Investigation of airborne nanoparticles emitted during the laser cleaning process of corroded metal surface

Laser surface cleaning is a promising surface-cleaning technique owing to its numerous benefits, including its noncontact behavior, ease of control, high precision, and no secondary waste generation. However, it cannot prevent airborne nanoparticle emissions during the laser cleaning process. Therefore, the effects of laser-cleaning parameters on airborne nanoparticle generation are analyzed to design potential remediation methods. In this study, the nanoparticles released during the laser cleaning of corroded 304L stainless steel surfaces were investigated. Electrical low-pressure impactor analysis and electron microscopy were conducted to determine how laser parameters influenced the size and amount of emitted nanoparticles. Based on these findings, the feasibility of the filtering emitted nanoparticles using high-efficiency particulate air filters was examined.

Real-time characterization of chemical threat agent aerosols for improvement of inhalation studies

OBJECTIVES

Deliberate or accidental release of chemical treat agents in the aerosol form can cause an inhalation hazard. Since the relationship between aerosol properties and health hazards is poorly understood, research into the toxicological consequences of exposure to aerosols is needed. The aim of the present study was to improve the characterization of particles for inhalation studies.

METHODS

Several aerosol measurement technologies were compared for their potential to physically and chemically characterize particles in the inhalation size range in real-time. For that purpose, we compared the performance of an aerodynamic particle sizer (APS), a scanning mobility particle sizer (SMPS) and an electrical low-pressure impactor (ELPI) in an experimental set-up in which particles were generated by a Collison nebulizer and subsequently delivered into a nose-only inhalation exposure system.

RESULTS

We found that more than 95% of the number of particles, equating to more than 83% of the mass generated by the 6-jet Collison nebulizer, were below 0.5 µm. To characterize the entire size range, the APS as single detector has only limited value, therefore the addition of supplementary instrumentation such as the SMPS or the ELPI is required. After real-time measurements in the size range of 30 nm to 10 µm, ex-situ chromatographic chemical analysis is essential for quantification of the delivered mass concentration.

CONCLUSIONS

In summary, the present work demonstrates the utility of the ELPI technology, in combination with off-line analysis, for characterizing aerosols with various size, shape, charge, and composition. This makes the aerosol generation and analysis suite described a promising tool for quantitative inhalation exposure studies.

Real-Time Measurements and Characterization of Airborne Particulate Matter from a Primary Silicon Carbide Production Plant

Airborne particulate matter in the silicon carbide (SiC) industry is a known health hazard. The aims of this study were to elucidate whether the particulate matter generated inside the Acheson furnace during active operation is representative of the overall particulate matter in the furnace hall, and whether the Acheson furnaces are the main sources of ultrafine particles (UFP) in primary SiC production. The number concentration of ultrafine particles was evaluated using an Electrical Low Pressure Impactor (ELPI^TM, Dekati Ltd., Tampere, Finland), a Fast Mobility Particle Sizer (FMPS^TM, TSI, Shoreview, MN, USA) and a Condensation Particle Counter (CPC, TSI, Shoreview, MN, USA). The results are discussed in terms of particle number concentration, particle size distribution and are also characterized by means of electron microscopy (TEM/SEM). Two locations were investigated; the industrial Acheson process furnace hall and a pilot furnace hall; both of which represent an active operating furnace. The geometric mean of the particle number concentration in the Acheson process furnace hall was 7.7 × 10⁴ particles/cm³ for the UFP fraction and 1.0 × 10⁵ particles/cm³ for the submicrometre fraction. Particulate matter collected at the two sites was analysed by electron microscopy. The PM from the Acheson process furnace hall is dominated by carbonaceous particles while the samples collected near the pilot furnace are primarily rich in silicon.

Resolution of the mediators of in vitro oxidative reactivity in size-segregated fractions that may be masked in the urban PM(10) cocktail

PM10 (particulate matter 10 μm or less in aerodynamic diameter) has consistently been linked with adverse human health effects, but the physicochemical properties responsible for this effect have not been fully elucidated. The aim of this work was to investigate the potential for carbon black (CB) particles and PM to generate ROS (Reactive Oxygen Species) and to identify the physicochemical properties of the particles responsible for in vitro oxidative reactivity (OR). PM10 was collected in 11 size fractions at a traffic site in Swansea, UK, using an Electrical Low Pressure Impactor (ELPI). The PM physicochemical properties (including size, morphology, type, and transition metals) were tested. The plasmid scission assay (PSA) was used for OR testing of all particles. The ultrafine and fine PM fractions (N28-2399; 28-2399 nm) caused more DNA damage than coarse PM (N2400-10,000), and the increased capacity of the smaller particles to exhibit enhanced (OR) was statistically significant (p<0.05). The most bioreactive fraction of PM was N94-155 with a toxic dose (TD50; mass dose capable of generating 50% plasmid DNA damage) of 69 μg/ml. The mean TD35 was lower for PM than CB particles, indicating enhanced OR for PM. A difference between CB and PM in this study was the higher transition metal content of PM. Zn was the most abundant transition metal (by weight) in the ultrafine-fine PM fractions, and Fe in the fine-coarse PM. Through this comparison, part of the observed increased PM OR was attributed to Zn (and Fe). In this study PM-derived DNA damage was dependent upon; 1) particle size, 2) surface area, and 2) transition metals. This study supports the view that ROS formation by PM10 is related to physicochemistry using evidence with an increased particle size resolution.