This study investigated the effects of particle transfer to the covers of aerosol samplers during transportation of wood dust and welding fume samples. Wood dust samples were collected in a sanding chamber using four sampler types: closed-face cassettes (CFC), CFC with Accu-CAP inserts, disposable inhalable samplers (DIS), and Institute of Occupational Medicine (IOM). Welding fumes were collected in a walk-in chamber using the same samplers, with Solu-Sert replacing Accu-CAP. The samples were divided into two groups, with one group transported by air and the other by land. They were returned in the same manner and analyzed gravimetrically for wood dust and chemically for welding fumes. For wood dust, IOM showed a significantly higher percentage of particles transferred to the covers compared with the other samplers regardless of the transportation mode (p < 0.0001; 64% by air and 15% by land), while other samplers showed less than or close to 10% (3.5-12%). When the percentages of particle transfer to the covers were compared between the air and land transportation, both IOM and CFC samples showed differences between modes of transportation, while others did not. For welding fumes, most samples (61% of samples for copper [Cu] and 76% of samples for manganese [Mn]) showed nondetectable amounts of the analyte on the covers. For all samplers, the particle transfer to the covers for both transportation modes ranged from 0.2-33% for Cu and less than 4.5% for Mn. Overall, this study confirms that particle transfer to sampler covers during transport highly depends upon the transportation mode and sampler type for wood dust, whereas particle transfer seems minimal for welding fumes. The findings of this study are based on two materials and limited sample sizes. Further investigation considering different industry types and tasks, particle size ranges, and materials might be necessary. Nevertheless, occupational professionals should account for this transfer when handling and analyzing samples in practice.

This study experimentally evaluates the performance of different sorbent tubes for sampling acetone vapor in workplace air. A dynamic atmosphere system produced an acetone alone and a mixture with other analytes containing ~73, 483, and 1898 microg acetone mass loading at 25, 50, and 75% relative humidity (RH) at 25 degrees C. Sorbent samples were analyzed in accordance with OSHA Method 69 (Carbosieve S-III) and NMAM 1501, modified to use Anasorb 747 sorbent. Both methods were modified to include the additional analytes. Additional extraction procedures with and without 1% dimethylformamide and anhydrous magnesium sulfate were included in the modified NMAM 1501 using Anasorb 747. Silica gel sorbent tubes analyzed according to NMAM 2027 were included. There were significant reductions in the recovery of acetone from both Anasorb 747 and Carbosieve S-III collected from air at 75% RH, relative to collection at 25 or 50% RH at very low loading compared with that of samples collected at mid to high loading. Silica gel provided a consistent recovery of acetone at all RHs and in the presence of other chemical interferences at 75% RH. The likely cause of mass dependence may arise from the humidity effect on acetone adsorption onto both beaded active carbon and carbon molecular sieve either in sampling or in analysis. The present study confirms not only previous observations but also adds to the literature showing carbonaceous sorbents are not well suited for sampling ketones at high humidity and low concentration.

This study evaluates the performance of the disposable inhalable aerosol sampler (DIAS), a new sampler developed to be more cost-effective than the traditional inhalable particle samplers and comparable to the inhalable particle sampling convention. Forty-eight pairs of the DIAS prototype and the IOM sampler were utilized to collect copper exposure measurements (23 personal and 25 area) at an electrorefinery facility. The geometric mean (GM) value of ratios of exposure data (DIAS/IOM) was 1.1, while the GM of ratios (DIAS/IOM) was 1.6 for the area exposure data, revealing 84%of the ratios were greater than one. For both personal and area exposure data, the concordance correlation coefficient tests revealed significant disagreements between the two types of samplers and suggested precision as the source of the disagreement. The estimated mean concentration was higher for the DIAS compared that for the IOM for the area exposure data (p < 0.05), while the results were comparable for the personal exposure data (p = 0.49). Overall, the DIAS generated higher exposure results compared to the IOM sampler for the area exposures. For the personal exposures, the findings were inconclusive due to inconsistent results of factors aforementioned. This study is limited to one metal component (copper) of the dust at a worksite. To date, this is the first field evaluation using personal exposure data to test the performance of the DIAS and the second evaluation using area exposure data. Thus, it will be necessary to conduct additional field evaluations with various elements to further evaluate the performance of the DIAS. In addition, particle migration to the internal walls of the cap was observed during the transportation of collected samples to a laboratory for both sampler types (6.4% for the DIAS and 7.4% for the IOM). Occupational health and safety professionals should be aware of potential errors caused from transferring samples from a field to a laboratory and should be careful not to exclude particles collected on the caps.

Rock dusting is used to prevent secondary explosions in coal mines, but inhalation of rock dusts can be hazardous if the crystalline silica (e.g., quartz) content in the respirable fraction is high. The objective of this study is to assess the quartz content and physical characteristics of four selected rock dusts, consisting of limestone or marble in both treated (such as treatment with stearic acid or stearates) and untreated forms. Four selected rock dusts (an untreated and treated limestone and an untreated and treated marble) were aerosolized in an aerosol chamber. Respirable size-selective sampling was conducted along with particle size-segregated sampling using a Micro-Orifice Uniform Deposit Impactor. Fourier Transform Infrared spectroscopy and scanning electron microscopy with energy-dispersive X-ray (SEM-EDX) analyses were used to determine quartz mass and particle morphology, respectively. Quartz percentage in the respirable dust fraction of untreated and treated forms of the limestone dust was significantly higher than in bulk samples, but since the bulk percentage was low the enrichment factor would not have resulted in any major change to conclusions regarding the contribution of respirable rock dust to the overall airborne quartz concentration. The quartz percentage in the marble dust (untreated and treated) was very low and the respirable fractions showed no enrichment. The spectra from SEM-EDX analysis for all materials were predominantly from calcium carbonate, clay, and gypsum particles. No free quartz particles were observed. The four rock dusts used in this study are representative of those presented for use in rock dusting, but the conclusions may not be applicable to all available materials.

Cobalt monoxide (CoO) and lanthanum oxide (La2O3) nanoparticles are two metal oxide nanoparticles with different redox potentials according to their semiconductor properties. By utilizing these two nanoparticles, this study sought to determine how metal oxide nanoparticle's mode of toxicological action is related to their physio-chemical properties in human small airway epithelial cells (SAEC). We investigated cellular toxicity, production of superoxide radicals and alterations in gene expression related to oxidative stress and cellular death at 6 and 24 h following exposure to CoO and La2O3 (administered doses: 0, 5, 25, and 50 microg/ml) nanoparticles. CoO nanoparticles induced gene expression related to oxidative stress at 6 h. After characterizing the nanoparticles, transmission electron microscope (TEM) analysis showed SAEC engulfed CoO and La2O3 nanoparticles. CoO nanoparticles were toxic after 6 h and 24 h of exposure to 25.0 and 50.0 microg/ml administered doses, whereas, La2O3 nanoparticles were toxic only after 24 h using the same administered doses. Based upon the Volumetric Centrifugation Method in vivo Sedimentation, Diffusion and Dosimetry (VCM-ISDD), the dose of CoO and La2O3 nanoparticles delivered at 6 and 24 h were determined to be: CoO: 1.25, 6.25, and 12.5 microg/ml; La2O3: 5, 25, and 50 microg/mland CoO: 4, 20, and 40 microg/ml; and La2O3: 5, 25, 50 microg/ml respectively. CoO nanoparticles produced more superoxide radicals and caused greater stimulation of total tyrosine and threonine phosphorylation at both 6 h and 24 h when compared to La2O3 nanoparticles. Taken together, these data provide evidence that different toxicological modes of action were involved in CoO and La2O3 metal oxide nanoparticle-induced cellular toxicity.

The objective of the present study is to compare and characterize nylon, polypropylene (PP), and polyvinyl chloride (PVC) membrane filters that might be used to replace the vinyl/acrylic co-polymer (DM-450) filter currently used in the Mine Safety and Health Administration (MSHA) P-7 method (Quartz Analytical Method) and the National Institute for Occupational Safety and Health (NIOSH) Manual of Analytical Methods 7603 method (QUARTZ in coal mine dust, by IR re-deposition). This effort is necessary because the DM-450 filters are no longer commercially available. For example, the MSHA Pittsburgh laboratory alone analyses annually approximately 15,000 samples according to the MSHA P-7 method that requires DM-450 filters. There is an impending shortage of DM-450 filters. Membrane filters suitable for on-filter analysis should have high infrared (IR) transmittance in the spectral region 600-1000 cm-1. Nylon (47 mm, 0.45 microm pore size), PP (47 mm, 0.45 microm pore size) and PVC (47 mm, 5 microm pore size) filters meet this specification. Limits of detection and limits of quantification were determined from Fourier transform infrared spectroscopy (FTIR) measurements of blank filters. The average measured quartz mass and coefficient of variation were determined from test filters spiked with respirable alpha-quartz following MSHA P-7 and NIOSH 7603 methods. Quartz was also quantified in samples of respirable coal dust on each test filter type using the MSHA and NIOSH analysis methods. The results indicate that PP and PVC filters may replace the DM-450 filters for quartz measurement in coal dust by FTIR. PVC filters of 5 microm pore size was seemed to be suitable replacement although their ability to retain small particulates should be checked by filter experiment.

A field study was conducted to estimate the amount of Cr, Mn and Ni deposited in the respiratory system of 44 welders in two facilities. Each worker wore a nanoparticle respiratory deposition (NRD) sampler during gas metal arc welding (GMAW) of mild and stainless steel and flux-cored arc welding (FCAW) of mild steel. Several welders also wore side-by-side NRD samplers and closed- face filter cassettes for total particulate samples. The NRD sampler estimates the aerosol's nano-fraction deposited in the respiratory system. Mn concentrations for both welding processes ranged 2.8-199 mug/m3; Ni concentrations ranged 10 -51 mug/m3; Cr concentrations ranged 40-105 mug/m3. Cr(VI) concentrations ranged between 0.5-1.3 mug/m3. For the FCAW process the largest concentrations were reported for welders working in pairs. As a consequence this often resulted in workers being exposed to their own welding fumes and to those generated from the welding partner. Overall no correlation was found between air velocity and exposure (R2=0.002). The estimated percentage of the nano-fraction of Mn deposited in a mild-steel-welder's respiratory system ranged between 10 and 56%. For stainless steel welding, the NRD samplers collected 59% of the total Mn, 90% of the total Cr and 64% of the total Ni. These results indicate that most of the Cr and more than half of the Ni and Mn in the fumes were in the fraction smaller than 300 nm.

A laboratory study was conducted to determine the mass of total Cr, Cr(VI), Mn, and Ni in 15 size fractions for mild and stainless steel gas-metal arc welding (GMAW) fumes. Samples were collected using a nano multi orifice uniform deposition impactor (MOUDI) with polyvinyl chloride filters on each stage. The filters were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) and ion chromatography. Limits of detection (LODs) and quantitation (LOQs) were experimentally calculated and percent recoveries were measured from spiked metals in solution and dry, certified welding-fume reference material. The fraction of Cr(VI) in total Cr was estimated by calculating the ratio of Cr(VI) to total Cr mass for each particle size range. Expected, regional deposition of each metal was estimated according to respiratory-deposition models. The weight percent (standard deviation) of Mn in mild steel fumes was 9.2% (6.8%). For stainless steel fumes, the weight percentages were 8.4% (5.4%) for total Cr, 12.2% (6.5%) for Mn, 2.1% (1.5%) for Ni and 0.5% (0.4%) for Cr(VI). All metals presented a fraction between 0.04 and 0.6 ?m. Total Cr and Ni presented an additional fraction <0.03 ?m. On average 6% of the Cr was found in the Cr(VI) valence state. There was no statistical difference between the smallest and largest mean Cr(VI) to total Cr mass ratio (p-value = 0.19), hence our analysis does not show that particle size affects the contribution of Cr(VI) to total Cr. The predicted total respiratory deposition for the metal particles was ?25%. The sites of principal deposition were the head airways (7?10%) and the alveolar region (11?14%). Estimated Cr(VI) deposition was highest in the alveolar region (14%).

Welders are exposed to high concentrations of nanoparticles. Compared to larger particles, nanoparticles have been associated with more toxic effects at the cellular level, including the generation of more reactive oxygen species activity. Current methods for welding-fume aerosol exposures do not differentiate between the nano-fraction and the larger particles. The objectives of this work are to establish a method to estimate the respiratory deposition of the nano-fraction of selected metals in welding fumes and test this method in a laboratory setting. Manganese (Mn), Nickel (Ni), Chromium (Cr) and hexavalent chromium (Cr(VI)) are commonly found in welding fume aerosols and have been linked with severe adverse health outcomes. Inductively coupled plasma mass spectrometry (ICP-MS) and ion chromatography (IC) were evaluated as methods for analyzing the content of Mn, Ni, Cr and Cr(VI) nanoparticles in welding fumes collected with nanoparticle respiratory deposition (NRD) samplers. NRD samplers collect nanoparticles at deposition efficiencies that closely resemble physiological deposition in the respiratory tract. The limits of detection (LODs) and quantitation (LOQs) for ICP-MS and IC were determined analytically. Mild and stainless steel welding fumes generated with a robotic welder were collected with NRD samplers inside a chamber. LODs (LOQs) for Mn, Ni, Cr, and Cr(VI) were 1.3 mug (4.43 mug); 0.4 mug (1.14 mug), 1.1 mug (3.33 mug), and 0.4 mug (1.42 mug), respectively. Recovery of spiked samples and certified welding fume reference material was greater than 95%. When testing the method, the average percentage of total mass concentrations collected by the NRD samplers was approximately 30% for Mn, approximately 50% for Cr and approximately 60% for Ni, indicating that a large fraction of the metals may lay in the nanoparticle fraction. This knowledge is critical to the development of toxicological studies aimed at finding links between exposure to welding fume nanoparticles and adverse health effects. Future work will involve the validation of the method in workplace settings.

A polyvinyl chloride (PVC) cassette insert with PVC filter (ACCU-CAP) in a 37-mm closed -face cassette (CFC) was designed for gravimetric analysis. A customized version of the ACCU-CAP, also to be used in the CFC, was manufactured from an acid-digestible cellulose-acetate cassette insert joined to a mixed cellulose ester (MCE) filter for wet chemical analysis. The aim of this study was to compare metal particle concentrations as sampled by the customized insert (CI) in a CFC sampler with the traditional sampling method using only a MCE filter in the CFC. Thirty-nine personal and 13 area samples were taken using paired filter-based CFC and the CI in CFC samplers at a solder manufacturing plant. The CI was removed from its CFC, digested and analyzed as a whole. The MCE filter from the typical CFC was removed for analysis and then the interior of the cassette was wiped with Ghost Wipe for a separate analysis. The MCE filter only, Ghost Wipe, and CI were separately dissolved in heated nitric acid for ICP-MS analysis. Overall, the geometric mean concentration of the filter-only (FO) samples was considerably lower than that of the CI samples, by 53% for lead and 32% for tin. However, if the FO analysis was added to the corresponding Ghost Wipe analysis, i.e., filter+interior wipe (FW), the geometric mean concentrations of the FW results were similar to those of the CI results (by 113% for lead and 98% for tin). For both lead and tin the comparison of (log-transformed) metal concentrations between the FW and CI results showed no statistically significant difference (p-value = 0.3009 for lead and 0.800 for tin), while the comparison between the FO and CI results shows statistically significant differences (all p-values<0.05). In conclusion, incorporating the sampler internal non-filter deposits by wiping or use of an internal filter capsule gave higher results than analyzing only the filter. Close agreement between the two methods of including non-filter deposits is an indication of general equivalency.

Kaolinite interferes with the infrared analysis of quartz. Improper correction can cause over- or underestimation of silica concentration. The standard sampling method for quartz in coal mine dust is size selective, and, since infrared spectrometry is sensitive to particle size, it is intuitively better to use the same size fractions for quantification of quartz and kaolinite. Standard infrared spectrometric methods for quartz measurement in coal mine dust correct interference from the kaolinite, but they do not specify a particle size for the material used for correction. This study compares calibration curves using as-received and respirable size fractions of nine different examples of kaolinite in the different correction methods from the National Institute for Occupational Safety and Health Manual of Analytical Methods (NMAM) 7603 and the Mine Safety and Health Administration (MSHA) P-7. Four kaolinites showed significant differences between calibration curves with as-received and respirable size fractions for NMAM 7603 and seven for MSHA P-7. The quartz mass measured in 48 samples spiked with respirable fraction silica and kaolinite ranged between 0.28 and 23% (NMAM 7603) and 0.18 and 26% (MSHA P-7) of the expected applied mass when the kaolinite interference was corrected with respirable size fraction kaolinite. This is termed "deviation," not bias, because the applied mass is also subject to unknown variance. Generally, the deviations in the spiked samples are larger when corrected with the as-received size fraction of kaolinite than with the respirable size fraction. Results indicate that if a kaolinite correction with reference material of respirable size fraction is applied in current standard methods for quartz measurement in coal mine dust, the quartz result would be somewhat closer to the true exposure, although the actual mass difference would be small. Most kinds of kaolinite can be used for laboratory calibration, but preferably, the size fraction should be the same as the coal dust being collected.

A laboratory study was performed to measure quartz in coal dust using high-flow rate samplers (CIP10-R, GK2.69 cyclone, and FSP10 cyclone) and low-flow rate samplers [10-mm nylon and Higgins-Dewell type (BGI4L) cyclones] and to determine whether an increased mass collection from high-flow rate samplers would affect the subsequent quartz measurement by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analytical procedures. Two different sizes of coal dusts, mass median aerodynamic diameter 4.48 m (Coal Dust A) and 2.33 m (Coal Dust B), were aerosolized in a calm air chamber. The mass of coal dust collected by the samplers was measured gravimetrically, while the mass of quartz collected by the samplers was determined by FTIR (NIOSH Manual of Analytical Method 7603) and XRD (NIOSH Manual of Analytical Method 7500) after one of two different indirect preparations. Comparisons between high-flow rate samplers and low-flow rate samplers were made by calculating mass concentration ratios of coal dusts, net mass ratios of coal dusts, and quartz net mass. Mass concentrations of coal dust from the FSP10 cyclone were significantly higher than those from other samplers and mass concentrations of coal dust from 10-mm nylon cyclone were significantly lower than those from other samplers, while the CIP10-R, GK2.69, and BGI4L samplers did not show significant difference in the comparison of mass concentration of coal dusts. The BGI4L cyclone showed larger mass concentration of 9% compared to the 10-mm nylon cyclone. All cyclones provided dust mass concentrations that can be used in complying with the International Standard Organization standard for the determination of respirable dust concentration. The amount of coal dust collected from the high-flow rate samplers was found to be higher with a factor of 2-8 compared to the low-flow rate samplers but not in direct proportion of increased flow rates. The high-flow rate samplers collected more quartz compared to low-flow rate samplers in the range of 2-10. There was no significant difference between the per cent (%) quartz in coal dust between the FTIR and XRD analyses. The findings of this study indicated that the increased mass of quartz collected with high-flow rate samplers would provide precise analytical results (i.e. significantly above the limit of detection and/or limit of quantification) compared to the mass collected with low-flow rate samplers, especially in environments with low concentrations of quartz or where short sampling times are desired. (2011 The Author.)

Pairs of Institute of Occupational Medicine (IOM) and 37 mm closed face cassette samplers (CFC) were deployed where occupational exposures to lead-containing dusts were known to occur. Discrete particle analyses of wall and filter deposits were performed by Scanning Electron Microscopy-Energy Dispersive X-ray Spectrometry (SEM-EDX). From the elemental composition and projected area diameter of each particle a density, volume, and mass were calculated, and a mass-weighted size distribution for each filter and corresponding wall deposit determined. Comparison of pairs of wall and filter mass-weighted size distributions by Mann-Whitney statistical analysis shows that in only 3 of 72 examples from either sampler were the distributions significantly different that suggests that the mechanisms of particle deposition on the sampler walls for particles in this size range (0.5 mcm through 20 mcm) do not differ for the different samplers. Furthermore, in only 4 of 33 sampler pairs did the IOM and CFC results differ. Although these results originate from several distinct processes characterized by different chemical and physical dust generation mechanisms, they suggest that in these environments the measurement of "total dust" by the CFC and inhalable dust by the IOM will be very similar when both samplers are processed the same way with respect to the including or excluding wall deposits with the filter catch. However, these results may not be applicable to environments where larger particles exist.

Carbon nanotubes (CNTs) are novel materials with unique electronic and mechanical properties. The extremely small size, fiberlike shape, large surface area, and unique surface chemistry render their distinctive chemical and physical characteristics and raise potential hazards to humans. Several reports have shown that pulmonary exposure to CNTs caused inflammation and lung fibrosis in rodents. The molecular mechanisms that govern CNT lung toxicity remain largely unaddressed. Here, we report that multiwalled carbon nanotubes (MWCNTs) have potent, dose-dependent toxicity on cultured human lung cells (BEAS-2B, A549, and WI38-VA13). Mechanistic analyses were carried out at subtoxic doses (≤20 mcg/mL, ≤ 24 h). MWCNTs induced substantial ROS production and mitochondrial damage, implicating oxidative stress in cellular damage by MWCNT. MWCNTs activated the NF-kB signaling pathway in macrophages (RAW264.7) to increase the secretion of a panel of cytokines and chemokines (TNFa, IL-1b, IL-6, IL-10, and MCP1) that promote inflammation. Activation of NF-kB involved rapid degradation of IkBa, nuclear accumulation of NF-kBp65, binding of NF-kB to specific DNA-binding sequences, and transactivation of target gene promoters. Finally, MWCNTs induced the production of profibrogenic growth factors TGFb1 and PDGF from macrophages that function as paracrine signals to promote the transformation of lung fibroblasts (WI38-VA13) into myofibroblasts, a key step in the development of fibrosis. Our results revealed that MWCNTs elicit multiple and intertwining signaling events involving oxidative damage, inflammatory cytokine production, and myofibroblast transformation, which potentially underlie the toxicity and fibrosis in human lungs by MWCNTs.

The American Conference of Governmental Industrial hygienists (ACGIH) lowered the threshold limit value (TLV) for respirable crystalline silica (RCS) exposure from 0.05 to 0.025 mg m(-3) in 2006. For a working environment with an airborne dust concentration near this lowered TLV, the sample collected with current standard respirable aerosol samplers might not provide enough RCS for quantitative analysis. Adopting high flow rate sampling devices for respirable dust containing silica may provide a sufficient amount of RCS to be above the limit of quantification even for samples collected for less than full shift. The performances of three high flow rate respirable samplers (CIP10-R, GK2.69, and FSP10) have been evaluated in this study. Eleven different sizes of monodisperse aerosols of ammonium fluorescein were generated with a vibrating orifice aerosol generator in a calm air chamber in order to determine the sampling efficiency of each sampler. Aluminum oxide particles generated by a fluidized bed aerosol generator were used to test (i) the uniformity of a modified calm air chamber, (ii) the effect of loading on the sampling efficiency, and (iii) the performance of dust collection compared to lower flow rate cyclones in common use in the USA (10-mm nylon and Higgins-Dewell cyclones). The coefficient of variation for eight simultaneous samples in the modified calm air chamber ranged from 1.9 to 6.1% for triplicate measures of three different aerosols. The 50% cutoff size ((50)d(ae)) of the high flow rate samplers operated at the flow rates recommended by manufacturers were determined as 4.7, 4.1, and 4.8 mum for CIP10-R, GK2.69, and FSP10, respectively. The mass concentration ratio of the high flow rate samplers to the low flow rate cyclones decreased with decreasing mass median aerodynamic diameter (MMAD) and high flow rate samplers collected more dust than low flow rate samplers by a range of 2-11 times based on gravimetric analysis. Dust loading inside the high flow rate samplers does not appear to affect the particle separation in either FSP10 or GK2.69. The high flow rate samplers overestimated compared to the International Standards Organization/Comite Europeen de Normalisation/ACGIH respirable convention [up to 40% at large MMAD (27.5 mum)] and could provide overestimated exposure data with the current flow rates. However, both cyclones appeared to be able to provide relatively unbiased assessments of RCS when their flow rates were adjusted.

The study presented here investigates the number weighted particle size distributions of aerosols generated in the laboratory from lead oxide and lead sulfide dusts and sampled by Institute of Occupational Medicine (IOM) and closed face cassette (CFC) samplers as determined by scanning electron microscopy (SEM). The wall deposits and filter deposits from each sampler were characterized separately. A Mann-Whitney statistical analysis revealed that differences in the number weighted distributions of particles captured by the filter and the wall were not significant over the size range ( up to 20 mu m aerodynamic equivalent diameter) present in these laboratory-generated aerosols. Furthermore, for these samples it was not possible to distinguish an absolute difference between the IOM and CFC filter catches. By comparing direct measurements of aerodynamic equivalent diameter (AED) made by an Aerodynamic Particle Sizer (APS) to AEDs calculated from SEM images, empirical shape factors for lead oxide and lead sulfide were determined. To validate this approach APS and SEM measurements of the AED of 2 mu m and 6 mu m physical diameter monodisperse glass and polystyrene microspheres were made. Using the shape factors of spheres and the known densities of these materials, it was found that the SEM determinations of AED agreed with the APS results. To demonstrate the reliability of the redeposition method of sample preparation, lead sulfide and lead oxide aerosols were briefly sampled by IOM samplers such that sufficient particles were collected for SEM examination directly on the filter but not so many that particles were likely to touch or overlap. Half of each filter was analyzed in the SEM directly; the other half was ultrasonically