Development of Nano-Sized Copper-Deposited Antimicrobial Air Filters Using a Mixed Melt-Blown Process.

Air purification devices, such as air purifiers, provide fresh air by filtering out airborne pollutants, dust, and other harmful substances using various filter systems. While air filters are generally effective in filtering pollutants such as dust, they encounter a challenge when filtering harmful microorganisms such as mites, bacteria, mold, and viruses. These microorganisms, which are present in public transport and public indoor spaces, tend to proliferate on the surface of the filter media, eventually reintroducing themselves into the air or causing unpleasant odors. To address this issue, herein, copper particles were prepared as one masterbatch and deposited on polypropylene (PP) pellets through plasma vacuum deposition to effectively filter dust and microorganisms and prevent their growth on the surface of the filter media. After adding 3-10 wt.% of the masterbatch to conventional PP pellets to fabricate a filter media, the distribution of copper on the surface of the filter media was observed through a scanning electron microscope. To verify the safety and effectiveness of the antimicrobial material, the filter media containing antimicrobial particles was tested using Escherichia coli (E. coli) and Staphylococcus aureus through a filter emission test.

Accurate measurements of particle emissions from a three-dimensional printer using a chamber test with a mixer-installed sampling system.

Recently, three-dimensional (3D) printing has attracted attention as a new manufacturing technology. However, there is lack of data and regulations regarding the emissions of ultrafine particles from 3D printers. Therefore, we investigated particle emissions from a 3D printer using a chamber system. The test system was improved by installing a developed mixer for accurate measurement. Without a mixer, the particle concentration was unstable depending on the sampling point; however, reliable data with good uniformity were obtained by installing a mixer. Using the test system with a mixer, we investigated particle emissions from a 3D printer during operation. Filaments made each of acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) were used as the printing material. The effects of nozzle temperature and printing time were investigated. Compared to the effect of the printing time, the nozzle temperature had greater impact on the particle emissions. The dominant particle size for the emissions from a 3D printer is less than 10 nm, and the particle concentration decreased with increasing particle size.

Estimate of the critical exposure time based on 70 confirmed COVID-19 cases.

The transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) occurs via contact with contaminated surfaces and inhalation of large airborne droplets and aerosols. As growing evidence of airborne SARS-CoV-2 transmission has been reported worldwide, ventilation is an effective method of reducing the infection probability of SARS-CoV-2. This leads to such questions as "What is a sufficient ventilation rate for avoiding the risk of COVID-19 infection?" Therefore, this study evaluates the critical ventilation rates according to room size and exposure time when a susceptible person is in the same room as an infector. The analytical results were based on data obtained from 70 confirmed COVID-19 cases transmitted in confined spaces without an operational ventilation system. The results reveal that even with active ventilation (20 h-1 air exchange rate), the critical exposure time for a susceptible person with a COVID-19 infector in a small space of 20 m3 is less than 1 h. For other cases (different space sizes), the estimated air exchange rates for avoiding the risk of infection are generally higher than various requirements for good indoor air quality. The findings of this study will provide guidelines for determining sufficient ventilation rates to protect against the highly contagious COVID-19.

Application of an aerosol electrical mobility spectrum analyzer: Charged-particle polarity ratio measurement in the Antarctic and Arctic regions.

An aerosol electrical mobility spectrum analyzer (AEMSA), developed at Hanyang University, was employed to investigate the particle charge characteristics in the Antarctic and Arctic regions. The particle charge characteristics in these areas were compared with the charging state in Ansan, South Korea, located in the midlatitude, where artificial factors, such as human activity, urbanization, and traffic, might result in a higher total concentration. Furthermore, in Ansan, South Korea, the charged-particle polarity ratio was very stable and was close to 1. However, notably different particle charge characteristics were obtained in the Antarctic and Arctic regions. The imbalance between the numbers of positively and negatively charged particles was evident, resulting in more positive charges on the atmospheric particles. On average, the positively charged particle concentrations in the Antarctic and Arctic areas were 1.4 and 2.8 times higher, respectively, compared with the negatively charged particles. The developed AEMSA system and the findings of this study provide useful information on the characteristics of atmospheric aerosols in the Antarctic and Arctic regions and can be further utilized to study particle formation mechanisms.

Using miniaturised scanning mobility particle sizers to observe size distribution patterns of quasi-ultrafine aerosols inhaled during city commuting.

Portable miniaturised scanning mobility particle sizer (SMPS) instruments measuring atmospheric particles within the 10-241 nm size range were used to track particle number size distributions and concentrations during near-simultaneous pedestrian, bicycle, bus, car, tram and subway commuting journeys in Barcelona, Spain on 4th-6th July 2018. The majority of particles in this size range were <100 nm, with k-means cluster analysis identifying peaks at 15-22 nm, 30-40 nm, and 45-75 nm. Around 10-25% of the particles measured however were >100 nm (especially in the subway environment) and so lie outside the commonly defined range of "ultrafine" particles (UFP, or <100 nm particles). The study demonstrated in detail how personal exposure to quasi-UFP (QUFP, <241 nm), most of which present in the city streets are produced by road traffic, varies greatly depending on the transport mode and route chosen. Proximity to fresh traffic exhaust sources, such as in a car with open windows, on-road cycling, walking downwind of busy roads, or in a subway station contaminated by roadside air, enhances commuter exposure to particles <30 nm in size. In contrast, travelling inside air-conditioned bus or tram offers greater protection to the commuter from high concentrations of fresh exhaust. Ultrafine number size distributions in traffic-contaminated city air typically peak in the size range 30-70 nm, but they can be shifted to finer sizes not only by increased content of fresh proximal exhaust emissions but also by bursts of new particle formation (NPF) events in the city. One such afternoon photochemical nucleation NPF event was identified during our Barcelona study and recognised in different transport modes, including underground in the subway system. The integration of static urban background air monitoring station information with particle number concentration and size distribution data obtained from portable miniaturised SMPS instruments during commuting journeys opens new approaches to investigating city air quality by offering a level of detail not previously available.

Extensive evaluation and classification of low-cost dust sensors in laboratory using a newly developed test method.

An extensive evaluation of low-cost dust sensors was performed using an exponentially decaying particle concentration. A total of 264 sensors including 27 sensors with light-emitting diodes (LEDs) and 237 sensors with laser lighting sources were tested. Those tested sensors were classified into 4 groups based on the deviation from the reference data obtained by a reference instrument. The response linearities of all the tested samples for PM1 , PM2.5 , and PM10 were in excellent agreement with the reference instrument, except a few samples. For the measurements of PM1 and PM2.5 , the lighting source, that is, LED or laser, did not show any significant difference in overall sensor performance. However, LED-based sensors did not perform well for PM10 measurements. The 32, 24, and 16% of all the tested sensors for PM1 , PM2.5 , and PM10 measurement, respectively, are in the category of Class 1 (reference instrument reading ± 20%) requirement. The performance of the low-cost dust sensors for PM10 measurement was relatively less satisfactory.

Measurements of atmospheric aerosol vertical distribution above North China Plain using hexacopter.

In this study, a novel setup was developed to measure the vertical profile of particle number size distribution (PNSD) and meteorological parameters by using hexacopter equipped with a portable instrument package including a custom-built scanning mobility particle sizer, an optical particle counter and temperature and relative humidity (RH) sensors. By using this setup, a field experiment was carried out to investigate the vertical profiles of RH, temperature, PNSD ranged from 8 to 245 nm, and particle number concentration with the diameter ranges of 0.3-0.5 µm and 0.5-1.0 µm from the ground up to 300 m above ground level in a rural site of the North China Plain. New particle formation (NPF) event in a vertical scale was observed during the daytime cruises. The newly formed particles showed a heterogeneous vertical distribution, indicating the inhomogeneous occurrence of the NPF event vertically. During the daytime, the vertical variations in number concentration of particles larger than 0.3 µm was not obvious, while, showed a tendency to decrease associated with the increasing altitude in the evening. The newly-developed unmanned aerial vehicle research platform could be applied to study the vertical NPF events and transport processes of air pollutants within the atmospheric boundary layer and urban canopy, and to monitor source emissions with the purpose of environment management.

Short-term inhalation study of graphene oxide nanoplates.

Graphene oxides possess unique physicochemical properties with important potential applications in electronics, pharmaceuticals, and medicine. However, the toxicity following inhalation exposure to graphene oxide has not yet been clarified. Therefore, this study conducted a short-term graphene oxide inhalation toxicity analysis using a nose-only inhalation exposure system and male Sprague-Dawley rats. A total of four groups (15 rats per group) were exposed: (1) control (fresh air), (2) low concentration (0.76 ± 0.16 mg/m3), (3) moderate concentration (2.60 ± 0.19 mg/m3), and (4) high concentration (9.78 ± 0.29 mg/m3). The rats were exposed to graphene oxide for 6 h/day for 5 days, followed by recovery for 1, 3, and 21 days. No significant body or organ weight changes were noted after the short-term exposure or during the recovery period. Similarly, no significant systemic effects of toxicological importance were noted in the hematological assays, bronchoalveolar lavage fluid (BAL) inflammatory markers, BAL fluid cytokines, or blood biochemical assays following the graphene oxide exposure or during the post-exposure observation period. Moreover, no significant differences were observed in the BAL cell differentials, such as lymphocytes, macrophages, or polymorphonuclear cells. Graphene oxide-ingested alveolar macrophages as a spontaneous clearance reaction were observed in the lungs of all the concentration groups from post 1 day to post 21 days. Histopathological examination of the liver and kidneys did not reveal any significant test-article-relevant histopathological lesions. Importantly, similar to previously reported graphene inhalation data, this short-term nose-only inhalation study found only minimal or unnoticeable graphene oxide toxicity in the lungs and other organs.

Testing of Nanoparticle Release from a Composite Containing Nanomaterial Using a Chamber System.

With the rapid development of nanotechnology as one of the most important technologies in the 21st century, interest in the safety of consumer products containing nanomaterials is also increasing. Evaluating the nanomaterial release from products containing nanomaterials is a crucial step in assessing the safety of these products, and has resulted in several international efforts to develop consistent and reliable technologies for standardizing the evaluation of nanomaterial release. In this study, the release of nanomaterials from products containing nanomaterials is evaluated using a chamber system that includes a condensation particle counter, optical particle counter, and sampling ports to collect filter samples for electron microscopy analysis. The proposed chamber system is tested using an abrasor and disc-type nanocomposite material specimens to determine whether the nanomaterial release is repeatable and consistent within an acceptable range. The test results indicate that the total number of particles in each test is within 20% from the average after several trials. The release trends are similar and they show very good repeatability. Therefore, the proposed chamber system can be effectively used for nanomaterial release testing of products containing nanomaterials.

Three-Day Continuous Exposure Monitoring of CNT Manufacturing Workplaces.

Continuous monitoring for possible exposure to carbon nanotubes was conducted over a period of 2 to 3 days at workplaces that manufacture multiwall carbon nanotubes (MWCNTs) and single wall carbon nanotubes (SWCNTs). To estimate the potential emission of carbon nanotubes (CNTs) and potential exposure of workers, personal sampling, area monitoring, and real-time monitoring using an scanning mobility particle sizer (SMPS) and dust monitor were conducted at workplaces where the workers manufactured CNTs. The personal and area sampling of the total suspended particulate (TSP) at the MWCNT manufacturing facilities ranged from 0.031 to 0.254 and from N.D (not detected) to 0.253 mg/m(3), respectively. This 2- to 3-day monitoring study found that nanoparticles were released when opening the chemical vapor deposit (CVD) reactor door after the synthesis of MWCNTs, when transferring the MWCNTs to containers and during blending and grinding. However, distinguishing the background concentration from the work process particle emission was complicated due to sustained and even increased particle concentrations after the work processes were terminated. The MWCNTs sampled for transmission electron microscopy (TEM) observation exhibited a tangled shape with no individual dispersed CNT structures.

In vivo genotoxicity evaluation of lung cells from Fischer 344 rats following 28 days of inhalation exposure to MWCNTs, plus 28 days and 90 days post-exposure.

Despite their useful physico-chemical properties, carbon nanotubes (CNTs) continue to cause concern over occupational and human health due to their structural similarity to asbestos. Thus, to evaluate the toxic and genotoxic effect of multi-wall carbon nanotubes (MWCNTs) on lung cells in vivo, eight-week-old rats were divided into four groups (each group = 25 animals), a fresh air control (0 mg/m(3)), low (0.17 mg/m(3)), middle (0.49 mg/m(3)), and high (0.96 mg/m(3)) dose group, and exposed to MWCNTs via nose-only inhalation 6 h per day, 5 days per week for 28 days. The count median length and geometric standard deviation for the MWCNTs determined by TEM were 330.18 and 1.72 nm, respectively, and the MWCNT diameters ranged from 10 to 15 nm. Lung cells were isolated from five male and five female rats in each group on day 0, day 28 (only from males) and day 90 following the 28-day exposure. The total number of animals used was 15 male and 10 female rats for each concentration group. To determine the genotoxicity of the MWCNTs, a single cell gel electrophoresis assay (Comet assay) was conducted on the rat lung cells. As a result of the exposure, the olive tail moments were found to be significantly higher (p < 0.05) in the male and female rats from all the exposed groups when compared with the fresh air control. In addition, the high-dose exposed male and middle and high-dose exposed female rats retained DNA damage, even 90 days post-exposure (p < 0.05). To investigate the mode of genotoxicity, the intracellular reactive oxygen species (ROS) levels and inflammatory cytokine levels (TNF-α, TGF- ß, IL-1, IL-2, IL-4, IL-5, IL-10, IL-12 and IFN-γ) were also measured. For the male rats, the H2O2 levels were significantly higher in the middle (0 days post-exposure) and high- (0 days and 28 days post-exposure) dose groups (p < 0.05). Conversely, the female rats showed no changes in the H2O2 levels. The inflammatory cytokine levels in the bronchoalveolar lavage (BAL) fluid did not show any statistically significant difference. Interestingly, the short-length MWCNTs deposited in the lung cells were persistent at 90 days post-exposure. Thus, exposing lung cells to MWCNTs with a short tube length may induce genotoxicity.

Evaluation of newly developed nose-only inhalation exposure chamber for nanoparticles.

In this study, a direct-flow-type nose-only exposure chamber developed for inhalation toxicity experiments using a numerical analysis and experiments is evaluated. Maintaining a uniform flow rate and test article concentration are the critical factors when designing an inhalation exposure chamber. Therefore, this study evaluated whether the flow rate and particle size distribution at the injection nozzles at each port could be maintained with a deviation below 10%. To achieve this requirement, a nose-only exposure chamber flow field was simulated using a numerical analysis method, i.e. computational fluid dynamics (CFD) code FLUENT 6.3.26. Based on the simulation results, a test chamber was built and tested. The flow velocity was measured at the injection nozzle of the chamber and the aerosol particle size distribution was also measured at each port while inserting the test material into the exposure chamber. The results indicated that a uniform flow field distribution at each stage and port, the deviation of the flow velocity, and particle size distribution were all within 10%. Thus, the resulting nose-only exposure chamber could be described as well-designed.

Persistent DNA damage measured by comet assay of Sprague Dawley rat lung cells after five days of inhalation exposure and 1 month post-exposure to dispersed multi-wall carbon nanotubes (MWCNTs) generated by new MWCNT aerosol generation system.

Carbon nanotubes (CNTs) have specific physico-chemical properties that are useful for the electronics, automotive, and construction industries. Yet, despite their many advantages, there is a current lack of available information on the human health and environmental hazards of CNTs. For this reason, the current study investigated the inhalation toxicity potential of multiwall CNTs (MWCNTs). Eight-week-old rats were divided into four groups (10 rats in each group), the fresh-air control (0mg/m(3)), low-concentration group (0.16mg/m(3)), middle-concentration group (0.34mg/m(3)), and high-concentration group (0.94mg/m(3)), and the whole body was exposed to MWCNTs for 5 days (6h/day). Lung cells were then isolated from five rats in each group on day 0 and 1 month after the 5-day exposure, respectively. The MWCNTs were generated by a newly designed generation system, and the MWCNT concentrations in the exposure chambers monitored in accordance with National Institute for Occupational Safety and Health (NIOSH) 0500 using a membrane filter. The MWCNTs were also sampled for an elemental carbon concentration analysis using a glass filter. The animals exhibited no significant body weight changes, abnormal clinical signs, or mortality during the experiment. A single-cell gel electrophoresis assay (Comet assay) was conducted to determine the DNA damage in lung cells obtained from the right lung. As a result, the Olive tail moments were 23.00±1.76, 30.39±1.96, 22.96±1.26, and 33.98±2.21 for the control, low-, middle-, and high-concentration groups, respectively, on day 0 postexposure. Meanwhile, 1 month postexposure, the Olive tail moments were 25.00±2.71, 28.39±3.55, 22.56±1.36, and 31.97±3.16 for the control, low-, middle-, and high-concentration groups, respectively. Thus, the MWCNTs caused a statistically significant increase in lung DNA damage at high concentration (0.94mg/m(3)) when compared with the negative control group on day 0 and 1 month postexposure.

Outbreak of bioaerosols with continuous use of humidifier in apartment room.

The effect of continuous humidifier use on the bioaerosol concentration in an indoor environment was investigated. An ultrasonic humidifier was operated for 10 hr per day for 15 days in an apartment room. During this time period, viable bioaerosol samples were taken using a single-stage Andersen sampler containing culture media plates for bacteria and fungi. The culture plates were then incubated at room temperature for 2~7 days depending on the media. The counts for the air sample plates were corrected for multiple impactions using the positive hole conversion method and are reported as the colony forming units per cubic meter of air (CFU/m(3)). While the bacterial concentration measured using the tryptic soy agar (TSA) did not show any significant change during the first 3 days, the concentration increased from the 6(th) day (6979 CFU/m(3)) and reached a maximum on the 9(th) day (46431 CFU/m(3)). The concentration then decreased to 2470 CFU/m(3) on the 12(th) day, at which point the fungal concentration increased rapidly to 14424~16038 CFU/m(3). Also, while the fungal concentration showed a significant change until the 9(th) day of humidifier use, fungal growth was observed on the wallpaper and increased rapidly from the 12(th) day. However, the bacterial concentration increased rapidly after the fungi were removed by remediation. The major fungal species identified in the samples were Penicillium representing 34%, Aspergillus representing 31%, Cladosporium representing 24%, and Alternaria representing 1%. The results also indicated that a relative humidity over 80% was easily achieved with continuous humidifier use. Yet, maintaining a high humidity in a room can cause a rapid outbreak of microbial growth.

Single-particle characterization of summertime Antarctic aerosols collected at King George Island using quantitative energy-dispersive electron probe X-ray microanalysis and attenuated total reflection Fourier transform-infrared imaging techniques.

Single-particle characterization of Antarctic aerosols was performed to investigate the impact of marine biogenic sulfur species on the chemical compositions of sea-salt aerosols in the polar atmosphere. Quantitative energy-dispersive electron probe X-ray microanalysis was used to characterize 2900 individual particles in 10 sets of aerosol samples collected between March 12 and 16, 2009 at King Sejong Station, a Korean scientific research station located at King George Island in the Antarctic. Two size modes of particles, i.e., PM(2.5-10) and PM(1.0-2.5), were analyzed, and four types of particles were identified, with sulfur-containing sea-salt particles being the most abundant, followed by genuine sea-salt particles without sulfur species, iron-containing particles, and other species including CaCO(3)/CaMg(CO(3))(2), organic carbon, and aluminosilicates. When a sulfur-containing sea-salt particle showed an atomic concentration ratio of sulfur to sodium of >0.083 (seawater ratio), it is regarded as containing nonsea-salt sulfate (nss-SO(4)(2-)) and/or methanesulfonate (CH(3)SO(3)(-)), which was supported by attenuated total reflection Fourier transform-infrared imaging measurements. These internal mixture particles of sea-salt/CH(3)SO(3)(-)/SO(4)(2-) were very frequently encountered. As nitrate-containing particles were not encountered, and the air-masses for all of the samples originated from the Pacific Ocean (based on 5-day backward trajectories), the oxidation of dimethylsulfide (DMS) emitted from phytoplanktons in the ocean is most likely to be responsible for the formation of the mixed sea-salt/CH(3)SO(3)(-)/SO(4)(2-) particles.

Exposure assessment of workplaces manufacturing nanosized TiO2 and silver.

With the increased production and widespread use of nanomaterials, human and environmental exposure to nanomaterials is inevitably increasing. Therefore, this study monitored the possible exposure to nanoparticles at workplaces that manufacture nano-TiO(2) and nano-silver. To estimate the potential exposure of workers, personal sampling, area monitoring, and real-time monitoring using a scanning mobility particle sizer (SMPS) and dust monitor were conducted at workplaces where the workers handle nanomaterials. The gravimetric concentrations of TiO(2) ranged from 0.10 to 4.99 mg/m(3), which were lower than the occupational exposure limit 10 mg/m(3) set by the Korean Ministry of Labor or American Conference of Governmental Industrial Hygienists (ACGIH). Meanwhile, the silver metal concentrations ranged from 0.00002 to 0.00118 mg/m(3), which were also lower than the silver dust 0.1 mg/m(3) and silver soluble compound 0.01 mg/m(3) occupational exposure limits set by the ACGIH. The particle number concentrations at the nano-TiO(2) manufacturing workplaces ranged from 11,418 to 45,889 particles/cm(3) with a size range of 15-710.5 nm during the reaction, although the concentration decreased to 14,000 particles/cm(3) when the reaction was stopped. The particle concentrations at the TiO(2) manufacturing workplaces increased during the reactor and vacuum pump operations, and during the collection of the synthesized TiO(2) particles. Similarly, the particle concentrations at the silver nanoparticle manufacturing workplaces increased when the sodium citrates were weighed or reacted with the silver nitrates, and during the cleaning of the workplace. The number of silver nanoparticles in the samples obtained from the workplace manufacturing silver nanoparticles using induced coupled plasma ranged from 57,789 to 2,373,309 particles/cm(3) inside the reactor with an average size of 20-30 nm and 535-25,022 particles/cm(3) with a wide range of particle sizes due to agglomeration or aggregation after the release of nanoparticles into the workplace air. In contrast, the silver nanoparticles manufactured by the wet method ranged from 393 to 3526 particle/cm(3) with an average size of 50 nm. Thus, when taken together, the TiO(2) and silver nanoparticle concentrations were relatively lower than existing occupational exposure limits.

Multi-Walled Carbon Nanotube (MWCNT) Dispersion and Aerosolization with Hot Water Atomization without Addition of Any Surfactant.

OBJECTIVES: Carbon nanotubes are an important new class of technological materials that have numerous novel and useful properties. Multi-walled carbon nanotubes (MWCNTs), which is a nanomaterial, is now in mass production because of its excellent mechanical and electrical properties. Although MWCNTs appear to have great industrial and medical potential, there is little information regarding their toxicological effects on researchers and workers who could be exposed to them by inhalation during the handling of MWCNTs. METHODS: The generation of an untangled MWCNT aerosol with a consistent concentration without using surfactants that was designed to be tested in in vivo inhalation toxicity testing was attempted. To do this, MWCNTs were dispersed in deionized water without the addition of any surfactant. To facilitate the dispersion of MWCNTs in deionized water, the water was heated to 40℃, 60℃, and 80℃ depending on the sample with ultrasonic sonication. Then the dispersed MWCNTs were atomized to generate the MWCNT aerosol. After aerosolization of the MWCNTs, the shapes of the NTs were examined by transmission electron microscopy. RESULTS: The aerosolized MWCNTs exhibited an untangled shape and the MWCNT generation rate was about 50 mg/m(3). CONCLUSION: Our method provided sufficient concentration and dispersion of MWNCTs to be used for inhalation toxicity testing.

Toxicity and clearance of intratracheally administered multiwalled carbon nanotubes from murine lung.

Carbon nanotubes (CNT) are known to have widespread industrial applications; however, several reports indicated that these compounds may be associated with adverse effects in humans. In this study, multiwalled carbon nanotubes were administered to murine lungs intratracheally to determine whether acute and chronic pulmonary toxicity occurred. In particular, pristine multiwalled carbon nanotubes (PMWCNT) and acid-treated multiwalled carbon nanotubes (TMWCNT) were used in this study. In broncheoalveolar lavage fluid (BALF) cell analysis, PMWCNT induced more severe acute inflammatory cell recruitment than TMWCNT. Histopathologically, both PMWCNT and TMWCNT induced multifocal inflammatory granulomas in a dose-dependent manner. The observed granulomas were reversible, with TMWCNT-induced granulomas diminishing faster than PMWCNT-induced granulomas. Although the area of granuloma reduced with time, hyperplasia and dysplastic characteristics such as mitotic figures, anisokaryosis, and anisocytosis were still observed. These findings demonstrate that MWCNT induces granulomatous inflammation, and the duration and pattern of inflammation seem to vary depending upon the types of MWCNT to which mice are exposed. Therefore, toxicity studies on various types of CNT are needed as the responsiveness to these compounds differs.

Combined use of optical and electron microscopic techniques for the measurement of hygroscopic property, chemical composition, and morphology of individual aerosol particles.

In this work, an analytical method for the characterization of the hygroscopic property, chemical composition, and morphology of individual aerosol particles is introduced. The method, which is based on the combined use of optical and electron microscopic techniques, is simple and easy to apply. An optical microscopic technique was used to perform the visual observation of the phase transformation and hygroscopic growth of aerosol particles on a single particle level. A quantitative energy-dispersive electron probe X-ray microanalysis, named low-Z particle EPMA, was used to perform a quantitative chemical speciation of the same individual particles after the measurement of the hygroscopic property. To validate the analytical methodology, the hygroscopic properties of artificially generated NaCl, KCl, (NH(4))(2)SO(4), and Na(2)SO(4) aerosol particles of micrometer size were investigated. The practical applicability of the analytical method for studying the hygroscopic property, chemical composition, and morphology of ambient aerosol particles is demonstrated.

Single-particle characterization of summertime arctic aerosols collected at Ny-Alesund, Svalbard.

Single-particle characterization of summertime Arctic aerosols is useful to understand the impact of air pollutants on the polar atmosphere. In the present study, a quantitative single particle analytical technique, low-Z particle electron probe X-ray microanalysis, was used to characterize 8100 individual particles overall in 16 sets of aerosol samples collected at Ny-Alesund, Svalbard, Norway on 25-31 July, 2007. Based on their X-ray spectral and secondary electron image data of individual particles, 13 particle types were identified, in which particles of marine origin were the most abundant, followed by carbonaceous and mineral dust particles. A number of aged (reacted) sea salt (and mixture) particles produced by the atmospheric reaction of genuine sea-salts, especially with NO(x) or HNO(3), were significantly encountered in almost all the aerosol samples. They greatly outnumbered genuine sea salt particles, implying that the summertime Arctic atmosphere, generally regarded as a clean background environment, is disturbed by anthropogenic air pollutants. The main sources of airborne NO(x) (or HNO(3)) are probably ship emissions around the Arctic Ocean, industry emission from northern Europe and northwestern Siberia, and renoxification of NO(3)(-) within or on the melting snow/ice surface.