Respirable Dust Fractions Research Articles

Measuring Respirable Crystalline Silica (Quartz) from Powdery Materials through Sedimentation and X-ray Diffractometry.

When possible, choosing materials with a low quartz content is the most effective and cost-efficient way to prevent the respirable quartz exposure of workers and other end users of powdery products. Therefore, methods are needed to analyze low amounts of quartz from powdery products, such as sand, gravel, plaster, cement, and concrete. To this end, we present a method to analyze respirable dust and quartz from powdered materials, such as construction products. The method includes separation of the respirable dust fraction by liquid sedimentation, followed by gravimetric analysis and determination of the crystalline silica content by X-ray diffractometry. While also aiding in the development of less harmful products, analysis of the quartz concentration of powdery products is statutory in Eu countries, excluding natural products not chemically modified. According to EU Regulation No. 1272/2008, products must be classified if they contain harmful substances in concentrations above 0.1 wt.%, and clauses pertaining to cancerous properties and harmfulness to lungs should be included. Also, mineral producers in the EU recommend that products containing respirable quartz should be labelled based on their quartz concentration, provided the concentration exceeds 1 wt.%. The present method meets these needs. The analysis can be performed in parallel from 50 to 1000 mg (dry weight) of powdery materials. The quantitative limit of determination was 10 µg per sample, corresponding to 0.01 wt.%, and the linear range 0.02-10 wt.% (10-5000 µg quartz per sample, Pearson correlation coefficient 0.99). The accuracy of the method was 82% and the repeatability 11%.

1 Comparison of Ni Speciation Using Methods of Sequential Leaching and Quantitative Mineralogy for Workplace Aerosol at a Stainless Steel Plant

Abstract Based on epidemiological records of workers at Ni operations, regulatory guidelines often target specific Ni compounds for setting exposure limits. Thus, reliable methods of Ni speciation in airborne dust samples are required for effective monitoring of workplace exposure. In this study, Ni speciation of dust collected from a stainless steel operation was performed using a variety of methods: Zatka sequential leaching (original and modified protocols), soluble and insoluble Ni as described in ISO 15202, and quantitative mineralogy (QEMSCAN). Mineral characterization was also performed on bulk material collected from selected work areas at the plant. The quantitative mineralogical analysis determined that the Ni dust is composed of oxidic Ni (Ni in chromite and trevorite, > 80 % of the Ni in most samples) and metallic Ni (Ni-Fe alloy), and the results were validated against chemical assays and alternate methods of mineral characterization (Electron Probe Microanalysis, EPMA). In contrast, the original Zatka method erroneously identified soluble Ni as a major Ni contributor, whereas the modified Zatka method identified sulfidic Ni. The mineralogy identified ambient dust and grain sizes and textures of individual Ni compounds as potential factors that can affect leaching selectivity. Improving methods of sequential leaching is important because the resolution of quantitative mineralogical techniques diminishes at < 3 µm (respirable dust fraction). We recommend that quantitative mineralogy be performed in parallel with methods of sequential leaching to provide a robust system of characterization.

114 Development of High Volume Personal Aerosol Samplers

Abstract The tendency for decreasing a series of occupational exposure limit values is seen the last years. Especially metal species are linked to a larger health effect in latest toxicological assessments. These changes imply further reductions of the limits of quantification for both the sampling and analysis methods. The personal sampling methods (as a set of sampler, filter and pump) used today comprise air flows up to 10 l/min. In order to achieve higher amounts of sampled aerosols an airflow of 20 l/min is aimed for a new set of samplers for the inhalable and respirable dust fraction. This also enables shorter sampling times than a full shift, e.g. task based exposure assessment. A small set of prototypes was designed to go into testing. A filter size of 47 mm was chosen to realise a higher dust load and an acceptable pressure drop for a personal air sampling pump. Such a pump was recently developed and is now available. Samplers for the inhalable fraction with different numbers and orientation of orifices are tested in a calm air dust chamber and a wind tunnel according to the test standard EN 13205 in the particle size range up to 100 µm. A cyclone design according to the GK family of cyclones (Mesalabs) was chosen to meet the respirable convention. First test results will be shown, either in comparison with validated samplers or in terms of the sampling efficiency in dependence of the aerodynamic diameter.

130 An Exposure Assessment of dust- and Respirable Quartz Levels During Indoor Renovations

Abstract Construction workers are exposed to a complex mix of inorganic dust and other components. Workers doing interior demolition and renovation work are particularly at risk as the work operations can produce large quantities of dust in areas with low ventilation. The aim of this work is to assess the dust- and respirable quartz levels that workers in the construction industry are exposed to. An additional goal with the study is to investigate the inorganic components present in the respirable dust fraction using Rietveld as a multicomponent analysis with XRD. Workers in the construction industry have been carrying personal respirable air samplers during work with concrete and building bricks. Quartz content in respirable air samples is determined by X-ray powder diffraction (XRD) by using the NISOH 7500 method. Gravimetric analysis of 67 respirable dust samples gave a mean of 1.34 mg/m3 (min 0.028 mg/m3 to max 6.0 mg/m3). Initial determination of quartz content by XRD revealed a mean of 0.109 mg/m3 (n=52) respirable quartz, with a minimum, maximum and median of 0.0074 mg/m3, 0.60 mg/m3 and 0.045 mg/m3 respectively. The X-ray diffractograms show a complex mixture of inorganic components. These results show that construction workers may be exposed to levels above the current OEL for respirable quartz. It is therefore important to measure the quartz levels in this industry.

28 Evaluation of Work-Related Exposures to the Inhalable and Respirable Dust Fraction and to Respirable Quartz

Abstract Dust is found in the entire environment as well as in working areas. When assessing dust exposure at workplaces, measurements on inhalable and respirable dust are performed. Furthermore, quartz is used as an agent or is released in the form of respirable dust in a number of work processes. Between 2005 and 2016, 35,000 measurements on each dust fraction were performed in the “Measurement System for Exposure Assessment” – MGU. In addition, 15,000 measurements on respirable quartz were performed in this data period. These exposure data on the dust fractions and quartz was stored in the IFA exposure-database MEGA. Statistic evaluations of these data were done according to industrial sectors and work areas. Further grouping criteria like the measurement strategy ("personal measurements" and "stationary sampling") and the sampling time (≥ 2 hours and < 2 hours) help to describe the dust and quartz exposure at work places. Dust and quartz exposures occurring in working areas were analysed for about 20 different industrial sector groups like ceramic and glass industry, foundries, or metalworking and mechanical engineering. These sector groups were further divided in individual sectors and typical tasks performed in these sectors. For example, the tasks stone cutting in stone masonry, mixing and filling in the chemical industry or powder coating in the metalworking sector. The statistical evaluations from the MEGA database are published in IFA-reports about the exposure to inhalable and respirable dust and to quartz for prevention and for retrospective considerations.

Rapid Assessment of Oxidative Damage Potential: A Comparative Study of Engineered Stone Dusts Using a Deoxyguanosine Assay.

The popularity of engineered stone (ES) has been associated with a global increase in occupational lung disease in workers exposed to respirable dust during the fabrication of benchtops and other ES products. In this study, the reactivity and subsequent oxidative reduction potential of freshly generated ES dusts were evaluated by (i) comparing different engineered and natural stones, (ii) comparing settled and respirable stone dust fractions and (iii) assessing the effect of ageing on the reactivity of freshly generated stone dust. An established cell-free deoxyguanosine hydroxylation assay was used to assess the potential for oxidative DNA damage. ES dust exhibited a higher relative reactivity than two of the three natural stones tested. Respirable dust fractions were found to be significantly more reactive than their corresponding settled fraction (ANOVA, p < 0.05) across all stone types and samples. However, settled dust still displayed high relative reactivity. The lower reactivity of the settled dust was not due to decay in reactivity of the respirable dust when it settled but rather a result of the admixture of larger nonrespirable particles. No significant change in respirable dust reactivity was observed for three ES samples over a 21-day time period, whereas a significant decrease in reactivity was observed in the natural stone studied. This study has practical implications for dust control and housekeeping in industry, risk assessment and hazard management.

Estimating cobalt exposure in respirable dust from cobalt in inhalable dust.

Cobalt is a commonly used element in metal industry. Exposure to workers occurs mainly by inhalation of cobalt-containing dust. For the evaluation of cobalt exposure, risk assessment and investigations on occupational diseases, measurements of cobalt in respirable dust are needed. Up to now, often only data for cobalt in inhalable dust are available, which is due to the earlier classification of the limit value in this fraction. Therefore, a possibility to convert cobalt concentrations mathematically from inhalable into respirable concentrations is desirable. In this study, 639 parallel measurements of cobalt concentrations in inhalable (cI(Co)) and respirable dust fractions (cR(Co)) were extracted from the non-public exposure database MEGA (Measurement data relating to workplace exposure to hazardous substances, maintained at the Institute for Occupational Safety and Health of the German Social Accident Insurance) and investigated by regression analysis. For the whole dataset regression shows high quality measures (correlation coefficient R=0.888, adjusted coefficient of determination adj. R2=0.788 - R2 is adjusted to sample size). Further description of the data is achieved by splitting the dataset according to the type of sampling ('stationary' and 'personal') and three working activity groups, 'high temperature processing', 'filling/transport/storage', and 'machining/abrasive techniques' (0.845 ≤ R≤0.876; 0.711 ≤ adj. R2 ≤ 0.762). As subgroups of 'high temperature processing' and 'machining/abrasive techniques' two further groups could be determined. These groups are called heuristic groups, since they have to be formed non-systematically by trial and error. These heuristic groups are 'welding' and 'grinding'. They are more selective on the included working activities with adj. R2 of 0.703 and 0.748 respectively. The resulting conversion functions of all groups are power functions with exponents between 0.704 and 0.794. For the estimation of cobalt in respirable dust in other studies, it is possible to use the conversion functions of the heuristic and working activity groups. Limitations of the possibility to use the conversion functions are discussed.

Chemistry and particle size distribution of respirable coal dust in underground mines in Central Eastern Europe

Despite international efforts to limit worker exposure to coal dust, it continues to impact the health of thousands of miners across Europe. Airborne coal dust has been studied to improve risk models and its control to protect workers. Particle size distribution analyses shows that using spraying systems to suppress airborne dusts can reduce particulate matter concentrations and that coals with higher ash yields produce finer dust. There are marked chemical differences between parent coals and relatively coarse deposited dusts (up to 500 µm, DD500). Enrichments in Ca, K, Ba, Se, Pb, Cr, Mo, Ni and especially As, Sn, Cu, Zn and Sb in the finest respirable dust fractions could originate from: (i) mechanical machinery wear; (ii) variations in coal mineralogy; (iii) coal fly ash used in shotcrete, and carbonates used to reduce the risk of explosions. Unusual enrichments in Ca in mine dusts are attributed to the use of such concrete, and elevated K to raised levels of phyllosilicate mineral matter. Sulphur concentrations are higher in the parent coal than in the DD500, probably due to relatively lower levels of organic matter. Mass concentrations of all elements observed in this study remained below occupational exposure limits.

Comparison of quantitative mineralogy and sequential leaching for characterization of Ni in workplace dust collected at a stainless steel operation

Based on epidemiological records of workers at Ni operations, regulatory guidelines commonly target specific Ni compounds for setting exposure limits. Thus, reliable methods of Ni speciation in airborne dust samples are required for effective monitoring of workplace exposure. Zatka sequential leaching has been routinely performed industry-wide since the 1990s for characterization of Ni in dust samples; however, limitations related to leaching kinetics have been identified, and optimization of the methodology is required to improve accuracy of data. In this study, Ni characterization of dust collected from a stainless steel operation was performed using Zatka sequential leaching (original and modified protocols) and quantitative mineralogy (QEMSCAN), a method novel to the field of industrial hygiene. Mineral analysis was also performed on bulk material collected from selected work areas at the plant. The results are compared with the objective of identifying opportunities to optimize the methods for characterizing dust that is unique to stainless steel manufacturing. The quantitative mineralogical analysis determined that the Ni dust is composed of oxidic Ni (chromite and trevorite, >80% of the Ni in most samples) and metallic Ni (Ni-Fe alloy), and the results were validated against chemical assays and alternate methods of mineral characterization. In contrast, the original Zatka method erroneously identified soluble Ni as a major Ni contributor, whereas the modified Zatka method identified sulfidic Ni. The mineralogy identified Ni-barren dust and grain sizes and liberation of individual Ni compounds as potential factors that can affect leaching selectivity. Clearly, for any sequential leaching method to be useful for these workplaces, they should be optimized by including reference materials that are representative of Ni substances present at stainless steel operations (chromite, trevorite, and Ni-Fe alloy). Improving methods of sequential leaching is important because the resolution of quantitative mineralogical techniques diminishes at <3 μm (respirable dust fraction). We recommend that quantitative mineralogy be performed in parallel with methods of sequential leaching to provide a robust system of characterization.

Estimating nickel exposure in respirable dust from nickel in inhalable dust.

The conversion of dust components is of high importance for retrospective evaluations of exposure levels, of occupational diseases or the time trend of occupational dust exposure. For this purpose, possibilities to convert nickel concentrations from inhalable to respirable dust are discussed in this study. Therefore, 551 parallel measurements of nickel concentrations in inhalable and respirable dust fractions were extracted from the exposure database MEGA (maintained at the Institute for Occupational Safety and Health of the German Social Accident Insurance) and investigated by linear regression analysis of ln-transformed concentrations. Inhalable dust is the most important predictor variable, showing an adjusted coefficient of determination (adj. R2) of 0.767 (R2 adjusted to sample size). Since multilinear regression analysis, cannot be applied, further description of data is gained by splitting the whole dataset into working activity groups (e. g. 'high temperature processing', adj. R2=0.628,' filling/transport/storage' adj. R2=0.741, 'machining/abrasive techniques', adj. R2=0.777). From these groups, four task restrictive subgroups, so-called 'heuristic groups', can be derived by pooling similar working tasks with similar regression coefficients and enhanced quality measures (adj. R2 between 0.724 and 0.924): 'welding (grinding time fraction [GTF]<5%)', 'welding (grinding time fraction [GTF]>5%)', 'high temperature cutting' and 'grinding'. For the working activity group 'high temperature processing' and the heuristic group 'welding' the determination of the grinding time fraction and its inclusion or exclusion from a dataset has a huge impact on the description of data and whether a transformation of nickel concentrations using the natural logarithm (ln) is necessary or not. In case of GTF < 5%, the conversions functions are linear, all other conversion functions are power functions with exponents between 0.713 and 0.986. It is possible to develop conversion functions for estimating the nickel concentration in the respirable dust fraction (cR(Ni)) out of the nickel concentration in the inhalable dust fraction (cI(Ni)). For the estimation of Nickel in respirable dust other studies, it is recommend to use the conversion functions of the heuristic trial and error groups. Limitations of the possibility to use the conversion functions are discussed.

Assessment of Occupational Exposure to Indium Dust for Indium-Tin-Oxide Manufacturing Workers.

According to recent research, indium nanoparticles (NPs) are more toxic than micro-sized particles. While cases of indium lung disease have been reported worldwide, very little research has been conducted on the occupational exposure to indium NPs. Recently, an indium-related lung disease was reported in Korea, a global powerhouse for display manufacturing. In this study, we conducted an assessment ofoccupational exposure at an indium tin oxide (ITO) powder manufacturing plant, where the first case of indium lung disease in Korea occurred. Airborne dustwas obtained from a worker’s breathing zone, and area sampling in the workplace environment was conducted using real-time monitoring devices. Personal samples were analyzed for the indium concentrations in total dust, respirable dust fraction, and NPs using personal NPs respiratory deposition samplers. The total indium concentration of the personal samples was lower than the threshold limit value recommended by the American Conference of Governmental Industrial Hygienists (ACGIH TLV), which was set as occupational exposure limit (OEL). However, the respirable indium concentration exceeded the recently set ACGIH TLV for the respirable fraction of indium dust. The concentration of indium NPs ranged between 0.003 and 0.010 × 10−2 mg/m3, accounting for only 0.4% of the total and 2.7% of the respirable indium particles. This was attributed to the aggregating of NPs at the µm sub-level. Given the extremely low fraction of indium NPs in the total and respirable dust, the current OEL values, set as the total and respirable indium concentrations, do not holistically represent the occupational exposure to indium NPs or prevent health hazards. Therefore, it is necessary to set separate OEL values for indium NPs. This study covers only the process of handling ITO powder. Therefore, follow-up studies need to be conducted on other ITO sputtering target polishing and milling processes, which typically generate more airborne NPs, to further investigate the effects of indium on workers and facilitate the necessary implementation of indium-reducing technologies.

Assessment of Worker Exposure to Occupational Organic Dust in a Hemp Processing Facility.

The cultivation and processing of industrial hemp, Cannabis sativa L., is a developing industry in Australia. Exposure to hemp dust is demonstrated as producing reactive and respiratory health effects, potentially causing permanent lung disease or damage. The aim of this study was to assess the airborne organic dust concentrations generated in an Australian hemp processing facility. Personal sampling, in the breathing zone of exposed workers was undertaken for exposure to respirable dust, along with parallel static sampling for airborne concentrations of inhalable and respirable dust fractions. Both static and personal sampling showed that respirable dust concentrations (mg m-3) exceeded the Australian Institute of Occupational Hygienists (AIOH) recommended maximum exposure limit of 1 mg m-3 (respirable fraction) for dusts not otherwise specified, with mean exposures (mg m-3) of M = 1.33, standard deviation (SD) = 1.09 (range 0.07-3.67 mg m-3) and M = 4.49, SD = 4.49 (range 0.77-11.08 mg m-3). The results of the investigation indicate that workers in the hemp processing industry are at risk of developing permanent and disabling respiratory disease due to high dust exposure. There is no Australian occupational exposure limit specifically for hemp dust. It is recommended further research is needed and industry-specific guidance material or model code of practice developed to effectively control exposures.

Estimating Respirable Dust Exposure from Inhalable Dust Exposure.

In the sector of occupational safety and health only a limited amount of studies are concerned with the conversion of inhalable to respirable dust. This conversion is of high importance for retrospective evaluations of exposure levels or of occupational diseases. For this reason a possibility to convert inhalable into respirable dust is discussed in this study. To determine conversion functions from inhalable to respirable dust fractions, 15 120 parallel measurements in the exposure database MEGA (maintained at the Institute for Occupational Safety and Health of the German Social Accident Insurance) are investigated by regression analysis. For this purpose, the whole data set is split into the influencing factors working activity and material. Inhalable dust is the most important predictor variable and shows an adjusted coefficient of determination of 0.585 (R2 adjusted to sample size). Further improvement of the model is gained, when the data set is split into six working activities and three material groups (e.g. high temperature processing, adj. R2 = 0.668). The combination of these two variables leads to a group of data concerned with high temperature processing with metal, which gives rise to a better description than the whole data set (adj. R2 = 0.706). Although it is not possible to refine these groups further systematically, seven improved groups are formed by trial and error, with adj. R2 between 0.733 and 0.835: soldering, casting (metalworking), welding, high temperature cutting, blasting, chiseling/embossing, and wire drawing. The conversion functions for the seven groups are appropriate candidates for data reconstruction and retrospective exposure assessment. However, this is restricted to a careful analysis of the working conditions. All conversion functions are power functions with exponents between 0.454 and 0.946. Thus, the present data do not support the assumption that respirable and inhalable dust are linearly correlated in general.

Exposure to respirable silica among clay brick workers in Kathmandu valley, Nepal

ABSTRACTPrevious studies report high respirable silica exposures among clay brick workers globally; however, there are little data on exposures among workers in fixed chimney Bull's trench kilns, the predominant kiln type in Kathmandu valley, Nepal. We investigated respirable silica exposures among workers (N = 46) in five similar exposure groups (SEGs). Mean exposures were highest for red brick loading/carrying (331 μg/m3), followed by green brick stacking (223 μg/m3), fireman (102 μg/m3), coal crushing/carrying (92 μg/m3), and green brick molding (71 μg/m3). The average free silica content (13.8%) in the respirable dust fraction was similar to levels reported for clay brick workers employed in other types of kilns. Dust control measures and respiratory protection are recommended, with priority given to workers assigned to red brick loading and stacking and green brick stacking and carrying.

CONDITIONS OF THE DEVELOPMENT AND PECULIARITIES OF THE COURSE OF RESPIRATORY DISEASES IN SMELTERS OF TITANIUM ALLOYS

The working conditions, occupational and non-occupational risk factors, prevalence rate and peculiarities of the course of respiratory diseases in smelters of titanium alloys were studied. Working conditions of smelters are estimated as harmful (class of working conditions: 3.3-3.4.) due to factors: heating microclimate, chemicals (chlorine and hydrochloride, sulfur dioxide, nitrogen oxide), industrial dust. A feature of the respirable dust fraction is the high content of titanium oxide particles of the PM10 dimension. There was made an analysis of the health status of workers exposed to industrial dust, depending on the length of service. Diseases of the upper respiratory tract in smelters of titanium alloys were shown to be prevalent, simple catarrhal nasopharyngitis prevails with the subsequent formation of atrophic rhinitis, its prevalence rate among smelters of titanium alloys increases with the experience. The peculiarity of the development of diseases of the upper respiratory tract in smelters of titanium alloys are: deterioration of nasal breathing in workers with experience of from 1 year to 5 years already, in patients with experience from 10 to 15 years the prevalence of catarrhal nasopharyngitis and atrophic rhinitis as its outcome in cases with experience from 15 to 20 years. The bronchial damage in the smelters of titanium alloys develops under the experience more than 5 years. The clinical forms are dominated by the phenomena of catarrhal bronchitis followed by obstruction of the bronchi progressing with the experience, with the formation of irreversible ventilation disorders. With the depletion of antioxidant protection, as a rule, with long duration of the exposure of up to 10 years, aseptic inflammation is formed, which is pronounced clinically as catarrhal endobronchitis. This is a partially reversible pathological process. The described features of the development and course of respiratory diseases in smelters of titanium alloys should be taken into account during periodic medical examinations in order to timely prevent them

PM2.5 or respirable dust measurement and their use for assessment of dust separators

Abstract Different dust fractions, e.g. PM2.5 for environment- and PM4 for workplace limits, are in use to describe the respirable dust amount. International and national standards describe thereby different cut-off limits, measurement methods and calculation procedures. Especially continuous measuring devices that commonly work with optical or electronical auxiliary aids, cannot measure the same absolute respirable dust fraction, because of possible measuring errors. In order to solve this problem, laborious and costly procedures are necessary to have valid results merely for the calibrated dust. If not the measurement of a PM2.5 value for controlling standard dust limits, which are gravimetric defined, is the priority and regarding only the assessment and optimization of dust separators concerning to their respirable dust separation, a simplest possible measurement technique would be sufficient. In this paper, a method for the assessment of the respirable dust separation efficiency using solely an optical particle counter is presented. In addition, the application of this method is shown on the optimization of a special wet-scrubber and on the classification of cleanable dust filter media regarding their respirable dust separation efficiency and their energy consumption.

Personal indium exposure concentration in respirable dusts and serum indium level.

The aim of this study was to assess the relationship between indium exposure concentration in the respirable dust fraction (In-E) and indium in serum (In-S) in workers. Methods: A total of 39 workers were studied. The study subjects were categorized into 3 groups, namely, smelting workers (n=7), ITO workers (n=6) in an ITO grinding plant, and other workers (n=26). In-E and In-S ranged from 0.004–24.0 μg/m3 and 0.1–8.50 μg/L, respectively. The simple regression equation was log(In-S)=0.322×log(In-E)−0.443. The simple correlation coefficients for the smelting workers, ITO workers and other workers were 0.489, 0.812 and 0.163, respectively. The differences in the relationships among the three groups suggest that In-S may vary with the chemical form to which the workers were exposed. In-E and In-S seem to be positively correlated. The correlation coefficient was higher for both smelting and ITO workers than for other workers.

Treated and untreated rock dust: Quartz content and physical characterization

ABSTRACTRock 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.

Physicochemical properties of respirable-size lunar dust

We separated the respirable dust and other size fractions from Apollo 14 bulk sample 14003,96 in a dry nitrogen environment. While our toxicology team performed in vivo and in vitro experiments with the respirable fraction, we studied the size distribution and shape, chemistry, mineralogy, spectroscopy, iron content and magnetic resonance of various size fractions. These represent the finest-grained lunar samples ever measured for either FMR np-Fe0 index or precise bulk chemistry, and are the first instance we know of in which SEM/TEM samples have been obtained without using liquids.The concentration of single-domain, nanophase metallic iron (np-Fe0) increases as particle size diminishes to 2µm, confirming previous extrapolations. Size-distribution studies disclosed that the most frequent particle size was in the 0.1–0.2µm range suggesting a relatively high surface area and therefore higher potential toxicity.Lunar dust particles are insoluble in isopropanol but slightly soluble in distilled water (~0.2wt%/3 days). The interaction between water and lunar fines, which results in both agglomeration and partial dissolution, is observable on a macro scale over time periods of less than an hour.Most of the respirable grains were smooth amorphous glass. This suggests less toxicity than if the grains were irregular, porous, or jagged, and may account for the fact that lunar dust is less toxic than ground quartz.

Uncertainty of Dust Mass Concentration Measurement

Paper deals with dust mass concentration measurement in working environment. The measurement is focused to respirable dust fraction, which is dangerous for people. Light scattering principle of dust mass concentration measurement is used for this purpose. Also cyclone as mechanical way of separation of respirable fraction can be used for this purpose. Next problem is determination of uncertainty of this measurement.