Assessment of the contribution of electron microscopy to nanoparticle characterization sampled with two cascade impactors.

This study assessed the contribution of electron microscopy to the characterization of nanoparticles and compared the degree of variability in sizes observed within each stage when sampled by two cascade impactors: an Electrical Low Pressure Impactor (ELPI) and a Micro-Orifice Uniform Deposit Impactor (MOUDI). A TiO(2) nanoparticle (5 nm) suspension was aerosolized in an inhalation chamber. Nanoparticles sampled by the impactors were collected on aluminum substrates or TEM carbon-coated copper grids using templates, specifically designed in our laboratories, for scanning and transmission electron microscopy (SEM, TEM) analysis, respectively. Nanoparticles were characterized using both SEM and TEM. Three different types of diameters (inner, outer, and circular) were measured by image analysis based on count and volume, for each impactor stage. Electron microscopy, especially TEM, is well suited for the characterization of nanoparticles. The MOUDI, probably because of the rotation of its collection stages, which can minimize the resuspension of particles, gave more stable results and smaller geometric standard deviations per stage. Our data suggest that the best approach to estimate particle size by electron microscopy would rely on geometric means of measured circular diameters. Overall, the most reliable data were provided by the MOUDI and the TEM sampling technique on carbon-coated copper grids for this specific experiment. This study indicates interesting findings related to the assessment of impactors combined with electron microscopy for nanoparticle characterization. For future research, since cascade impactors are extensively used to characterize nano-aerosol exposure scenarios, high-performance field emission scanning electron microscopy (FESEM) should also be considered.

Immunological responses in C3H/HeJ mice following nose-only inhalation exposure to different sizes of beryllium metal particles.

Beryllium is used in a wide variety of industries. Chronic beryllium disease is the most common occupational disease among workers following exposure to Be. The objective of this study was to determine the immunologic effects of two different particle sizes of Be metal, <2.5 microm (fine Be or Be-F) and <10 microm (inhalable Be or Be-I) on C3H/HeJ mice following 3 weeks of nose-only inhalation exposure at a target concentration of 250 microg m(-3). Mice were sacrificed either on day 28 or day 42 (Be-F group only) after exposure. The mass median aerodynamic diameter obtained in the inhalation chamber was 1.5 +/- 0.1 microm for Be-F and 4.1 +/- 0.6 microm for Be-I. Results showed peri-bronchial inflammation with early granulomatous changes in exposed mice. The extent of the inflammation appeared more severe for mice sacrificed at day 42. Splenocyte proliferation was higher for mice exposed to fine particles compared with Be-I and control animals. Flow-cytometric analysis indicated a significantly greater expression of CD4(+), CD8(+) and intracellular IFN-gamma expression for both Be particle sizes, particularly for fine particles. Cytokine assays of bronchoalveolar lavage revealed significantly greater levels of IL-12, TNF-alpha and IFN-gamma for mice exposed to fine particles. Our findings suggest that exposure to fine particles may induce more pronounced immunological effects than inhalable particles.

Characterization of beryllium particles from CAlSiFrit.

Aluminum smelters produce in excess thousand of tons of spent pot lining (SPL) each year. CAlSiFrit technology is a recycling process in which spent pot lining (SPL) is recovered and transformed into commercial value-added products. Since SPL contains beryllium (Be), exposures encountered by workers may result in adverse effects. This study aimed to establish the level at which Be is present in the CAlSiFrit and to determine the chemical and physical characteristics of the Be-containing particles. Three samples of CAlSiFrit powder supplied by the recycling industry were analyzed using several methods in order to (1) detect and characterize Be-containing particles, (2) identify the Be chemical form, and (3) quantify the amount of other major chemical elements present. These methods were: inductively coupled plasma-mass spectrometry, instrumental neutron activation analysis, time-of-flight secondary-ion mass spectrometry (TOF-SIMS), analytical transmission electron microscopy (ATEM), and x-ray diffraction. Results show that the three samples have a similar chemical composition, with high concentrations, of Si, Ca, Al, Na, F, Fe, K, Mg, and Ti, in decreasing order. Be concentrations were low and totaled less than 3 ppm. The size of the areas where Be was detected by TOF-SIMS is approximately 0.3 mum or less in diameter. A large quantity of oxygen in the particles of dusts was observed. As the majority of elements present have a great affinity for oxygen, the presence of oxygen indicates that these elements are probably oxides. Finally, the particle size varied from approximately 0.05 to 1 mum. This is consistent with the interpretation of the TOF-SIMS results that suggest a size of approximately 0.3 mum or less for the particles containing Be. These results are important from the perspective that thousands of tons of CAlSiFrit, a supplementary cement material, might be produced and used.

Physical and chemical characterization of beryllium particles from several workplaces in Québec, Canada--part B: time-of-flight secondary-ion mass spectroscopy.

The problems associated with detecting and characterizing beryllium (Be) particles in industrial samples from Québec were addressed in the companion article (Rouleau et al., 2005). The present study is a continuation of the work aimed at redefining the current occupational exposure level for beryllium. The goals were to determine the principal chemical forms and the principal physical characteristics of Be particles sampled in four Québec industries. Bulk particle chemistry was determined using inductively coupled plasma-mass spectroscopy (ICP-MS) and flame atomic absorption spectrophotometry (FAAS). Time-of-flight secondary-ion mass spectroscopy (TOF-SIMS) was used to characterize particle surface chemistry and physical particle size. The dust samples collected had Be concentrations varying from 58 to 146 microg/g. Results showed that numerous fine Be particles or aggregates were evenly dispersed throughout the samples. Thus, Be does not appear to be concentrated in large particles. However, it was not possible to confirm if these fine particles were combined to specific compounds, chemically or physically, or independent Be particles. Most of the particles containing Be were fine, with diameters less than 10 microm, which is important from an occupational health and safety standpoint. TOF-SIMS should be considered as an appropriate technique for qualitative characterization of Be particles, and a valuable complement to the recognized quantitative methods ICP-MS and FAAS.

Physical and chemical characterization of beryllium particles from several workplaces in Québec, Canada--part A: determining methods for the analysis of low levels of beryllium.

Chemical and physical characterizations of beryllium (Be) particles found in settled dust samples from four industries based in Québec were attempted using a variety of analytical methods. Bulk particle chemistry was determined using inductively coupled plasma-mass spectrometry (ICP-MS), graphite furnace atomic absorption spectrometry (GFAAS), and instrumental neutron activation analysis (INAA). Time-of-flight secondary-ion mass spectrometry (TOF-SIMS), transmission electron microscopy, scanning electron microscopy, energy-dispersive spectroscopy, x-ray diffraction (XRD), electron energy loss spectrometry (EELS), and Auger microscopy were used to characterize physicochemical properties of particles. These analyses were deemed important based on the hypotheses that (1) different chemical forms of Be do not present the same risks, and (2) different morphologies lead to different risks. Standards were used to prove the adequacy of XRD, EELS, and Auger microscopy prior to the analyses of industrial samples. However, low concentrations of Be in samples were a limiting factor for most methods; few detected Be in industrial samples. Only ICP-MS, GFAAS, and TOF-SIMS were able to detect Be in industrial samples analyzed in this study. Characterization of settled dust samples showed high number of Be particles, even for Be concentrations below 100 ppm. Furthermore, Be seems to be present as fine particles of Be metal, possibly mechanically agglomerated or aggregated to larger particles or compounds such as cryolite. Other major elements detected with INAA present in the samples were limited to Na, Al, Ca, and F. It was concluded that TOF-SIMS is a valid method for characterizing particles containing approximately 0.01% Be.

Physical and chemical characterization of mn phosphate/sulfate mixture used in an inhalation toxicology study.

The use of methylcyclopentadienyl manganese tricarbonyl (MMT) in unleaded gasoline has given rise to numerous debates on the potential public health risk associated with manganese emissions. In fact, combustion products are mainly Mn phosphate, Mn sulfate, and Mn phosphate/sulfate mixture. Our research group did several inhalation studies in order to assess the toxicity of each Mn species. The objective of this study is to determine the physical and the chemical characteristics of a mixture of Mn phosphate/sulfate used in one of these inhalation toxicology studies. First, the mixture was analyzed by X-ray diffraction in order to obtain the specific peak of Mn phosphate and Mn sulfate. These peaks were used as reference. Second, samples of the mixture were collected on filters in the inhalation chamber at a concentration level of 3000 microg/m(3). They were analyzed by scanning electron microscopy (SEM), analytical transmission electron microscopy (ATEM), and x-ray energy-dispersive spectrometry (EDS) to show their size, morphology, and chemical composition. Results indicate that 33% of the particles were found to be agglomerated, while free particles accounted for 44% for Mn phosphate and 23% for Mn sulfate.