Published papers

© 2020 Previous studies on haze formation focused mainly on the various chemical components in aerosol particles and their physicochemical effects on particle behaviour (e.g., generation, growth, and agglomeration). This paper describes the measurement of the charging state on atmospheric aerosol particles, which could be affected by meteorological conditions. A series of experiments on particle charging state and meteorological factors was undertaken on the roof of the west 4th building on the Qujiang Campus at Xi'an Jiaotong University (China). Measurements were conducted approximately 20 m above ground level. Our results showed that most atmospheric particles carried net negative or positive charge and that the electric charge on the particles varied diurnally and seasonally. The average amount of charge on particles was higher in winter than in summer. The number concentration of charged particles was higher during the day than overnight. Obvious difference in the average charge of aerosol particles was found between sand–dust days and haze days. A strong relationship was found between the PM2.5 concentration, charge amount on particles, and humidity. Our findings show that particle formation and growth could partly be attributed to variation in particle charging state, which is related to meteorological conditions including atmospheric humidity.

© 2019 Turkish National Committee for Air Pollution Research and Control We conducted a field study to characterize water-soluble ionic species in PM2.5 from peatland fires using ground-based samplings at fire sources and receptor sites in the Riau Province, Sumatra, Indonesia. We determined the concentrations of PM2.5 mass, water-soluble ions, and some chemical elements. Through PM2.5 field samplings at three peatland fire sources, we have shown that the mass fractions of typical peatland fire water-soluble ionic components tend to differ between peatland fire sources. Thus, our results indicate that PM2.5 source profiles of water-soluble ionic components for peatland fire must be selected with extreme caution if applied to a receptor model. From the viewpoint of ionic composition of each peatland fire sample, Cl− and NH4+ were consistently dominant anions and cations, respectively, for all peatland fire samples, i.e., NH4Cl was a consistently dominant component. Through field samplings of the ambient PM2.5 in Pekanbaru during peatland fire-induced haze and non-haze periods, we found differences in PM2.5 mass and total water-soluble ionic component concentrations between haze and non-haze samples. Four components, C2O42−, NO3−, SO42−, and NH4+, showed highly elevated levels during haze periods. Since these four ions are recognized as the major secondarily formed aerosol components, the increased total concentrations of water-soluble ionic components during haze periods can mainly be derived from the gas-to-aerosol conversion process. The ionic compositions of haze samples at receptor sites are obviously different from those at peatland fire source samples. In particular, NH4Cl, which is characteristic of peatland fire PM2.5 sources, is low at sites during haze periods.

© Taiwan Association for Aerosol Research. Recent studies have shown that air pollution is intense and hazardous in Asia compared to other parts of the world due to the late and poor implementation of updated technology in automobiles and industry as well as to the high population density. Respiratory disease, including asthma, is exacerbated by air pollution. However, the effects of PM2.5, especially on respiratory allergies in Asian cities, have not yet been examined in detail. In this study, airway epithelial cells were exposed to crude PM2.5 particles collected by cyclonic separation from three different Asian cities, namely, Sakai, Bangkok, and Taipei. We compared the cytotoxicity and inflammatory potential of the PM2.5 from these cities by measuring IL-6 and IL-8. The samples from Sakai and Bangkok caused cytotoxic effects at a dose of 75 µg mL–1 and, moreover, induced the release of IL-6 and IL-8 even at low doses. The release of these two interleukins was highly associated with fluoranthene derivatives, microbial factors (endotoxin and β-glucan), metals (e.g., Ti), and organic (OC2 and OC3) and elemental carbon (EC1) in the PM2.5. Thus, these components potentially contribute to cellular damage and a pro-inflammatory response in the airway epithelial cells, and the effect depends on PM2.5 sources in the locations.

The valence state and concentration of metallic pollutants are important factors contributing to the health effects of respirable particulate matter (PM); however, they have not been well studied. In this study, coarse and fine powder samples of atmospheric PM were collected using a cyclone system at Kanagawa (KO), Saitama (SA), and Fukuoka (FU) in Japan in 2017. Energy dispersive X-ray fluorescence spectroscopy (EDXRF) was used to measure the concentrations of nine metallic elements (Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, and Pb), and X-ray absorption fine structure (XAFS) spectroscopy was used to analyze the valence states of target elements (Cr, Mn, Fe, Cu, and Zn). The EDXRF results indicated that the average contents of Fe, Ti, and Zn were much higher than those of the other six elements in all samples. The XAFS results showed that the major valence states of the elements were Cr(III), Mn(II), Fe(III), Cu(II), and Zn(II). The percentages of Mn(IV), Fe(II), and Cu(0) were higher in KO and SA samples than in FU samples. Mn(0) and Zn(0) were detected in some samples only, and Cu(I) was not detected in any samples. Correlation analysis, principal component analysis, and cluster analysis were performed on the EDXRF and XAFS data of the target elements. The source identification results showed that the sources of metal contaminants in the samples varied considerably between sampling sites and depended on the industrial structure and geographical location of the sampling area. Our findings on the different valence states of the elements may be important for determining the toxicity of PM at different locations.

Dithiothreitol-measured oxidative potential (OPDTT) can chemically quantify the adverse health effects of atmospheric aerosols. Some chemical species are characterized with DTT activities, and the particle diameter and surface area control DTT oxidizability; however, the physical contribution to OPDTT by atmospheric aerosols is controversial. Therefore, we performed field observations and aerosol sampling at urban and rural sites in Japan to investigate the effect of both physical and chemical properties on the variation in OPDTT of atmospheric aerosols. The shifting degree of the representative diameter to the ultrafine range (i.e., the predominance degree of ultrafine parti-cles) was retrieved from the ratio between the lung-deposited surface area and mass concentrations. The chemical components and OPDTT were also elucidated. We discerned strong positive correlations of K, Mn, Pb, NH4+, SO42−, and pyrolyzable organic carbon with OPDTT. Hence, anthropogenic combustion, the iron–steel industry, and secondary organic aerosols were the major emission sources governing OPDTT variations. The increased specific surface area did not lead to the increase in the OPDTT of atmospheric aerosols, despite the existing relevance of the surface area of water-insoluble particles to DTT oxidizability. Overall, the OPDTT of atmospheric aerosols can be estimated by the mass of chemical components related to OPDTT variation, owing to numerous factors control-ling DTT oxidizability (e.g., strong contribution of water-soluble particles). Our findings can be used to estimate OPDTT via several physicochemical parameters without its direct measurement.

The 2020 Olympic/Paralympic Games have been postponed to 2021, due to the COVID-19 pandemic. We developed a model that integrated source–environment–receptor pathways to evaluate how preventive efforts can reduce the infection risk among spectators at the opening ceremony of Tokyo Olympic Games. We simulated viral loads of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emitted from infectors through talking/coughing/sneezing and modeled temporal environmental behaviors, including virus inactivation and transfer. We performed Monte Carlo simulations to estimate the expected number of newly infected individuals with and without preventive measures, yielding the crude probability of a spectator being an infector among the 60,000 people expected to attend the opening ceremony. Two indicators, i.e., the expected number of newly infected individuals and the newly infected individuals per infector entry, were proposed to demonstrate the extent of achievable infection risk reduction levels by implementing possible preventive measures. A no-prevention scenario produced 1.5–1.7 newly infected individuals per infector entry, whereas a combination of cooperative preventive measures by organizers and the spectators achieved a 99% risk reduction, corresponding to 0.009–0.012 newly infected individuals per infector entry. The expected number of newly infected individuals was calculated as 0.005 for the combination of cooperative preventive scenarios with the crude probability of a spectator being an infector of 1 × 10−5. Based on our estimates, a combination of cooperative preventions between organizers and spectators is required to prevent a viral spread at the Tokyo Olympic/Paralympic Games. Further, under the assumption that society accepts < 10 newly infected persons traced to events held during the entire Olympic/Paralympic Games, we propose a crude probability of infectors of < 5 × 10−5 as a benchmark for the suppression of the infection. This is the first study to develop a model that can assess the infection risk among spectators due to exposure pathways at a mass gathering event.

This study presents the results of designing a low-cost air sampler for multi-component analysis of PM2.5. We developed a multi-channel air sampling device using sonic venturi (critical nozzle) that supplies a constant airflow rate of 16.7 L/min. The constant flow rate is achieved with a backpressure ratio of 0.8 or less with a nozzle diameter of 1.375 mm. The sampler halves the cost of comparable devices and simplifies the hardware by replacing the flow meters with critical nozzles. For quantitative evaluation, we measured the coefficient of variation (CV) of each component simultaneously collected five samples at various particulate matter concentrations. This sampler can use different types of filters such as polytetrafluoroethylene and quartz fiber filter at the same time. Meteorological conditions such as ambient temperature, relative humidity and atmospheric pressure did not seem to affect much the flow rate of the sampler. The CV of multi sample analysis for TSP and PM2.5 concentrations in all sampling periods were less than 10%. CV of multi sample analysis for most of the major inorganic elements being within the range of 15% or less shows that the precision is sufficient for reliable measurement. We believe that the low-cost multiple air sampler will be used world-widely, and it can contribute to many researchers in both developed and developing countries.

We evaluated the effects of ambient particulate matter (PM) on the corneal epithelium using a reconstructed human corneal epithelium (HCE) model. We collected two PM size fractions [aerodynamic diameter smaller than 2.4 µm: PM0.3–2.4 and larger than 2.4 µm: PM>2.4] and exposed these tissues to PM concentrations of 1, 10, and 100 µg/mL for 24 h. After exposure, cell viability and interleukin (IL) IL-6 and IL-8 levels were determined, and haematoxylin and eosin and immunofluorescence staining of the zonula occludens-1 (ZO-1) were performed on tissue sections. In addition, the effects of a certified reference material of urban aerosols (UA; 100 µg/mL) were also examined as a reference. The viability of cells exposed to 100 μg/mL UA and PM>2.4 decreased to 76.2% ± 7.4 and 75.4% ± 16.1, respectively, whereas PM0.3–2.4 exposure had a limited effect on cell viability. These particles did not increase IL-6 and IL-8 levels significantly even though cell viability was decreased in 100 μg/mL UA and PM>2.4. ZO-1 expression was reduced in a dose-dependent manner in all groups. Reconstructed HCE could be used as an in vitro model to study the effects of environmental PM exposure on ocular surface cell viability and inflammation.

Fine particulate matter (PM2.5) exposure has a risk of inducing several health problems, especially in the respiratory tract. The skin is the largest organ of the human body and is therefore the primary target of PM2.5. In this study, we examined the effects of PM2.5 on the skin using a human 3-dimensional cultured epidermis model. PM2.5 was collected by cyclonic separation in Yokohama, Japan. Global analysis of 34 proteins released from the epidermis revealed that the chemokines, chemokine C-X-C motif ligand 1 (CXCL1) and interleukin 8 (IL-8), were significantly increased in response to PM2.5 exposure. These chemokines stimulated neutrophil chemotaxis in a C-X-C motif chemokine receptor 2-dependent manner. The oxidative stress and signal transducer and activator of transcription 3 pathways may be involved in the increased expression of CXCL1 and IL-8 in the human epidermis model. Interestingly, in the HaCaT human keratinocyte cell line, PM2.5 did not affect chemokine expression but did induce IL-6 expression, suggesting a different effect of PM2.5 between the epidermis model and HaCaT cells. Overall, PM2.5 could induce the epidermis to release chemokines, followed by neutrophil activation, which might cause an unregulated inflammatory reaction in the skin.

Cyclone sampling devices have been helpful in assessing the toxic effects of fine particulate matter (PM2.5). The particle collection efficiency of sampling devices is critical. This study investigated the effect of cyclone size on particle size, chemical composition, and particle toxicity. Three cyclones with different inner diameters (12-68 mm) were tested for penetration using an aerodynamic particle sizer, fluorescent polystyrene latex, and a differential mobility analyzer. The elemental and water-soluble ion compositions of the particles collected by different cyclones were compared. An evaluation of the particles’ toxicity was conducted by comparing the results of dithiothreitol (DTT), limulus amebocyte lysate (LAL), and cell exposure assays. The experimental evaluation showed a 50% cut-size of the cyclones between 0.17-0.28, 0.34-0.36, and 0.70 μm for the small, medium, and large cyclones, respectively. To collect PM2.5 and evaluate separation performance in the real environment, the small and large cyclones were selected according to the particle penetration and flow rate. A comparison of chemical composition and enrichment factor values found that the particles in the small cyclone samples contained smaller and more anthropogenic sources than those in the large cyclone samples. The oxidative potential (OP) measured by the DTT assay of the samples collected using the small and large cyclones differed across sampling periods and associated with the transition metals. The viability of human epithelial A549 cells after exposure to the collected particles using the cyclones was different across sampling periods and associated with OP. The endotoxin concentrations measured in the LAL assay were found only in the large cyclone samples; they affected the estimated level of cytokine based on IL(interleukin)-6 release from human leukemia monocytic (THP-1) cells derived macrophage like cells. Regardless of the size, the cyclone techniques used in this study to collect aerosol particles would be a powerful tool for a detailed evaluation of particle toxicity.

Experimental and epidemiological studies have demonstrated that fine particulate matter with a diameter of <2.5 μm (PM2.5) affects both the respiratory and immune systems. However, effective approaches to reduce PM2.5-induced hazardous effects have not been discovered yet. Streamer discharge is a category of plasma discharge in which high-speed electrons collide with oxygen and nitrogen molecules. Although streamer discharge can reportedly eliminate bacteria, molds, chemical substances, and allergens, its ability to decontaminate PM2.5 has not been previously demonstrated. The present study explored whether streamer discharge treatment could reduce PM2.5-induced inflammatory responses by employing an in vitro system. PM2.5 was collected under four conditions (Bangkok (Sep.–Dec.), Bangkok (Dec.–Mar.), Singapore, and Taipei). Airway epithelial cells and antigen-presenting cells exposed to non-treated PM2.5 in several conditions resulted in inflammatory responses. Streamer-discharged PM2.5 (Bangkok (Sep.–Dec.)) decreased the expression of interleukin (IL)-6 and IL-8 compared to non-treated PM2.5. Moreover, composition analysis demonstrated that streamer discharge reduced some compounds, such as endotoxins and polycyclic aromatic hydrocarbons, included in PM2.5 that can elicit inflammatory responses. Streamer discharge treatment can reduce endotoxins, polycyclic aromatic hydrocarbons, and the subsequent inflammatory responses induced by PM2.5 in vitro.

Atmospheric aerosols, including primary aerosols emitted directly into the atmosphere and secondary aerosols generated in the atmosphere from various chemically complex particles, cause a variety of environmental problems such as climate change, photochemical smog formation, and a decrease in incoming solar radiation. Therefore, it is important to understand the causes of aerosol particles and their impact on human society. In particular, particle size is an important indicator of lung penetration depth, aerosol transport, and optical properties. Hence, we mathematically estimated the airborne particle size distributions of each chemical component by collecting aerosol samples from the atmosphere using two types of cyclone samplers, large and small cyclone samplers. This study’s findings also suggest that calculated changes in particle size distribution can reflect changes in particle sources. The higher resolution of the continuous functions will enable the detection of the subtle changes in particle size distributions of each chemical component, which is helpful to understand the temporal changes in the chemical properties of the airborne aerosol particles.

Eggshell-based reversed-phase packing materials were applied to an analytical column for high-performance liquid chromatography. Commercially available eggshell powder was classified by a cyclone system to obtain three types of particles with different diameters (arithmetic mean ± standard deviation: 4.3 ± 3.8, 5.6 ± 3.3, and 9.5 ± 5.5 μm). Sedimentation separation removed tiny particles from each sample, resulting in particles with arithmetic means of 6.6 ± 5.5, 7.3 ± 4.5, and 10.2 ± 5.0 μm, respectively. The unclassified particles and three particle types treated with sedimentation separation were subsequently packed into analytical columns (150 mm × 4.6 mm I.D.), and their separation efficiencies were evaluated by comparing their height equivalent to a theoretical plate (HETP). The column without sedimentation separation exhibited the highest HETP, whereas the columns with sedimentation separation showed better separation efficiency and lower back pressure. The column with the best separation efficiency was applied for the separation of 10 alkylbenzenes and 5 steroids, and all peaks were observed with complete separation (peak resolution: RS > 1.5). Finally, the column was used for quantitative analysis of voriconazole, an azole antifungal agent, and imatinib, a first-generation molecularly targeted drug for cancer treatment, in spiked whole blood. Excellent accuracy (99.1-102.8%) and precision (0.6-1.9%) were observed for the spiked drugs and long-term stability (>3000 column volumes of mobile phase flow) indicated good applicability of the developed eggshell-based column as an analytical column for routine analyses of therapeutic drugs in blood.

Suspended particulate matter (PM) in subway premises contain high concentrations of metal components and distinctive compounds owing to their unique emission processes. However, little is known regarding the detailed chemical states of airborne PM and their biological effects. Therefore, to demonstrate the unique chemical states of the PM collected from subway premises and outdoors, this study compared the chemical speciation of iron (Fe) and copper (Cu) components using X-ray absorption fine structure analysis. The potential biological effects of these chemical states on humans were also investigated in vitro by assessing cell damage and its pathways in cells after exposure to several compounds. Compared with a reference outdoor PM sample, Fe was enhanced by at least 10 times in subway PM and the concentrations of several metal components, including Cu, contained in railway bodies, rail, overhead wires, and tunnel walls, also increased. In these chemical speciations, the compounds derived from wear processes with relatively high-temperature oxidation (Fe3O4, γ-Fe2O3, and monovalent Cu compounds) were detected among the Fe and Cu components in subway PM. Our cell-based bioassay suggested that the contribution of the Fe component to cell damage can be enhanced by the predominance of Fe3O4 in subway PM. In contrast to typical bivalent Cu compounds in the atmosphere, monovalent Cu compounds, which are characteristically identified in subway PM, exacerbate cell damage via different cell death pathways. Our results indicate that the chemical states of the distinctive compounds in the PM of subway premises differ from those in the typical atmosphere, thus exerting different biological effects. These findings suggest that the detailed chemical speciation is an important factor in accurately understanding their PM toxicities.

The chemical components and mechanisms underlying the toxicity and adverse health effects of particulate matter (PM) in the atmosphere have not been fully elucidated. After designing a small, openable, stainless steel cyclone to collect PM samples effectively in powder form for use in toxicological experiments, we evaluated its performance. We compared it with a commercially available aluminum cyclone of similar dimensions, but which is unopenable. The aerodynamic cutoff diameter of the openable cyclone was found by experimentation to be approximately 0.2 µm at a flow rate of 90 L min−1, which is comparable to the unopenable commercial cyclone. The sampling yields, representing the fraction of obtained sample mass relative to the total mass of PM with aerodynamic diameter smaller than 2.5 μm (PM2.5) drawn into the sampler, were approximately 1.3 times higher, on average, for the openable cyclone than for the unopenable cyclone. The openable design of the cyclone might contribute to a marked increase in the finally obtained amounts of PM samples. Analyses of metal concentrations in the PM samples collected simultaneously using the stainless steel openable cyclone and aluminum unopenable cyclone suggest that the stainless steel cyclone is less likely than the aluminum cyclone to cause sample contamination from its material. The openable cyclone developed for this study facilitates the effective collection of powder-form PM samples suitable for use in toxicological experiments.

Characteristics of the elemental composition were investigated for PM10 samples at four sites in Noumea, New Caledonia, where health effects due to nickel production activities such as mining and refining were concerned. The concentration of nickel in the aerosol sample collected in New Caledonia was approximately the same level in Japan while those of other elements were lower in comparing to Japan. Enrichment factor of nickel in aerosol in New Caledonia was approximately 250 which was about 20 times greater than that in Japan. The reasons for this were thought to be (1) influence of soil particles that have relatively higher nickel content from surrounding sampling site, and (2) influence of emission from nickel smelter near the sampling site; however, there was no clear evidence to prove them. Alternatively, the nickel-enriched particles, which were generated as a result of nickel production activities such as a refinement of laterite-nickel ore, could be contributed as a potential source of the aerosol in this area.

Total suspended particulates (TSP) samples were collected from Sep., 2003 to Jul., 2004 in Beijing, and 15 kinds of PAHs, ranging from 3 to 7 rings were analyzed. The maximum concentrations of ∑PAHs and BaP were 705 ng/m3 and 52 ng/m3 respectively. Average ∑PAHs concentrations in four seasons were 46 ng/m3, 16 ng/m3, 52ng/m3 and 268ng/m3 respectively; and the average BaP concentrations in four seasons were 2.8 ng/m3, 0.23 ng/m3, 3.3 ng/m3, 16 ng/m3 respectively. Regarding to the meteorological parameters, precipitation distinctly lowered the concentration in heating period; PAHs concentrations fall when the temperature goes up in non-heating period, but there is no obvious relation between concentration and temperature in heating period; the increase of wind speed level causes the decrease of PAH concentrations in the heating period, but relation between PAH concentrations and wind speed varied with aromatic rings of PAHs and levels of wind speed in the non-heating period.

To understand the chemical composition and temporal variations of precipitation in Beijing, one-week integrated dry deposition samples were collected for more than four years. Among 222 dry deposition samples, there existed more or less anion deficits. SO42- and Ca2+ were the most abundant anion and cation, followed by NO3- and NH4+, respectively. SO42-,NO3- and NH4+ exhibited similar seasonal pattern, with higher and lower concentrations occurring in summer and winter, respectively. Dry deposition samples usually appeared neutral, with narrow variations in their monthly averages but an evident seasonal pattern, i.e., lower level in summer and higher level in spring.

Several empirical studies have linked subway and ambient particle exposure to toxicity, pro-inflammatory responses, and vascular dysfunction. However, the health effects of pollutants generated from varying sources, particularly when combined with lipopolysaccharide (LPS), are still unexplored. Therefore, the aim of this study was to investigate the characteristic health effects of iron oxide particles (the main components of subway particles) in comparison with urban aerosols (UA) and vehicle exhaust particles (VEP), alone and in combination with LPS. This study revealed that iron oxides caused a more significant reduction in human umbilical vein endothelial cell viability, increased lactate dehydrogenase release, and decreased the production of plasminogen activator inhibitor-1, a fibrinolytic modulator, and endothelin-1, a vasoconstrictor, compared to those by VEP and UA at marginally toxic and toxic concentrations. While VEP and UA induced an increase in interleukin (IL)-6 production, iron oxides, particularly Fe3O4, increased IL-8 production at slightly toxic and non-cytotoxic concentrations. In addition, co-exposure of all particles and LPS at non-cytotoxic concentrations promoted pro-inflammatory cytokine (IL-6 and IL-8) production relative to exposure to the particles alone. Interestingly, the tendency towards either coagulation or fibrinolytic conditions was dependent on the concentration of exposed particles at the same LPS concentration. Furthermore, increases in inflammation, neutrophil and lymphocyte recruitment around blood vessels, and edema were observed in murine lungs exposed to a combination of iron oxides and LPS compared to those in mice exposed to iron oxide alone. Thus, iron oxide-rich subway particulate poses more health risks than outdoor ambient particles since they can significantly impair endothelial function, particularly through gross cellular and vascular homeostatic protein damage, and induce exacerbated inflammatory responses during co-exposure. These findings provide novel empirical evidence for epidemiological studies seeking mechanisms responsible for the observed health impact of transport- and occupational-related exposures on vascular dysfunction.