Aerosol Particle Size Research Articles

In vitro Evaluation of Dry Powder Inhaler Devices of Corticosteroid Preparations

Although investigations of the drug aerosols generated from inhaled corticosteroid (ICS) preparations and combined drug preparations provide basic information about inhalation therapy, many clinicians have one-sided data about the precision of drug aerosols from the manufacturer. The present study was conducted to analyze and compare the performances of dry powder inhaler (DPI) devices of ICS and combined drug preparations. The particle size of individual aerosols was measured according to the time-of-flight principle in terms of their aerodynamic diameter by using the aerodynamic particle sizer spectrometer Model 3321. Percent aerosolization was measured using only stage #0 and backup filters of the Andersen non-viable sampler model AN-200. The particle size distribution of aerosols generated from a Turbuhaler™ and Twisthaler™ showed a mono-modal distribution of less than 5 μm. In contrast, Diskus™ showed a polydisperse distribution, ranging from 0.5 to 20 μm. The percentages of DPI preparations converted into aerosols with a particle size less than 11 μm at a suction flow rate of 28.3 L/min were 5.7-6.2% for Diskus, 37.5-47.0% for Turbuhaler, and 19.8% for Twisthaler. At a suction flow rate of 60 L/min, the conversion percentages for DPI preparations into aerosols with a particle size less than 7.6 μm were 5.9-7.5%, 78.2-86.7%, and 43.5%, respectively. Because in vitro differences in the aerosolization among different DPI devices containing ICS and combined drug preparations were observed, prescribers of these preparations should consider whether the patients will benefit more from the treatment of the central airways versus the peripheral airways.

Exploring the complexity of aerosol particle properties and processes using single particle techniques

The complex interplay of processes that govern the size, composition, phase and morphology of aerosol particles in the atmosphere is challenging to understand and model. Measurements on single aerosol particles (2 to 100 μm in diameter) held in electrodynamic, optical and acoustic traps or deposited on a surface can allow the individual processes to be studied in isolation under controlled laboratory conditions. In particular, measurements can now be made of particle size with unprecedented accuracy (sub-nanometre) and over a wide range of timescales (spanning from milliseconds to many days). The physical state of a particle can be unambiguously identified and its composition and phase can be resolved with a high degree of spatial resolution. In this review, we describe the advances made in our understanding of aerosol properties and processes from measurements made of phase behaviour, hygroscopic growth, morphology, vapour pressure and the kinetics of water transport for single particles. We also show that studies of the oxidative aging of single particles, although limited in number, can allow the interplay of these properties to be investigated. We conclude by considering the contributions that single particle measurements can continue to make to our understanding of the properties and processes occurring in atmospheric aerosol.

Selection and characterization of aerosol particle size using a bessel beam optical trap for single particle analysis

Bessel beams were used to create a counter-propagating optical trap for capturing and manipulating aerosol particles. Aerosol droplets were characterized through measurement of the elastic scattered light at three wavelengths; the trapping wavelength of 532 nm was used in conjunction with two probe beams at 405 nm and 633 nm to reduce the uncertainty in estimating droplet radii of 1 μm or less. Control of the aerosol size distribution sampled by the counter-propagating trap was demonstrated by varying the trapping beam core diameters and intensities. Smaller droplet sizes were preferentially selected with a 1.7 μm core diameter compared to cores of 2.7 μm and 4.5 μm. Further, an increase in core intensity was shown to broaden the range in droplet sizes that were optically trapped. The possibility of using such an approach to isolate and analyze the properties of single accumulation mode aerosol particles is discussed.

7Be atmospheric concentration at mid latitudes (40°N) during a year of solar minimum

In this paper we present the variation of 7Be concentration in the surface air of Thessaloniki, Greece (40°62′N, 22°95′E) over the year 2009, a year of a deep solar minimum, and, as a consequence, a year of maximum concentration of 7Be in surface air. The mean annual activity concentration of 7Be for the year 2009 was 6.0 mBq m−3. The relative variability of 7Be surface concentration related to the solar cycle was calculated to be deviated by about 20% from maximum to mean. A positive correlation (R = 0.97) was revealed between the activity of 7Be and the temperature T (°C), confirming that the increased rate of vertical transport within the troposphere, especially during warmer months, that make descend air masses enriched in 7Be down to the surface layer. The anticorrelation (R = –0.65) with RH% is due to intense condensation during high relative humidity conditions, which results in increased aerosol particle sizes and as a consequence in higher scavenging rate of aerosols and lower concentration of 7Be in the atmosphere. The influence of precipitation on the 7Be atmospheric concentration variability was approximately 10%, with greater the influence of rainfall events of low precipitation rate e.g. drizzling.

Ultrafine Particle (UFP) Exposures in an Aluminium Smelter: Soderberg vs. Prebake Potrooms

The objectives of this work were to evaluate ultrafine particle (UFP) exposures during aluminium smelting in Soderberg and prebake potrooms. Particle concentrations were monitored using the P-Trak 8525 and aerosol particle size distributions were monitored with the electrical low pressure impactor (ELPI). UFP samples were analyzed for chemical composition by transmission electron microscopy (TEM). Workers who accomplished tasks in the Soderberg cell environment were more exposed to UFP than those who worked in the prebake; however, the specific task of anode shift in the prebake process was an important source of UFPs. More than 92 % and 98 % of particles had aerodynamic diameters less than 98 nm in the Soderberg and prebake processes, respectively. TEM/EDS analysis suggests that workers are exposed to short fibrous aluminium particles with a nanometric aerodynamic diameter. Overall, this study suggests that occupational hygiene practices aimed at evaluating UFP exposures should include monitoring of the particle number concentration, monitoring of the particle size distribution, and characterization of the nanoscale fraction of the aerosol.

Air quality implications of theDeepwater Horizonoil spill

During the Deepwater Horizon (DWH) oil spill, a wide range of gas and aerosol species were measured from an aircraft around, downwind, and away from the DWH site. Additional hydrocarbon measurements were made from ships in the vicinity. Aerosol particles of respirable sizes were on occasions a significant air quality issue for populated areas along the Gulf Coast. Yields of organic aerosol particles and emission factors for other atmospheric pollutants were derived for the sources from the spill, recovery, and cleanup efforts. Evaporation and subsequent secondary chemistry produced organic particulate matter with a mass yield of 8 ± 4% of the oil mixture reaching the water surface. Approximately 4% by mass of oil burned on the surface was emitted as soot particles. These yields can be used to estimate the effects on air quality for similar events as well as for this spill at other times without these data. Whereas emission of soot from burning surface oil was large during the episodic burns, the mass flux of secondary organic aerosol to the atmosphere was substantially larger overall. We use a regional air quality model to show that some observed enhancements in organic aerosol concentration along the Gulf Coast were likely due to the DWH spill. In the presence of evaporating hydrocarbons from the oil, NO(x) emissions from the recovery and cleanup operations produced ozone.

Mechanical and electret properties of polypropylene unwoven fabrics reinforced with POSS for electret filter materials

A novel polypropylene/Polyhedral oligomeric silsesquioxanes (PP/POSS) composite unwoven fabric with permanent electret was prepared through melt-blown process with corona charging. Field-emission scanning electron microscope (FESEM) and wide-angle X-ray diffraction (WAXRD) were employed to investigate the morphology of the composite fibers and the distribution of POSS nanoparticles on the surface of the fibers, respectively. POSS acted as nucleating agent and accelerated the crystallization process during nonisothermal cooling. The utmost stable charge density of PP/POSS melt-blown unwoven fabric was improved by 78.4% compared with the neat PP unwoven fabric. The maximum value of collection efficiency measured by monodisperse polystyrene aerosol (PSL) (particle size: 0.3 μm) collection could reach 97.36% for PP/POSS composite melt-blown unwoven fabric, which improved by 9% compared with neat PP melt-blown unwoven fabric. Moreover, both stress and elongation at break of the PP/POSS melt-blown unwoven fabrics were improved compared with PP unwoven fabric.

A numerical method for the analysis of polydisperse aerosol particles charging in a coaxial electrode system

Abstract In this paper, charging kinetics of polydisperse aerosol particles in a corona field of a coaxial electrode system is numerically analyzed for a logarithmic normal distribution of aerosol particle size. The particle charging and the particle current are calculated by using a charging model considering ion concentration and particle mobility. Particle charging profiles under varying ion density and electrical field intensity distributions of the charging chamber were revealed. A low charging profile in the transition region of bipolar corona field was demonstrated in the simulation results.

Probing the Time Scale for Bulk Equilibration and Mass Transport of Water in Amorphous Inorganic Aerosol

New techniques are required to explore directly the kinetics of water transport in aerosol between the gas and condensed phases, both at high relative humidity (RH) close to saturation and at low RH where the role of amorphous states must be considered. Here, we present micro-Raman measurements of the kinetics of water transport between the bulk of a particle and the surrounding gas phase by examining the rate of exchange of D(2)O by H(2)O in droplets initially composed of MgSO(4)/D(2)O. The formation of an amorphous gel inhibits the response of the droplet composition to changes in the ambient RH and leads to a substantial reduction of the mass transfer rate of water in the droplet bulk with an apparent diffusion constant of 10(-15) to 10(-14) m(2) s(-1). These measurements are consistent with the imposition of a kinetic limitation on the time response of the aerosol particle size to changes in RH.

Relation between Neonatal Endotracheal (ET) Tube Size and Aerosol Penetration- Computational Fluid Dynamic Study (CFD)

Introduction: There are several aerosolized drugs used in the treatment of neonatal respiratory illnesses, including bronchodilators, diuretics and steroids. In vitro and in vivo studies identified variables that affect aerosol efficiency, including particle size, aerosol flows, and nebulizer choice. Type of patient interface can also be a critical variable in determining particle size of therapeutic aerosols delivered to mechanically ventilated patients. Unfortunately there are limited data on the influence of neonatal ET tube size on aerosol characteristics and lung inhaled and deposited dose in in vivo studies. Aim: To establish a relationship between neonatal ET tube size and penetration of aerosols with different particle sizes and flow characteristics. Methods: Three different ET tube sizes were tested: 2.5; 3.0 and 3.5 mm. Computations of the airflow field and aerosol particle dynamics during realistic inhalations have been performed with the commercial CFD package Fluent (Fluent, Inc.) as described earlier. The simulated breathing curves were based on two different inspiratory flows: 3 and 5 L/min. Penetration % was calculated based on spherical monodisperse aerosol particles with MMAD ranging from 1 to 10 µm. Results: 50% penetration was achieved only for 3.5 ET tube for all range of particle size. There was lower penetration profile for higher inspiratory flows. Conclusions: ET tube size can significantly influence the inhaled therapeutic dose by limiting aerosol ET tube penetration for non optimized particle size of the aerosols given to infants with breathing support. CFD can be very useful tool for designing optimal aerosol delivery system.

Determination of the concentration of aerosol particles in a vertical atmospheric column from satellite measurements of the spectral optical depth

We propose a method for fast retrieval of the inhalable particle concentration (PM2.5 and PM10) in a vertical atmospheric column from satellite measurements of the aerosol optical depth (AOD) without using a priori assumptions concerning the refractive index and the aerosol particle size distribution function. The method is based on a polynomial regression between PM2.5, PM10, and AOD at the wavelengths 466 nm and 644 nm, established from AERONET data. We have studied the sensitivity of the method to errors in the optical measurements and have estimated the errors in retrieval of PM2.5 and PM10 for different atmospheric situations. We carry out parametrization of the regressions on the value of the integrated air moisture content.

Penetration Performance of Melt-Blown Polypropylene Electret Nonwoven Web against DEHS Aerosols

High filtration efficiency of melt-blown polypropylene nonwoven web used as air filter extremely depends on its elelctret characteristics. In this paper, penetration performance of DEHS(diethyl hexyl sebacate) aerosol while flowing through melt-blown polypropylene electret nonwoven web is studied by the method of aerosol penetration measurement as a function of particle size, and the contribution of mechanical and electrostatic mechanism to its capture ability is proposed. The stability of filtration performance after exposure to DEHS for a period of time is measured and the impact of DEHS and other challenge aerosols with different chemical properties on filtration performance is compared. The results show that the higher filtration efficiency of melt-blown polypropylene electret nonwoven web mainly depends on its high electret charge. Aerosol penetration drops off with the increase of aerosol particle size and decreases in the order of basic weight sequence of 20, 40 and 60 g/m2. The most penetration particle size (MPPS) appears at 0.08 m in diameter. The electret charge of the web was cleared away during the course of exposure to challenge aerosol after 5 minutes. The electriferous property of aerosol particle also influences the filtration performance of polypropylene electret nonwoven web. The electret web displays the best filtration performance for ionized aerosol.

Characterization of novel spray-dried polymeric particles for controlled pulmonary drug delivery

Numerous studies have addressed the controlled pulmonary drug delivery properties of colloidal particles. However, only scant information on the potential of spray-drying for submicron particle preparation is available. By exploiting the advantages of spray-drying, the characteristics of submicron particles can be optimized to meet the requirements necessary for lung application.Submicron particles were prepared from organic poly(d,l-lactide-co-glycolide) (PLGA) solutions, and composite particles were spray-dried from aqueous PLGA nanosuspensions. The feed concentration, as well as the spray-mesh diameter influenced the resulting particle sizes. Nanoparticles were virtually unaffected after spray-drying. The aerodynamic characteristics of both particle species revealed aerosol particle sizes suitable for deposition in the deep lungs (≤4μm). While the entrapped drug was released within ~90min from the composite particles, extensive drug retardation (~480min) was observed for PLGA particles spray-dried from organic solution.These results suggest that nanospray-drying is a convenient method to prepare submicron, controlled drug delivery vehicles useful for pulmonary application potentially allowing access to alveolar tissue.

El Niño–Southern Oscillation correlated aerosol Ångström exponent anomaly over the tropical Pacific discovered in satellite measurements

El Nino.Southern Oscillation (ENSO) is the dominant mode of interannual variability in the tropical atmosphere. ENSO could potentially impact local and global aerosol properties through atmospheric circulation anomalies and teleconnections. By analyzing aerosol properties, including aerosol optical depth (AOD) and Angstrom exponent (AE; often used as a qualitative indicator of aerosol particle size) from the Moderate Resolution Imaging Spectrometer, the Multiangle Imaging Spectroradiometer and the Sea ]viewing Wide Field ]of ]view Sensor for the period 2000.2011, we find a strong correlation between the AE data and the multivariate ENSO index (MEI) over the tropical Pacific. Over the western tropical Pacific (WTP), AE increases during El Nino events and decreases during La Nina events, while the opposite is true over the eastern tropical Pacific (ETP). The difference between AE anomalies in the WTP and ETP has a higher correlation coefficient (>0.7) with the MEI than the individual time series and could be considered another type of ENSO index. As no significant ENSO correlation is found in AOD over the same region, the change in AE (and hence aerosol size) is likely to be associated with aerosol composition changes due to anomalous meteorological conditions induced by the ENSO. Several physical parameters or mechanisms that might be responsible for the correlation are discussed. Preliminary analysis indicates surface wind anomaly might be the major contributor, as it reduces sea ]salt production and aerosol transport during El Nino events. Precipitation and cloud fraction are also found to be correlated with tropical Pacific AE. Possible mechanisms, including wet removal and cloud shielding effects, are considered. Variations in relative humidity, tropospheric ozone concentration, and ocean color during El Nino have been ruled out. Further investigation is needed to fully understand this AE ]ENSO covariability and the underlying physical processes responsible for it.

Sizer for Neutral Weakly Bound Ultrafine Aerosol Particles Based on Sodium Doping and Mass Spectrometric Detection

The determination of accurate size distributions and chemical composition of volatile and semivolatile ultrafine aerosol particles with sizes in the subnanometer to several tens of nanometers range is a problem that plagues many studies in aerosol research. We propose to employ sodium-doping of the aerosol particles with subsequent photoionization in the ultraviolet combined with mass spectrometric detection to solve this problem. Comparison with “soft” EUV ionization demonstrates that this technique can determine size distributions and to some extent the chemical composition of weakly bound ultrafine aerosol particles largely destruction-free. We also discuss how sodium-doping can be turned into a viable quantitative technique for the sizing of ultrafine aerosol particles.

Aerosol Delivery and Humidification With the Boussignac Continuous Positive Airway Pressure Device

A simple method for effective bronchodilator aerosol delivery while administering continuing continuous positive airway pressure (CPAP) would be useful in patients with severe bronchial obstruction. To assess the effectiveness of bronchodilator aerosol delivery during CPAP generated by the Boussignac CPAP system and its optimal humidification system. First we assessed the relationship between flow and pressure generated in the mask with the Boussignac CPAP system. Next we measured the inspired-gas humidity during CPAP, with several humidification strategies, in 9 healthy volunteers. We then measured the bronchodilator aerosol particle size during CPAP, with and without heat-and-moisture exchanger, in a bench study. Finally, in 7 patients with acute respiratory failure and airway obstruction, we measured work of breathing and gas exchange after a β(2)-agonist bronchodilator aerosol (terbutaline) delivered during CPAP or via standard nebulization. Optimal humidity was obtained only with the heat-and-moisture exchanger or heated humidifier. The heat-and-moisture exchanger had no influence on bronchodilator aerosol particle size. Work of breathing decreased similarly after bronchodilator via either standard nebulization or CPAP, but P(aO(2)) increased significantly only after CPAP aerosol delivery. CPAP bronchodilator delivery decreases the work of breathing as effectively as does standard nebulization, but produces a greater oxygenation improvement in patients with airway obstruction. To optimize airway humidification, a heat-and-moisture exchanger could be used with the Boussignac CPAP system, without modifying aerosol delivery.

Assessment of Airborne Fine Particulate Matter and Particle Size Distribution in Settled Chalk Dust during Writing and Dusting Exercises in a Classroom

Airborne PM1, PM2.5, PM5 and PM10 generated during writing with three types of chalk sticks on a board and particle size distribution of chalk dust fall during writing and dusting of board were studied by portable aerosol spectrometer and particle size analyzer. ‘Local Gypsum’ chalk led to the highest increase in airborne particulate matter while ‘Clean-Write’ the least during writing. About 10% of particles in chalk dust fall during writing were finest from: ‘Clean Write’ (0.5 µm) followed by ‘Abroad Quality’ (0.67 µm) and ‘Local Gypsum’ (1.15 µm), while 50% was finest in abroad quality (5.12 µm) followed by ‘Clean Write’ (6.36 µm) and ‘Local Gypsum’ (77.65 µm). In dusting samples, 10%, 50% and 90% of particles were finest in ‘Clean Write’ followed by ‘Abroad Quality’ and ‘Local Gypsum’ chalks. ‘Clean Write’ chalk produced least total amount of PM1, PM2.4 and PM5 and PM10 per unit time in dust fall during writing. Although short-term exposure to airborne fine chalk particles may be low in classrooms, several years of exposure may be a matter of concern. Purpose of this work was to provide data that would lead to measures for minimization of health risk due to chalk dusts in classrooms.

Out-scaling electrohydrodynamic atomization systems for the production of well-defined droplets

Industrial use of single-nozzle electrohydrodynamic atomization for producing aerosol particles of uniform size is limited by the small throughput of the method. To increase it, out-scaling by means of multiple nozzles is inevitable. We designed and tested a multi-nozzle system with a circular symmetry that provides a uniform flow rate and the same electric field intensity to all nozzles. Stability of particle production from multi-nozzle electrospray systems strongly depends on the precision of the liquid feeding system that typically requires high-cost pumps. A constant-head feeding system is a cost-effective alternative that can deliver the same performance. In order to describe the relation between flow rate and particle size in the constant-head operating mode, we developed a semi-empirical model that predicts the flow rate through the system. This model can be used with the conventional scaling law for predicting the diameter of the produced droplets.

Application of a graded screen array for size measurements of radioactive aerosols in accelerator rooms

Abstract A rapid measurement method for aerosol particle size is required to clarify the formation mechanism of freshly-formed radioactive aerosols in accelerator rooms. A graded screen array (GSA) method only requires brief sampling. Therefore, the GSA method is suitable for the measurement of radioactive aerosols in the accelerator rooms. In this work, a conventional GSA was applied to measure the particle size distribution of an aerosol. An influence of the radioactive gas on the GSA measurement was found. The adsorption of radioactive gases resulted in a discrepancy between the results of the GSA method and those of the diffusion battery method. An improved GSA method was developed to measure the radioactive aerosol formed in the accelerator room. The adsorption was measured by the improved GSA, and the influence of the radioactive gas was eliminated. The result of the improved GSA showed fair agreement with that of the diffusion battery system.

Computational Fluid Dynamics Study of Airflow and Particle Transport in Third to Sixth Generation Human Respiratory Tract

The computational fluid dynamics (CFD) technique is used to simulate airflow and aerosol-particle deposition in human respiratory tract. The three dimensional respiratory tract is extended from third to six generation bronchus based on Weibel model (1963). The computation is performed for laminar flow condition. Discrete phase modeling (DPM) is used to study the two phase flow. The aerosol-particles of three different diameters 1, 5 and 10 μm are considered to obtain the effect of aerosol-particle size on deposition efficiency. The results of velocity contours, aerosol-particle deposition efficiency and aerosol-particle trapping process are determined at different locations of the respiratory tract. It is obtained that deposition efficiency increases with the increase of aerosol-particle size. It is also found that more are deposited at the bifurcation junctions because of the direct inertial impaction at these locations. Computational results are found useful to correlate the medical and engineering aspects.