Particle Aerodynamic Diameter Research Articles

Effects of pretreatment temperature on the analysis of size‐fractionated aerosol particles using ToF‐SIMS

Size‐fractionated aerosol particles were collected with a MOUDI 10‐stage cascade impactor from an urban roadside place in a downtown area of Hong Kong. Fine aerosol particulate samples from stage 6 (aerodynamic particle diameter between 0.56 and 1 μm) and stage 9 (aerodynamic particle diameter between 0.10 and 0.18 μm) were pretreated at a chosen temperature, including −100°C, −50°C, 25°C, and 60°C, in a load lock chamber and then analyzed using time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) at the same temperature (−100°C). Principal component analysis (PCA) was applied to further analyze ToF‐SIMS spectra of aerosol particles with different pretreatment temperatures from two selected stages. ToF‐SIMS results showed that the intensities of aliphatic hydrocarbon ions such as C4H7+ and C4H9+ and amine ions such as C2H8N+ and C4H12N+ decreased with an increase of the pretreatment temperature under ultrahigh vacuum conditions. We have shown that analyses of this type of aerosol particles using ToF‐SIMS should not be conducted at ambient temperature but at low temperature (eg, −50°C). In addition, we also developed a procedure that can be used to analyze aerosol particle samples under ultrahigh vacuum environment.

Comparative numerical simulation of inhaled particle dispersion in upper human airway to analyse intersubject differences

This study predicted the total and regional deposition of particles in realistic upper human airways and demonstrated the effects of intersubject variations in deposition fraction. Two airway models were studied under flow rates ranging from 0.45 to 2.4 m3/h and particle aerodynamic diameters from 1 to 10 μm. The total deposition predictions were validated using in vivo and in vitro experimental data. The intricate airway structures generated heterogeneities of airflow distributions and corresponding particle dispersions and depositions in the models. Nevertheless, with modified inertial parameters, the total deposition fraction curves of the two human upper airway models, as functions of flow rates, converged to a single function. However, regional particle deposition fractions differed significantly among the two models. The surface pressure and wall-shear stress distribution were investigated to assess the relationship of surface pressure and wall-shear stress with hotspot locations in upper airways of both models. For one subject (model A), the central nasal passage regions were found to be sites of higher deposition over the range of particle sizes and flow rates targeted in this study. For the other subject (model B), higher deposition was mostly observed in the vestibule region, caused due to particle inertia as the airway consisted of curvatures. The accelerated flow regions acted as a natural filter to high inertial particles. The results indicated that both total and regional depositions exhibited significant intersubject differences.

Effect of Particle–Wall Interaction and Particle Shape on Particle Deposition Behavior in Human Respiratory System

Dry powder inhalation (DPI) has attracted much attention as a treatment for respiratory diseases owing to the large effective absorption area in a human respiratory system. Understanding the drug particle motion in the respiratory system and the deposition behavior is necessary to improve the efficiency of DPI. We conducted computer simulations using a model coupling a discrete element method and a computational fluid dynamics method (DEM-CFD) to evaluate the particle deposition in human respiratory system. A simple artificial respiratory model was developed, which numerically investigated the effect of particle properties and inhalation patterns on the particle deposition behavior. The DEM-CFD simulations demonstrated that the smaller- and lower-density particles showed higher reachability into the simple respiratory model, and the particle arrival ratio to the deep region strongly depended on the aerodynamic diameter. The particle arrival ratio can be described as an exponential function of the aerodynamic diameter. Furthermore, the exponential relationship between the particle reachability into the depth of the simple respiratory model and the aerodynamic diameter predicted the particle aerodynamic diameter based on the required reachability. The particle shape also had an impact on the particle deposition behavior. The rod-like particles with a larger aspect ratio indicated higher reachability into the depth of the simple respiratory model. This was attributed to the high velocity motion of the particles whose long axis was in the direction of the deep region.

Removal efficiency of central vacuum system and protective masks to suspended particles from dental treatment.

BackgroundHigh levels of suspended particulate matters (PMs) and bioaerosols are created by dental procedures. The present study aimed to evaluate the size and concentration of PMs produced by drilling and grinding teeth, and to assess the efficiency of central vacuum system and protective masks for the removal of PMs.MethodsA total of 20 extracted permanent teeth were collected. A novel experimental system and particle counter were used to evaluate the PMs produced by dental procedures and the PM removal efficiency of a central vacuum system and surgical/N95 masks.ResultsThe number concentration of total PMs produced by drilling and grinding teeth was significantly higher than the indoor background concentration. The average aerodynamic diameter of particle was generally less than 1 μm. The average number concentration of ultrafine particles was 2.1x1011 particles/m3 during tooth drilling and grinding. The efficiency of the central vacuum system was 35.74% for PM≥0.5 and 35.41% for PM10. For PM≥0.5, the ratios of inside and outside masks were 0.8–1.34 without vacuum and 1.18–1.36 with vacuum. No difference was found with the use of surgical/N95 masks during dental therapy, with or without vacuum use.ConclusionsHigh levels of PMs were found during tooth drilling and grinding procedures, especially among PM1. The PM removal efficiency of a central vacuum system and surgical/N95 masks were limited.

Ultrafine particles: Levels in ambient air during outdoor sport activities

Conducting aerobic activity on regular basis is recognised as one of the steps to maintain healthier lifestyle. The positive outcomes though can be outweighed if conducted in polluted atmosphere. Furthermore, the specific inhalation during exercising, which results in bypass of nasal filtration systems and deeper penetration into the respiratory system, might result in higher risks especially to pollutants such as ultrafine particles (UFP), which aerodynamic particle diameter are <100 nm. Thus, this work aims to evaluate UFP levels at sites used for conducting physical sport activities outdoors and to estimate the respective inhalation doses considering various scenarios and different physical activities. Monitoring of UFP was conducted during three weeks (May–June 2015) at four different sites (S1–S4) regularly used to conduct physical exercising. The results showed that UFP highly varied (medians 5.1–20.0 × 103 # cm−3) across the four sites, with the highest UFP obtained when exercising next to trafficked streets whereas S3 and S4 (a garden and city park) exhibited 2–4 times lower UFP. In view of the obtained UFP concentrations, the estimated inhalation doses ranged 1.73 × 108–3.81 × 108 # kg−1 when conducting moderately intense sport activities and 1.93 × 108–5.95 × 108 # kg−1 for highly intense ones. Highly intense activities (i.e. running) led to twice higher UFP exposure; children and youths (5–17 yrs old) experienced 203–267% higher doses. Considering the age– and gender– differences, estimated UFP doses of males were 1.1–2.8 times higher than of females. Finally, UFP inhalation doses estimated for walking (commuting to work and/or schools) were 1.6–7.5 times lower than when conducting sport activities. Thus to protect public health and to promote healthy and physically active lifestyle, strategies to minimize the negative impacts of air pollution should be developed and implemented.

Studies of Atmospheric PM2.5 and its Inorganic Water Soluble Ions and Trace Elements around Southeast Asia: a Review

Air pollution is a worldwide issue that is mainly caused from excessive inhalation of hazardous PM2.5 pollutant that is emitted into the air. The objective of this study is to assess the fundamental knowledge revolving PM2.5 (particles aerodynamic diameter of lower than or equal to 2.5 μm) and its inorganic composition in ambient air of urban areas, mainly in Malaysia in comparison to other Southeast Asia countries. This research also investigates the theory of particle number concentration (PNC) with PM2.5, also the health effects and origins of the emissions. The factors affecting the PM2.5 mass include the local emission, El Nino phenomenon, land, meteorological effects, monsoons, rainfall events, sea breeze, transboundary pollution and seasonal changes. 24 h mean PM2.5 mass concentration for metropolitan regions in the SEA is in the range of 11 μgm−3 and 72.3 μgm−3, while between 5.30 μgm−3 and 55.89 μgm−3 for semi-urban zones. For rural area, the 24 h mean PM2.5 value is about 30 μgm−3. The findings indicate that metals in PM2.5 emission are frequently Pb, Se, Zn, Cd, As, Bi, Ba, Cu, Rb, V, Ni, Fe, Ca, Mn, Cr, Al, Si and K, where Zn has the uppermost range of 133.50 to 419.30 ngm−3 while the major water-soluble ions exist are NH4+, K+, Ca2+, Na+, in which Na+, NH4+ and Cl- are present in aged sea salt and mixed industrial, Ca2+ and Mg2+ present in mineral dust, NH4+, K+ and SO42− present in mixture of SIA and biomass burning. There is a high correlation between the particle mass concentration and PNC level, especially the ones in accumulation mode (PNC0.1–1.0) which are mostly originated from the emission of heavy traffic streets.

Radiocesium concentration in indoor air during residential house cleaning in Fukushima Dai-ichi nuclear power plant evacuation areas

After the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, outdoor decontamination was conducted by the Japanese Government, whereas indoor contamination was the responsibility of individual residents. However, no data exist regarding 137Cs exposure during indoor cleaning. Therefore, indoor 137Cs radioactivity concentrations in indoor air were determined during cleaning in 60 houses within the evacuation area near the FDNPP, Fukushima Prefecture, Japan. Radiocesium activity concentrations per cubic meter of indoor air during dusting (mean ± SD (median)) was 6.8 ± 7.9 (4.7) and 1.6 ± 2.7 (0.78) Bq/m3 for all aerodynamic diameter of aerosol particle and PM2.5, respectively. Radiocesium activity concentrations in indoor air decreased with decreasing the aerodynamic diameter of aerosol particles (mean: 0.099, 0.22, 0.41, 0.92, 2.2, and 2.9 Bq/m3 for the aerodynamic diameter of <0.25, 0.25–0.5, 0.5–1.0, 1.0–2.5, 2.5–6.6, and >6.6 μm, respectively) and was inversely proportional to the square of the distance from the FDNPP. Indoor 137Cs radioactivity concentrations were significantly higher during dusting than during vacuuming with either a cyclone handy cleaner or a normal vacuum cleaner. The mean deposited activities in tracheobronchial and alveolar regions was estimated to be 1.9 and 2.8 Bq, respectively, during a 2-h dusting period in the studied houses. For values below the detection limit, half of the detection limit was used for calculating the means and SDs.

Airborne particulate matter emissions from vehicle brakes in micro- and nano-scales: Morphology and chemistry by electron microscopy

Brake wear particles constitute a significant part of the non-exhaust related particulate matter (PM) associated to traffic. These particles derive from various components of the vehicles’ brake system and were recognized as an important pollution source only recently. In the present study, electron microscopy was applied to elucidate brake wear particle morphology and associated chemical composition. Sampling was carried out on a brake test bench. Particles were collected on 13 successive polycarbonate foil bags and a backup filter by means of a Dekati Low Pressure Impactor (DLPI), based on the equivalent aerodynamic particle diameter. The results revealed a broad size range from the micro-to the nano-scale, as measured on electron microscope images, including coarse (2.5–10 μm), fine (0.1–2.5 μm) and ultrafine ones (<0.1 μm), down to a few nanometers. It cannot be implied with certainty to what extent the particle size spectrum identified under the experimental conditions of the present study strictly applies to real-world conditions. The particles occur typically in form of aggregates, also in the ultrafine scale; single, i.e. non-agglomerated particles are more common in the ultrafine fraction than at larger sizes. Imaged particles have commonly rounded outlines probably due to friction and associated abrasion during braking; melting/evaporation at high temperature braking phases, associated with the rate of the generated frictional energy of braking, and subsequent rapid solidification can be invoked to interpret the nearly spherical shape of nanometer size particles. The individual constituents of the aggregates have various sizes and chemical composition. Energy dispersive X-ray analysis of the imaged aggregates and of their constituents showed that Fe is prevalent in all size fractions but is less pronounced in the smaller sizes, where Ca, occasionally in combination with S and/or P becomes more frequent. Other frequently analysed elements are Al, Sn, Mg, Si, Cr, Ti, K and W; less frequent are Ni, Zn, Zr, Ba, S, C, P, F, Mn and rarely Bi and Sb.

Establishment of PM2.5 Prediction Model Based on MAIAC AOD Data of High Resolution Remote Sensing Images

Long-term exposure to seriously polluted atmospheric environment is closely related to a variety of human diseases. The long-term and continuous monitoring of PM[Formula: see text] (the aerodynamic particle diameter is less than or equal to 2.5[Formula: see text][Formula: see text]m) is of great significance as it is one of the major air pollutants. Because of the small number of PM[Formula: see text] monitoring stations in China, it is very difficult to accurately estimate the continuous scale of air pollution, but PM[Formula: see text] concentration can be acquired by using the aerosol products inversed by remote sensing data. However, due to the limitation of the inversion algorithm, the traditionally used moderate resolution imaging spectroradiometer (MODIS) aerosol products cannot meet the precision and practical requirements in both spatial resolution and effective numerical coverage. This paper adopts MAIAC AOD, i.e. the aerosol optical depth (AOD) products produced by using the new multi-angle implementation of atmospheric correction (MAIAC) algorithm, and we take the Beijing–Tianjin–Hebei region in China as the research area. Based on the neural network algorithm, the MAIAC AOD data is mainly used and the meteorological parameter data is supplemented to establish the PM[Formula: see text] concentration prediction model to obtain the PM[Formula: see text] concentration distribution map. The prediction accuracy, the effective numerical coverage and spatial resolution have been greatly improved.

Tunable Properties of Poly-DL-Lactide-Monomethoxypolyethylene Glycol Porous Microparticles for Sustained Release of Polyethylenimine-DNA Polyplexes.

Direct pulmonary delivery is a promising step in developing effective gene therapies for respiratory disease. Gene therapies can be used to treat the root cause of diseases, rather than just the symptoms. However, developing effective therapies that do not cause toxicity and that successfully reach the target site at therapeutic levels is challenging. We have developed a polymer-DNA complex utilizing polyethylene imine (PEI) and DNA, which was then encapsulated into poly(lactic acid)-co-monomethoxy poly(ethylene glycol) (PLA-mPEG) microparticles via double emulsion, solvent evaporation. Then, the resultant particle size, porosity, and encapsulation efficiency were measured as a function of altering preparation parameters. Microsphere formation was confirmed from scanning electron micrographs and the aerodynamic particle diameter was measured using an aerodynamic particle sizer. Several formulations produced particles with aerodynamic diameters in the 0-5μm range despite having larger particle diameters which is indicative of porous particles. Furthermore, these aerodynamic diameters correspond to high deposition within the airways when inhaled and the measured DNA content indicated high encapsulation efficiency. Thus, this formulation provides promise for developing inhalable gene therapies.

Spatiotemporal Variation in Composition of Submicron Particles in Santiago Metropolitan Region, Chile

The chemical composition of submicron particles (aerodynamic diameter Da < 1.0 μm) was investigated at three locations in the Santiago Metropolitan Region (SMR), Chile. Measurements campaigns were conducted in winter and spring 2016, at representative sites of a rural, urban and urban receptor environment. Instrumentation consisted of an optical analyzer to determine Black Carbon (BC) and the Aerosol Chemical Speciation Monitor (ACSM) to measure concentrations of particulate chloride (Cl-), nitrate (NO3-), sulfate (SO42-), ammonium (NH4+) and non-refractory carbonaceous species (organics). Complementary data, such as ozone concentration and meteorological parameters were obtained from the public air quality network. Results showed that in both the winter and spring seasons the organics predominated in the mass of submicron particles. This fraction was followed in decreasing order by NO3-, NH4+, BC, SO42- and Cl-. The highest average organics concentrations were measured in winter at the urban (32.2 µg m–3) and urban receptor sites (20.1 µg m–3). In winter, average concentrations of both NO3- and NH4+ were higher at the urban receptor site (12.3 and 4.5 µg m–3, respectively) when compared to the urban site (6.4 and 3.1 µg m–3, respectively). In general, all the measured species were present in higher concentrations during winter, excepting SO42-, which was the only one that increased during spring. The transition towards spring was also associated with an acidification of the aerosol at the rural and urban receptor site, while at the urban site the aerosol was observed alkaline. The highest average ozone concentration during both the winter and spring seasons were recorded at the urban receptor site (7.2 and 24.0 ppb, respectively). The study reports data showing that the atmosphere in the SRM has a considerable load of particulate organic compounds, NO3- and NH4+, which are in higher concentrations at urban sites during the winter season. Based on wind patterns and the hourly profiles of chemical species, the study suggests that during daytime the polluted air masses from the urban center can move to the northeast part of the region (namely urban receptor site) leading to the formation of submicron particles as well as photochemical ozone.

The effect of disintegrated iron-ore pellet dust on deposit formation in a pilot-scale pulverized coal combustion furnace. Part I: Characterization of process gas particles and deposits

To initiate the elucidation of deposit formation during the iron-ore pelletization process, a comprehensive set of experiments was conducted in a 0.4 MW pilot-scale pulverized-coal-fired furnace where three different scenarios were considered as follows; Case 1 (reference case): Coal was combusted without the presence of pellet dust. Case 2: Natural gas was combusted together with simultaneous addition of pellet dust to the gas stream. Case 3: Coal was combusted together with the addition of pellet dust simulating the situation in the large-scale grate-kiln setup. Particles and deposits were sampled from 3 positions of different temperature via a water-cooled sampling probe. Three distinct fragmentation modes were identified based on the aerodynamic particle diameter (Dp). The fine mode: Particles with 0.03 < Dp < 0.06 μm. The first fragmentation mode: Particles with 1 < Dp < 10 μm. The second fragmentation mode: Coarse particles (cyclone particles, Dp > 10 μm). A transition from a bimodal PSD (particle size distribution) to a trimodal PSD was observed when pellet dust was added (Case 3) and consequently the elemental bulk composition of the abovementioned modes was changed. The most extensive interaction between pellet dust and coal-ash particles was observed in the coarse mode where a significant number of coal ash globules were found attached to the surface of the hematite particles. The morphology of the sharp-edged hematite particles was changed to smooth-edged round particles which proved that hematite particles must have interacted with the surrounding aluminosilicate glassy phase originating from the coal ash. The short-term deposits collected during coal combustion (Case 1) were highly porous in contrast to the high degree of sintering observed in the experiments with pellet dust addition (Case 3) which is attributed to the dissolution of hematite particles in the aluminosilicate glassy phase. The results suggest that pellet dust itself (Case 2) has low slagging tendency, independent of temperature. However, when coal-ash is present (Case 3), auxiliary phases are added such that tenacious particles are formed and slagging occurs.

Seasonal variabilities in chemical compounds and acidity of aerosol particles at urban site in the west Pacific

Mass concentrations of chemical compounds in both PM2.5 (particle aerodynamic diameter, Dp < 2.5 μm) and PM2.5-10 (2.5 < Dp < 10 μm), and acidity of aerosol particles were measured at an urban site in western Japan using a continuous dichotomous Aerosol Chemical Speciation Analyzer (ACSA-12) throughout 2014. Mass concentrations of both PM2.5 and sulfate had distinct seasonal variabilities with maxima in spring and winter, mostly due to long-range transport with the prevailing westerly wind. Mass concentration of nitrate in PM2.5 (fNO3) showed an obvious warm-season-low and cold-season-high pattern as a result of both gas-aerosol phase equilibrium processes under high temperature conditions as well as transport. Nitrate in PM2.5-10 (cNO3) increased during long-range transport of dust, implying the great importance of heterogeneous processes at the surface of coarse mode particles. In this study, Δ[H+] (derived from the difference in pH of extract liquid with/without sampling) was used to indicate the acidity of particles. We found that acidity of particles in PM2.5 (fΔH) was mostly positive with a maximum in August because of the large fraction of nitrate and sulfate. Acidity of particles in PM2.5-10 (cΔH) was negative in winter and spring due to presence of alkaline matter from crustal sources. This study highlights the great importance of anthropogenic pollutants on the acidity of particles in the western Pacific Ocean and further impact on the marine environment and climate.

Analysis of aerosol composition data for western United States wildfires between 2005 and 2015: Dust emissions, chloride depletion, and most enhanced aerosol constituents.

This study examines major wildfires in the western United States between 2005 and 2015 to determine which species exhibit the highest percent change in mass concentration on day of peak fire influence relative to preceding nonfire days. Forty-one fires were examined using the Environmental Protection Agency (EPA) Interagency Monitoring of Protected Visual Environments (IMPROVE) data set. Organic carbon (OC) and elemental carbon (EC) constituents exhibited the highest percent change increase. The sharpest enhancements were for the volatile (OC1) and semivolatile (OC2) OC fractions, suggestive of secondary organic aerosol formation during plume transport. Of the noncarbonaceous constituents, Cl, P, K, NO3-, and Zn levels exhibited the highest percent change. Dust was significantly enhanced in wildfire plumes, based on significant enhancements in fine soil components (i.e., Si, Ca, Al, Fe, and Ti) and PMcoarse (i.e., PM10-PM2.5). A case study emphasized how transport of wildfire plumes significantly impacted downwind states, with higher levels of fine soil and PMcoarse at the downwind state (Arizona) as compared to the source of the fires (California). A global model (Navy Aerosol Analysis and Prediction System, NAAPS) did not capture the dust influence over California or Arizona during this case event because it is not designed to resolve dust dynamics in fires, which motivates improved treatment of such processes. Significant chloride depletion was observed on the peak EC day for almost a half of the fires examined. Size-resolved measurements during two specific fires at a coastal California site revealed significant chloride reductions for particle aerodynamic diameters between 1 and 10 μm.

Sampling Efficiency and Performance of Selected Thoracic Aerosol Samplers.

Measurement of worker exposure to a thoracic health-related aerosol fraction is necessary in a number of occupational situations. This is the case of workplaces with atmospheres polluted by fibrous particles, such as cotton dust or asbestos, and by particles inducing irritation or bronchoconstriction such as acid mists or flour dust. Three personal and two static thoracic aerosol samplers were tested under laboratory conditions. Sampling efficiency with respect to particle aerodynamic diameter was measured in a horizontal low wind tunnel and in a vertical calm air chamber. Sampling performance was evaluated against conventional thoracic penetration. Three of the tested samplers performed well, when sampling the thoracic aerosol at nominal flow rate and two others performed well at optimized flow rate. The limit of flow rate optimization was found when using cyclone samplers.

Inhalable nanocomposite particles using amino acids with improved drug content and humidity resistance

In this study, we prepared various rifampicin-loaded poly(DL-lactide-co-glycolide) nanoparticles by changing the volume and pH of the aqueous phase to improve the content of rifampicin in the nanoparticles. The rifampicin content in the nanoparticles prepared in the aqueous phase volume of 40mL (pH 4) was 1.36 times higher than that in the nanoparticles prepared in the aqueous phase volume of 100mL (pH 7). From the results of in vitro release tests in phosphate-buffered saline at 37°C for 24h, we found that by reducing the volume and pH of the aqueous phase, the cumulative release rate of rifampicin from nanoparticles was significantly decreased. Then, we prepared nanocomposite particles using arginine and leucine as diluents. The aerodynamic diameters of the nanocomposite particles were measured using a cascade impactor. We found that the nanocomposite particles prepared using a diluent with arginine to leucine ratio of 1: 20 had the highest fine particle fraction value (32.63±1.49%) and the particles were suitable for pulmonary delivery of bioactive materials deep in the lungs.

Assessment of recent nebulizer delivery systems using urinary pharmacokinetics method and aerodynamic characteristics of TOBI® nebulized dose following inhalation

BackgroundChronic infections with Pseudomonas aeruginosa are a leading cause of morbidity in patients with cystic fibrosis (CF). Tobramycin nebulizer solution (TNS) is indicated for maintenance therapy in CF patients. TOBI® is a tobramycin nebulizer solution (TNS) approved by FDA for maintenance therapy for patient with CF. Adherence to recommended therapy in CF has always been a challenge and new generation nebulizers are increasingly used “off label” to reduce the time required for inhalation, potentially improving patient compliance. ObjectivesTo assess the performance of selected recent nebulizer delivery systems for determination the optimum combinations to deliver TOBI®. Using the relative lung bioavailability of TOBI® to the lungs in healthy volunteers, following inhalation from selected nebulizer delivery systems, using a urinary pharmacokinetics method. In vitro aerodynamic characteristics of the nebulized dose were also determined. MethodsSerial urine samples were collected from 12 healthy volunteers up to 24 h post-inhalation of TOBI® inhaled solution following delivery by Pari LC Plus®, Sidestream®, NE-U22-E Omron® and Aeroneb® Go nebulizers. In vitro aerodynamic characteristics of the nebulized dose were also determined according to the CEN (Committee European de Normalization) method. ResultsThe mean (SD) relative lung bioavailability from Pari LC Plus®, Sidestream®, Omron®, and Aeroneb® Go nebulizers was 4.9 (0.5), 3.9 (0.5), 7.1 (1.3), and 7.7 (0.7) %, respectively. The mean (SD) mass median aerodynamic diameter (MMAD) of the drug particles from the same systems was 2 (0.2), 2 (0.2), 1.2 (0.03) and 2.0 (0.1) μm, and the corresponding fine particle doses (FPD) were 2.2 (0.23), 1.5 (0.2), 3.44 (0.3) and 2.8 (0.3) mg. ConclusionThe data obtained from in-vitro and in-vivo studies reflect poor relative lung bioavailability of tobramycin following jet nebulization.

Demographic and Environmental Factors Associated with Mental Health: A Cross-Sectional Study.

Relevant demographic and environmental conditions need to be understood before tailoring policies to improve mental health. Using community health survey data from 25 communities in Seoul, 2013, cross-sectional associations between mental health and community level environments were assessed. Mental health outcomes (self-rated stress levels (SRS) and depressive symptoms (DS)) were analyzed. Community environmental factors included green space, green facilities, and annual PM10 level (AnnPM10); socio-demographic factors included sex, age, education, labor market participation, comorbidity, sleep hours, physical activity, smoking, and drinking. A total of 23,139 people with the following characteristics participated: men (44.2%); age groups 19−39 (36.0%), 40−59 (39.4%), 60−74 (19.2%), and 75+ (5.4%). Women had higher odds ratios (OR) for SRS [OR 1.22, 95% Confidence interval (CI) 1.17–1.27] and DS [OR 1.55, 95% CI 1.42–1.71]. Regular physical activity predicted SRS [OR 0.90, 95% CI 0.84–0.95] and DS [OR 0.98, 95% CI 0.88–1.10]; current smoking and drinking were adversely associated with both SRS and DS. Higher accessibility to green space (Q4) was inversely associated with DS [OR 0.89, 95% CI 0.81−0.97] compared to lower accessibility (Q1). AnnPM10, annual levels for particles of aerodynamic diameter <10 µm (PM10), among communities was associated with poorer SRS [OR 1.02, 95% CI 1.00–1.04] by 10 μg/m3 increases. Therefore, both demographic and environmental factors should be considered to understand mental health conditions among the general population.

Analysis of Airborne Dust as a Result of Plaster Cast Sawing.

Plaster splints are used daily in surgical and orthopedic fields in order to immobilize injured children and adults. The aim of this study was to measure the aerodynamic diameter and concentration of dust particles in the air caused by sawing plaster splints (calcium sulfate dehy-drate). We performed fractional measurements of airborne dust particles. The measured particles, which can potentially be inhaled, may have a specific negative effect on human health. Measurements were conducted in laboratory research facilities that simulated hospital conditions within a casting room and the associated waiting room. Measurements within the casting room were made using two particle collector devices and one laser photometer. The measurement for the simulated waiting room was performed using the same principles and devices. The collected plaster dust particles differed in aerodynamic diameter and concentration according to the various locations observed. The highest concentration of particles of all sizes was recorded at the site of cast sawing. There was direct correlation between distance from the source and concentration of airborne particles; this concentration was lowest in the waiting room. The concentrations of plaster dust recorded were lower than the recommended minimal limit values for total and respiratory fractions in Croatia. Accordingly, it can be assumed that sawing of plaster splints has no harmful health effects on the exposed patients and health personnel.

Characterizing PM2.5 in Beijing and Shanxi Province using terahertz radiation

Particles of aerodynamic diameter⩽2.5 μm (PM2.5) caused extremely severe and persistent haze pollution is of concern in many cities. In this study, samples of PM2.5 were collected from atmosphere environment of Beijing and Shanxi Province, and analyzed using terahertz (THz) radiation. The transmission spectrum of PM2.5 in Shanxi Province had two distinct absorption peaks at 6.0 and 6.7 THz, and the curve was increasing on the whole. However, the transmission spectrum of PM2.5 in Beijing had obviously different variation tendency and the absorption peak was studied by monitoring PM2.5 masses in conjunction with two-dimensional correlation spectroscopy (2DCOS). By comparing the pollutant species and concentrations of Shanxi Province and Beijing over the time of collecting samples, the concentrations of sulfate and ammonium were similar, which contributed to emerge absorption bands in the same position. While the concentrations of organic matter (OM), nitrate, chloride and elemental carbon (EC) were different. Furthermore, dust and some other inorganic ion are unique to Shanxi province, which lead to different variation tendency of the transmission spectrum of PM2.5. These results will be of importance for environmental monitoring and for controlling PM emissions. According to this research, optical techniques, and especially spectral methods, should be considered for PM2.5 monitoring.