Characterization Of Ultrafine Particles Research Articles

Cytotoxicity and Characterization of Ultrafine Particles from Desktop Three-Dimensional Printers with Multiple Filaments.

Previous research has indicated that ultrafine particles (UFPs, particles less than 100 nm) emitted from desktop three-dimensional (3D) printers exhibit cytotoxicity. However, only a limited number of particles from different filaments and their combinations have been tested for cytotoxicity. This study quantified the emissions of UFPs from a commercially available filament extrusion desktop 3D printer using three different filaments, including acrylonitrile butadiene Styrene (ABS), thermoplastic polyurethane (TPU), and polyethylene terephthalate glycol (PETG). In this study, controlled experiments were conducted where the particles emitted were used to expose cells grown in an air-liquid interface (ALI) system. The ALI exposures were utilized for in vitro characterization of particle mixtures, including UFPs from a 3D printer. Additionally, a lactate dehydrogenase (LDH) assay was used to evaluate the cytotoxic effects of these UFPs. A549 cells were exposed at the ALI to UFPs generated by an operational 3D printer for an average of 45 and 90 min. Twenty-four hours post-exposure, the cells were analyzed for percent cytotoxicity in a 24-well ALI insert (LDH assay). UFP exposure resulted in diminished cell viability, as evidenced by significantly increased LDH levels. The findings demonstrate that ABS has the most significant particle emission. ABS was the only filament that showed a significant difference compared to the high efficiency particulate arrestance (HEPA) following 90 min of exposure (p-value < 0.05). Both ABS and PETG exhibited a significant difference compared to the HEPA control after 45 min of exposure. A preliminary analysis of potential exposure to these products in a typical environment advises caution when operating multiple printer and filament combinations in poorly ventilated spaces or without combined gas and particle filtration systems.

Characterization of ultrafine particles and the occurrence of new particle formation events in an urban and coastal site of the Mediterranean area

Abstract. In this work, new particle formation events (NPFs) occurring at two locations in southern Italy, the urban background site of Lecce (ECO station) and the coastal site of Lamezia Terme (LMT station), are identified and analyzed. The study aims to compare the properties of NPF events at the two sites, located 225 km away from each other and characterized by marked differences in terms of emission sources and local weather dynamics. Continuous measurements of particle number size distributions, in the size range from 10 to 800 m, were performed at both sites by a mobility particle size spectrometer (MPSS). The occurrence of NPF events, observed throughout the study period that lasted 5 years, produced different results in terms of frequency of occurrence: 25 % of the days at ECO and 9 % at LMT. NPF events showed seasonal patterns: higher frequency during spring and summer at the urban background site and the autumn–winter period at the coastal site. Some of these events happened simultaneously at both sites, indicating the occurrence of the nucleation process on a large spatial scale. Cluster analysis of 72 h back trajectories showed that during the NPF events the two stations were influenced by similar air masses, most of which originated from the north-western direction. Local meteorological conditions characterized by high pressure, with a prevalence of clear skies, low levels of relative humidity (RH &lt; 52 %), and moderate winds (3–4 m s−1) dominated the NPF events at both sites. Notable differences were observed in SO2 and PM2.5 concentrations and H2SO4 proxy levels, resulting in ∼65 %, ∼80 %, and 50 % lower levels at LMT compared to ECO, respectively. It is likely that the lower level of that which is recognized as one of the main gas precursors involved in the nucleation process could be responsible for the smaller NPF frequency of occurrence (∼60 % less than ECO) observed in LMT.

Characterization of ultrafine particles from hardfacing coated brake rotors

Automotive brake rotors are commonly made from gray cast iron (GCI). During usage, brake rotors are gradually worn off and periodically replaced. Currently, replaced brake rotors are mostly remelted to produce brand-new cast iron products, resulting in a relatively high energy consumption and carbon footprint into the environment. In addition, automotive brakes emit airborne particles. Some of the emitted particles are categorized as ultrafine, which are sized below 100 nm, leading to a series of health and environmental impacts. In this study, two surface treatment techniques are applied, i.e., high-velocity oxygen fuel (HVOF) and laser cladding (LC), to overlay wear-resistant coatings on conventional GCI brake rotors in order to refurbish the replaced GCI brake rotor and to avoid the remelting procedure. The two coating materials are evaluated in terms of their coefficient of friction (CoF), wear, and ultrafine particle emissions, by comparing them with a typical GCI brake rotor. The results show that the CoF of the HVOF disc is higher than those of the GCI and LC discs. Meanwhile, HVOF disc has the lowest wear rate but results in the highest wear rate on the mating brake pad material. The LC disc yields a similar wear rate as the GCI disc. The ultrafine particles from the GCI and LC discs appeared primarily in round, chunky, and flake shapes. The HVOF disc emits unique needle-shaped particles. In the ultrafine particle range, the GCI and HVOF discs generate particles that are primarily below 100 nm in the running-in period and 200 nm in the steady state. Meanwhile, the LC disc emitted particles that are primarily ∼200 nm in the entire test run.

Characterization of Ultrafine Particles and VOCs Emitted from a 3D Printer.

Currently, widely available three-dimensional (3D) printers are very popular with the public. Previous research has shown that these printers can emit ultrafine particles (UFPs) and volatile organic compounds (VOCs). Several studies have examined the emissivity of filaments from 3D printing, except glycol modified polyethylene terephthalate (PETG) and styrene free co-polyester (NGEN) filaments. The aim of this study was to evaluate UFP and VOC emissions when printing using a commonly available 3D printer (ORIGINAL PRUSA i3 MK2 printer) using PETG and NGEN. The concentrations of UFPs were determined via measurements of particle number concentration and size distribution. A thermal analysis was carried out to ascertain whether signs of fiber decomposition would occur at printing temperatures. The total amount of VOCs was determined using a photoionization detector, and qualitatively analyzed via gas chromatography-mass spectrometry. The total particle concentrations were 3.88 × 1010 particles for PETG and 6.01 × 109 particles for NGEN. VOCs at very low concentrations were detected in both filaments, namely ethylbenzene, toluene, and xylene. In addition, styrene was identified in PETG. On the basis of our results, we recommend conducting additional measurements, to more accurately quantify personal exposure to both UFPs and VOCs, focusing on longer exposure as it can be a source of potential cancer risk.

Development and validation of an intra-calibration procedure for MiniDISCs measuring ultrafine particles in multi-spatial indoor environments

Since the real exposure to indoor ultrafine particles depends on temporal and spatial variation of aerosol concentration, particles dynamic behavior becomes relevant in studying indoor pollution. With this aim, the characterization of Ultrafine Particles (UFPs) variability within different environments (multi-spatial indoor environments) can be regarded as a specific tool in assessing the human exposure. In the case of urban indoor environments, instruments able to measure UFPs at high time resolution with high sensitivity are needed, lightweight and silent. For this purpose, personal monitors unipolar diffusion charging based could be used for their ease of use. Among them, Miniature DIffusion Size Classifier (MiniDISC), a small, silent and wearable analyzer measures particle number concentration, particle modal size and lung deposited surface area of nanoparticles at high time resolution, for dynamic or static use. Nevertheless, the typical ±30% accuracy specified by the manufacturer does not make this sensor reliable enough to measure gradients of urban doses of UFPs occurring in multi-spatial indoor environments.The presented work aims at improving the performances of MiniDISCs for their use in simultaneous measurement of urban UFPs by a multiple set-up, such as in indoor environments inside a building.For this purpose, a new intra-calibration procedure has been developed among MiniDISCs, named Best Intra-calibration (BIC), which corrects data of electrical signals of two or more instruments to those of one selected as reference. Compared to a linear regression analysis for PNC of UFPs, BIC procedure has two main advantages. First, it makes it possible to improve simultaneously the precision of particle number concentration (PNC) and particle modal size (PMS). Secondly, it allows multiple instruments to operate as a fleet, such as a spatial delocalization of an instrument in multiple environments.The procedure was tested in realistic environmental conditions, evaluating indoor PNC and PMS of UFPs by both parallel samplings and multi-spatial samplings. Three types of monitoring campaigns were carried out: inter-comparisons between PNC of UFPs from three MiniDISCs and one Condensation Particle Counter; intra-comparisons between PNC and PMS of UFPs from three MiniDISCs; urban monitoring in-field campaign of UFPs with three MiniDISCs in an indoor workplace, a physic laboratory, in the next hallway and outside. The latter campaign aimed at evaluating how UFPs are influenced by the interaction among different environments inside the building and by the work activity. For these purposes, the dynamical behavior and the ratios Indoor to Outdoor were investigated, in addition to a novel ratio Indoor to Hallway. The BIC procedure allows increasing the precision measured by the weighted coefficients of variation CVs of about 7 times. The results support the novel Intra-calibration procedure to improve the intra variability of MiniDISCs in parallel sampling, making them attractive for measuring UFPs by both the metrics PNC and PMS in multi-spatial indoor environments.

Caracterización de partículas ultrafinas generadas en alimentos asados en parrillas al carbón en Armenia (Colombia). Caso de estudio

Caracterización de partículas ultrafinas generadas en alimentos asados en parrillas al carbón en Armenia (Colombia). Caso de estudio

Measurement of airborne ultrafine particles in work and life environments: study design and preliminary trends in an Italian university site.

Airborne ultrafine particles (UFPs) potentially have adverse health effects for the exposed population both in life and work environments. Main objective of this study is to propose a strategy to measure multiple parameters that may influence human exposure to UFPs and apply it in a case study at the university site of “La Sapienza” in Rome (Italy). The measurements allow the characterization of UFPs in terms of particle number concentration (PNC), particle size distribution (PSD), lung deposited surface area (LDSA), geometric mean diameter (GMD) and polycyclic aromatic hydrocarbons concentration (PAHs), using data collected in indoor and outdoor conditions by real-time instruments with high time resolution. The study design includes: i) inter-comparison of devices based on different principles of operation to harmonize the outputs in relation to a reference instrument; ii) case study site description and sampling points identification to allow indoor vs outdoor relations at different height; iii) extensive measurement campaigns to provide a dataset useful to data comparison; iv) statistical data series analysis. The preliminary results reported here are related to the values of PNC and calculated average diameter (Davg) for airborne UFPs, obtained in three different sampling points of the research workplaces at the university site: auditorium (about 300 places - ground floor), computer science laboratory (about 50 workstations - first floor) and external roof (top of the building). Major relations between PNC and Davg have been highlighted in daily trends.

Characterization of Ultrafine Particles and Other Traffic Related Pollutants near Roadways in Beijing

The mass concentrations of PM2.5 (particles with aerodynamic diameter < 2.5 um), number concentration of ultrafine particles (UFP, particles with aerodynamic diameter < 100 nm), concentrations of carbon dioxide (CO2), as well as mass concentrations of black carbon (BC, results from incomplete combustion of fossil fuels and biomass, usually consists of several linked carbon atoms, commonly referred to as soot ) were measured near the Peking University (PKU) campus in Beijing from December 10th to December 23rd, 2011. Correlation between UFP number concentrations and PM2.5 mass concentrations, as well as PM2.5 mass concentrations and BC mass concentrations were determined while taking into consideration the local meteorological conditions and traffic densities determined from recorded video footage. Traffic emissions were calculated using ultrafine particle number concentration (PNC) and CO2 concentrations. The PM2.5 mass concentration, PNC, BC mass concentration as well as calculated traffic emission data were compared with existing data for the Los Angeles metropolitan region. The differences and similarities between the two data sets were compared and discussed.No correlation was found between PNC and PM2.5 mass concentrations. However, a high correlation between BC and PM2.5 mass concentrations was found. Also, correlations were identified between local meteorological conditions such as wind direction and PNC, PM2.5, and BC mass concentrations near roadways, especially when the site was downwind of local traffic. No correlation was found between wind speed and PNC, although strong correlations were found between wind speed and PM2.5, as well as BC mass concentrations. Days where both PM2.5 mass concentrations and PNC were higher at the control site were observed to be wind direction dependent, indicating the detection of regional emission sources. A strong correlation between PM2.5 mass concentrations and local visibility was also demonstrated. In terms of traffic, total traffic had almost no correlation with PNC. However, total diesel traffic was found to have some correlation to PNC, with higher diesel vehicle volume correlating to higher PNC. Finally, from the comparison between Los Angeles and Beijing data sets, Beijing tends to have higher emission factors, as well as near roadway PNC and PM2.5 mass concentrations, after controlling for wind direction.Data generated from this study could be used to model near roadway exposures to PM2.5 as well as UFP, especially from an occupational exposure standpoint for roadside workers such as food stand workers, traffic directing personnel, among others.

Size Distribution and Characterization of Ultrafine Particles in Roadside Atmosphere

The number concentration and number size distributions of ultrafine particles were measured with a Scanning Mobility Particle Sizer (SMPS) at a roadside in early autumn and winter, and the results are discussed with regard to the contribution of traffic activity and meteorological conditions. The number concentration of the <50 nm fraction increased in the morning under calm wind conditions, and this increase corresponded with the increase in total traffic volume and nitric oxide. The increase in ultrafine particles was influenced not only by the increase in total traffic but also by the high contribution of diesel engine vehicles. The number concentration decreased around noon as the wind speed increased, although the total traffic and the number of diesel engine vehicles were at the same level as in the morning. The number size distribution in the morning was bimodal, with a first peak diameter of around 30 nm and a second of around 90 nm in both periods. The volatility of ultrafine particles was investigated using a thermal denuder operating at 250°C. The first peak consisted mainly of volatile components, whereas the second one consisted of solid materials plus some volatile components. These results were consistent with the mass size distribution of elemental and organic carbon. The number size distribution with a peak diameter of around 30 nm was also observed in the afternoon at a suburban site; however, it was produced not by vehicle emissions directly but by photochemical reactions. Although a relatively high number concentration was also observed in the morning at the suburban site due to vehicle emission, the peak diameter ranged from 40 to 90 nm, which was larger than at the roadside.

Size Distribution and Characterization of Ultrafine Particles in Roadside Atmosphere

Size Distribution and Characterization of Ultrafine Particles in Roadside Atmosphere

Novel instrumentation for the characterization of ultrafine particles.

Techniques for the in situ characterization of ultrafine particles are often based on the interaction of the particles with the surrounding gas or with light. Approaches that allow a fast determination of properties as size, mass, and surface are discussed here. As carbon is an important component of combustion particles, one of the most important and abundant part of anthropogenic ultrafine particles, techniques to determine elemental carbon concentration are also discussed; these methods are based on measuring optical absorption. Besides the analysis itself, sampling and pretreatment (e.g., dilution) play a very important role in obtaining reliable results.

高分子膜中に分散した超微粒子調製とその特性

高分子膜中に分散した超微粒子調製とその特性