation source and an intensified charge-coupled device as the detector. Highly fluorescent particles, such as Ambrosia artemisiifolia pollen and Olea europaea pollen, can be distinguished by the S2FS on a single-particle level. For weakly fluorescent particles, fluorescence spectra can only be obtained by averaging multiple particles (between 100 and 3000) of the same kind. Preliminary ambient measurements in Mainz (Germany, central Europe) show that an emission peak at ∼440 nm was frequently observed for fluorescent fine particles (0.5-1 μm). Fluorescent fine particles accounted for 2.8% on average based on the number fraction in the fine mode. Fluorescent coarse particles (>1 μm) accounted for 8.9% on average based on the number fraction, with strongest occurrence observed during a thunderstorm and in the morning.

The use of waterpipes in the United States is increasing in a largely unregulated market. The shisha smoked in a waterpipe is a complex matrix of tobacco, flavorings, and humectant with smoke generated by an external heat source. This study explored the relationship between shisha components and the particulate matter size distributions and toxicity of smoke generated with heating. Standard waterpipe puff topography of charcoal- or electronic- heated whole shisha and shisha components generated smoke particulate matter that was characterized using a TSI Engine Exhaust Particle Sizer. Relative toxicity of the whole smoke was determined via measurement of lysosomal integrity and measures of membrane integrity following acute exposure of type II alveolar cells at the air-liquid interface. All waterpipe aerosols exhibited a unimodal particle size distribution, the peak and concentration of which varied depending upon the shisha components present. Acute exposure to charcoal-heated whole shisha, flavoring syrup, or humectant smoke, or electronic-heated whole shisha smoke caused significant alveolar cell damage and death, indicating neither tobacco nor charcoal are needed for these cytotoxic effects to occur.

PURPOSE Chairside prosthesis adjustment procedures generate contaminated acrylic particle debris that include visible splatter (particles >50μm) as well as invisible aerosols (

A single-particle mass spectrometer (SPMS) with laser ionization was constructed to determine the chemical composition of single particles in real time. The technique was evaluated using various polystyrene latex particles with different sizes (125 nm, 300 nm, 700 nm, and 1000 nm), NaCl, KCl, MgCO3, CaCO3, and Al2O3 particles with different chemical compositions, an internal mixture of NaCl and KCl, and an internal mixture of NaCl, KCl, and MgCl2 with different mixing states. The results show that the SPMS can be useful for the determination of chemical characteristics and mixing states of single particles in real time. The SPMS was then applied to obtain the chemical signatures of various combustion aerosols (diesel engine exhaust, biomass burning (rice straw), coal burning, and cooking (pork)) based on their single-particle mass spectra. Elemental carbon (EC)-rich and EC-organic carbon (OC) particles were the predominant particle types identified in diesel engine exhaust, while K-rich and EC-OC-K particles were observed among rice straw burning emissions. Only one particle type (ash-rich particles) was detected among coal burning emissions. EC-rich and EC-OC particles were observed among pork burning particles. The single-particle mass spectra of the EC or OC types of particles differed among various combustion sources. The observed chemical signatures could be useful for rapidly identifying sources of atmospheric fine particles. In addition, the detected chemical signatures of the fine particles may be used to estimate their toxicity and to better understand their effects on human health.

Aqueous extracts of biogenic secondary organic aerosols (BSOAs) have been found to exhibit fluorescence that may interfere with the laser/light-induced fluorescence (LIF) detection of primary biological aerosol particles (PBAPs). In this study, we quantified the interference of BSOAs to PBAPs by directly measuring airborne BSOA particles, rather than aqueous extracts. BSOAs were generated by the reaction of d-limonene (LIM) or α-pinene (PIN) and ozone (O3) with or without ammonia in a chamber under controlled conditions. With an excitation wavelength of 355 nm, BSOAs exhibited peak emissions at 464–475 nm, while fungal spores exhibited peak emissions at 460–483 nm; the fluorescence intensity of BSOAs with diameters of 0.7 μm was in the same order of magnitude as that of fungal spores with diameters of 3 μm. The number fraction of 0.7 μm BSOAs that exhibited fluorescence above the threshold was in the range of 1.9–15.9%, depending on the species of precursors, relative humidity (RH), and ammonia. Similarly, the number fraction of 3 μm fungal spores that exhibited fluorescence above the threshold was 4.9–36.2%, depending on the species of fungal spores. Normalized fluorescence by particle volumes suggests that BSOAs exhibited fluorescence in the same order of magnitude as pollen and 10–100 times higher than that of fungal spores. A comparison with ambient particles suggests that BSOAs caused significant interference to ambient fine particles (15 of 16 ambient fine particle measurements likely detected BSOAs) and the interference was smaller for ambient coarse particles (4 of 16 ambient coarse particle measurements likely detected BSOAs) when using LIF instruments., An online fluorescence spectrometer for bioaerosol detection suggests distinct contributions of biogenic secondary organic aerosols to fine-mode and coarse-mode fluorescent particles.

OBJECTIVES Gas sampling tubes are essential tools for the evaluation of air quality in work environments. It adsorbs toxic gaseous matters onto the surface of various granular adsorbents, such as silica gel or activated carbon packed in a thin glass tube, for quantitative analysis by gas chromatography. Currently, most of the semi-volatile matters are evaluated via aerosol filtration or solid-phase gas adsorption depending on the main phase of the substances; however, only a few substances have a sampling protocol regarding both solid and gaseous phases. Therefore, semi-volatile components evaluated by the solid-phase adsorption may result in the underestimation of the component concentrations due to particulate components passing through and remaining in the adsorbent. To highlight issues on sampling of semi-volatile matters by the solid-phase adsorption method, the collection efficiency of aerosol particles by 17 commercial gas sampling tubes were measured via pressure drop. METHODS To measure the particle collection efficiency of the gas collection tubes, precise control and dilution of the aerosol particle monitors are essential. However, we cannot apply typical filter test methods at a lower filtration flow rate than that of the aerosol particles monitors. Therefore, we developed a new experimental method that considers flow adjustment between the aerosol monitors. By assuming two specific particle size distributions and five inlet conditions, the collection efficiencies of total mass particles are estimated. From the gas-particle partitioning ratio of 16 polycyclic aromatic hydrocarbons (PAHs) in a coal tar pitch manufacturing industry, the underestimation of the concentration of semi-volatile matters using the gas collection tubes has been discussed. RESULTS The aerosol particles were collected in all kinds of layers in the gas sampling tubes, such as in the glass wool cap, gas adsorbent granular bed, and polyurethane foam. Furthermore, the collection efficiency curve of all 17 gas sampling tubes tested showed similar trends; a valley around particle sizes ranging from 0.2-0.3 μm between high collection zones below 0.1 μm and above 1 μm was observed. The observations suggested granular bed filters collection mechanisms such as inertial impaction, Brownian diffusion, gravity, and interception as same as air filters. CONCLUSIONS Solid-phase collection can underestimate the concentrations of multi-phase matters. Thus, we wish to highlight the importance of solid-phase collection methods along with filtration collection methods to collect all phases of semi-volatile matters.

The novel coronavirus pandemic has resulted in an urgent need to study the risk of infection from aerosols generated during dental care and to conduct a review of infection controls. However, existing studies on aerosol particles related to dental treatment have mainly evaluated only the scattering range. Few studies have been conducted on the specifics of the generation of aerosol particles in clinical settings, their mechanisms and patterns of distribution throughout open or enclosed spaces, the duration that they remain suspended in air, and the amount and size of particles present. To minimize the influence of background particles, laser lights, a high-sensitivity camera, and particle counters were used in a large super clean laboratory to investigate the dynamics of aerosols generated during the operation of dental micromotors. The results indicate that aerosols tend to scatter upward immediately after generation and then gradually disperse into the surroundings. Most of the particles are less than 5 µm in size (only a few are larger), and all particles are widely distributed over the long term. Our research clearly elucidates that aerosols produced in dental care are distributed over a wide area and remain suspended for a considerable time in dental clinics before settling.

The formation of trileucine-containing spray-dried microparticles intended for pulmonary delivery was studied in depth. A single-particle method was employed to study the shell formation characteristics of trileucine in the presence of trehalose as a glass former, and an empirical correlation was proposed to predict the instance of shell formation. A droplet chain instrument was used to produce and collect monodisperse particles to examine morphology and calculate particle density for different levels of trileucine. It was observed that the addition of only 0.5 mg/mL (10% w/w) trileucine to a trehalose system could lower dried particle densities by approximately 1 g/cm3. In addition, a laboratory-scale spray dryer was used to produce batches of trileucine/trehalose powders in the respirable range. Raman spectroscopy demonstrated that both components were completely amorphous. Scanning electron microscopy and time-of-flight secondary ion mass spectrometry were used to study the particle morphologies and surface compositions. For all cases with trileucine, highly rugose particles with trileucine coverages of more than 60% by mass were observed with trileucine feed fractions of as little as 2% w/w. Moreover, it was seen that at lower trileucine content, smaller and larger particles of a polydisperse powder had slightly different surface compositions. The surface activity of trileucine was also modeled via a modified form of the diffusion equation inside an evaporating droplet that took into account initial surface adsorption and eventual surface desorption due to droplet shrinkage. Finally, using the Flory-Huggins theory, it was estimated that at room temperature, liquid-liquid phase separation would start when the trileucine reached an aqueous concentration of about 18 mg/mL. Besides the surface activity of trileucine, this low concentration was assumed to explain the substantial effect of trileucine on the morphology of spray-dried particles due to early phase separation. The methodology proposed in this study can be used in the rational design of trileucine-containing microparticles.

Background Aerosol spread is key to interpret the risk of viral contamination during clinical procedures such as esophageal high‐resolution manometry (HRM). Installing an air purifier seems a legitimate strategy, but this has recently been questioned. Methods Patients undergoing an HRM procedure at the Leuven University Hospital were included in this clinical study. All subjects had to wear a surgical mask which was only lowered beneath the nose during the placement and removal of the nasogastric catheter. The number of aerosol particles was measured by a Lasair® II Particle Counter to obtain data about different particles sizes: 0.3; 0.5; 1.0; 3.0; 5.0; and 10.0 µm. Measurements were done immediately before the placement and the removal of the HRM catheter, and one and 5 min after. A portable air purifier with high‐efficiency particle air filters was installed in the hospital room. Key Results Thirteen patients underwent a manometry examination. The amount of 0.3 µm‐sized particles was unaffected during the whole procedure. The larger particle sizes (1.0; 3.0; 5.0; and 10.0 µm) decreased when the catheter was positioned, but not 0.5 µm. During the HRM measurements itself, these numbers decreased further. Yet, 1 min after catheter removal a significant elevation of particles was seen, which did not recover within 5 min. Conclusions & Interferences Based on this study, there is no evidence that filtration systems reduce aerosol particles properly during a clinical investigation.

BACKGROUND: Peak flow testing is a common procedure performed in ambulatory care. There are currently no data regarding aerosol generation during this procedure. Given the ongoing debate regarding the potential for aerosol transmission of SARS-CoV-2, we aimed to quantify and characterize aerosol generation during peak flow testing. METHODS: Five healthy volunteers performed peak flow maneuvers in a particle-free laboratory space. Two devices continuously sampled the ambient air during the procedure. One device can detect ultrafine particles 0.02–1 μm in diameter, while the second device can detect particles 0.3, 0.5, 1.0, 2.0, 5.0, and 10 μm in diameter. Five different peak flow meters were compared to ambient baseline during masked and unmasked tidal breathing. RESULTS: Ultrafine particles (0.02–1 μm) were generated during peak flow measurement. There was no significant difference in ultrafine particle mean concentration between peak flow meters (P = .23): Respironics (1.25 ± 0.47 particles/mL), Philips (3.06 ± 1.22), Clement Clarke (3.55 ± 1.22 particles/mL), Respironics Low Range (3.50 ± 1.52 particles/mL), and Monaghan (3.78 ± 1.31 particles/mL). Ultrafine particle mean concentration with peak flow testing was significantly higher than masked (0.22 ± 0.29 particles/mL) and unmasked tidal breathing (0.15 ± 0.18 particles/mL, P = .01), but the ultrafine particle concentrations were small compared to ambient particle concentrations in a pulmonary function testing room (89.9 ± 8.95 particles/mL). CONCLUSIONS: In this study, aerosol generation was present during peak flow testing, but concentrations were small compared to the background particle concentration in the ambient clinical environment. Surgical masks and eye protection are likely sufficient infection control measures during peak expiratory flow testing in asymptomatic patients with well controlled respiratory symptoms, but COVID-19 testing remains prudent in patients with acute respiratory symptoms prior to evaluation and peak expiratory flow assessment while the community prevalence of SARS-CoV-2 cases remains high.

Of the various particle properties that affect deposition in the respiratory tract, particle diameter and particle density are the most commonly considered, since their effect on deposition is well known and important, as has been discussed earlier in this chapter. However, there are several other particle properties that can affect particle deposition in the lungs. These include: 1) electrostatic charge on the particle, which can cause electrostatic forces to enhance deposition; 2) the shape of the particle, which can cause its trajectory to differ from that of a spherical particle and thereby alter its deposition; and 3) volatility of the particle i.e., its ability to condense or evaporate at its surface, which can change its diameter and in turn affect its deposition. In this section, we examine each of these three factors individually.

Soil has always been the most complex biomaterial on the planet. The rapid determination of the components in the soil and their original source is a prerequisite for soil quality, environmental, and human health risk assessments. In this study, the chemical compositions and source apportionment of surface soil samples collected from five sites in Shanghai, China, were successfully investigated using a laboratory-developed laser ablation single-particle aerosol mass spectrometry (LA-SPAMS) instrument combined with an adaptive resonance theory-based neural network algorithm (ART-2a) data-processing method for the first time. In total, more than 35,000 particles, ranging from 200 to 2000 nm, were sized, and around 15-20% of the particles were chemically analyzed by LA-SPAMS to generate both positive and negative mass spectra. The results show that there are significant differences in particle size distribution among the five samples, with peaks of various sizes and different profiles, while all five soil samples contain crustal elements, heavy metals, organic and inorganic components, and so forth. The chemical composition of each sample varied considerably, so different classes of SPAMS particle classes were identified, which were later grouped into seven general categories: EC-rich (containing elemental carbon), secondary components, organic nitrogen, crust, HM (containing heavy metal), PAH (containing polycyclic aromatic hydrocarbons), and NaK-rich particles, based on the dominant marked ions. The composition analysis and source apportionment showed that soil components in different areas have been affected by the local environment, such as local industrial emissions and automobile exhaust, which are usually characterized by varying degrees of mixing between the crust and environmental aerosols. In combination with the ART-2a method, LA-SPAMS enables rapid and direct analysis of soil samples based on real-time single-particle measurements, which will help in understanding the distribution, transport, and fate of the soil components, thus providing new insights into soil-quality assessment. Moreover, the established LA-SPAMS can also be practically applied to other daily inspection tasks, such as rocks, minerals, metals, ceramics, polymers, and other solid materials for ingredient analysis and quality evaluation.

Low-cost optical particle counters effectively measure particulate matter (PM) mass concentrations once calibrated. Sensor calibration can be established by deriving a linear regression model by performing side-by-side measurements with a reference instrument. However, calibration differences between environmental and occupational settings have not been demonstrated. This study evaluated four commercially available, low-cost PM sensors (OPC-N3, SPS30, AirBeam2, and PMS A003) in both settings. The mass concentrations of three aerosols (salt, Arizona road dust, and Poly-alpha-olefin-4 oil) were measured and compared with a reference instrument. OPC-N3 and SPS30 were highly correlated (r = 0.99) with the reference instrument for all aerosol types in environmental settings. In occupational settings, SPS30, AirBeam2, and PMS A003 exhibited high correlation (&gt, 0.96), but the OPC-N3 correlation varied (r = 0.88–1.00). Response significantly (p &lt, 0.001) varied between environmental and occupational settings for most particle sizes and aerosol types. Biases varied by particle size and aerosol type. SPS30 and OPC-N3 exhibited low bias for environmental settings, but all of the sensors showed a high bias for occupational settings. For intra-instrumental precision, SPS30 exhibited high precision for salt for both settings compared to the other low-cost sensors and aerosol types. These findings suggest that SPS30 and OPC-N3 can provide a reasonable estimate of PM mass concentrations if calibrated differently for environmental and occupational settings using site-specific calibration factors.

Wearing surgical masks or other similar face coverings can reduce the emission of expiratory particles produced via breathing, talking, coughing, or sneezing. Although it is well established that some fraction of the expiratory airflow leaks around the edges of the mask, it is unclear how these leakage airflows affect the overall efficiency with which masks block emission of expiratory aerosol particles. Here, we show experimentally that the aerosol particle concentrations in the leakage airflows around a surgical mask are reduced compared to no mask wearing, with the magnitude of reduction dependent on the direction of escape (out the top, the sides, or the bottom). Because the actual leakage flowrate in each direction is difficult to measure, we use a Monte Carlo approach to estimate flow-corrected particle emission rates for particles having diameters in the range 0.5–20 μm. in all orientations. From these, we derive a flow-weighted overall number-based particle removal efficiency for the mask. The overall mask efficiency, accounting both for air that passes through the mask and for leakage flows, is reduced compared to the through-mask filtration efficiency, from 93 to 70% for talking, but from only 94–90% for coughing. These results demonstrate that leakage flows due to imperfect sealing do decrease mask efficiencies for reducing emission of expiratory particles, but even with such leakage surgical masks provide substantial control.

Lipopolysaccharides (LPS) in sea spray aerosol (SSA) particles have recently been shown to undergo heterogeneous reactions with HNO3 in the atmosphere. Here, we integrate theory and experiment to further investigate how the most abundant sea salt cations, Na+, Mg2+, and Ca2+, impact HNO3 reactions with LPS-containing SSA particles. Aerosol reaction flow tube studies show that heterogeneous reactions of SSA particles with divalent cation (Mg2+ and Ca2+) and LPS signatures were less reactive with HNO3 than those dominated by monovalent cations (Na+). All-atom molecular dynamics simulations of model LPS aggregates suggest that divalent cations cross-link the oligosaccharide chains to increase molecular aggregation and rigidity, which changes the particle phase and morphology, decreases water diffusion, and consequently decreases the reactive uptake of HNO3. This study provides new insight into how complex chemical interactions between ocean-derived salts and biogenic organic species can impact the heterogeneous reactivity of SSA particles.

The composition, morphology and dissolution profile of particles and micro-sized agglomerates delivered upon inhalation may have a significant impact on the product clinical effect. However, although several efforts are ongoing, a methodology that considers deposition structures and dissolution performance evaluation in a biorelevant set-up is not yet standardized. The goal of this work is to apply a collection and dissolution methodology able to discriminate dry powder inhaler (DPI) formulations in terms of deposition structures and dissolution profile in vitro. Hence, Fluticasone Propionate (FP) engineered particles and formulated products (used as a case study) were collected employing a breath simulator and characterized regarding (i) aerodynamic particle size distribution; (ii) deposited microstructures; and (iii) dissolution/absorption profiles using the DissolvIt® bio-relevant dissolution equipment. The results indicated that the particle engineering technology had an impact on the generated and deposited microstructures, here associated to the differences on surface properties of jet milled and wet polished particles quantified by the specific surface area. Differences on surface properties modulate particle interactions, resulting in agglomerates of drug substance and excipient upon actuation with significant different morphologies, observed by microscope, as well as quantified by Marple cascade impactor. These observations allow for a further understanding of the DPI aerosolization and deposition mechanisms. The dissolution and absorption assessment indicates that the presence of lactose may accelerate the drug substance dissolution kinetics, and the FP dissolution can be significantly enhanced when formulated as a spray-dried dispersion particle. Ultimately, the results suggest dissolution testing can be an essential tool to both optimize an innovator DPI and de-risk generics development.

High drug load inhalable particles were prepared by co-spray drying a hydrophobic, crystalline, small molecule drug with various lipid or phospholipid excipients at a 9:1 molar ratio to understand the primary drivers of aerosol performance. The effect of excipient structure on solid-state, surface characteristics, and aerodynamic performance of the co-spray dried particles was studied while keeping the spray drying parameters constant. Spray drying of the drug with lipids produced crystalline drug particles, whereas phospholipids produced partially amorphous drug particles. All of the co-spray dried particles were nearly spherical with a smooth surface, except for the spray dried drug particles without excipients – which showed the presence of rough crystals on the surface. All co-spray dried particles showed surface enrichment of the excipient. The surface enrichment of the phospholipids was higher compared to the lipids. Co-spray dried particles that showed higher surface enrichment of excipients showed improved aerosol performance. In comparing all the excipients studied, distearyolphosphatidylcholine (DSPC) showed maximum enrichment on the particle surface and thereby significantly improved aerosol performance. This study demonstrated that the addition of small amounts of lipid excipients during spray drying can change surface morphology, composition, and cohesion, impacting aerosol performance of drugs.

Particle engineering via spray drying was used to develop a dry powder presentation of an adjuvanted tuberculosis vaccine candidate. This presentation utilizing a trileucine-trehalose excipient system was designed to be both thermostable and suitable for respiratory delivery. The stability of the spray-dried vaccine powder was assessed over one year at various storage temperatures (-20, 5, 25, 40, 50 °C) in terms of powder stability, adjuvant stability, and antigen stability. A formulation without trileucine was included as a control. The results showed that the interior particle structure and exterior particle morphology of the powder was maintained for one year at 40 °C, while the control case exhibited a small extent of particle fusing under the same storage conditions. Moisture content was maintained, and powder solid state remained amorphous for all storage temperatures. Aerosol performance was assessed with a commercial dry powder inhaler in combination with a human mouth-throat model. The emitted dose and lung dose were maintained for all samples after one year at temperatures up to 40 °C. Nanoemulsion size and oil content of the adjuvant system were maintained after one year at temperatures up to 40 °C, and the agonist content was maintained after one year at temperatures up to 25 °C. The antigen was completely degraded in the control formulation at seven months of storage at 40 °C; by contrast, 45% of the antigen was still present in the trehalose-trileucine formulation after one year of storage at 50 °C. Comparatively, the antigen was completely degraded in a liquid sample of the vaccine candidate after only one month of storage at 37 °C. The spray-dried trehalose-trileucine vaccine powder clearly maintained its inhalable properties after one year’s storage at high temperatures and improved overall thermostability of the vaccine.

Vaporizable cannabis concentrates (VCCs) consumed as a liquid (vaping) or a waxy solid (dabbing) are becoming increasingly popular. However, their associated emissions and impacts have not been fully described. Mixtures containing different proportions of 12 VCC terpenoids and high MW compounds were heated at 100-500 °C inside a room-sized chamber to simulate emissions. Terpenoids, thermal degradation byproducts, and ultrafine particles (UFPs) were quantified in the chamber air. Air samples contained over 50% of emitted monoterpenes and less than 40% of released sesquiterpenes and terpene alcohols. Eleven degradation byproducts were quantified, including acrolein (1.3-3.9 μg m-3) and methacrolein (2.0 μg m-3). A large amount of UFPs were released upon heating and remained airborne for at least 3 h. The mode diameter increased from 80 nm at 100 °C to 140 nm at 500 °C, and particles smaller than 250 nm contributed to 90% of PM1.0. The presence of 0.5% of lignin, flavonoid, and triterpene additives in the heated mixtures resulted in a threefold increase in the particle formation rate and PM1.0 concentration, suggesting that these high-molecular-weight compounds enhanced aerosol inception and growth. Predicted UFP emission rates in typical consumption scenarios (6 × 1011-2 × 1013 # min-1) were higher than, or comparable with, other common indoor sources such as smoking and cooking.

Particle release from human skin and clothing has been identified as an important contributor to particulate matter burden indoors. However, knowledge about modeling the coarse particle release from skin and clothing is limited. This study developed a new empirically validated CFD modeling methodology for particle release and transport from seated occupants in an office setting. We tested three modeling approaches for particle emissions: Uniform; Uniform + Localized; and Uniform + Localized with Body Motion; applied to four office scenarios involving a single occupant and two occupants facing each other at 1- and 2-m distances. Uniform particle emissions from skin and clothing underpredicted personal inhalation exposure by as much as 55%-80%. Combining uniform with localized emissions from the armpits drastically reduced the error margin to

Medical procedures that produce aerosolized particles are under great scrutiny due to the recent concerns surrounding the COVID-19 virus and increased risk for nosocomial infections. For example, thoracostomies, tracheotomies and intubations/extubations produce aerosols that can linger in the air. The lingering time is dependent on particle size where, e.g., 500 μm (0.5 mm) particles may quickly fall to the floor, while 1 μm particles may float for extended lengths of time. Here, a method is presented to characterize the size of 600 μm particles resulting from surgery in an operating room (OR). The particles are measured in-situ (next to a patient on an operating table) through a 75mm aperture in a ∼400 mm rectangular enclosure with minimal flow restriction. The particles and gasses exiting a patient are vented through an enclosed laser sheet while a camera captures images of the side-scattered light from the entrained particles. A similar optical configuration was described by Anfinrud et al.; however, we present here an extended method which provides a calibration method for determining particle size. The use of a laser sheet with side-scattered light provides a large FOV and bright image of the particles; however, the particle image dilation caused by scattering does not allow direct measurement of particle size. The calibration routine presented here is accomplished by measuring fixed particle distribution ranges with a calibrated shadow imaging system and mapping these measurements to the in-situ imaging system. The technique used for generating and measuring these particles is described. The result is a three-part process where 1) particles of varying sizes are produced and measured using a calibrated, high-resolution shadow imaging method, 2) the same particle generators are measured with the in-situ imaging system, and 3) a correlation mapping is made between the (dilated) laser image size and the measured particle size. Additionally, experimental and operational details of the imaging system are described such as requirements for the enclosure volume, light management, air filtration and control of various laser reflections. Details related to the OR environment and requirements for achieving close proximity to a patient are discussed as well.

The accumulation of electrostatic charge on drug particles and excipient powders arising from interparticulate collisions or contacts with other surfaces can lead to agglomeration and adhesion problems during the manufacturing process, filling, and delivery of dry powder inhaler (DPI) formulations. The objective of the study was to investigate the role of triboelectrification to better understand the influence of electrostatic charge on the performance of DPIs with 2 capsule-based dimensionally similar devices constructed with different materials. In addition, strategies to reduce electrostatic charge build up during the manufacturing process, and the processes involved in this phenomenon were investigated. Electrostatic charge measurements showed that there was a significant difference in electrostatic charge generated between tested formulations and devices. This affects particle detachment from carrier and thus significantly impacts aerosol performance. Conditioning fluticasone DPI capsules at defined temperature and humidity conditions reduced electrostatic charges acquired during manufacturing. Conditioning salmeterol DPI capsules at same conditions seemed disadvantageous for their aerosol performance because of increasing capillary forces and solid bridge formation caused by water absorption. Knowledge and understanding of the role of electrostatic forces in influencing DPI formulation performance was increased by these studies.

The mixing state of black carbon (BC) affects its environmental fate and impacts. This work investigates particle diversity and mixing state for refractory BC (rBC) containing particles in an urban environment. The chemical compositions of individual rBC-containing particles were measured, from which a mixing state index and particle diversity were determined. The mixing state index (χ) varied between 26% and 69% with the average of 48% in this study and was slightly enhanced with the photochemical age of air masses, indicating that most of the rBC-containing particles cannot be simply explained by fully externally and internally mixed model. Clustering of single particle measurements was used to investigate the potential effects of different primary emissions and atmospheric processes on rBC-containing particle diversity and mixing state. The average particle species diversity and the bulk population species diversity both increased with primary traffic emissions and elevated nitrate concentrations in the morning but gradually decreased with secondary organic aerosol (SOA) formation in the afternoon. The single particle clustering results illustrate that primary traffic emissions and entrainment of nitrate-containing rBC particles from the residual layer to the surface could lead to more heterogeneous aerosol compositions, whereas substantial fresh SOA formation near vehicular emissions made the rBC-containing particles more homogeneous. This work highlights the importance of considering particle diversity and mixing state for investigating the chemical evolution of rBC-containing particles and the potential effects of coating on BC absorption enhancement.