Добірка наукової літератури з теми "Asbestos quantification"

Analytical electron microscopy has contributed a great deal to our understanding of asbestosrelated diseases. Exposure to the various forms of asbestos, which include the serpentine form known as chrysotile asbestos, and the amphibole forms referred to as amosite, crocidolite, tremolite, anthophyllite, and actinolite asbestos, has been associated with the development of a number of diseases in man. These include asbestosis (scarring of the lung parenchyma), pleural plaques (scarring of the pleura), malignant mesothelioma of the pleura and peritoneum, and carcinoma of the lung, especially among those who also smoke cigarettes.Analysis of the mineral fiber content of the lung in patients with these various diseases has provided a powerful investigative tool to researchers interested in the relationship between fiber burdens and disease. Such studies have shown that when sufficiently sensitive digestion concentration techniques are employed, some asbestos can be found in lung tissue from virtually every adult in the general population.

Abstract Asbestosis is defined as diffuse pulmonary fibrosis caused by the inhalation of excessive amounts of asbestos fibers. Pathologically, both pulmonary fibrosis of a particular pattern and evidence of excess asbestos in the lungs must be present. Clinically, the disease usually progresses slowly, with a typical latent period of more than 20 years from first exposure to onset of symptoms. Differential Diagnosis: Idiopathic Pulmonary Fibrosis The pulmonary fibrosis of asbestosis is interstitial and has a basal subpleural distribution, similar to that seen in idiopathic pulmonary fibrosis, which is the principal differential diagnosis. However, there are differences between the 2 diseases apart from the presence or absence of asbestos. First, the interstitial fibrosis of asbestosis is accompanied by very little inflammation, which, although not marked, is better developed in idiopathic pulmonary fibrosis. Second, in keeping with the slow tempo of the disease, the fibroblastic foci that characterize idiopathic pulmonary fibrosis are infrequent in asbestosis. Third, asbestosis is almost always accompanied by mild fibrosis of the visceral pleura, a feature that is rare in idiopathic pulmonary fibrosis. Differential Diagnosis: Respiratory Bronchiolitis Asbestosis is believed to start in the region of the respiratory bronchiole and gradually extends outward to involve more and more of the lung acinus, until the separate foci of fibrosis link, resulting in the characteristically diffuse pattern of the disease. These early stages of the disease are diagnostically problematic because similar centriacinar fibrosis is often seen in cigarette smokers and is characteristic of mixed-dust pneumoconiosis. Fibrosis limited to the walls of the bronchioles does not represent asbestosis. Role of Asbestos Bodies Histologic evidence of asbestos inhalation is provided by the identification of asbestos bodies either lying freely in the air spaces or embedded in the interstitial fibrosis. Asbestos bodies are distinguished from other ferruginous bodies by their thin, transparent core. Two or more asbestos bodies per square centimeter of a 5-μm-thick lung section, in combination with interstitial fibrosis of the appropriate pattern, are indicative of asbestosis. Fewer asbestos bodies do not necessarily exclude a diagnosis of asbestosis, but evidence of excess asbestos would then require quantitative studies performed on lung digests. Role of Fiber Analysis Quantification of asbestos load may be performed on lung digests or bronchoalveolar lavage material, employing either light microscopy, scanning electron microscopy, or transmission electron microscopy. Whichever technique is employed, the results are only dependable if the laboratory is well practiced in the method chosen, frequently performs such analyses, and the results are compared with those obtained by the same laboratory applying the same technique to a control population.

This study aimed to compare sample pretreatment procedures for the identification and quantification of asbestos. The performance of visual estimation and point counting procedures for evaluating asbestos-containing waste was investigated, and the effect of analytical experience was studied. The efficacy of pretreatments for the identification and quantification of asbestos in various sample matrices was compared. To evaluate the effect of experience on analytical accuracy, three analysts with different analytical experiences were selected. There were significant differences in the quantitative analysis results obtained using different pretreatments. False negatives were reported when asbestos, especially amphiboles, were analyzed by a less-experienced analyst. Quantification via point counting and visual estimation resulted in differences in the asbestos content. The results of point counting were more accurate than those of visual estimation for all analysts, regardless of the asbestos type and concentration. Experience in asbestos analysis affected accuracy and precision. The findings show that pretreatment is an important factor in qualitative analysis. Appropriate pretreatments should be assigned based on the properties of the sample. For quantitative analysis, the accuracy of the results depends on the experience of the analyst. Until analysts are fully trained, all their analysis results should be checked by an experienced analyst. Point counting is an adequate quantitative method for analyzing samples with low concentrations.

The aim of this work was to inspect the presence of asbestos fibers in colon tissue from a patient, with history of indirect exposure to asbestos and affected by colon cancer, who underwent surgery. Variable pressure scanning electron microscopy, coupled with energy dispersive spectroscopy (VP-SEM/EDS), was used for identification of inorganic fibers and for their morphological- chemical characterization. Fresh tissue samples from both, healthy area close to the neoplasia and from the neoplastic regions, were separately digested to eliminate the biological matrix. The precipitate was analyzed by VP-SEM/EDS, identifying in samples from healthy tissue asbestos bodies and small asbestos fibers, and in samples from neoplastic tissue long fibers of asbestos, free from covering. A quantification of the asbestos bodies and the free fibers in the two type of specimens is proposed. Moreover, to locate the fibers in the biological medium, histological sections from the colon of the same patient were also examined. Free asbestos fibers appeared concentrated in the tissue bridge between the healthy and the neoplastic areas. Immuno-histochemical investigation performed on the neoplasia seems to exclude a role of microsatellite instability in the carcinogenesis process, suggesting an influence of the fibers.

Microscopy remains the primary tool for the analysis and quantification of asbestos in occupational and environmental studies. The American Society for Testing and Materials (ASTM) has recently approved two new Standard Methods for the analysis of asbestos in settled dust. Both methods require the use of a transmission electron microscope (TEM) equipped with an energy dispersive x-ray analysis system. Other methods curently in use require the use of a polarized light microscope {PLM) or phase contrast microscope (PCM).

The aim of this work was to establish whether asbestos fibers homogeneously occur in the different fractions ground from naturally occurring asbestos lithotypes, and to calculate the contribution of fibers from each fraction to the overall concentration in the sample. Serpentinite, metabasalt, calc-schist, clay, debris material, and soil, were addressed. Grain size fractions below 20 mm were sieved at 2 mm and 0.106 mm; they were then were mechanically milled to obtain powders below 0.106 mm. The three powdered fractions were characterized using a scanning electron microscope coupled with energy dispersive spectroscopy following M.D. 06/09/94. The still in use (in some cases), Italian normative M.D. 161/2012 specifies that analyses must be performed on the <2 mm fraction and the concentration (mg/kg) correlated with the weight of the whole sample <20 mm. However, the fiber counts yielded asbestos concentrations 50–60% lower compared with total asbestos analyses according to the new R.P.D. 120/2017. Consequently, there is a need to standardize the normative worldwide regulations for the management of asbestos-containing materials, by re-evaluation of sample preparation and quantification of asbestos.

Background: pleural mesothelioma is a rare cancer in the general population, but it is more common in subjects occupationally exposed to asbestos. Studies with asbestos fiber quantification in pleural tissue are scarce: for this reason, we aimed at undertaking a scoping review to summarize the evidence provided by studies in which asbestos fibers were determined by electron microscopy (SEM or TEM) in human pleural tissues, whether normal or pathologic. Materials and methods: A scoping review of articles that quantified asbestos fibers in human pleural tissue (normal or pathologic) by electron microscopy (SEM or TEM), in subjects with asbestos exposure (if any) was performed. Results: The 12 studies selected comprised 137 cases, out of which 142 samples were analyzed. Asbestos fibers were detected in 111 samples (78%) and were below the detectable limit in 31 samples (22%). The concentration of asbestos fibers detected in the positive samples was distributed from as low as 0.01 mfgdt (millions of fibers per gram of dry tissue) up to 240 mfgdt. However, the minimum concentration of fibers overlaps in the three types of tissues (normal pleura, pleural plaque, mesothelioma) in terms of magnitude; therefore, it is not possible to distinguish a definite pattern which differentiates one tissue from the other. Conclusions: The studies included were heterogeneous as to the representativeness of the samples and analytical techniques; the possibility of false negatives must be considered. It would be desirable to systematically search for asbestos fibers to fill the knowledge gap about the presence of asbestos fibers in normal or pathological pleural tissue in order to better understand the development of the different pleural diseases induced by this mineral.

ABSTRACT The presence of naturally occurring asbestos (NOA) in many areas worldwide requires an enhanced geological risk evaluation to ensure workplace safety from asbestos during large construction projects. Due to the complexity of the geological risk definition, health and safety regulations for working with asbestos-bearing materials are often not enforceable in NOA settings. Therefore, to correctly estimate the risk of NOA in these scenarios, new procedures are urgently needed to provide (1) a detailed geological model representative of the possible presence of the asbestos, (2) representative sampling, and (3) a reliable quantitative determination of asbestos content in rocks. This work aims to discuss the improvements on the two latter points specifically developed during the design of the “Gronda di Genova” project, a 50-km-long tunnel bypass partially designed in the NOA-bearing meta-ophiolites of the Ligurian Alps and ophiolites of the northern Apennines in Italy. Implementation of Gy's theory on sampling was used to maintain statistical validity during sample processing from the primary sample to the analytical sample and is here described. The scanning electron microscopy/energy dispersive spectroscopy procedure for the quantification of NOA was improved with an error analysis delivering the minimum number of fibers to be measured to achieve the best analytical results.

Because of their potential to induce a number of pathological diseases and their widespread industrial usage in the past, the fibrous minerals forming asbestos have been the subject of a number of studies in the past. Although quantification of asbestos minerals by optical and electron microscopy (SEM, TEM) is a routine technique in the case of dispersed airborn fibers, the detection and the quantification of small amount of fibrous minerals like chrysotile in bulk materials such as building materials is exceedingly difficult. A method for the detection and evaluation of asbestos minerals in massive samples is described, based on a combination of Rietveld and RIR (Reference Intensity Ratio) methods. Lower detection limits are about 0.5-1.0 wt % for chrysotile, depending on powder pattern, counting statistics, and matrix absorption. The chrysotile wt % determined on powder diffraction profiles collected on a conventional instrument is precise to about 1.0 wt % absolute (relative error in the range 0-10%). The technique is of straightforward application. If compared with the commonly used microscopic or spectroscopic techniques, it is of much advantage from the point of view of time, and the results are more accurate and statistically significant of the bulk material. A model for the cylindrically disordered structure of fibrous chrysotile is especially developed for the simulation of the X-ray powder patterns, and it is proposed here.

Le mot “asbeste” (incombustible) est utilisé pour indiquer un groupe de silicate à habitus fibreux, appartenant aux familles des serpentines et des amphiboles. Selon la législation italienne (D.L. 15/08/91), les six silicates fibreux définis comme asbeste sont: le chrysotile, l'amosite et la crocidolite (variétés fibreuses de la grunérite et de la riébeckite), l'anthophyllite, la trémolite et l'actinolite. Ces minéraux sont constitués de fibres incombustibles, chimiquement stables, inertes et flexibles. A cause de leurs propriétés chimiques et physiques, les asbestes ont été considérés comme les plus importants matériaux inorganiques en vue d'applications industrielles et technologiques. À la fin des années 50, on découvrit la corrélation entre l'exposition à l'asbeste et le développement du mésotéliome pleural et du carcinome. Depuis quelques décennies, le risque asbeste n'est pas considéré comme seulement confiné au cadre professionnel, mais également en tant que risque potentiel pour l'environnement. Par conséquent, l'actuelle législation impose des lois sévères pour la réglementation de l'utilisation des roches et des sols potentiellement porteurs d'asbestes.
Le caractère pathogène des fibres d'asbeste est associé aux facteurs suivants : i) faciès fibreux (un minéral est défini comme fibreux si le rapport longueur/diamètre est plus grand de 3 :1) ; ii) facteurs chimiques et minéralogiques (types de fibre, composition chimique, réactivité de surface) ; iii) la bio persistance. Ces facteurs sont interconnectés car les dimensions de la fibre influencent sa réactivité superficielle, la composition de la fibre contrôle sa bio persistance et la bio persistance est aussi associée au faciès de la fibre.
Dans les Alpes Occidentales, les minéraux fibreux sont concentrés dans la Zone Piémontaise des Schistes Lustrès à méta-ophiolites. Cette étude fait partie d'une projet multidisciplinaire intitulé « Le risque asbeste dans les Alpes Occidentales », visé à l'étude de la présence, du risque et de la possible inactivation des minéraux fibreux dans les Alpes Occidentales. Ce projet, financé par l'Assessorato all'Ambiente de la Regione Piemonte, a été coordonné par le Centro Interdipartimentale « G. Scansetti » de l'Université de Torino. Cette étude se fonde sur les questions suivantes : i) Quels sont les minéraux fibreux dans les vallées de Susa et de Lanzo ? ii) Où ces minéraux sont-ils concentrés ? Quelles conditions génétiques contrôlent leur croissance ? iii) Quel est le pourcentage les minéraux fibreux dans les serpentines? Sur la base de ces questions, cette thèse a été organisée en six chapitres :
•Chapitre 1 – Les six minéraux fibreux définis comme asbeste sont présentés et leur potentiel pathogène est discuté.
•Chapitre 2 – La Zone Piémontaise des Schistes Lustrés à méta-ophiolites est décrite brièvement.
•Chapitre 3 – Ce chapitre traite de la caractérisation minéralogique et chimique des minéraux fibreux reconnus dans les serpentinites étudiées, c'est-à-dire des minéraux du groupe des serpentines (chrysotile et lizardite), la balangéroïte, le diopside, la trémolite et la carlosturanite. Pour chacun de ces minéraux sont présentées la structure cristallographique, les propriétés optiques, la composition chimique et les propriétés vibrationnelles (Μ-Raman et FTIR).
•Chapitre 4 – Ce chapitre traite de l'étude pétrologique des serpentinites des vallées de Susa et de Lanzo, réalisée par microscopie optique et électronique, et spectroscopie Μ-Raman. Dans la première partie, les mécanismes de la serpentinisation sont présentés et les microstructures des serpentinites sont décrits en détail. Dans la deuxième partie, les cinq générations de veines métamorphiques reconnues dans les serpentines sont décrites en détail et des modes de formation sont proposés. La trajectoire P-T estimée pour les serpentinites, sur la base des observations microstructurales et des données thermobarométriques, est discutée à la lumière des diagrammes Μ(Ca2+/Mg2+)-Μ(SiO2) et P-T, calculés grâce à la technique des pseudosections.
•Chapitre 5 – Ce chapitre traite du problème de la détermination quantitative des minéraux fibreux dans les roches. Dans la première partie, les techniques traditionnelles pour la détermination quantitative de l'asbeste dans le matériel solide sont présentées. Dans la deuxième partie, deux nouvelles techniques sont décrites en détail. La première est basée sur la spectroscopie FTIR appliquée à une mélange de antigorite + chrysotile. La deuxième sur l'analyse des images SEM (BSE) associée à la spectroscopie micro-Raman.
•Chapitre 6 – Il s'agit du chapitre de conclusion, où sont brièvement discutés les résultats, les questions encore ouvertes et les perspectives futures de ce travail.