Characterization of particle exposure during tunnel excavation by tunnel boring machines.

Tunnel boring machines (TBMs) are used to excavate tunnels in a manner where the rock is constantly penetrated with rotating cutter heads. Fine particles of the rock minerals are thereby generated. Workers on and in the vicinity of the TBM are exposed to particulate matter (PM) consisting of bedrock minerals including α-quartz. Exposure to respirable α-quartz remains a concern because of the respiratory diseases associated with this exposure. The particle size distribution of PM and α-quartz is of special importance because of its influence on adverse health effects, monitoring and control strategies as well as accurate quantification of α-quartz concentrations. The major aim of our study was therefore to investigate the particle size distribution of airborne PM and α-quartz generated during tunnel excavation using TBMs in an area dominated by gneiss, a metamorphic type of rock. Sioutas cascade impactors were used to collect personal samples on 3 separate days. The impactor fractionates the dust in 5 size fractions, from 10 µm down to below 0.25 µm. The filters were weighted, and the α-quartz concentrations were quantified using X-ray diffraction (XRD) analysis and the NIOSH 7500 method on the 5 size fractions. Other minerals were determined using Rietveld refinement XRD analysis. The size and elemental composition of individual particles were investigated by scanning electron microscopy. The majority of PM mass was collected on the first 3 stages (aerodynamic diameter = 10 to 0.5 µm) of the Sioutas cascade impactor. No observable differences were found for the size distribution of the collected PM and α-quartz for the 3 sampling days nor the various work tasks. However, the α-quartz proportion varied for the 3 sampling days demonstrating a dependence on geology. The collected α-quartz consisted of more particles with sizes below 1 µm than the calibration material, which most likely affected the accuracy of the measured respirable α-quartz concentrations. This potential systematic error is important to keep in mind when analyzing α-quartz from occupational samples. Knowledge of the particle size distribution is also important for control measures, which should target particle sizes that efficiently capture the respirable α-quartz concentration.

The variability of arsenic in blood and urine of humans.

BACKGROUND: Humans are exposed to inorganic and organic arsenic. The total arsenic (As) concentration in urine is a commonly used biomarker of exposure. However, little is known about variability of As in biological fluids and the diurnal variation of As excretion. OBJECTIVES: Main objectives were to assess the variability of As in urine, plasma (P-As), whole blood (B-As), and the blood cell fraction (C-As), and to assess diurnal variation of As excretion. METHODS: Six urine samples were collected at fixed times during 24 h on two different days around one week apart among 29 men and 31 women. Blood samples were collected when the morning urine samples were delivered. The intra-class correlation coefficient (ICC) was calculated as the ratio of the between-individuals variance to the total observed variance. RESULTS: Geometric mean (GM) 24 h urinary excretions of As (U-As24 h) were 41 and 39 µg/24 h on the two days of sampling. Concentrations of B-As, P-As and C-As were highly correlated with U-As24 h and As in first void morning urine. No statistically significant differences were observed for the urinary As excretion rate between the different sampling times. A high ICC was observed for As in the cellular blood fraction (0.803), while ICC for first morning urine corrected for creatine was low (0.316). CONCLUSIONS: The study suggests that C-As is the most reliable biomarker for use in exposure assessment of individual exposure. Morning urine samples have low reliability for such use. No apparent diurnal variation was observed in the urinary As excretion rate.

Chemical Composition of Thoracic Dust at Workplaces During Cement Production.

OBJECTIVES: Cement belongs to the most used building materials. Clinker is the major constituent of cement, and it is believed that the strong increase of pH after hydration of clinker minerals is responsible for the observed decline in lung function of cement production workers. Information on clinker exposure at workplaces in the cement production industry is scarse. The aims of this study are to determine the chemical composition of thoracic dust and to quantify workplace exposure to clinker in cement production. METHODS: The elemental composition of 1250 personal thoracic samples collected at workplaces in 15 plants located in 8 different countries (Estonia, Greece, Italy, Norway, Sweden, Switzerland, Spain, Turkey) was determined by inductively coupled plasma optical emission spectrometry (ICP-OES), separately for water- and acid-soluble fraction. Positive matrix factorization (PMF) was used to determine the contribution of different sources to the dust composition and to quantify the clinker content in 1227 of the thoracic samples. In addition, 107 material samples were analysed to facilitate interpretation of the factors obtained by PMF. RESULTS: The median thoracic mass concentrations varied for individual plants between 0.28 and 3.5 mg/m3. PMF with 8 water-soluble and 10 insoluble (i.e., acid-soluble) element concentrations yielded a five-factor solution: Ca, K, Na sulfates; silicates; insoluble clinker; soluble clinker-rich; and soluble Ca-rich. The clinker content of the samples was calculated as sum of the insoluble clinker and soluble clinker-rich factors. The median clinker fraction of all samples was 45% (range 0-95%), and varied between 20% and 70% for individual plants. DISCUSSION: The 5-factor solution of PMF was selected on the basis of several mathematical parameters recommended in the literature as well as the mineralogical interpretability of the factors. In addition, interpretation of the factors was supported by the measured apparent solubility of Al, K, Si, Fe, and to a lesser extent Ca in material samples. The total clinker content obtained in the present study is considerably lower than estimates based on the Ca concentrations in a sample, and somewhat lower than estimates based on Si concentrations after selective leaching with a methanol/maleic acid mixture. The clinker abundance in workplace dust of one plant investigated in the present contribution was also estimated in a recent study by electron microscopy, and the good agreement between both studies gives confidence in the results of PMF. CONCLUSIONS: The clinker fraction in personal thoracic samples could be quantified from the chemical composition by positive matrix factorization. Our results allow for further epidemiological analyses of health effects in the cement production industry. As these estimates are more accurate for clinker exposure than aerosol mass, stronger associations with respiratory effects are expected if clinker is the main cause of these effects.

Urinary iodine excretion and optimal time point for sampling when estimating 24-h urinary iodine.

Iodine deficiency may cause thyroid dysfunction. The iodine intake in a population is measured by urinary iodine concentration (UIC) in spot samples or 24-h urinary iodine excretion (24UIE). 24UIE is considered the gold standard and may be estimated using an equation including UIC, urinary creatinine concentration, sex and age (e24UIE). The aims of this study were to evaluate the preferable timing of UIC when using this equation and assess the variability of UIE. Sixty healthy non-smoking women (n 31) and men (n 29) were included in Gothenburg, Sweden. Twelve urine samples were collected at six fixed times on two separate days. Variability was calculated for UIC, 24UIE, e24UIE, iodine excretion per hour (iHr) and UIC adjusted for creatinine and specific gravity. Median 24UIE was 156 µg/24 h and the median UIC (all spot samples) was 104 µg/l. UIC (P < 0·001), 24UIE (P = 0·001) and e24UIE (P < 0·001) were significantly higher in men. e24UIE was relatively similar to 24UIE. However, when e24UIE was calculated from UIC in the first void, it was about 15 % lower than 24UIE (P < 0·001). iHr was lowest in the morning and highest in the afternoon. Median iHr was higher in men (7·4 v. 5·3 µg/h, P < 0·001). The variability of UIE was higher within individuals than between individuals. This study suggests that most time points for estimation of individual 24UIE are appropriate, but they should preferably not be collected in the first void.

Occupational Exposure among Electronic Repair Workers in Ghana.

Electronic repair workers may be exposed to lead, mercury, cadmium and other elements including rare earth elements used in electronic equipment. In this study, repair work took place in small repair shops where, e.g., televisions, radios, video players, compact discs and computers were repaired. Personal full-shift air samples of particulate matter were collected among 64 electronic repair workers in Kumasi (Ghana) and analysed for 29 elements by inductively coupled plasma mass spectrometry. Results showed that air concentrations of all elements were low. The highest air concentration was measured for iron with a geometric mean concentration and geometric standard deviation of 6.3 ± 0.001 µg/m3. The corresponding concentration of Pb and Hg were 157 ± 3 ng/m3 and 0.2 ± 2.7 ng/m3, respectively. The cerium concentration of 5 ± 2 ng/m3 was the highest among the rare earth elements. Source apportionment with ranked principal component analysis indicated that 63% of the variance could be explained by the repair and soldering of electronic components such as batteries, magnets, displays and printed circuit boards. An association between concentrations of lead in the workroom air and lead in whole blood was found (Pearson's correlation coefficient r = 0.42, p < 0.001). There was, however, no statistically significant difference between whole blood lead concentrations in the workers and references indicating that lead did not exclusively originate from occupational exposure.

Physicochemical characterization of particulate matter in a cement production plant.

Employees working in cement production plants are exposed to airborne particulate matter (PM) which may lead to lung function impairments and airway symptoms. The PM consists of raw materials, clinker and additives which vary depending on cement blend. The aim of this work was to characterize the thoracic fraction of PM with regard to size, phase composition and mixing state. Both stationary and personal impactors were used to collect size-fractionated samples in a cement production plant in Norway. Stationary samples were measured with aerosol particle counters and collected with a 13-stage cascade impactor, which were stationed at three locations of the cement production plant: at the raw meal mill, clinker conveyor belt and cement mill. Sioutas cascade impactors, and thoracic and respirable dust samplers were used in parallel for personal sampling. Additionally, particles for electron microscopy were collected with the stationary cascade impactor for size-fractionated single particle characterization. Gravimetric measurements and element compositions of the samples from the stationary impactors show that the PM mass is dominated by calcium-rich particles of size >1 µm. The size distribution results of stationary and personal impactors were similar. Characterization of single particles reveals that limestone is the dominating material in the raw meal mill, whereas clinker and limestone dominate at the clinker conveyor belt and at the cement mill. The element composition of clinker PM did not change with particle size. The PM collected on impactor stages with aerodynamic diameter cut-offs below 0.56 µm was dominated by soot and volatile secondary particles at the three locations. The number of ultrafine particles of the cement related compounds was low. Air concentrations of PM in personal respirable and thoracic samples ranged from 0.14-10 mg m-3 to 0.37-9.5 mg m-3, respectively. Considerable local variations exist, both in composition and air concentration of the PM.

Variability of lead in urine and blood in healthy individuals.

BACKGROUND: Lead is a non-essential toxic trace element. Lead in blood (BPb) is the most common biomarker of lead exposure but lead in urine (UPb) has also been used. There is, however, limited data on the variability of UPb in the general population and the association with BPb. OBJECTIVES: Our aims were to assess variability of lead in repeated blood and urine samples. The diurnal variation of UPb was also examined as well as associations with BPb. METHODS: We established an openly available biobank including 60 healthy non-smoking individuals, 29 men and 31 women, 21-64 years of age (median 31 years), with repeated sampling of blood and urine. Timed urine samples were collected at six fixed time points in two 24 h periods, about one week apart, and adjusted for creatinine and specific gravity (SG). BPb and UPb were analyzed by inductively coupled plasma mass spectrometry. The within- and between-individual variabilities and intra-class correlation coefficients (ICCs; ratios of the between-individual to total observed variances) were calculated using mixed-effects models. RESULTS: The ICCs for UPb samples were mostly above 0.5, when adjusted for creatinine or SG, and higher for overnight samples compared with daytime samples. The highest ICCs were obtained for BPb (ICC = 0.97) and for urine samples corrected for dilution by SG or creatinine. The ICC was 0.66 for overnight samples adjusted for creatinine. High correlations with BPb were found for 24 h UPb (rs = 0.77) and overnight samples, e.g. rs = 0.74 when adjusted for SG. There was diurnal variation of UPb with lowest excretion rate in overnight samples. There was also a significant association between the Pb excretion rate and urinary flow rate. CONCLUSIONS: In addition to BPb, UPb adjusted for creatinine or SG seems to be a useful biomarker for exposure assessment in epidemiological studies.

Particle characterisation and bioaccessibility of manganese in particulate matter in silico- and ferromanganese smelters.

The aim of this study was to characterise particulate matter (PM) collected in the furnace area during SiMn and high carbon (HC)-FeMn production in terms of single particle analysis and to determine the bioaccessibility of Mn in the PM in a simulated lung fluid. Airborne PM was collected with Sioutas cascade impactors and respirable cyclones in the breathing zone of tappers and crane operators. Stationary samples were collected from the furnace area with a nanoMOUDI cascade impactor and an ESPnano electrostatic particle collector. Individual particles were characterised by scanning and transmission electron microscopy. Bioaccessibility of Mn was studied in terms of the dissolution of Mn in Gamble solution (24 hours leaching at 37 °C) relative to total Mn. Slag particles, alloy fragments, Mn and Fe oxides as well as carbonaceous particles were observed in the size fraction > 1 µm aerodynamic diameter (dae). Thermally generated condensation particles dominated the dae size range of 0.18-1 µm collected from the tapping fumes, while carbonaceous particles dominated the fraction below 0.18 µm. Condensation generated particles from the furnace area of HC-FeMn production were coated with an amorphous Si-O rich surface layer which seemed to hold primary particles together as aggregates. In the same size range, the particles from the furnace area of SiMn production were dominated by spherical condensation particles rich in Si, Mn and O, but without a Si-O rich surface layer. Instead, the Mn oxides were enclosed in an amorphous Si-O rich matrix. The bioaccessibility of Mn was low to moderate (<30%), but higher for SiMn furnace workers (highest median = 23%) than HC-FeMn furnace workers (highest median = 12%). This difference in bioaccessibility was significant for PM with dae up to 2.5 µm, and most pronounced in the dae size range between 0.25 and 1.0 µm. Also, a significantly higher bioaccessibility of Mn was found for PM larger than dae of 0.5 µm collected among crane operators compared to tappers in the HC-FeMn smelter.

Normal variability of 22 elements in 24-hour urine samples - Results from a biobank from healthy non-smoking adults.

BACKGROUND: Urine is often used for biomonitoring the exposure to elements. However, most studies report concentrations in spot urine samples, which may not accurately mirror the "gold standard" of complete 24-h (24 h) urine samples. There are relatively few data published for 24 h samples, and little information on the within- and between person variability. OBJECTIVES: The present study aimed at assessing variability within and between individuals in 24 h excretion for a number of elements in adults from the general population and the typical 24 h excretion of these elements. In addition, we assessed concentrations adjusted for creatinine and specific gravity (SG), and associations between elements. METHODS: 60 healthy non-smokers (31 women and 29 men) from Sweden, aged 21-64 years, collected all urine during 24 h (split into six separate samples) on two occasions, about one week apart. Concentrations of As, Br, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, P, Pb, S, Sb, Se, Sn, U, V, W, and Zn in urine were analyzed by inductively coupled plasma sector-field mass spectrometry (ICP-SF-MS) and 24 h excretion rates were calculated for each day. The ratio of between-individual variance and the total variance, the intra-class correlation (ICC) was calculated based on natural log-transformed 24 h excretion. Correlation coefficients were calculated between excretion rates (mass/24 h), and concentrations adjusted for creatinine and SG. RESULTS: Geometric means (GM), and 90-percentiles are presented for each element. The 24 h excretion was higher in men than in women for most elements, and the difference was statistically significant for Cr, Cu, Fe, Li, P, Pb, S, Se, U, V, and Zn. However, for Cd and Co, the excretion was higher in women. Variability between days was low for Cd, Co, Hg, Pb, Sn, Se, V, and Zn (ICC 0.75-0.90), highest for Cr (ICC = 0.3) and Sb (ICC = 0.18), and moderate for the other elements. Spearman's rank correlation coefficients were about 0.8-0.9 for 17 elements, and 0.3-0.7 for Br, Cu, P, S, Se. Excretion of P and S were highly correlated, and also associated with excretion of most of the other elements, especially Cu, Se, V, and Zn. A high correlation was also found between As and Hg, between Mo and W, as well as between Cr, Fe and Mn. CONCLUSIONS: These data present normal variability of 24 h excretion of a number of elements, and can also be used as updated reference levels for elements with no or limited previous literature available. Information on variability within- and between individuals is important to know when designing studies with urine levels of elements used as exposure biomarker in studies of associations with health outcomes.

Per- and Polyfluoroalkyl Substances in Human Serum Samples of Selected Populations from Ghana.

The aims of this study were to assess serum concentrations of per- and polyfluoroalkyl substances (PFASs) in selected populations from Ghana, including workers engaged in the repair of electronic equipment (ERWs), and to elucidate PFAS concentrations in relation to blood mercury concentrations (B-Hg) as a biomarker of seafood consumption. In all, 219 participants were recruited into the study, of which 26 were women and 64 were ERWs. Overall, the PFAS concentrations were low. The most abundant components were perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonic acid (PFHxS). Women had generally lower PFAS concentration than men. The ERWs had statistically significantly higher concentrations of perfluorooctanoate (PFOA), which was associated with the concentration of tin in urine. This could indicate exposure during soldering. The concentration of B-Hg was associated with several of the PFASs such as PFOA, PFOS and perfluoroheptane sulfonate (PFHpS). Additionally, the concentrations of perfluorodecanoic acid (PFDA) and perfluoroundecanoate (PFUnDA) were highly associated with the concentrations of B-Hg. It is noteworthy that the linear isomer of PFHxS was strongly associated with B-Hg while the branched isomers of PFHxS were not. In conclusion, the PFAS concentrations observed in the present study are low compared to other populations previously investigated, which also reflects a lower PFAS exposure within the Ghanaian cohorts. ERWs had significantly higher PFOA concentrations than the other participants. Several PFASs were associated with B-Hg, indicating that seafood consumption may be a source of PFAS exposure.

A study of atherothrombotic biomarkers in welders.

INTRODUCTION: Studies have shown that welders have increased cardiovascular mortality. This may be due to airborne particulate matter (PM) exposure. Elevated levels of PM in polluted urban air have been associated with increased cardiovascular mortality and morbidity. This study seeks to explore potential mechanisms for the increased cardiovascular mortality in welders. METHODS: Seventy welders were compared to 74 referents. Exposure to PM was assessed by personal full-shift sampling of work room air the last 2 days before collection of blood samples. Selected biomarkers of pro-coagulant activity, endothelial/platelet activation and systemic inflammation were determined in the samples. RESULTS: The welders had been occupationally exposed to PM for 15 years on average. The geometric mean current exposure to PM was 8.1 mg/m3. They had statistically significantly higher concentrations of TNF-α, P-selectin, CD40L, prothrombin fragment 1 + 2 and D-dimer than the referents. Increasing concentrations of D-dimer and CD40L were observed by increasing current exposure to PM. DISCUSSION: The study shows that welders highly exposed to welding PM were in a pro-thrombotic state with increased thrombin generation and consequently higher D-dimer concentrations. The welders had also increased endothelial/platelet activation as compared to the referents. These alterations are compatible with increased cardiovascular mortality as previously reported among welders.

Workplace exposure to particulate matter, bio-accessible, and non-soluble metal compounds during hot work processes.

While exposure to air contaminants from metal arc welding at workplaces has been intensively investigated over the last five decades, other hot work processes, such as flame and plasma cutting, air carbon arc gouging, and surface grinding have not received as much attention. Exposures to particulate matter (PM) during selected hot work processes, such as metal active gas (MAG) and manual metal arc (MMA) welding, flame and plasma cutting, air carbon arc gouging, and surface grinding were measured. Respirable, inhalable, and "total" fractions of the PM were collected with different air samplers in the workers' breathing zone. Concentrations of PM, chromium (Cr), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), copper (Cu), and lead (Pb) were determined in the samples by using gravimetric analysis and plasma-based analytical atomic spectrometry techniques. Bio-accessibility of the elements was investigated by using a synthetic lung lining fluid (Hatch´s solution) for the leaching of soluble metal compounds in the collected samples. Short term (15-75 min) workplace air concentrations of PM, Cr, Fe, Mn, Ni and Cu in the workers´ breathing zone during hot work processes were found to be high compared to the current 8-hr time-weighted average (TWA) exposure limit values (ELVs) in use in many countries. The short-term median concentrations of PM during the different hot work processes varied between 6.0 and 88.7 mg m-3 and between 15.1 and 193 mg m-3 in the respirable and inhalable fractions, respectively. The highest median concentration of Fe (107 mg m-3) and Mn (28.7 mg m-3) was found in the inhalable fraction during plasma cutting and air carbon arc gouging, respectively. More than 40% of the inhalable PM generated during flame and plasma cutting, air carbon arc gouging and surface grinding was present in the respirable fraction. There was large variation in the bio-accessibility of the elements in PM collected during the different hot work processes.

On the bio-accessibility of 14 elements in welding fumes.

The bio-accessibility of 14 elements in welding fume particulate matter was investigated in 325 personal air samples collected during welding in two shipyards and one factory producing heavy machinery. The apparent solubility in a synthetic lung lining fluid (Hatch's solution) was used as proxy for the bio-accessibility. The Hatch solubility of the different elements was highly variable with a median < 1% for Al, Fe, Pb, Ti, between 4 and 6% for Co, Cr, Ni, V, W, between 13 and 27% for Cd, Cu, Mn, Zn, and 41% for Mo. For many elements, the solubility varied over a wide range of several tens of percent. The welding techniques used influenced the solubility of Co, Cr, Cu, Mn and V significantly. The plants investigated (i.e., the welded materials and used electrodes) had a significant influence on the solubility of Co, Cr, Cu, Mn, Mo, V and W. According to principal component analysis (PCA), the variation in solubility can be described by four components, which explain 69% of the variance. The first principal component mostly comprises elements that can predominantly occur as divalent cations, the second principal component elements often forming oxyanions. The principal components are independent of the absolute value of the Hatch solubility. The results of PCA indicate that the co-variation of Hatch solubility is mainly controlled by the most soluble compounds in contrast to the absolute value of apparent solubility, which is strongly influenced by the distribution of the elements between compounds with different equilibrium solubilities. The observed large variability and the significant differences between welding techniques and plants clearly show that the bio-accessibility cannot be obtained from the literature but has to be studied experimentally at each location of interest.

Elemental Carbon and Nitrogen Dioxide as Markers of Exposure to Diesel Exhaust in Selected Norwegian Industries.

Elemental carbon (EC) and nitrogen dioxide (NO2) in air as markers for diesel exhaust (DE) emission exposure were measured in selected work environments in Norway where diesel-powered engines are in use. Two hundred and ninety personal full-shift air samples were collected in primary aluminium production, underground and open-pit mining, road tunnel finishing, transport of ore, and among airport baggage handlers. EC was determined in the samples by a thermo-optical method, while NO2 was determined by ion chromatography. Highest EC air concentrations (geometric mean, GM) were found in aluminium smelters (GM = 45.5 µg m-3) followed by road tunnel finishing (GM = 37.8 µg m-3) and underground mining activities (GM = 18.9 µg m-3). Low EC air concentrations were measured for baggage handling at an international airport (GM = 2.7 µg m-3) and in an open-pit mine (GM = 1.2 µg m-3). Air concentrations of NO2 were similar in road tunnel finishing (GM = 128 µg m-3) and underground mining (GM = 108 µg m-3). Lower NO2 values were observed in open-pit mining (GM = 50 µg m-3), at the airport (GM = 37 µg m-3), and in the aluminium smelters (GM = 27 µg m-3). Highly significant (P < 0.001) positive correlations between NO2 and EC air concentrations in underground mining (r = 0.54) and road tunnel finishing (r = 0.71) indicate a common source of these pollutants. NO2 and EC were also correlated (P < 0.01) positively at the airport. However, due to the complex air chemistry and a potential contribution of various sources, the correlation between EC and NO2 cannot be regarded as unambiguous hint for a common source. The association between EC and NO2 was not of statistical significance in open-pit mining. In the aluminium smelters, EC and NO2 were negatively correlated, although not reaching statistical significance. The substantial differences in NO2/EC ratios across the investigated industries, ranging from around 0.2 in the primary aluminium production to around 25 during spring at the airport, clearly show that exposure to DE cannot be estimated based on NO2 concentrations, at least for outdoor environments. Results in the primary aluminium production suggest that the measured EC concentrations are related to DE emissions, although the NO2 concentrations were low. Further studies are required to assess the magnitude of exposure in primary aluminium production.

Size distribution and single particle characterization of airborne particulate matter collected in a silicon carbide plant.

The global SiC market is projected to grow in the coming years, and research on potential health effects as well as epidemiological studies is therefore of importance. A detailed characterization in terms of the phase composition, morphology and mixing state of airborne PM is still missing, though highly necessary to identify sources and to understand the risk factors in this industry. Particles in the size range of 10 nm to 10 µm were collected with a 13-stage NanoMOUDI impactor in the Acheson Furnace Hall as well as in processing departments during two sampling campaigns. Particle mass concentrations, including the fraction of ultrafine particles (UFPs), were lower in the processing departments in comparison to those in the Acheson Furnace Hall. The particle number size distribution measured with a scanning mobility particle sizer confirmed the low amount of UFPs in the processing departments compared to the furnace hall. Significant differences in the particle mass concentration and distribution were observed in the Acheson Furnace Hall during the two sampling campaigns. The PM size distribution depends upon the sampling location, on the cycle of the nearby furnaces and on special incidents occurring during a furnace run. Scanning and transmission electron microscopy (SEM and TEM) showed that the size range of 0.32-10 µm (aerodynamic diameter) is dominated by carbon (C)-rich particles, which were identified as petroleum coke, graphite, soot and amorphous spherical C-rich particles. Soot was further classified into three types based on the primary particle size, morphology and composition. Diesel-powered vehicles, pyrolysis of petroleum coke and incomplete combustion of volatile components from this pyrolysis are suggested as sources of different soot particle types. Amorphous spherical C-rich particles were also sub-classified based on their morphology and composition as tar balls (TBs) and C-spherical type 2. The amount of SiC fibers and crystalline SiO2 was found to be low. In the size fraction below 0.32 µm (aerodynamic diameter), sulphur (S)-rich particles dominate. This knowledge of the particle size distribution, and chemical and physical properties of the PM occurring in the SiC production is fundamental for an appropriate risk assessment, and these findings should have implications for future epidemiological studies and for the mitigation of worker exposure.

Characterization of air contaminants emitted during laser cutting of carbon fiber-reinforced composite materials.

The emission of ultrafine carbonaceous particles during the laser cutting of fiber-reinforced polymer (CFRP) composite materials was investigated. The study was based on characterization of air contaminants emitted during laser cutting of an epoxy-based CFRP material with respect to particle size distribution, particle morphology, and chemical composition. Results indicate that about 90% of the total particulate mass is present as fine particulate matter with an aerodynamic cut-off diameter of 0.25 µm, and considerable amounts of ultrafine carbonaceous particulate matter dominated by organic carbon are emitted during high-power laser cutting of CFRP.

Kinetics and tissue distribution of bismuth, tin and lead after implantation of miniature shotgun alloy pellets in rats.

INTRODUCTION: Shotgun pellets containing bismuth (Bi) as substitute for lead (Pb) are increasingly being used due to environmental concerns. Information on toxicokinetics of Bi is lacking for the assessment of humans accidentally shot by Bi-containing shotgun alloy pellets. METHODS: Male Wistar rats were exposed to miniature alloy pellets containing Bi, tin (Sn) and minor amounts of Pb by implantation in muscle tissues of the hind legs. RESULTS: The concentrations of Bi in whole blood and urine increased up to 53 weeks after implantation. The highest concentrations of Sn in whole blood were observed three weeks after implantation, then declining to background levels 53 weeks after implantation. Lead in whole blood increased up to 13 weeks of exposure, and declined for the remaining observation period. Bismuth and Sn accumulated mainly in kidney, but also in liver, testicle and brain. Analytical field emission scanning electron microscopy of post-implant pellets showed depletion of Pb towards the pellet surface. Oxygen and chlorine accumulated in Sn rich lamellas in areas next to the pellet surface. The distribution of Bi remained visually unaffected as compared to pre-implant pellets. CONCLUSION: The concentration of Bi increased during the whole observation period in blood, urine, kidney, brain, testicle and liver. The decline in the concentrations of Pb and Sn in blood and urine after reaching the peak concentration may be related to alterations in the chemical composition and element distribution of the implanted alloy pellets.

Phase identification of individual crystalline particles by combining EDX and EBSD: application to workplace aerosols.

This paper discusses the combined use of electron backscatter diffraction (EBSD) and energy dispersive X-ray microanalysis (EDX) to identify unknown phases in particulate matter from different workplace aerosols. Particles of α-silicon carbide (α-SiC), manganese oxide (MnO) and α-quartz (α-SiO2) were used to test the method. Phase identification of spherical manganese oxide particles from ferromanganese production, with diameter less than 200 nm, was unambiguous, and phases of both MnO and Mn3O4 were identified in the same agglomerate. The same phases were identified by selected area electron diffraction (SAED) in transmission electron microscopy (TEM). The method was also used to identify the phases of different SiC fibres, and both ß-SiC and α-SiC fibres were found. Our results clearly demonstrate that EBSD combined with EDX can be successfully applied to the characterisation of workplace aerosols. Graphical abstract Secondary electron image of an agglomerate of manganese oxide particles collected at a ferromanganese smelter (a). EDX spectrum of the particle highlighted by an arrow (b). Indexed patterns after dynamic background subtraction from three particles shown with numbers in a

Interlaboratory comparison for the determination of the soluble fraction of metals in welding fume samples.

There is interest in the bioaccessible metal components of aerosols, but this has been minimally studied because standardized sampling and analytical methods have not yet been developed. An interlaboratory study (ILS) has been carried out to evaluate a method for determining the water-soluble component of realistic welding fume (WF) air samples. Replicate samples were generated in the laboratory and distributed to participating laboratories to be analyzed according to a standardized procedure. Within-laboratory precision of replicate sample analysis (repeatability) was very good. Reproducibility between laboratories was not as good, but within limits of acceptability for the analysis of typical aerosol samples. These results can be used to support the development of a standardized test method.

Cellular responses of human astrocytoma cells to dust from the Acheson process: An in vitro study.

Silicon carbide (SiC) is largely used in various products such as diesel particulate filters and solar panels. It is produced through the Acheson process where aerosolized fractions of SiC and other by-products are generated in the work environment and may potentially affect the workers' health. In this study, dust was collected directly on a filter in a furnace hall over a time period of 24h. The collected dust was characterized by scanning electron microscopy and found to contain a high content of graphite particles, and carbon and silicon containing particles. Only 6% was classified as SiC, whereof only 10% had a fibrous structure. To study effects of exposure beyond the respiratory system, neurotoxic effects on human astrocytic cells, were investigated. Both low, occupationally relevant, and high doses from 9E-6µg/cm2 up to 4.5µg/cm2 were used, respectively. Cytotoxicity assay indicated no effects of low doses but an effect of the higher doses after 24h. Furthermore, investigation of intracellular reactive oxygen species (ROS) indicated no effects with low doses, whereas a higher dose of 0.9µg/cm2 induced a significant increase in ROS and DNA damage. In summary, low doses of dust from the Acheson process may exert no or little toxic effects, at least experimentally in the laboratory on human astrocytes. However, higher doses have implications and are likely a result of the complex composition of the dust.