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.

Asbestos and Other Hazardous Fibrous Minerals: Potential Exposure Pathways and Associated Health Risks.

There are six elongate mineral particles (EMPs) corresponding to specific dimensional and morphological criteria, known as asbestos. Responsible for health issues including asbestosis, and malignant mesothelioma, asbestos has been well researched. Despite this, significant exposure continues to occur throughout the world, potentially affecting 125 million people in the workplace and causing thousands of deaths annually from exposure in homes. However, there are other EMPS, such as fibrous/asbestiform erionite, that are classified as carcinogens and have been linked to cancers in areas where it has been incorporated into local building materials or released into the environment through earthmoving activities. Erionite is a more potent carcinogen than asbestos but as it is seldom used for commercial purposes, exposure pathways have been less well studied. Despite the apparent similarities between asbestos and fibrous erionite, their health risks and exposure pathways are quite different. This article examines the hazards presented by EMPs with a particular focus on fibrous erionite. It includes a discussion of the global locations of erionite and similar hazardous minerals, a comparison of the multiple exposure pathways for asbestos and fibrous erionite, a brief discussion of the confusing nomenclature associated with EMPs, and considerations of increasing global mesothelioma cases.

Nanoscale transformations of amphiboles within human alveolar epithelial cells.

Amphibole asbestos is related to lung fibrosis and several types of lung tumors. The disease-triggering mechanisms still challenge our diagnostic capabilities and are still far from being fully understood. The literature focuses primarily on the role and formation of asbestos bodies in lung tissues, but there is a distinct lack of studies on amphibole particles that have been internalized by alveolar epithelial cells (AECs). These internalized particles may directly interact with the cell nucleus and the organelles, exerting a synergistic action with asbestos bodies (AB) from a different location. Here we document the near-atomic- to nano-scale transformations induced by, and taking place within, AECs of three distinct amphiboles (anthophyllite, grunerite, "amosite") with different Fe-content and morphologic features. We show that: (i) an Fe-rich layer is formed on the internalized particles, (ii) particle grain boundaries are transformed abiotically by the internal chemical environment of AECs and/or by a biologically induced mineralization mechanism, (iii) the Fe-rich material produced on the particle surface does not contain large amounts of P, in stark contrast to extracellular ABs, and (iv) the iron in the Fe-rich layer is derived from the particle itself. Internalized particles and ABs follow two distinct formation mechanisms reaching different physicochemical end-states.

Reply to Mirabelli et al. Is Mesothelioma Unrelated to the Lung Asbestos Burden? Comment on "Visonà et al. Inorganic Fiber Lung Burden in Subjects with Occupational and/or Anthropogenic Environmental Asbestos Exposure in Broni (Pavia, Northern Italy): An SEM-EDS Study on Autoptic Samples. Int. J. Environ. Res. Public Health 2021, 18, 2053".

We appreciate very much the interest of Mirabelli et al. [...].

Multi-scale characterization of glaucophane from Chiavolino (Biella, Italy): implications for international regulations on elongate mineral particles.

In this paper, we present the results of a multi-analytical characterization of a glaucophane sample collected in the Piedmont region of northwestern Italy. Investigation methods included optical microscopy, powder X-ray diffraction, Fourier-transform infrared spectroscopy, µ-Raman spectroscopy, Mössbauer spectroscopy, electron probe microanalysis, environmental scanning electron microscopy and energy-dispersive X-ray spectroscopy, and scanning/transmission electron microscopy combined with energy-dispersive X-ray spectroscopy and electron energy-loss spectroscopy. In addition to the crystal-chemical characterization of the sample from the mesoscale to the near-atomic scale, we have also conducted an extended study on the morphology and dimensions of the mineral particles. The main finding is that studying the same particle population at different magnifications yields different results for mineral habit, dimensions, and dimensional distributions. As glaucophane may occur as an elongate mineral particle (e.g., asbestiform glaucophane occurrences in California and Nevada), the observed discrepancies therefore need to be considered when assessing potential breathability of such particles, with implications for future regulations on elongate mineral particles. While the sample preparation and particle counting methods are not directly investigated in this work, our findings suggest that different magnifications should be used when characterizing an elongate mineral particle population, irrespective of whether or not it contains asbestiform material. These results further reveal the need for developing improved regulation for elongate mineral particles. We thus propose a simple methodology to merge the datasets collected at different magnifications to provide a more complete description and a better risk evaluation of the studied particle population.

Alteration of yellow traffic paint in simulated environmental and biological fluids.

Pollution from heavy metals in urban environments is a topic of growing concern because many metals, including Pb and Cr, are a human health hazard. Exposure to Pb and Cr has been linked to the inhibition of neurological development as well as toxic effects on many organs. Yellow traffic paint (YTP) is a mixture that contains organic polymers, binders, and pigments, which in some cases consist of crocoite (PbCrO4) that may be coated by silica. The primary aim of this study was to investigate the behavior of the crocoite pigment grains within YTP and their silica coatings in simulated environmental and human body conditions. To do this, both YTP and asphalt were collected in Philadelphia, PA, USA. These samples as well as a standard PbCrO4 were investigated with powder X-ray diffraction, X-ray fluorescence, environmental scanning electron microscopy (ESEM), transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Using this multi-analytical approach, mineral phases were determined in the YTP, their shape, dimensional distributions, crystallinity, and chemical composition, as well as elemental distributions before and after experimental interactions. Three batch dissolution experiments with YTP, asphalt, and standard PbCrO4 were performed to simulate ingestion, inhalation, and environmental interaction with rainwater. Elemental releases were determined with inductively coupled plasma-optical emission spectrometry, and results indicated that little (ingestion) to no (environmental and inhalation) Pb and Cr were leached from the YTP during the three experimental procedures. This is likely due to the silica coating that encapsulates the crocoite particles, which persisted during all interactions. The ESEM results for YTP showed dimensional reductions after interactions with all three fluids. The silica coating must be further explored to determine how it breaks down in real environmental conditions.

Dimensional distribution control of elongate mineral particles for their use in biological assays.

The aim of the present method is to reduce the dimensional variability of asbestos, elongate mineral particles, and other asbestiform minerals for use in biological assays. Here, the pristine mineral sample is filtered through two nylon meshes of different sizes to obtain a narrower dimensional distribution following a power law. Furthermore, we show that anoxic preparation, autoclaving and storage of the mineral prior to addition into biological cultures did not affect the mineral's chemical properties. This approach avoids the use of highly reactive chemicals modifying mineralogical characteristics and surface properties, which can affect to a major extent mineral toxicity as well as interactions between minerals and biological matter or biofluids. The method can be combined with additional selective approaches to further refine the dimensional range of the minerals. The advantages of this protocol over previous methods are: •Exclusive use of distilled water and 2-propanol, thus eliminating chemicals that can modify bulk or surface properties of the studied minerals.•Successful sterilization of the resulting mineral particles for use in biological assays without compromising mineralogical characteristics.•Applicability of this method across various types of asbestos, elongate mineral particles and, potentially, other hazardous minerals.

Micro- and nano-scale mineralogical characterization of Fe(II)-oxidizing bacterial stalks.

Neutrophilic, microaerobic Fe(II)-oxidizing bacteria (FeOB) from marine and freshwater environments are known to generate twisted ribbon-like organo-mineral stalks. These structures, which are extracellularly precipitated, are susceptible to chemical influences in the environment once synthesized. In this paper, we characterize the minerals associated with freshwater FeOB stalks in order to evaluate key organo-mineral mechanisms involved in biomineral formation. Micro-Raman spectroscopy and Field Emission Scanning Electron Microscopy revealed that FeOB isolated from drinking water wells in Sweden produced stalks with ferrihydrite, lepidocrocite and goethite as main mineral components. Based on our observations made by micro-Raman Spectroscopy, field emission scanning electron microscopy and scanning transmission electron microscope combined with electron energy-loss spectroscopy, we propose a model that describes the crystal-growth mechanism, the Fe-oxidation state, and the mineralogical state of the stalks, as well as the biogenic contribution to these features. Our study suggests that the main crystal-growth mechanism in stalks includes nanoparticle aggregation and dissolution/re-precipitation reactions, which are dominant near the organic exopolymeric material produced by the microorganism and in the peripheral region of the stalk, respectively.

Depicting the crystal structure of fibrous ferrierite from British Columbia using a combined synchrotron techniques approach.

The ferrierite crystal structure has often been subject to discussion because of the possible lowering of symmetry from the space group Immm. It mainly occurs in nature with a fibrous crystal habit, and because of the existence of line/planar defects in the framework, texture and preferred orientation effects it has been difficult to obtain an exact crystallographic model based only on the results from powder diffraction data. Therefore, nano-single-crystal diffraction and tomography data have been combined in order to improve the refinement with a meaningful model. High-quality single-crystal data, providing reliable structural information, and tomography images have been used as input for a Rietveld refinement which took into account a phenomenological description of stacking disorder and the analytical description of the preferred orientation, by means of spherical harmonics for strong texture effects. This is one of the first examples of application of synchrotron nano-diffraction for the structure solution of fibrous minerals of micrometre to nanometre size. The high quality of the crystals allowed collection of single-crystal X-ray diffraction data of up to 0.6 Šresolution, leading to an unambiguous solution and precise anisotropic refinement. Nano-single-crystal diffraction and phase contrast tomography data were collected at ID11 and the high-resolution powder diffraction patterns at ID22 of the European Synchrotron Radiation Facility. This detailed crystallographic characterization provides a basis for understanding the potential of ferrierite for toxicity and carcinogenicity.

Assessment of the potential hazard represented by natural raw materials containing mineral fibres-The case of the feldspar from Orani, Sardinia (Italy).

This work describes the nature of the potentially hazardous fibrous amphibole found in the Orani's feldspar mine (Sardinia, Italy). To identify its nature, a protocol of analysis including morphometric, chemical and crystallographic characterizations was applied. Thanks to this approach, it was possible to classify the observed fibres as tremolite after comparing chemical data, SEM/TEM observations, FTIR/ Raman spectra and X-ray diffraction data with those reported for a standard sample. The unit cell parameters of the investigated tremolite phase are a = 9.82(1) Å, b = 18.08(3) Å, c = 5.27(1) Å, and the angle ß corresponds to 104.4(1)°. The mean concentration of asbestos tremolite in the Orani's feldspar is 0.28 wt%. Most of the fibres (0.26 wt%) are respirable 'regulated' fibres, representing a potential hazard. Because the total amount of tremolite in the sample is 0.6 wt%, a large fraction of it has a crystal habit other than fibrous-asbestiform or acicular. The obtained results allowed us to suggest possible solutions for a safe exploitation and mineral processing of the Orani's mine. The procedure proposed herein may be a general tool suitable to identify the mineralogical nature of fibrous minerals in raw materials and assess if they may represent a potential health/environmental hazard.

High-temperature behavior of natural ferrierite: In-situ synchrotron X-ray powder diffraction study.

In this paper, we report the results of the first study focused on the thermal stability and dehydration dynamics of the natural zeolite mineral ferrierite. A sample from Monastir, Sardinia [(Na0.56K1.19Mg2.02Ca0.52Sr0.14) (Al6.89Si29.04)O72·17.86H2O; a = 19.2241(3) Å; b = 14.1563(2) Å; c = 7.5106(1) Å, V = 2043.95(7) Å3] was investigated by thermogravimetric analysis and in-situ synchrotron X-ray powder diffraction. Thermogravimetric data show that H2O release begins already in the range 50-100 °C and is complete at ~600 °C. The results of the structure refinements performed in Immm space group by Rietveld analysis with data collected up to 670 °C show that ferrierite belongs to the group of zeolites that do not undergo phase transitions. Upon heating to 670 °C, ferrierite behaves as a non-collapsible structure displaying only a slight contraction of the unit-cell volume (ΔV = -3%). The unit-cell parameter reductions are anisotropic, more pronounced for a than for b and c (Δa = -1.6%; Δb = -0.76%; Δc = -0.70%). This anisotropic response to a temperature increase is interpreted as due to the presence in the ferrierite framework of five-membered ring chains of SiO4 tetrahedra, which impart a higher structural rigidity along b and c. Upon dehydration we observe: (1) the gradual H2O loss, beginning with the molecules hosted in the 10MR channel, is almost complete at 670 °C, in good agreement with the TG data; (2) as a consequence of the decreased H2O content, Mg and K migrate from their original positions, moving from the center of the 10MR channel toward the walls to coordinate the framework oxygen atoms. The observation of transmission electron microscopy selected-area electron diffraction patterns revealed defective crystals with an occasional and moderate structural disorder. Beyond providing information on the thermal stability and behavior of natural ferrierite, the results of this work have significant implications for possible technological applications. These data allow for comparison with the dehydration kinetics/mechanisms of the corresponding synthetic phases, clarifying the role played by framework and extra-framework species on the high-temperature behavior of porous materials with ferrierite topology. Moreover, the information on the thermal behavior of natural ferrierite can be used to predict the energetic performances of analogous synthetic Si-pure counterparts, namely "zeosil-electrolyte" systems, under non-ambient conditions. Specifically, the very high thermal stability of ferrierite determined in this study, coupled with the baric behavior determined in other investigations, suggests that the "Si-FER-electrolyte" system may be an excellent candidate for use as an energy reservoir. Indeed, ferrierite exhibits the so-called "spring behavior," i.e., upon compression in water or in an electrolyte solution, it converts the mechanical energy into interfacial energy, and-when pressure is released-it can completely restore the supplied mechanical energy accumulated during the compression step.

Mineralogical Characterization and Dissolution Experiments in Gamble's Solution of Tremolitic Amphibole from Passo di Caldenno (Sondrio, Italy).

In nature, asbestos is often associated with minerals and other non-asbestiform morphologies thought to be harmless, but not much is known about the potential toxic effects of these phases. Therefore, the characterization of natural assemblages should not be limited to asbestos fibers only. This paper combines a multi-analytical characterization of asbestos from Valmalenco (Italy) with data from dissolution experiments conducted in a simulated interstitial lung fluid (Gamble's solution), and a detailed dimensional study that compares the particle population before and after this interaction. The sample is identified as a tremolitic amphibole, exhibiting a predominance of fiber and prismatic habits at lower magnification, but a bladed habit at higher magnification. The results show that at different magnification, the dimensional and habit distributions are notably different. After the dissolution experiments, the sample showed rounded edges and pyramid-shaped dissolution pits. Chemical analyses suggested that a nearly stoichiometric logarithmic loss of Si and Mg occurred associated with a relatively intense release of Ca in the first 24 h, whereas Fe was probably redeposited on the fiber surfaces. A rearrangement of the more frequent habits and dimensions was recorded after the dissolution experiment, with a peculiar increase of the proportion of elongated mineral particles.

Infra Red Spectroscopy of the Regulated Asbestos Amphiboles.

Vibrational spectroscopies (Fourier Transform Infra Red, FTIR, and Raman) are exceptionally valuable tools for the identification and crystal-chemical study of fibrous minerals, and asbestos amphiboles in particular. Raman spectroscopy has been widely applied in toxicological studies and thus a large corpus of reference data on regulated species is found in the literature. However, FTIR spectroscopy has been mostly used in crystal-chemical studies and very few data are found on asbestos amphiboles. This paper is intended to fill this gap. We report new FTIR data collected on a suite of well-characterized samples of the five regulated amphibole species: anthophyllite, amosite, and crocidolite, provided by the Union for International Cancer Control (UICC) Organization, and tremolite and actinolite, from two well-known occurrences. The data from these reference samples have been augmented by results from additional specimens to clarify some aspects of their spectroscopic features. We show that the FTIR spectra in both the OH-stretching region and in the lattice modes region can be effective for rapid identification of the asbestos type.

New insights into the toxicity of mineral fibres: A combined in situ synchrotron µ-XRD and HR-TEM study of chrysotile, crocidolite, and erionite fibres found in the tissues of Sprague-Dawley rats.

Along the line of the recent research topic aimed at understanding the in vivo activity of mineral fibres and their mechanisms of toxicity, this work describes the morpho-chemical characteristics of the mineral fibres found in the tissues of Sprague-Dawley rats subjected to intraperitoneal/intrapleural injection of UICC chrysotile, UICC crocidolite and erionite-Na from Nevada (USA). The fibres are studied with in situ synchrotron powder diffraction and high resolution transmission electron microscopy to improve our understanding of the mechanisms of toxicity of these mineral fibres. In contact with the tissues of the rats, chrysotile fibres are prone to dissolve, with leaching of Mg and production of a silica rich relict. On the other hand, crocidolite and erionite-Na fibres are stable even for very long contact times within the tissues of the rats, showing just a thin dissolution amorphous halo. These findings support the model of a lower biopersistence of chrysotile with respect to crocidolite and erionite-Na but the formation of a silica-rich fibrous residue after the pseudo-amorphization of chrysotile may justify a higher cytotoxic potential and intense inflammatory activity of chrysotile in the short term in contact with the lung tissues.

Stability of mineral fibres in contact with human cell cultures. An in situ µXANES, µXRD and XRF iron mapping study.

Relevant mineral fibres of social and economic importance (chrysotile UICC, crocidolite UICC and a fibrous erionite from Jersey, Nevada, USA) were put in contact with cultured diploid human non-tumorigenic bronchial epithelial (Beas2B) and pleural transformed mesothelial (MeT5A) cells to test their cytotoxicity. Slides of each sample at different contact times up to 96 h were studied in situ using synchrotron XRF, µ-XRD and µ-XAS (I18 beamline, Diamond Light Source, UK) and TEM investigations. XRF maps of samples treated for 96 h evidenced that iron is still present within the chrysotile and crocidolite fibres and retained at the surface of the erionite fibres, indicating its null to minor mobilization in contact with cell media; this picture was confirmed by the results of XANES pre-edge analyses. µ-XRD and TEM data indicate greater morphological and crystallinity modifications occurring in chrysotile, whereas crocidolite and erionite show to be resistant in the biological environment. The contact of chrysotile with the cell cultures seems to lead to earlier amorphization, interpreted as the first dissolution step of these fibres. The formation of such silica-rich fibre skeleton may prompt the production of HO in synergy with surface iron species and could indicate that chrysotile may be much more reactive and cytotoxic in vitro in the (very) short term whereas the activity of crocidolite and erionite would be much more sluggish but persistent in the long term.

"Rinse and trickle": a protocol for TEM preparation and investigation of inorganic fibers from biological material.

The purpose of this work is to define a sample preparation protocol that allows inorganic fibers and particulate matter extracted from different biological samples to be characterized morphologically, crystallographically and chemically by transmission electron microscopy-energy dispersive spectroscopy (TEM-EDS). The method does not damage or create artifacts through chemical attacks of the target material. A fairly rapid specimen preparation is applied with the aim of performing as few steps as possible to transfer the withdrawn inorganic matter onto the TEM grid. The biological sample is previously digested chemically by NaClO. The salt is then removed through a series of centrifugation and rinse cycles in deionized water, thus drastically reducing the digestive power of the NaClO and concentrating the fibers for TEM analysis. The concept of equivalent hydrodynamic diameter is introduced to calculate the settling velocity during the centrifugation cycles. This technique is applicable to lung tissues and can be extended to a wide range of organic materials. The procedure does not appear to cause morphological damage to the fibers or modify their chemistry or degree of crystallinity. The extrapolated data can be used in interdisciplinary studies to understand the pathological effects caused by inorganic materials.

The wild rat as sentinel animal in the environmental risk assessment of asbestos pollution: a pilot study.

Asbestos has been banned in many countries, including Italy. However, sources of exposure may still exist, due to asbestos in-situ or past disposal of asbestos-containing waste. In an urban area with past high environmental exposure, like Casale Monferrato, the lung fiber burden in sentinel animals may be useful to identify such sources. A pilot study was conducted to assess the feasibility of its determination in wild rats, a suitable sentinel species never used before for environmental lung asbestos fiber burden studies. Within the framework of pest control campaigns, 11 adult animals from 3 sites in the urban area of Casale Monferrato and 3 control rats from a different, unexposed town were captured. Further, 3 positive and 3 negative control lung samples were obtained from laboratories involved in breeding programs and conducting experimental studies on rats. Tissue fiber concentration was measured by scanning electron microscopy with energy dispersive spectrometry. Asbestos (chrysotile and crocidolite) was identified in the lungs from rats from Casale Monferrato, but not in control rats and in negative control lung samples. Asbestos grunerite at high concentration was found in positive control lung samples. Measurement of the lung fiber burden in wild rats has proved feasible: it was possible not only to detect, but also to characterize asbestos fibers both qualitatively and quantitatively. The pilot study provides the rationale for using wild rats as sentinels of the soil contamination level in Casale Monferrato, to identify areas with the possible presence of previously unrecognized asbestos sources.