Respirable Fibers Research Articles

Evaluation of asbestos dispersion during laser ablation of rocks containing Naturally Occurring Asbestos (NOA)

Health risks are often overlooked when the short-term consequences are not immediately apparent. During restoration work, cleaning actions can generate particles that pose health risks to workers through inhalation. This is particularly true in the case of asbestos fibres that might be spread out from the laser cleaning of buildings or heritage artifacts made of stone, such as serpentinite and other ultramafic rocks, that have a high probability of containing asbestos (e.g., chrysotile, tremolite asbestos, actinolite asbestos). To show workers the importance of wearing proper protection to prevent health injuries, several serpentinite samples, ascertained to contain asbestos minerals by specific investigations, have been laser ablated using ad hoc modified equipment in order to collocate a HEPA filter prone to collect all dust emitted during ablation. The powder deposited on the surface of these filters after laser ablation was analyzed, by Powder X -ray Diffraction (PXRD), Transmission Electron Microscopy combined with Energy Dispersive Spectroscopy (TEM/EDS), micro-Raman spectroscopy (μ-Raman) and Fourier-transform infrared spectroscopy (FTIR/ATR). The results confirmed the presence of asbestos fibres during the laser ablation of rocks containing Naturally Occurring Asbestos (NOA), emphasizing the importance of wearing appropriate personal protective equipment (PPE) during these procedures. Noteworthy, approximately 33 % of the analyzed fibres met the WHO criteria in size for respirable fibres. Furthermore, through our experiments, we also demonstrated that using tools that integrate filters into working tools would definitively further decrease the risk of fibres inhalation to workers.

Characterization and potential toxicity of asbestiform erionite from Gawler Downs, New Zealand

Abstract Erionite is the name for a zeolite mineral series originating from diagenesis or hydrothermal alteration of volcanic rocks. The particular erionite “species” is based on the dominant extra-framework cation, erionite-Ca, erionite-K, or erionite Na. Irrespective of the species, erionite can display a fibrous/asbestiform morphology and has been linked with cases of malignant mesothelioma, a disease typically associated with asbestos exposure. Characterization of new discoveries of erionite is therefore important to assess any potential exposure hazards. This study describes a new asbestiform erionite from vesicles within the Upper Cretaceous Mt. Somers Volcanics Group (MSVG), Canterbury, New Zealand. The erionite is within the Hinds River Dacite, the youngest unit within the MSVG at Gawler Downs, ~100 km west of Christchurch, in the foothills of the Southern Alps. A multi-analytical approach was taken to analyze the sample which included micro-Raman spectroscopy, thermogravimetric analysis, electron microscopy, electron microprobe analysis, and X-ray powder diffraction with the Rietveld method. Results confirmed the mineral as fibrous erionite-K. The chemical composition of the mineral is unique due to the presence of higher levels of Mg. While Fe was also identified, this was due to smectite flakes occurring on the surface of the erionite fibers. According to the World Health Organization (WHO) respirable mineral fiber definition, where length ≥5 μm, width ≤3 μm, and aspect ratio (L/w) ≥3:1, the Gawler Downs erionite fibers are respirable, while the fibers themselves exceed respirable thickness. In addition to morphology, a value for the potential toxicity model was computed to be 2.28 for the Gawler Downs erionite. This is similar to those of other carcinogenic erionites from Karain, Turkey (2.33), and Nevada, U.S.A. (2.28). Taken together, results indicate Gawler Downs erionite represents an environmental hazard. Nevertheless, further investigation is required to determine potential environmental exposure pathways by which erionite may become airborne and assess the actual environmental risk in the Gawler Downs area.

Comparison of the effects of use, protection, improper renovation and removal of asbestos products on the example of typical old office buildings in Poland

The study focused on old, German building types “LIPSK” and “BERLIN” used in Poland, since the 1960s in Eastern Europe. The different operations on buildings were analysed: protection and maintenance of asbestos products, asbestos removal and inadvertent damage to asbestos as a result of building renovation. Measurements of respirable (countable) asbestos fibres in the air were carried out using the PCOM + PLM method and SEM–EDS. In the case of the accidental destruction of products, initial contamination was ≈7000 f/m3. After 16 weeks from the end of the activity and 20 days of extreme ventilation, contamination decreased to about 500 f/m3. At the same time, in similar rooms, without extreme ventilation, the pollution was above 4000 f/m3. The average increase in pollution in a dozen or so similar buildings, after asbestos removal in places beyond the work zones, ranged from ≈ 1700–2700 f/m3 and lasted for one or two years. These buildings, used without ACM destruction or after product impregnation, have maintained low asbestos contamination < 300 f/m3 for more than 10–20 years. So, due to the easy release of asbestos that occurs with any ACM removal and the increased risk of occupant exposure, these works are often inappropriate for the buildings in question.

Investigation of the Tendency of Carbon Fibers to Disintegrate into Respirable Fiber-Shaped Fragments

Recent reports of the release of large numbers of respirable and critically long fiber-shaped fragments from mesophase pitch-based carbon fiber polymer composites during machining and tensile testing have raised inhalation toxicological concerns. As carbon fibers and their fragments are to be considered as inherently biodurable, the fiber pathogenicity paradigm motivated the development of a laboratory test method to assess the propensity of different types of carbon fibers to form such fragments. It uses spallation testing of carbon fibers by impact grinding in an oscillating ball mill. The resulting fragments were dispersed on track-etched membrane filters and morphologically analyzed by scanning electron microscopy. The method was applied to nine different carbon fiber types synthesized from polyacrylonitrile, mesophase or isotropic pitch, covering a broad range of material properties. Significant differences in the morphology of formed fragments were observed between the materials studied. These were statistically analyzed to relate disintegration characteristics to material properties and to rank the carbon fiber types according to their propensity to form respirable fiber fragments. This tendency was found to be lower for polyacrylonitrile-based and isotropic pitch-based carbon fibers than for mesophase pitch-based carbon fibers, but still significant. Although there are currently only few reports in the literature of increased respirable fiber dust concentrations during the machining of polyacrylonitrile-based carbon fiber composites, we conclude that such materials have the potential to form critical fiber morphologies of WHO dimensions. For safe-and-sustainable carbon fiber-reinforced composites, a better understanding of the material properties that control the carbon fiber fragmentation is imperative.

137 Analysis of Debris Generated During the Process of Cutting and Grinding of Carbon Fibers-Reinforced Plastics

Abstract Carbon fiber reinforced plastics (CFRP) is a leading functional material with superior strength and low mass density compared to metal. Recently, due to its excellent property, it has spread to a wide range of fields from sporting goods, such as golf clubs and fishing rods, to aerospace products. However, there is concern that debris (microparticles) is easily released in the processing process of CFRP. The present study investigated the ambient level, size, and shape of particles generated from CFRP during various machining processes in an occupational setting. The size and shape of particles were observed using scanning electron microscopy (SEM) and their chemical compositions were also analyzed using energy dispersive spectroscopy (EDS). The majority of debris from CFRP was cylindrical with a diameter comparable to the diameter of the original carbon fiber, suggesting transversally split carbon fiber. However, some of the debris was fibrous, length &amp;gt;5 μm, width 3, suggesting longitudinally split carbon fiber. These fibrous fragments were morphologically compatible with the WHO definition of respirable fibers. The particles in the working environment were also monitored with a real-time monitoring device, NanoScan SMPS Model 3910. Measurement by real-time monitoring device showed that not only microparticles but also smaller particles were released in the processing process of CFRP. These particles are probably breakdown elements of the epoxy thermoset polymer (resin) in CFRP. The potential hazard of debris from CFRP in the processing process in an occupational setting and risk assessment is needed for the safe handling of CFRP.

Investigation of the occurrence of binder material on airborne respirable mineral wool fibers

Mineral wool fibers can be released into the air during the production and handling of a mineral wool product where a small fraction of fibers will stay airborne and can potentially be inhaled. The aerodynamic fiber diameter determines how far an airborne fiber can pass through the human airway. Respirable fibers with an aerodynamic diameter < 3 µm can reach the deep part of the lungs (i.e., the alveolar region). Binder material (i.e., organic binder and mineral oil) is used in the production of mineral wool products. However, at the current stage, it is unknown if airborne fibers can contain binder material. We explored binder presence on airborne respirable fiber fractions being released and collected during the installation of two mineral wool products (a stone wool product and a glass wool product). Fiber collection was done by pumping a controlled air volume (2, 13, 22, and 32 l/min) through polycarbonate membrane filters during the installation of the mineral wool products. The morphological and chemical composition of the fibers were studied using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDXS) analysis. The study demonstrates that binder material is found on the surface of the respirable mineral wool fiber mainly as circular or elongated droplets. Our findings suggest that respirable fibers explored in previous epidemiological studies, which have been used for proving a lack of hazardous effects of mineral wool on humans, may have also contained binder materials on the fibers.

Validation and Recalibration of the Asbestos Removal Exposure Assessment Tool (AREAT).

The Asbestos Removal Exposure Assessment Tool (AREAT) was previously developed to estimate exposure to respirable asbestos fibres during abatement processes. The current study describes the validation and recalibration of the AREAT model with external data. During model validation, the AREAT model was expanded to be able to estimate asbestos exposure from an additional source category: 'unspecified asbestos remnants'. The validation dataset (n = 281) was derived from exposure measurement studies where for each exposure measurement the AREAT model parameters were coded and estimates were calculated. Pearson correlation coefficients (r) and intra class correlation coefficients (icc) were calculated as an indication of the agreement between the AREAT estimates and measured concentrations. In addition, the bias and the proportion of measurements with higher concentrations than model estimates were calculated. To expand and investigate model performance on exposure from 'unspecified asbestos remnants', a separate dataset was created with measurements collected during working with unspecified asbestos remnants, and similar validation comparisons were performed. Lastly, linear regression techniques were used to investigate possible improvements in model parameters. The model was recalibrated on a combined dataset consisting of the validation dataset and the original calibration dataset to increase model robustness. The validation comparisons showed good relative agreement (r) between AREAT estimates and measurements (r = 0.73) and a moderate absolute agreement (icc = 0.53). The overall relative bias was 108%, indicating an overall overestimation of exposure, and 4% of the estimated concentrations were higher than the actual measured concentrations. For the data subset concerning unspecified asbestos remnants, a moderate correlation between model estimates and measurement outcomes was found (r = 0.63). However, based on the low number of data in this subset, and moderate r, it was decided that cleaning of unspecified asbestos remnants is out of scope until more data are available. The results of this validation study suggested that two input parameters (product type friable material, efficacy of control measure foam) underestimated exposure. The effects of these parameters were updated to improve model performance. Compared to the original model, the recalibrated model resulted in slightly higher explained variance (62% compared to 56%) and lower uncertainty (15 compared to 17.3). The original AREAT model provided reliable asbestos exposure estimates with a sufficient level of conservatism taking into account the 90-percentile estimates. The model was further improved via the addition of a new feature and recalibration to predict asbestos exposure during the clean-up of unspecified asbestos remnants.

Phosphasilazanes as Inhibitors for Respirable Fiber Fragments Formed during Burning of Carbon-Fiber-Reinforced Epoxy Resins

Carbon-fiber-reinforced polymer composites (CFRPs) exhibit additional hazards during and after burning due to respirable fragments of thermo-oxidatively decomposed carbon fibers. In this study, various phosphasilazanes are incorporated into the RTM 6 epoxy matrix of a CFRP to investigate their flame-retarding and fiber-protective properties via cone calorimetry. Residual carbon fibers are analyzed using SEM and EDX regarding their diameter and elemental composition of deposits. The decomposition process of phosphasilazanes is characterized by DIP-MS and infrared spectroscopy of char. Flame-retardant efficiency and mode of action are correlated with the chemical structure of the individual phosphasilazane and compared for neat resin and composite samples. Phosphasilazanes mainly acting in the condensed phase show beneficial fiber-protective and flame-retardant properties. Those with additional gas phase activity are less efficient. The phosphasilazanes degrade thermally via scission of the Si-N bond. The distribution and agglomeration of deposited particles, formed during the fire, influence the residual fiber diameters. Continuous layers show the best combination of flame retardancy and fiber protection, as observed for N-dimethylvinylsilyl-amidophosphorus diphenylester.

Проблема асбеста с позиции прикладной минералогии

The problem of asbestos geoecology remains relevant. Asbestos is considered potentially dangerous, because when asbestos-containing materials are destroyed, thin elongated fibers are released and damage organs and tissues of mammals and humans. On the other hand, unique fire-resistant thermal properties of asbestos support using it in a wide range of products.&#x0D; Mineralogical study of asbestos ore from the Kiembayevsky deposit, depositing media (dust) and production products used in shipbuilding was carried out by optical microscopy and X-ray analysis.&#x0D; We determined that the methods of optical microscopy and X-ray analysis, and, if necessary, their integration, allowed obtaining reliable information about the presence of chrysotile asbestos and its content in various objects, which was necessary for solving problems not only in the geological industry, but also in other areas of the national economy. A quantitative assessment of the content of chrysotile-asbestos, amphibole-asbestos and asbestos-like respirable fibers (natural and artificial) in rocks, technogenic formations (mainly deposit media), and anthropogenic production products is presented.

FIBERS RESPIRABLE IN THE AIR

Abstract. The paper presents the characteristics of respirable fibers. Respirable fibers are defined as fibers less than 3 μm in diameter, more than 5 μm in length, and a length to thickness ratio of the fiber greater than 3:1. Such dimensions of the fibers allow them to hang in the air and have the ability to travel long distances. Examples of respirable fibers are residues of asbestos products or artificial mineral fibers. The respirable size of the fibers is considered to be a physical carcinogen. The cause of diseases is long-term effects on the respiratory system. Asbestos is assigned a first hazard category. Its permissible concentration limit in the preparation is 0.1% by mass. Exceeding this value requires including this dangerous substance in the classification of any mixture. The need for research on the concentration of respirable asbestos fibers in the atmospheric air is emphasized.

NEUTRALISATION OF ASBESTOS-CONTAINING WASTE

Abstract. The paper presents the characteristics of asbestos as a mineral. Asbestos is a trade name for six serpentine fibrous minerals and amphiboles. The processes of removing asbestos-containing products, which poses a high risk of emission of asbestos fibers harmful to human health, is described. First, make an inventory of asbestos-containing waste to determine the sequence of actions. Products can be qualified for immediate disposal or for temporary preservation, as required by law. When removing asbestos-containing products, the contractor should set up warning boards, fence the area, and take technical measures to eliminate the emission of asbestos fibers. Asbestos-containing products must be moistened with water before being removed. Trained employees should be equipped with personal protective equipment as well as working clothes and footwear. Asbestos-containing waste should be taken to a hazardous waste landfill or an inert or other than inert waste landfill, and placed in areas specially adapted for this purpose. Precautions during inventory and liquidation of asbestos-containing waste are specified. An innovative technology for asbestos neutralization MTT (Microwave Thermal Treatment) is characterized. The impact of asbestos products on health is discussed. The most dangerous cases of diseases are asbestosis, pleural and pericardial diseases, as well as lung cancer and mesothelioma. The need for research on the concentration of respirable asbestos fibers in the atmospheric air is emphasized.

Occupational Exposure to Refractory Ceramic Fibers in the Semiconductor Scrubber Manufacturing Industry

BackgroundRefractory ceramic fibers (RCFs) are a suspected carcinogen but have been widely used as insulations. Depending on the temperature, RCFs can transform into crystalline SiO2, which is a carcinogen that can be present in the air during bulk RCF handling. This study analyzed the physicochemical and morphological characteristics of RCFs at high temperatures and determined the exposure levels during the semiconductor scrubber maintenance. MethodsSampling was conducted at a company that manufactures semiconductor scrubbers using RCFs as insulation. Bulk RCF samples were collected both before and after exposure to a scrubber temperature of 700°C. Airborne RCFs were collected during scrubber maintenance, and their characteristics were analyzed using microscopes. ResultsThe components of bulk RCFs were SiO2 and Al2O3, having an amorphous structure. Airborne RCFs were morphologically different from bulk RCFs in size, which could negatively affect maintenance workers’ health. 58% of airborne RCFs correspond to the size of thoracic and respirable fibers. RCFs did not crystallize at high temperatures. The exposure caused by airborne RCFs during the scrubber frame assembly and insulation replacement was higher than the occupational exposure limit. ConclusionWorkers conducting insulation replacement are likely exposed to airborne RCFs above safe exposure limits. As RCFs are suspected carcinogens, this exposure should be minimized through prevention and precautionary procedures.

Natural and anthropogenic sources of atmospheric air pollution by asbestos fibers

Introduction. Deposits of various types of asbestos are widespread in the earth’s crust. In these areas there may be a possibility of the atmospheric air pollution by asbestos fibers, especially in the case of industrial development of these deposits or active use by the resident population. The purpose of this study was to assess the possibility of air pollution by amphibole asbestos fibers in the areas of disused flooded quarries in Sverdlovsk region. Materials and methods. 5 samples of atmospheric air, water and soil were taken and analyzed at the territories in Sverdlovsk region where magnesio-arfvedsonite and anthophyllite were extracted in the past years. Results. An extremely high content of free fibers of magnesio-arfvedsonite and anthophyllite (up to 20% of the total weight of the samples) was discovered in the soil samples. The concentrations of asbestos fibers in the water averaged 67∙10 6 f/L and 79∙10 6 f/L, respectively. The average concentrations of respirable amphibole asbestos fibers were 0.06 f/ml and 0.05 f/ml, respectively. Limitations. The paper presents the results of a pilot study of air pollution by fibrous particles, based on which it is not possible to give a full description of the situation, taking into account all possible types of anthropogenic activity in the surveyed areas in different seasons of the year. Conclusion. The results obtained indicate an increased risk of air pollution and water environment contamination by free amphibole asbestos fibers due to their leaching and weathering from rocks, as a result of which disused flooded quarries should be considered as natural and anthropogenic sources of pollution. It is necessary to conduct regular monitoring of the environmental situation at these facilities, as well as to develop measures to prevent the exposure of amphibole asbestos fibers on the population.

Assessment of the possibility of air pollution by asbestos fibres during the operation of road surfaces containing stabilizing asbestos-containing additives

Introduction. Using materials containing mineral fibres in road construction requires consideration of the risk of air pollution by fibrous particles. The purpose of the study was to assess the possibility of air pollution by asbestos fibres during the operation of road surfaces containing chrysotile asbestos. Materials and Methods. Nine air samples, three dust samples and one asphalt pavement sample were taken on the federal highway. Results. The concentration of asbestos fibres in the air was below the detection limit of ≤ 0.0001 f/ml. When all nine air samples were examined, no asbestos fibres were found. Two agglomerates and one bundle of chrysotile asbestos fibres were found in all three dust samples, which were most likely a part of the road surface. Most fibres were bound with other particles in a single agglomerate in the asphalt sample. The content of asbestos fibres in all three dust samples was less than 0.1%, and the size of the conglomerates did not fit the definition of “respirable fibres”. Limitations. 1) the assessment of air pollution by asbestos fibres was carried out only at one stage (operation) of the pavement life cycle (from production to disposal); 2) a complete assessment of air pollution on highways by all types of particulate particles was not carried out (only asbestos fibres and other fibrous particles were taken into account). Conclusion. At the time of the study, no atmospheric air pollution by free chrysotile asbestos fibres was detected near the highway; the average concentration for the entire time of sampling, as well as the concentrations in each of the samples, was below the detection limit of the method and amounted to ≤0.0001 f/ml, thereby not exceeding the regulatory indicators provided for both in Russia (Sanitary rules and standards 1.2.3685-21 from 28.01.21) and in Germany (TRGS 519). This study is a single-stage screening study. More research is needed to assess the possibility of air pollution by asbestos fibres throughout the entire life cycle of road surfaces constructed using asbestos-containing stabilizing additives (from production to disposal).

Factory site analysis of respirable fibers generated during the process of cutting and grinding of carbon fibers-reinforced plastics.

Carbon fibers are used in a variety of industrial applications, based on their lightweight and high stiffness properties. There is little information on the characteristics and exposure levels of debris generated during the factory processing of carbon fibers or their composites. This study revisits the general assumption that carbon fibers or their debris released during composite processing are considered safe for human health. The present interventional study was conducted at a factory located in Japan, and involved on-site collection of debris generated during the industrial processing of polyacrylonitrile (PAN)-based carbon-fiber-reinforced plastic (CFRP). The debris were collected before being exhausted locally from around different factory machines and examined morphologically and quantitatively by scanning electron microscopy. The levels of exposure to respirable carbon fibers at different areas of the factory were also quantified. The collected debris mainly contained the original carbon fibers broken transversely at the fiber's major axis. However, carbon fiber fragments morphologically compatible with the WHO definition of respirable fibers (length: > 5μm, width: < 3μm, length/width ratio: > 3:1) were also found. The concentrations of respirable fibers at the six examined factory areas under standard working conditions in the same factory were below the standard limit of 10 fibers/L, specified for asbestos dust-generating facilities under the Air Pollution Control Law in Japan. Our study identified potentially dangerous respirable fibers with high aspect ratio, which was generated during the processing of PAN-based CFRP. Regular risk assessment of carbon fiber debris is necessary to ensure work environment safety.

Comprehensive hygienic assessment of the dust factor in the asbestos cement manufacturing industry

Objective: to conduct comprehensive hygienic studies of the dust factor in the asbestos cement manufacturing industry and to determine the presence of a relationship between the content level of respirable fibres and the mass concentration of suspended particles in order to actualize the methodology of the assessment of the air of a working area containing mineral fibrous aerosols. Materials and methods. The mass concentrations of dust and the content level of respirable fibres in the air of the working area and the morphological characteristics of dust aerosol were analyzed. Results. The content of dust in the air of the working area in terms of the mass measurements of suspended particles does not exceed the hygienic standards and ranges from 0.20 ± 0.004 mg/m 3 to 1.47 ± 0.085 mg/m 3 , and the content level of respirable fibres is from 0.20 ± 0.044 f/cm 3 to 1.13 ± 0.204 f/cm 3 . The presence of a positive correlation of moderate strength between the content level of respirable fibres and the mass concentration of suspended particles has been found. Conclusion. The microscopy of the preparations of dust samples makes it possible to determine a morphological picture which is characteristic for various stages of the technological process. There is a positive correlation of moderate strength between the content level of respirable fibres in the air of the working area and the concentration of suspended particles. However, the obtained patterns of dependence are capable of accounting up to 49.3 % of the variations of respirable fibres on the basis of the mass concentration of suspended particles, which does not make it possible to use them for the conversion of the values.

The Development and Calibration of a Mechanistic Asbestos Removal Exposure Assessment Tool (AREAT).

Exposure to asbestos fibres is linked to numerous adverse health effects and the use of asbestos is currently banned in many countries. Still, asbestos applications are present in numerous residential and professional/industrial buildings or installations which need to be removed. Exposure measurements give good insight in exposure levels on the basis of which the required control regime is determined to ensure that workers are protected against adverse health effects. However, it is a costly and time-consuming process to measure all situations as working conditions and materials may vary greatly. Therefore, the mechanistic model 'Asbestos Removal Exposure Assessment Tool (AREAT)' was developed to estimate exposure to respirable asbestos fibres released during asbestos abatement processes where measurements are not available. In such instances tailored control regimes can be implemented based on modelled exposure levels. The mechanistic model was developed using scientific literature, an in-house asbestos abatement dataset, and knowledge with regard to previously developed models. Several exposure determinants such as the substance emission potential, activity emission potential, control measures, and dilution in air were identified and specific modifiers were developed for each category. Through an algorithm, AREAT calculates a dimensionless score based on the model inputs. The model was calibrated using a statistical model on an extensive measurement dataset containing a broad variety of exposure scenarios. This statistical model enabled the translation of dimensionless AREAT scores to actual estimated fibre concentrations in fibres m-3. In total, 370 personal inhalation exposure measurements from 71 different studies were used for calibration of AREAT. Of these measurements, in 191 cases (52%) with microscopic analysis (all asbestos fibre analyses were conducted with scanning electron microscopy/energy dispersive X-ray analysis in accordance with ISO 14966) no fibres were detected and the limit of detection values(LODs) were given. To assess the influence of the large number of measurements with exposures below LOD values on the performance of the model, calibrations were performed on the total dataset and the selection of data excluding measurements below LOD. The AREAT model correlated well with the datasets, with a Pearson correlation of 0.73 and 0.8 and Spearman rank correlation of 0.56 and 0.8. The model was fitted to estimate a typical exposure value [i.e. geometric mean (GM) exposures], but it is recommended to use a more conservative worst case higher percentile (for example the 90th percentile; which adds a factor of 17.3 based on the model uncertainty on the GM estimate), to account for variability in the measurements and uncertainty in model estimates. This work has shown the development and calibration of a mechanistic model, capable of estimating asbestos fibre exposures during asbestos abatement processes. The AREAT model will be implemented as a lower tier exposure model in a risk assessment tool used within the Netherlands to plan abatement processes and to develop control strategies.

Morphological and chemical properties of fibrous antigorite from lateritic deposit of New Caledonia in view of hazard assessment

Exposure to natural occurrences of asbestos (NOA) and other potentially hazardous elongated mineral particles (EMPs) may pose a risk to human health and the environment. Weathering forces and anthropic activities may alter the cohesion of NOA-bearing outcrops and disperse EMPs in air, water, and soil. The current paradigm for fibre toxicity indicates that morphology and crystal chemistry are key parameters in determining the toxicological properties of a mineral. This work aims to assess and discuss the impact of sub-tropical supergene alteration and weathering on the morphology and the chemical composition of antigorite, a non-regulated serpentine that shares chemical composition with asbestos chrysotile. Antigorite naturally occurring in lateritic Ni ores of New Caledonia exhibits a unique asbestos-like habit at the microscopic scale. Standardized mechanical stress was performed on antigorites, selected to represent different cohesion states. The specimens produced a relevant amount of respirable fibres, between 32 and 42% (WHO counting criteria). PCA on chemical data and ternary diagrams show that all antigorites exhibit a similar Si content (from 2.05 to 2.09 a.f.u.) but were mainly differentiated by Mg and Ni content, ranging from 2.66 to 2.80 and 0.00 to 0.09 a.f.u., respectively. Si content in Caledonian antigorite is higher than Si in non-lateritic samples. This suggests that a main alteration process occurred after the obduction of the ultramafic protolith. The supergene alteration determined the Ni enrichment of lateritic deposits and is likely the main cause of the mineral alteration of antigorite under sub-tropical environments. Further, weathering processes prompt the disaggregation of altered antigorite causing the generation and dispersion of respirable, potentially hazardous, antigorite fibres in the environment.

Prevention of the formation of respirable fibers in carbon fiber reinforced epoxy resins during combustion by phosphorus or silicon containing flame retardants

The influence of different phosphorus containing flame retardants on fiber degradation during combustion of carbon fiber reinforced epoxy resins is described. A phosphazene, a phosphate and a phosphinate were investigated in HexFlow® RTM6, a high performance epoxy resin designed for resin transfer moulding processes, and composites thereof. UL94-V flammability tests of neat RTM6 samples showed a high flame retardant efficiency of the phosphate and the phosphazene. The burning behavior of carbon fiber reinforced composite samples with various amounts of flame retardants was investigated by cone calorimetry and the influence on fiber degradation was determined by scanning electron microscopy including energy dispersive X-ray spectroscopy. While phosphazene acting mainly in the gas phase showed the best flame retardant efficiency in the composite, the phosphate acting mainly in the condensed phase showed the best fiber protection. Mechanical properties were not affected significantly by the incorporation of flame retardants ensuring the application in components manufactured by resin transfer moulding. Finally combinations of phosphazene and a silicon compound were tested. No synergism regarding fiber protection or flame retardancy was observed in carbon fiber reinforced epoxy resins, but these investigations provide information about efficient fiber protection mechanisms.

Zdravstveni učinci vlakana azbesta u vazduhu

Since the beginning of the 20th century, thousands of tons of asbestos were used in all developed countries in industry and construction. After the serious illnesses and deaths caused by inhalation of asbestos fibers were reliably identified, the first asbestos use ban was prescribed by the World Health Organization (WHO) in 1972. Asbestos in the last 100 years to blame for the death of a large number of workers in industry and construction as well as the population. According to the World Health Organization in the next 40 years in the world is expected to illness and death of more than 500 000 people as a consequence of inhaling airborne particles of asbestos. That fact has led to a complete ban on any use of asbestos in most countries. The paper is particularly pronounced approach applied in the US, according to which each of respirable difficult soluble fiber is considered fibrinogen, and every fiber diameter ≤1mm and length ≥10mm potentially fibrinogen and carcinogenic, and in Germany that any inorganic fiber diameter of 5mm and the ratio length and diameter of&gt; 3: 1 is considered potentially carcinogenic. The question is whether it is justified to carcinogenic fibers prescribe and apply the limit values, and whether in BiH differently treated with carcinogens acting genotoxic than those operating epigenetic mechanisms.