Amphibole Research Articles

Asbestos-induced autoantibodies across Libby demographics

Asbestos-induced autoantibodies across Libby demographics Aiden Niblett, Jean Pfau, and Kinta Serve focus on asbestos-induced autoantibodies across different demographics in Libby. They emphasize the importance of understanding the impact of asbestos. Asbestos is a naturally occurring fibrous silicate mineral that has been used in construction due to its tensile strength and heat resistance. However, its small size and rigid shape allow it to enter deep into the respiratory tract upon inhalation, and exposures have been linked to serious lung diseases like pulmonary fibrosis and cancers. (1) The town of Libby, Montana, has a history of asbestos exposure due to a local vermiculite mine that operated from 1920-1990. Vermiculite mined from Libby and sold in products such as Zonolite Attic Insulation was found to be contaminated with Libby Amphibole (LA) asbestos, a unique mix of tremolite, winchite, and richterite fibers that is associated with severe lung diseases. (2)

Concordance between CDKN2A homozygous deletion and MTAP immunohistochemical loss in fluoroedenite-induced pleural mesothelioma: An immunohistochemical and molecular study on a single-institution series

Fluoroedenite-induced pleural mesothelioma (FE-induced-PM) is a rare and small subset of PM that shares with its asbestos-induced counterpart the same aggressive biological behavior and poor prognosis, but that differs from it from a pathogenetic point of view as it is associated with exposure to fluoroedenite, a carcinogenic agent that shows similarities with tremolite amphibolic asbestos fibers. Although it has been demonstrated that asbestos-induced PMs frequently harbor CDKN2A homozygous deletion and that the immunohistochemical loss of MTAP may represent a cheap and reliable surrogate marker for this molecular alteration, little is known about the molecular landscape and the reliability of MTAP immunohistochemistry in this peculiar subset of PM. The study herein presented investigated the prevalence of CDKN2A homozygous deletion and its concordance with MTAP immunohistochemical status on a cohort of 10 cases of FE-induced-PM from patients with environmental exposure to FE fibers, who were residents in the small town of Biancavilla (Sicily, Italy) or nearby areas. CDKN2A homozygous deletions were found in 3 out of 10 cases (30%) and all these cases showed concomitant cytoplasmic loss of MTAP with a concordance rate of 100%. Despite the relatively low number of cases included in our series, MTAP immunohistochemistry seemed to represent a reliable immunohistochemical surrogate marker of CDKNA homozygous deletion even in this subset of PMs.

Low Exposures to Amphibole or Serpentine Asbestos in Germline Bap1-mutant Mice Induce Mesothelioma Characterized by an Immunosuppressive Tumor Microenvironment.

We show that germline Bap1-mutant mice have enhanced susceptibility to MM upon minimal exposure to chrysotile asbestos, not only amphibole fibers. Chrysotile induced a more profound immune tumor response than crocidolite in Bap1-mutant mice by upregulating CD39/CD73-adenosine and Ccl2/Ccr2 pathways and recruiting more M2 macrophages, which together contributed to an immunosuppressive tumor microenvironment. Interrogation of human MM RNA-seq data revealed interconnected immunosuppressive pathways consistent with our mouse findings.

Amphibole Group Minerals in the Ozren Massif Ophiolites of Bosnia and Herzegovina as Petrogenetic Indicators

The Ozren ophiolite complex (OOC) of the Dinaridic Ophiolite Belt is one of the six ophiolite complexes in Bosnia and Herzegovina. This paper deals with the mineral chemistry of amphiboles determined by electron probe micro-analysis and micro-Raman spectroscopy. The detected amphibole generations and types in mafic, ultramafic, and metamorphic rocks suggest a polystage evolution and are therefore useful petrogenetic indicators of the investigated OOC. Most gabbroic rocks and dolerites contain primary magmatic amphibole1 (magnesio-hornblende to pargasite, occasionally hastingsite) and prismatic to needle-like aggregates of late magmatic amphibole2 (magnesio-hornblende), while plagiogranite contains ferri-winchite and ferro-ferri-winchite as primary magmatic amphibole. Post-magmatic amphiboles were detected in dolerites, troctolites, and lesser in peridotites. The Na-(Ti)-rich amphibole3 (ferri-winchite and ferro-ferri-winchite to katophorite and ferri-katophorite) with amphibole4 (grunerite) rim formed along the grain boundaries of clinopyroxene, amphibole1, and plagioclase in dolerites. A part of these amphiboles grows into amphibole1, 2. Kaersutite to ferri-kaersutite, associated with phlogopite, occur in troctolites and dunites, while Mhbl was detected in harzburgite. The ultramafic rocks (lherzolites, harzburgites, and dunites) and the gabbroic layer are crosscut by clinopyroxene–plagioclase gabbroic and clinopyroxene–plagioclase–amphibole gabbro–dolerite dykes, suggesting ‘dry’ and ‘hydrated’ percolating melts generated in inferred subridge and supra-subduction settings, respectively. The amphibole3 and 4 in gabbros and dolerites and similar amphibole types in ultramafic rocks could be related to inferred arc-type basaltic and plagiogranitic percolating melts and fluids. Low-Al amphibole5 (tremolite and actinolite) and associated chlorite, albite, and clinozoisite represent the ocean-floor alterations in mafic rocks. Amphibole6 (magnesio-hornblende to pargasite) was identified in metamorphic sole amphibolites. Micro-Raman spectroscopy provided typical Raman spectra for the studied amphiboles, highlighting distinct features such as bands related to CMg content, CFe3+ presence, TO4 ring-breathing mode, TiO6 stretching mode, presence > 0.3 apfu of CTi, and TO4 stretching indicating CFe2+ in the structure. Applied amphibole geothermobarometry revealed the formation P–T conditions of amphibole (Amp)1 (avg. 863 °C at 0.23 GPa), Amp2 (avg. 747 °C at 0.17 GPa), Amp in the mantle rocks (avg. 853 °C at 0.64 GPa), Amp5 (avg. 349 °C at 0.03 GPa), and Amp6 (avg. 694 °C at 0.46 GPa).

Classification of asbestos and their nonasbestiform analogues using FTIR and multivariate data analysis

This study presents a possible application of Fourier transform infrared (FTIR) spectrometry and multivariate data analysis, principal component analysis (PCA), and partial least squares-discriminant analysis (PLS-DA) for classifying asbestos and their nonasbestiform analogues. The objectives of the study are: 1) to classify six regulated asbestos types and 2) to classify between asbestos types and their nonasbestiform analogues. The respirable fraction of six regulated asbestos types and their nonasbestiform analogues were prepared in potassium bromide pellets and collected on polyvinyl chloride membrane filters for FTIR measurement. Both PCA and PLS-DA classified asbestos types and their nonasbestiform analogues on the score plots showed a very distinct clustering of samples between the serpentine (chrysotile) and amphibole groups. The PLS-DA model provided ∼95% correct prediction with a single asbestos type in the sample, although it did not provide all correct predictions for all the challenge samples due to their inherent complexity and the limited sample number. Further studies are necessary for a better prediction level in real samples and standardization of sampling and analysis procedures.

Heavy Liquid Separation Method for Enhancement of Trace Asbestos Detection

Powder X-ray diffraction (XRD) is a widely accepted technique for detecting trace asbestos content in solid samples. However, accurately quantifying asbestos concentrations below 0.5 wt% presents significant challenges with XRD alone. To address this limitation, we conducted a meticulous quantitative analysis using XRD on synthetic samples of talc-based powder spiked with varying amounts of natural tremolite and anthophyllite asbestos. At concentrations exceeding 0.5 wt%, both tremolite and anthophyllite displayed distinct XRD peaks. Yet, at lower concentrations (0.1 wt% and 0.05 wt%), the diffraction peaks of the contaminants became less prominent. To improve detection sensitivity, we explored different protocols of heavy liquid separation utilizing sodium polytungstate (SPT) to concentrate asbestos relative to the other mineral components. The optimized protocol, employing SPT with a density of 2.89 g/cm3, effectively separated amphibole asbestos from lighter, commonly associated minerals, like talc, clinochlore, and mica. Subsequent powder XRD analysis of the heavy fraction confirmed the successful removal of non-target materials, enhancing the diffraction peaks of tremolite and anthophyllite. Tremolite exhibited comparatively less weight loss than anthophyllite during this separation process. This study establishes the theoretical and practical viability of employing centrifugation in a heavy liquid to separate tremolite and anthophyllite from talc, providing valuable insights for asbestos detection and quantification in challenging scenarios.

Distribution of soil minerals along the toposequence of Hyang-Argopuro Volcanic Mountain, Jember, Indonesia

The study was conducted in the Hyang-Argopuro volcanic mountain in Jember, Indonesia, with the aim of assessing the distribution of soil minerals along a toposequence and their relationship to soil genesis. Three soil profiles representing the upper, middle, and lower slopes of the toposequence were analyzed. The results revealed that the predominant sand minerals in the soils are opaque minerals, weatherable minerals, amphibole groups, and ferromagnesian minerals. The presence of magnetite, primarily found in the soil profile on the upper slope, suggests the effect of the well-drained topography on its formation. Clay mineral analysis showed that halloysite dominates in soil profile 1, along with traces of gibbsite and cristobalite in the surface horizon. Soil profile 2 is characterized by a combination of halloysite and illite, while kaolinite and illite dominate in soil profile 3. The presence of illite in these soils aligns with previous studies conducted in volcanic regions. The degree of soil development follows the sequence: Soil Profile 2 > Soil Profile 1 > Soil Profile 3. This corresponds to the soil classification, where soil profile 3 is classified as an Alfisol, soil profile 1 as a Mollisol, and soil profile 3 as an Inceptisol. The Andic properties, such as low bulk density and high pH in NaF, observed in soil profile 1 suggest its development from an Andisol. Overall, the study findings highlight the significant influence of basaltic andesite parent material, mountainous topography, and warm and wet climate on the mineral composition and development in the area.

Localization and Dimensional Range of Amphibole Particles Retrieved from Human Alveolar Epithelial Cells

Amphibole asbestos is related to multiple diseases, mainly those targeting the lungs. Asbestos-related malignancies can also be caused by non-regulated asbestiform minerals and some elongated mineral particles (EMPs). In particular, the role of nano- and micro-sized EMPs internalized by lung epithelial cells must be clarified. This is of major importance when considering that EMPs to which humans are exposed are likely a highly heterogeneous mix of different mineral types, shapes, and sizes. Here, we document that particles smaller than 4.54 µm in length and smaller than 0.89 µm in width (e.g., particles that do not fit the regulatory categories to be identified as asbestos) are easily internalized because of their specific dimensions, surface charge, and shape (mostly dictated by the aspect ratio L/w). Once internalized, these particles can be found in proximity to the cell nucleus, in vesicles, and in the cytoplasm. Examining the localization of particles in cells provides important information, which helps in determining the physicochemical environment found inside the biological compartment, thus allowing for a better comprehension of the mineralogical transformation that might happen after internalization by cells.

Distinct Pro-Inflammatory Mechanisms Elicited by Short and Long Amosite Asbestos Fibers in Macrophages.

While exposure to long amphibolic asbestos fibers (L > 10 µm) results in the development of severe diseases including inflammation, fibrosis, and mesothelioma, the pathogenic activity associated with short fibers (L < 5 µm) is less clear. By exposing murine macrophages to short (SFA) or long (LFA) fibers of amosite asbestos different in size and surface chemistry, we observed that SFA internalization resulted in pyroptotic-related immunogenic cell death (ICD) characterized by the release of the pro-inflammatory damage signal (DAMP) IL-1α after inflammasome activation and gasdermin D (GSDMD)-pore formation. In contrast, macrophage responses to non-internalizable LFA were associated with tumor necrosis factor alpha (TNF-α) release, caspase-3 and -7 activation, and apoptosis. SFA effects exclusively resulted from Toll-like receptor 4 (TLR4), a pattern-recognition receptor (PRR) recognized for its ability to sense particles, while the response to LFA was elicited by a multifactorial ignition system involving the macrophage receptor with collagenous structure (SR-A6 or MARCO), reactive oxygen species (ROS) cascade, and TLR4. Our findings indicate that asbestos fiber size and surface features play major roles in modulating ICD and inflammatory pathways. They also suggest that SFA are biologically reactive in vitro and, therefore, their inflammatory and toxic effects in vivo should not be underestimated.

Mobility of crocidolite asbestos in sandy porous media mimicking aquifer systems

Asbestos is widely recognized as being a carcinogen when dispersed in air, but very little is known about its exposure pathways in water and its subsequent effects on human health. Several studies have proved asbestos presence in groundwater but failed to assess its mobility in aquifer systems. This paper aims to fill this gap by studying the transport of crocidolite, an amphibole asbestos, through sandy porous media mimicking different aquifer systems. To this purpose, two sets of column test were performed varying the crocidolite suspension concentration, the quartz sand grain size distribution, and the physicochemical water parameters (i.e., pH). The results proved that crocidolite is mobile in quartz sand due to the repulsive interactions between fibres and porous media. The concentration of fibres at the outlet of the column were found to decrease when decreasing the grain size distribution of the porous medium, with a bigger impact on highly concentrated suspensions. In particular, 5-to-10-µm-long fibres were able to flow through all the tested sands while fibres longer than 10 µm were mobile only through the coarser medium. These results confirm that groundwater migration should be considered a potential exposure pathway while implementing human health risk assessment.

Separation of asbestos concentrates in a hydrocyclone

Relevance. Issues related to the operation of hydrocyclones in the asbestos industry for the separation of finely split asbestos fibers from rock impurities and non-fluffed asbestos needles used in the wet enrichment of brittle chrysotile asbestos, as well as some types of amphibole asbestos and in the purification of commercial grades of chrysotile asbestos of normal strength from magnetite are considered. Purpose. The purpose and objectives of the research is to study the operating modes of a hydrocyclone for the separation and desliming of asbestos products. Particular attention is paid to the behavior of particles inside the hydrocyclone. Methodology. The formulas presented in the literature for calculating the volumetric delivery of hydro-cyclones are analyzed. As a result, it was determined that the volumetric delivery of the hydrocyclone does not depend on the size of the sand nozzle and that the influence of the latter affects mainly the specific distribution of water between the discharge and sand products. Results. In the course of processing the obtained experimental data, the calculation results showed that, at different nozzles and feed heads, the movement of grains of separation mesh in the internal flow of hydrocyclones of the tested design occurs within 1 &lt; Re &lt; 20. Therefore, the accepted dependences of Ψ on Re when deriving the calculated formulas are correct. Conclusions. The volumetric delivery of hydrocyclones D = 75 mm and D = 200 mm of the tested design for feeding and draining depends on the feed head and the diameter of the framework nozzle. The established regularities in the behavior of particles of asbestos concentrates in hydrocyclones are of practical importance and can be used when choosing the technological parameters of their operation to achieve the specified conditions for the size of particle separation mesh.

Microbe-Mineral Interactions between Asbestos and Thermophilic Chemolithoautotrophic Anaerobes.

The Fe content and the morphometry of asbestos are two major factors linked to its toxicity. This study explored the use of microbe-mineral interactions between asbestos (and asbestos-like) minerals and thermophilic chemolithoautotrophic microorganisms as possible mineral dissolution treatments targeting their toxic properties. The removal of Fe from crocidolite was tested through chemolithoautotrophic Fe(III) reduction activities at 60°C. Chrysotile and tremolite-actinolite were tested for dissolution and potential release of elements like Si and Mg through biosilicification processes at 75°C. Our results show that chemolithoautotrophic Fe(III) reduction activities by Deferrisoma palaeochoriense were supported with crocidolite as the sole source of Fe(III) used as a terminal electron acceptor during respiration. Microbial Fe(III) reduction activities resulted in higher Fe release rates from crocidolite in comparison to previous studies on Fe leaching from crocidolite through Fe assimilation activities by soil fungi. Evidence of biosilicification in Thermovibrio ammonificans did not correspond with increased Si and Mg release from chrysotile or tremolite-actinolite dissolution. However, overall Si and Mg release from chrysotile into our experimental medium outmatched previously reported capabilities for Si and Mg release from chrysotile by fungi. Differences in the profiles of elements released from chrysotile and tremolite-actinolite during microbe-mineral experiments with T. ammonificans underscored the relevance of underlying crystallochemical differences in driving mineral dissolution and elemental bioavailability. Experimental studies targeting the interactions between chemolithoautotrophs and asbestos (or asbestos-like) minerals offer new access to the mechanisms behind crystallochemical mineral alterations and their role in the development of tailored asbestos treatments. IMPORTANCE We explored the potential of chemosynthetic microorganisms growing at high temperatures to induce the release of key elements (mainly iron, silicon, and magnesium) involved in the known toxic properties (iron content and fibrous mineral shapes) of asbestos minerals. We show for the first time that the microbial respiration of iron from amphibole asbestos releases some of the iron contained in the mineral while supporting microbial growth. Another microorganism imposed on the two main types of asbestos minerals (serpentines and amphiboles) resulted in distinct elemental release profiles for each type of asbestos during mineral dissolution. Despite evidence of microbially mediated dissolution in all minerals, none of the microorganisms tested disrupted the structure of the asbestos mineral fibers. Further constraints on the relationships between elemental release rates, amount of starting asbestos, reaction volumes, and incubation times will be required to better compare asbestos dissolution treatments studied to date.

Characteristics of transcription profile, adhesion and migration of SETD2-loss Met-5A mesothelial cells exposed with crocidolite.

Asbestos is a fibrous silicate mineral exhibiting biopersistence and carcinogenic properties and contributes to mesothelioma. Despite the concept of gene-environmental interaction in pathogenesis of mesothelioma, the possible pathophysiological changes of mesothelial cells simultaneously with SET domain containing 2 (SETD2) loss and asbestos exposure remains obscure. Herein, CRISPR/Cas9-mediated SETD2 knockout Met-5A mesothelial cells (Met-5ASETD2-KO ) were established and exposed with crocidolite, an amphibole asbestos. Cell viability of Met-5ASETD2-KO appeared to dramatically decrease with ≥2.5μg/cm2 crocidolite exposure as compared with Met-5A, although no cytotoxicity and apoptosis changes of Met-5ASETD2-KO and Met-5A was evident with 1.25 μg/cm2 crocidolite exposure for 48 h. RNA sequencing uncovered top 50 differentially expressed genes (DEGs) between 1.25 μg/cm2 crocidolite exposed Met-5ASETD2-KO (Cro-Met-5ASETD2-KO ) and 1.25 μg/cm2 crocidolite exposed Met-5A (Cro-Met-5A), and ITGA4, THBS2, MYL7, RAC2, CADM1, and CLDN11 appeared to be the primary DEGs involved with adhesion in gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. Cro-Met-5ASETD2-KO had strong migration but mild adhesion behavior as compared with Cro-Met-5A. Additionally, crocidolite tended to increase migration of Met-5ASETD2-KO but inhibited migration of Met-5A when compared with their corresponding cells without crocidolite exposure, although no further adhesion property changes was evident for both cells in response to crocidolite. Therefore, crocidolite may affect adhesion-related gene expression and modify adhesion and migration behavior for SETD2-depleted Met-5A, which could provide preliminary insight regarding the potential role of SETD2 in the cell behavior of asbestos-related malignant mesothelial cell.

Exaggerated risk perception of asbestos-related diseases: commentary

Health risks from asbestos have been evaluated on the basis of professional histories from remote past, when exposures at workplaces were greater than today. The linear no-threshold model has been applied, although its relevance has not been demonstrated. Fibers are often found in the lungs and pleura at post mortem examinations. The fnding of fbers does not prove that a disease was caused by asbestos. It can be reasonably assumed that targeted search for mesothelioma and other asbestos-related diseases in exposed people resulted in increased detection rate. Histological and immunochemical characteristics of malignant mesothelioma partly overlap with other cancers, which may contribute to overdiagnosis in exposed populations. Amphibole asbestos is more toxic than chrysotile but there are discrepancies between experimental and epidemiological data. The promising way to obtain reliable information is lifelong animal experiments. Asbestos bans applied in some countries are excessive and should be reconsidered on the basis of independent research. It can be reasonably assumed that non-use of asbestos-containing brakes, freproofng, and insulation increases the harm from fres, armed conflicts and trafc accidents.

Manufactured doubt and the EPA 2020 chrysotile asbestos risk assessment

While all forms of asbestos have been determined to be carcinogenic to humans by the International Agency for Research on Cancer (IARC) as well as other authoritative bodies, the relative carcinogenic potency of chrysotile continues to be argued, largely in the context of toxic tort litigation. Relatively few epidemiologic studies have investigated only a single form of asbestos; however, one study that included an asbestos textile plant located in Marshville, North Carolina that processed chrysotile asbestos was used by the United States Environmental Protection Agency (EPA) in 2020 to help inform the agency's chrysotile asbestos risk assessment. During the EPA proceedings toxic tort defense consultants submitted comments to the EPA docket and made public presentations asserting that the Marshville plant had processed amphibole asbestos types and should not be used for the chrysotile risk assessment. A detailed evaluation of defense consultant assertions and supporting information and a full assessment of the available information concerning asbestos types used at the Marshville plant was undertaken. The preponderance of evidence continues to support the conclusion that neither amosite nor crocidolite were likely to have been processed in the Marshville textile plant. Defense consultants' assertions about chrysotile use are not supported by the preponderance of evidence and constitute an example of manipulation of information to cast uncertainty and doubt rather than to seek truth and contribute to the body of scientific evidence.

Diagnostic limitations of lung fiber counts in asbestos-related diseases

Background Lung dust fibre analyses have been used by some pathologists to estimate past asbestos exposure in the workplace and its related health risks. Asbestos, however, especially the predominately applied chrysotile asbestos type, undergoes translocation, clearance and degradation in the lungs. Objectives We quantified the asbestos fibre and ferruginous (asbestos) body (FB) content in human tissue with respect to the German asbestos ban in 1993 and the interim period of more than 20 years in order to evaluate the diagnostic evidence of these analyses for asbestos-related diseases (ARD). Methods Lung dust analyses have been used in empirical assessments of ARD since 1982. Tissue samples of about 2 cm3 were used and processed in standardized manner. FB was analysed by light microscopy and asbestos fibres by scanning transmission electron microscopy (STEM). Results Chrysotile and amphibole fibre concentrations in the lung tissue depend roughly on the cumulative asbestos exposure levels in the workplace. However, the concentration of lung asbestos fibre and FB depends on the year of examination and especially on the interim period. As the interim period increases, the asbestos fibre burden decreases. There is no relationship between FB and chrysotile asbestos fibre concentrations and only a weak correlation between FB and crocidolite fibre concentrations. There was no significant difference in chrysotile and amphibole fibre concentrations as well as in FB counts between the different ARD. Conclusions Due to the length of interim periods, a past exposure to chrysotile or amphibole asbestos can no longer be detected with FB or asbestos fibre measurement in lung tissue. This means that negative results of such measurements cannot disprove a qualified occupational case history of asbestos exposures and the related health risks due to the fibrogenic and carcinogenic potential of asbestos.

Asbestiform fibers and cleavage Fragments: Conceptual approaches for differentiation in laboratory practice and data analysis

The respirable fractions from 46 different crushed amphibole samples were separated by water elutriation. The dimensions of approximately 200 elongate mineral particles (EMPs) longer than 5 μm in each of these fractions were measured by transmission electron microscopy (TEM). The data were used to address three questions:1. Can amphiboles be classified on a scale that represents the level of inhalation hazard they present?2. Can prismatic amphibole be discriminated from amphibole asbestos on the basis of EMP size distributions and concentration measurements?3. How do different exposure indices (Phase Contrast Microscopy Equivalent (PCME), Berman & Crump protocol fibers, Chatfield extra-criteria EMPs) compare when applied to these amphibole samples?For each sample, the number of respirable EMPs longer than 5 μm per gram of respirable dust and the number of extra-criteria EMPs per gram of respirable dust were calculated. The number of respirable EMPs longer than 5 μm per gram of respirable dust and the proportion of those with dimensions associated with mesothelioma in animal studies were considered to be contributors to the inhalation hazard presented by amphibole dust. In addition to these concentration measurements, the median EMP width, median aspect ratio and the aspect ratio geometric standard deviation (GSD) were considered to be relevant parameters in discriminating prismatic amphibole from asbestiform amphibole. A plot of the aspect ratio GSD against either the concentration of respirable EMPs per gram of respirable dust, the median aspect ratio or the median width allowed discrimination.The data showed a close correspondence between exposures in terms of Chatfield extra-criteria EMPs and Berman and Crump protocol structures for all of the amphibole samples. However, although for commercial asbestos varieties exposures in terms of PCME fibers were comparable to those of the other two metrics, they greatly exceeded those for non-asbestiform amphiboles.

Characterization of elongate mineral particles including talc, amphiboles, and biopyriboles observed in mineral derived powders: Comparisons of analysis of the same talcum powder samples by two laboratories

Elongate mineral particles, including asbestos, have long been screened in talc and other mineral powders. In recent years, there has been a renewed scrutiny of talc containing asbestos due to allegations in civil litigation in the United States as well as reports, proposals, and white papers by international laboratories and government bodies related to this subject. This study demonstrates the importance of the fundamental understanding of both mineralogy and its application, using microscopy with empirical examples from conflicting analyses of the same talc powders by two independent laboratories in civil litigation in the United States. Methods include polarized light microscopy (PLM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) in the accurate measurement of morphological, optical, compositional, and structural data to characterize mineral-based samples. Discussions in this study include: 1) contrasting the interlaboratory findings of amphibole and amphibole asbestos by PLM and TEM using various preparation techniques, 2) the use of multiple analytical tools on a singular particle for identification, 3) the misidentification of anthophyllite asbestos by inexpert use of electron diffraction using TEM, and 4) the misidentification of chrysotile in talc by PLM. These examples emphasize the importance of not only maintaining the existing requirements, but of the need for even more rigorous analytical requirements in routine monitoring of elongate mineral particles that may occur in mineral-based powders.

Discriminant analysis of amphiboles: Additional considerations

Amphibole minerals are found throughout nature and could pose a respiratory hazard if these exist in the asbestiform growth habit. Though amphibole asbestos has not been used in commercial products as an added material for more than 30 years, these minerals could exist in other materials as trace contaminants as well as occurring in mines and earth-moving environments. It is necessary, then, that the asbestiform amphibole minerals be properly identified in order to appropriately use health-protective measures. Recent analyses of various amphibole data sets have been used to derive a discriminant function that can be used to differentiate asbestiform amphibole from non-asbestiform amphibole minerals. This paper expands on this function and examines the validity of the procedure for different size fractions of minerals. This analysis suggests that the derived function is appropriate for fibers 10 μm and longer. For fibers shorter than 10 μm, the data suggest that a broader acceptance limit may be needed. The data also suggest that current analytical procedures may require some adjustment to provide more accurate details on the widths of fibers. With additional samples, the accuracy of the discriminate function can be improved by calculating functions for each mineral.

Nucleation of naturally occurring calcic amphibole asbestos

This article proposes an initial model of natural asbestiform minerals growing in four stages. Structures dating from the early stages of the development were observed in the damaged zone surrounding meso-fractures, more particularly in microfractures, microcavities and microcracks that lie in front of and along mesofractures. This study is limited to calcium amphiboles cross-fibers, which develop from altered calcium amphiboles. The observations were made using PLM, with some using TEM. The samples are amphibolites, dolerites and skarns from France. All these rocks have in common that they have been exposed to hydrothermal circulation which gives them a propylite character. The earliest phenomenon was the development of metasomatic veins. In these veins, actinolite form pseudomorphs after hornblendes. The new amphiboles preserve the original morphology of hornblende, in particular the appearance of the cleavages. In the second stage, hydrothermal Fluid circulation promotes the development of subgrains (DSG) with boundaries generally parallel to the cleavage. Some sub-grains become thinner and more and more individualized due to dissolution by the hydrothermal fluid. The third stage is fracturing. The irregular ends of DSGs and amphibole debris can form the substrate of asbestiform mineral nuclei. Further dissolution of DSGs can also lead to the creation of substrates. The last stage is the nucleation and growth. The nuclei have a conical shape and variable widths, from a few microns to about ten microns. The basal parts of the asbestos minerals (BPAMs) extend the DSGs along the c axis. BPAMs have variable widths and can divide during their development at the level of transverse microcracks. BPAMs when not dividing have a morphology comparable to that of whisker nanocrystals synthesized using the vapor-liquid-crystal mechanism. The shape of the fragments from BPMAs is close to that of DSGs as both have variable widths and both have lengths controlled by microcracks.