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Elucidating the high-temperature behavior of rock-forming minerals such as amphiboles (AB2C5 T8O22W2) is critical for the understanding of large-scale geological processes in the lithosphere and, in particular, the development of high conductivity in the Earth's interior. Recently, we have shown that at elevated temperatures, CFe-bearing amphiboles with a vacant A site develop two types of charge carriers: (1) small polarons and (2) delocalized H+ ions. To elucidate the effect of A-site cations on the formation and stability of charge carriers within the amphibole structure, here we analyzed synthetic potassic-ferro-richterite as a model Fe-rich amphibole with a fully occupied A site via in situ temperature-dependent Raman spectroscopy. We further compare the results from in situ time-dependent Raman-scattering experiments on pre-heated and rapidly quenched potassic-ferro-richterite and riebeckite as a model Fe-rich amphibole with a vacant A site. We show that the presence of A-site cations (1) reduces the activation temperature of mobile polarons and delocalized H+ cations; (2) decreases the magnitude of the polaron dipole moment; (3) slows down the process of re-localization of electrons on cooling; and (4) makes the electrons inert to rapid change in external conditions, supporting the persistence of a metastable state of pre-activated delocalized electrons even at room temperature. Our results have important geological implications demonstrating that the A-site cations may control the depth of development of high conductivity in subducted amphibole-bearing rocks. Moreover, from the viewpoint of mineral-inspired materials science, our results suggest that the amphibole-structure type has great potential for designing functional materials with tunable anisotropic-conductivity properties. [ABSTRACT FROM AUTHOR]

The sedimentary successions of the Permian-Triassic rifting related to the Alpine Tethys in the easternmost Lower Alpujarride units (Internal Betic Zone, south Spain) host shallow-intrusive basic bodies of Mesozoic age. These gabbroic bodies experienced low-grade Alpine metamorphic overprint, singularly recorded in three outcrops nearby Alicante city in southeast Spain: Callosa and Orihuela Ranges and Nueva Tabarca Island. Overall, the metabasic bodies still preserve magmatic ophitic/subophitic texture and relicts of magmatic augite and ferropargasite-ferroedenite-edenite and kaersutite. In contrast, metamorphic minerals include magnesioriebeckite, actinolite, albite, stilpnomelane, phengite, and chlorite. Major and trace element geochemical data suggest crystallization of the igneous protoliths from subalkaline (tholeiitic) to alkaline within-plate (continental) basaltic magmas slightly enriched in incompatible elements. These magmas with E-MORB geochemical affinity very likely intruded at shallow crustal levels in an extensional-synrift-geodynamic setting related to the breakoff of Pangea in the region. Pressure-Temperature (P-T) conditions estimated by average P-T method and pseudosection calculations suggest metamorphic peak at ca. 6 kbar at 340°C consistent with burial metamorphism down to ca. 18 km depth with intermediate thermal gradients of ca. 18°C/km. These conditions are different to the typical subduction-related blueschist facies conditions of the Lower Alpujarride units and suggest, instead, a collisional (Barrovian) event. This can be explained by a late-stage accretion of the studied units after the main subduction-related event, pointing to the dispersion of the corresponding Lower Alpujarride sections along the margin in different palaeogeographic positions before deformation and movement to their actual structural position. The metamorphic correlation of the studied units with the accreted passive margin of South Iberia (Subbetic zone) is also discussed. [ABSTRACT FROM AUTHOR]

In this work we address the stability of riebeckite at high temperatures and compare the different behaviors observed under various oxidation conditions. For this purpose, we annealed powders of a sample from Mt. Malosa (Malawi), which is compositionally close to the end-member; the run products obtained after annealing in air vs. in vacuum were studied by Mossbauer spectroscopy and powder X-ray diffraction. The results show that riebeckite follows two distinct paths depending on the external environment. Under oxidizing conditions, it is stable in the hydrous form up to relatively low temperatures (400-450 °C), then it undergoes a rapid (within ~50 °C) dehydrogenation, forming oxo-riebeckite, which is stable up to ~900 °C. The final breakdown products of the oxo-amphibole include aegirine + cristobalite + hematite. Based on the relative intensity of the (310) Bragg reflection, the activation energy (Ea) for the riebeckite to oxo-riebeckite transition is 166 ± 6 kJ/mol. Under vacuum conditions, no Fe oxidation is observed, and riebeckite is stable up to much higher temperatures (750-800 °C); however, in the 550 < T < 700 °C range, it undergoes a significant rearrangement of the C cations (those hosted in the strip of octahedra). Indeed, the amphibole stable in the 700-800 °C range has the same chemical formula as riebeckite but has a disordered and nonstandard cation distribution at the octahedra, i.e., ^(1)(Fe3+Fe2+)M(2)(Fe3+Fe2+)M(3)Fe2+; we call this phase "CR3+ disordered riebeckite". For T > 800 °C, it decomposes to aegirine + fayalite + cristobalite + H2O. External oxygen is required for the release of water into the surrounding system, being a prerequisite for the Fe-amphiboles to be a carrier of H2O in the lower crust and upper mantle. One important implication of our results is that characterization of the overall oxidation state of iron does not necessarily provide the redox conditions of the environment of formation because a crystal-chemical re-arrangement under reducing conditions allows riebeckite to maintain its Fe3+/Fe2+ composition up to higher temperatures. [ABSTRACT FROM AUTHOR]

In this work, we address the kinetics of dehydrogenation occurring at high temperatures (HT) in riebeckite, a sodic amphibole with the ideal composition Na 2 Fe 2 3 + Fe 3 2 + Si 8 O 22 (OH) 2. ${\rm{N}}{{\rm{a}}_2}{\rm{Fe}}_2^{3 + }{\rm{Fe}}_3^{2 + }{\rm{S}}{{\rm{i}}_8}{{\rm{O}}_{22}}{({\rm{OH}})_2}.$ We performed isothermal experiments on both powders and single-crystals up to 560 °C and monitored the O-H stretching signal by Fourier transform infrared (FTIR) spectroscopy. Single-crystals show an initial increase in IR absorption intensity due to increasing vibrational amplitudes of the O-H bond stretching, not observed for powders. The OH-intensities vs. time were fitted using the formalism for first-order reactions. The calculated activation energies for H+ diffusion in riebeckite are 159 ± 15 kJ/mol for powders and 216 ± 20 kJ/mol for single crystals, respectively. The exponential factor m in the Avrami-Erofeev equation obtained for crystals ranges between 1.02 and 1.31, suggesting that, unlike powders, the dehydration process in crystals is not a purely first-order reaction. This implies that a second energy barrier must be considered, i.e., diffusion of H+ through the crystal. FTIR imaging showed that H+ diffusion occurs mainly perpendicular to the silicate double-chain. Our results confirm that the release of H+ from riebeckite occurs after the irreversible Fe2+-to-Fe3+ exchange, thus at temperatures >550 °C. To be effective, the process needs the presence of external oxygen that, by interacting with H+ at the crystal surface, triggers the release of H2O molecules. This implies that oxidizing conditions are required for the amphibole to be an efficient water source at depth. [ABSTRACT FROM AUTHOR]

In this paper, we address two key features of the behaviour of Fe-rich amphibole at high temperatures: (1) the Fe2+ → Fe3+ + e − exchange within the crystal bulk, and (2) the consequent rise in electrical conductivity. Cycling heating-cooling experiments were done in situ up to 542 °C (815 K) at beamline B11 of the Diamond Synchrotron Laboratory (UK). X-ray absorption spectra at the Fe K-edge and electrical resistivity were measured simultaneously on a single crystal of riebeckite with a composition very close to the ideal formula A□BNa 2 C(Fe2+ 3 Fe3+ 2)TSi 8 O 22 W(OH) 2. The Fe3+/Fe tot ratio was monitored via analysis of the pre-edge feature in the XANES spectra. Our data show slight oscillations of the oxidation state of Fe with temperature cycling up to around 400 °C (673 K), followed by a substantial gradual increase in Fe2+ → Fe3+ oxidation that starts at ~450 °C (~723 K) and is completed at ~525 °C (~798 K). The conductivity (σ) measured along the crystallographic c-axis oscillates strongly with cycling temperature allowing us to conclude that it is intrinsically related to the electron hopping induced by thermal treatment. The activation-energy derived from the σ(T) trend is E a = 74.4 ± 0.6 kJ/mol (0.77 ± 0.01 eV), in agreement with small-polaron conduction. This study provides direct and robust support of the conduction mechanisms in Fe-amphibole previously inferred from indirect methods. Given that riebeckite is a significant component in the glaucophanitic amphiboles common in blueschists associated with subducted oceanic crust, our data provide a link between atomic-scale processes and Earth-scale anomalous conductivity observed via geophysical measurements. [Display omitted] [ABSTRACT FROM AUTHOR]

Pigments from paint palettes and a grindstone excavated from the pharaonic town of AmaraWest (c. 1300-1050 BCE), which lies between the Second and Third Cataracts of the Nile, were examined using polarized light microscopy, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction, and scanning electron microscopy with energy dispersive X-ray spectroscopy. Most of the pigments were consistent with the typical ancient Egyptian palette, but the greens and some blues were unusual. Two types of green pigment were identified, chlorite (varieties clinochlore and penninite) and copper chloride hydroxide (atacamite type). The former constitutes a type of green earth which has only rarely been identified in pharaonic Egyptian contexts and may be more widespread than is currently reported. The majority of the blue pigment samples were Egyptian blue, but some were found to be a blue earth, the main component of which being sodic amphibole riebeckite. The use of this mineral as a pigment has not previously been reported in any Nile Valley context. These results prompt questions around local and potentially indigenous practices within an ancient colonial context, and highlight avenues for future research. [ABSTRACT FROM AUTHOR]

This study aimed at investigating the surface modifications occurring on amphibole asbestos (crocidolite and tremolite) during leaching in a mimicked Gamble's solution at pH of 4.5 and T = 37 °C, from 1 h up to 720 h. Results showed that the fibre dissolution starts with the release of cations prevalently allocated at the various M- and (eventually) A-sites of the amphibole structure (incongruent dissolution). The amount of released silicon, normalized to fibre surface area, highlighted a leaching faster for the crocidolite sample, about twenty times higher than that of tremolite. Besides, the fast alteration of crocidolite promotes the occurrence of Fe centres in proximity of the fibre surface, or possibly even exposed, particularly in the form of Fe(II), of which the bulk is enriched with respect to the oxidized surface. Conversely, for tremolite fibres the very slow fibre dissolution prevents the underlying cations of the bulk to be exposed on the mineral surface, and the iron oxidation, faster than the leaching process, significantly depletes the surface Fe(II) centres initially present. Results of this work may contribute to unravel possible correlations between surface properties of amphibole asbestos and its long-term toxicity. [ABSTRACT FROM AUTHOR]

The small peralkaline microgranite intrusion that forms the island of Ailsa Craig in the Firth of Clyde represents the southern-most intrusion of the British Palaeogene Volcanic Province (BPVP) within Scotland. The granitic rocks of Ailsa Craig, famous for their use in making curling stones, are thought to be the result of fractionation from a mantle-derived basic magma with no crustal contamination. The rocks of Ailsa Craig also contain the comparatively rare alkaline ferromagnesian minerals riebeckitic arfvedsonite, hedenbergite-acmite and aenigmatite. These factors make the Ailsa Craig intrusion unique in the BPVP. The distinctive 'spotty' appearance of the Ailsa Craig granites, which is invaluable as a tracer in establishing Pleistocene glacial transport, results from the close association of ferromagnesian minerals with drusy cavities. This suggests that, unlike the more common dark minerals, they formed late in the cooling and crystallisation history of the magma. Ailsa Craig was selected as part of the Geological Conservation Review network covering the rocks of the British Palaeogene Volcanic Province, which for historic reasons, is known as the 'Tertiary Igneous' GCR block. Site descriptions for GCR sites of the Tertiary Igneous block are contained in the 4th published GCR volume (Emeleus and Gyopari, 1992). Ailsa Craig GCR site was, however, omitted for reasons unknown. A full GCR site description for Ailsa Craig is, therefore, provided in this paper in order to complete the published description of the Tertiary Igneous GCR block. [ABSTRACT FROM AUTHOR]

There are very few petrographic studies on the Lower Pleistocene gravels of the Getic Piedmont and for those in the Cotmeana Piedmont this is the first. The study highlights an extremely varied range of petrographic types of pebbles. Among them, there are some petrographic types with particular mineralogical composition, very rare or without correspondent in the proximal Carpathian source area north of the piedmont. Three such petrographic types ofpebbles are described in the paper: glaucophane rocks (actinolite and quartz type), olivine basalts and riebeckite trachytes. The same glaucophane rocks have recently been identified inside the Infragetic Complexe (Severin Nappe) in the Parang Mountains. Theoretically speaking, the source of the riebeckite trachytes could be the Liassic dykes complex in the FagaraF Mountains where riebeckite syenite and bostonite are mentioned. The source area of the olivine basalts seems to be farther away. Such rocks outcrop inside the Quaternary Volcanics in the Persani Mountains. [ABSTRACT FROM AUTHOR]

Rationale: Asbestos exposure is associated with a dose-dependent risk of lung cancer. The association between lung cancer and the presence of pleural plaques remains controversial.Objectives: To define the relationship between pleural plaques and lung cancer risk.Methods: Subjects were from two cohorts: 1) crocidolite mine and mill workers and Wittenoom Township residents and 2) a mixed-asbestos-fiber, mixed-occupation group. All subjects underwent annual review since 1990, chest X-ray or low-dose computed tomography scan, and outcome linkage to national cancer and mortality registry data. Cox regression, with adjustment for age (as the underlying matching time variable), was used to estimate hazard ratios (HRs) for lung cancer incidence by sex, tobacco smoking, asbestos exposure, presence of asbestosis, and pleural plaques.Measurements and Main Results: For all 4,240 subjects, mean age at follow up was 65.4 years, 3,486 (82.0%) were male, 1,315 (31.0%) had pleural plaques, and 1,353 (32.0%) had radiographic asbestosis. Overall, 3,042 (71.7%) were ever-smokers with mean tobacco exposure of 33 pack-years. In total, 200 lung cancers were recorded. Risk of lung cancer increased with cumulative exposure to cigarettes, asbestos, and presence of asbestosis. Pleural plaques did not confer any additional lung cancer risk in either cohort (cohort 1: HR, 1.03; 95% confidence interval, 0.64-1.67; P = 0.89; cohort 2: HR, 0.75; 95% confidence interval, 0.45-1.25; P = 0.28).Conclusions: The presence of pleural plaques on radiologic imaging does not confer additional increase in the risk of lung cancer. This result is consistent across two cohorts with differing asbestos fiber exposures and intensity. [ABSTRACT FROM AUTHOR]

A thermochemical study of six natural sodium and sodium-calcium amphiboles was carried out using high-temperature melt solution calorimetry in a Tian–Calvet microcalorimeter. The enthalpies of formation from elements have been obtained for three arfvedsonite samples K0.5(Na1.5Ca0.5)(Mg4.0 Al0.1)[Si8.0O22](OH)2 from the Inagli Massif, central Aldan Shield, Russia (–11626.6 ± 8.9 kJ/mol), (Na0.5K0.1)(Na1.6Ca0.4)(Mg3.6 Al0.2)[Si8.0O22](OH)2 from the Khibiny Massif, Kola Peninsula, Russia (–11520.8 ± 14.6 kJ/mol), and (Na0.7K0.3)Na2.0( Mn0.1Ti0.1Al0.2)[Si8.0O22](OH)2 from the Katuginskoe deposit, Transbaikalia, Russia (–11384.7 ± 17.1 kJ/mol); for two riebeckite samples Na2.0(Mg2.5 Al0.5)Si8O22(OH)2 from the Kumula deposit, Central Kazakhstan (–10791.0 ± 10.1 kJ/mol) and Na2.0(Mg0.9 Al0.1)[Si8O22](OH)2 from Krivoy Rog, Ukraine (–10260.8 ± 10.9 kJ/mol), and for one richterite sample (Na0.7K0.3)(Ca1.2Na0.8)(Mg4.6 )[Si7.8Al0.2O22](OH)2 from the Kovdor Massif, Kola Peninsula, Russia (–12154.2 ± 9.7 kJ/mol). The values of the standard entropies, enthalpies, and Gibbs energies of formation are estimated for the end members of the isomorphic series arfvedsonite–magnesioarfvedsonite, riebeckite–magnesioriebeckite, and richterite–ferrorichterite. [ABSTRACT FROM AUTHOR]

Abstract Background The mechanisms by which mineral fibers induce adverse effects in vivo are still not well understood. The mechanisms of fiber dissolution in the lungs and subsequent release of metals in the extracellular/intracellular environment must be taken into account. Aim For the first time, the kinetics of release of metals during the acellular in vitro dissolution of chrysotile, crocidolite and fibrous erionite were determined. Methods In vitro acellular dissolution of chrysotile, crocidolite, and fibrous erionite-Na was conducted using a solution mimicking the phagolysosome environment active during the phagocytosis process (pH=4.5, at 37 °C). The kinetics of release of a representative selection of metals were determined over a period of three months. Results Despite the fact that the difference in Fe content between chrysotile and crocidolite is one order of magnitude, the much faster dissolution rate of chrysotile compared to crocidolite prompts greater release of available active surface Fe in the first weeks of the dissolution experiment and comparable amounts after 90 d. Such active iron may promote the formation of toxic hydroxyl radicals. The fast release of metals like Cr, Ni and Mn from chrysotile is also a source of concern whereas the release of V in solution is negligible. Conclusion Because chrysotile undergoes fast dissolution with respect to crocidolite and fibrous erionite, it behaves like a carrier that releases its metals' cargo in the lung environment, mimicking the phenomenon that explains the toxicity of nanoparticles. Hence, the toxicity paradigm of a non biodurable fiber like chrysotile should also take into account the release of toxic metals in the intracellular/extracellular medium during the rapid dissolution process. Graphical abstract fx1 Highlights • Metals released during the dissolution of asbestos and erionite fibers were determined. • Fast release of Cr, Ni and Mn from chrysotile is a source of concern. • The model of in vitro dissolution of nanoparticles may also apply to mineral fibers. • Rapid dissolution of the fibers prompts intracellular/extracellular release of toxic metals. • 'Fiber toxicity paradigm' should consider the release of toxic metals during dissolution. [ABSTRACT FROM AUTHOR]

Abstract The alkaline granites of the study area are characterized by the predominance of alkali feldspars, quartz minor amounts of riebeckite, plagioclase and biotite. Accessories are represented by zircon, apatite, titanite, allanite, chevkinite with secondary chlorite. They have peralkaline to slightly metalumminous character and were emplaced during post orogenic stages. The chondrite-normalized REE patterns display enrichment of light REE against depletion of heavy REE with significant Eu anomaly indicating extreme feldspar fractionation. They belong to A-type granites and have mantle derived source characterized by high K 2 O, extremely Low MgO and CaO contents, the pronounced Eu anomaly and depleted in Ba, Sr and Ta against enrichment of (HFSE) Zr, Y, Rb,Nb and ƩREE. They have formed under low oxygen fugacity (f O2) conditions with high magmatic temperature up to 896 °C with fairly low water pressures. Intrusions of alkali feldspar granite followed by riebeckite granite (alkaline granite) are consistent with fractional crystallization model. This was supported by the presence of syenitic microgranular enclaves with felsic alkaline granite. The most plausible source of these alkaline granites is mantle derived potassium rich source, that may accompanied by further magma mixing or assimilations. Highlights • Geological and geochemical study of the alkaline granites indicates that they have mantle sources. [ABSTRACT FROM AUTHOR]

Exposure to asbestos fiber is central to mesothelial carcinogenesis, for which iron overload in or near mesothelial cells is a key pathogenic mechanism. Alternatively, iron chelation therapy with deferasirox or regular phlebotomy was significantly preventive against crocidolite-induced mesothelial carcinogenesis in rats. However, the role of iron transporters during asbestos-induced carcinogenesis remains elusive. Here, we studied the role of divalent metal transporter 1 (DMT1; Slc11a2), which is a Fe(II) transporter, that is present not only on the apical plasma membrane of duodenal cells but also on the lysosomal membrane of every cell, in crocidolite-induced mesothelial carcinogenesis using DMT1 transgenic (DMT1Tg) mice. DMT1Tg mice show mucosal block of iron absorption without cancer susceptibility under normal diet. We unexpectedly found that superoxide production was significantly decreased upon stimulation with crocidolite both in neutrophils and macrophages of DMT1Tg mice, and the macrophage surface revealed higher iron content 1 h after contact with crocidolite. Intraperitoneal injection of 3 mg crocidolite ultimately induced malignant mesothelioma in ∼50% of both wild-type and DMT1Tg mice (23/47 and 14/28, respectively); this effect was marginally (p = 0.069) delayed in DMT1Tg mice, promoting survival. The promotional effect of nitrilotriacetic acid was limited, and the liver showed significantly higher iron content both in DMT1Tg mice and after crocidolite exposure. The results indicate that global DMT1 overexpression causes decreased superoxide generation upon stimulation in inflammatory cells, which presumably delayed the promotional stage of crocidolite-induced mesothelial carcinogenesis. DMT1Tg mice with low-stamina inflammatory cells may be helpful to evaluate the involvement of inflammation in various pathologies. [ABSTRACT FROM AUTHOR]

The Triassic geodynamic evolution of the Pontides Belt, which geographically corresponds to northern Anatolia, is still a matter of debate. We present and interpret geological, petrographical, geochemical, and geochronological data from small, discordant, metagabbroic rocks exposed in the Tokat Massif. Field and petrographic characteristics distinguish four subgroups: (i) medium‐grained, slightly lineated, clinopyroxene‐rich metagabbros; (ii) fine‐grained, nonlineated, clinopyroxene‐rich metagabbros; (iii) medium‐grained, nonlineated, brown amphibole‐rich metagabbros; and (iv) medium‐grained, slightly lineated, brown and blue amphibole‐rich metagabbros. Magmatic kaersutites give 39Ar/40Ar plateau ages of 244.6 ± 0.5 and 243.16 ± 0.92 Ma and overlap the U‐Pb age of titanite from a clinopyroxene‐rich sample. Inherited zircons (~460, ~880, and ~2600 Ma) in fine‐grained clinopyroxene‐rich metagabbros indicate interaction with a range of crustal rocks during the intrusion. The blue amphiboles are magnesioriebeckites that formed during metamorphism or late‐stage crystallization. Geochemical data, including whole rock major and trace element concentrations, and Sr‐Nd‐Pb isotope compositions reveal that both clinopyroxene‐ and amphibole‐rich metagabbros are alkaline in composition but derived from distinct mantle sources. They are compositionally distinct from mafic igneous rocks in the contemporaneous Permo‐Triassic Karakaya Complex that is well exposed in the western part of the Pontides Belt. Considering all data, we suggest that the Pontides Belt was shaped above a south dipping subduction zone during Permo‐Triassic and the alkaline gabbros that were emplaced into crustal rocks during Early Triassic back‐arc rifting of the northern margin of Gondwana. Key Points: Geochemical data reveal that both clinopyroxene‐ and amphibole‐rich metagabbros are alkaline in compositionThere is no evidence in the gabbros of a high‐pressure metamorphic event as previously suggestedThey were emplaced into crustal rocks during Early Triassic rifting of the northern margin of Gondwana [ABSTRACT FROM AUTHOR]

In this work we report on a complete crystal-chemical characterization of a near end-member riebeckite from Malawi, and use the available data to critically compare information obtained from different analytical methods. The sample occurs as well-formed and very large single crystals in pegmatitic rocks. Accurate site-populations were determined by combining single-crystal structure refinement and electron microprobe analysis (EMPA). The Fe3+/Fe2+ ratio was obtained from Mössbauer spectroscopy. Lithium was quantified by Laser Ablation Inductively Coupled Plasma Mass Spectroscopy (LA-ICP-MS). Fourier-Transform Infrared (FTIR) spectra, collected both on powders and single crystals, are presented and discussed. FTIR spectra in the NIR region are also presented for the first time for this amphibole. The FTIR data are compatible with complete local ordering of A cations close to F, and complete Fe2+/Mg disorder at M (1,3). Polarized Raman-scattering data collected from single crystals confirm this conclusion. In addition, it was found that FTIR data collected on powders provide the best agreement with the site occupancies derived from chemical (EMPA and LA-ICP-MS) and crystal-chemical data, possibly because they do not depend on experimental issues such as orientation and polarization. [ABSTRACT FROM AUTHOR]

In this work, we investigate the oxidation behavior of a nearly end-member riebeckite, ideally Na2 ( Fe 3 2 + Fe 2 3 + ) $\begin{array}{} (\text{Fe}^{2+}_3\text{Fe}^{3+}_2) \end{array} $ Si8O22(OH)2, by using vibrational FTIR and Raman spectroscopies. Combining these results with previous studies performed on the same sample by single-crystal structure refinement and Mössbauer spectroscopy, we conclude that iron oxidation in riebeckite is a multi-step process. (1) In the ~523 K < T < 623 K temperature range, the O-H bond lengthens and both the electrons and the hydrogen cations delocalize. Raman analysis shows that this step is reversible upon cooling to room temperature. (2) In the 623 K < T < 723 K range, the kinetic energy increases so that the electrons can be ejected from the crystal; beyond 723 K an irreversible oxidation of Fe occurs that couples with irreversible changes in the SiO4 double-chains leading to a contraction of the unit-cell volume, i.e., to structural changes detectable at the long-range scale. (3) Beyond 823 K, the irreversible oxidation is completed and H+ ions are forced to leave the crystal bulk. Because of this multi-step process, the onset of the deprotonation process is detected at ~700 K by single-crystal XRD analysis of the unit-cell parameters, but starts at 623 K as indicated by Mössbauer spectroscopy on powders (and by changes in the cation distribution observed by structure refinement). Also, Raman scattering shows that the release of H+ from the crystal surface starts ~100 K before the complete deprotonation of the crystal bulk is witnessed by FTIR absorption. Hence, the oxidation of Fe starts at the crystal surface and induces electron and H+ migration from the crystal interior to the rim and thus subsequent oxidation through the crystal bulk. No deprotonation is observed by FTIR either in powders embedded in KBr or in crystals heated in N2 atmosphere, implying that the release of H+ needs surficial (atmospheric) oxygen to form H2O molecules. Fe2+ → Fe3+ oxidation produces a flux of electrons throughout the crystal matrix, which generates electrical conductivity across the amphibole. An important implication of this work, which might have interesting applications in material science, is that iron oxidation in riebeckite (and possibly in other Fe-rich silicates) is reversible in a given range of temperature. Also, this work shows that complex processes cannot be fully understood or even monitored accurately without using a proper combination of independent techniques. [ABSTRACT FROM AUTHOR]

Background: Studies comparing different forms of asbestos are rare, and limited by the failure to compare results with unexposed populations. We compare autoimmune responses among former workers and residents of the crocidolite mining and milling town of Wittenoom, Western Australia, with an unexposed population. Methods: ANA testing using indirect immunofluorescence was performed on randomly selected serum samples from Wittenoom workers or residents and compared with those from participants of another unexposed cohort study. Results: ANA scores were higher in the Wittenoom participants compared with Busselton and the odds of being ANA positive was fivefold greater among Wittenoom participants than Busselton (OR 5.5, 95%CI 2.3‐13.0). Conclusions: This study is the first to report increased ANA positivity among persons exposed exclusively to crocidolite. This finding of a high frequency of positive ANA tests among crocidolite‐exposed subjects may be an indicator for an increased risk of systemic autoimmune diseases and needs further scrutiny. [ABSTRACT FROM AUTHOR]

Inhalation exposure to asbestos is associated with lung and pleural diseases in humans and remains a major public health issue worldwide. Human bronchial epithelial cells (16HBE) were exposed to UICC amosite, crocidolite and chrysotile. Cytotoxicity, genotoxicity, global DNA methylation on cytosine residues (using LC-MS/MS) were investigated at different doses (2.5–100 μg/ml). Gene-specific DNA methylation alterations at the whole genome were investigated using a microarray that interrogates >450 thousand CpG sites. Subsequently, gene functional analyses (KEGG pathway, Gene Ontology and functional classification) were performed on genes with differentially methylated gene promoters. At non-cytotoxic doses, global DNA methylation was altered after 24 h exposure to amosite and crocidolite (>2.5 μg/ml). Exposure to amosite and crocidolite (amphibole type asbestos) induced both hypomethylation and hypermethylation at single CpG site and gene promoter levels whereas exposure to chrysotile (serpentine type asbestos) induced hypomethylation at the gene promoter level. Gene functional classification analyses revealed that all types of asbestos fibres induce alterations on GO-clusters i.e. on regulation of Rho-protein signal transduction, nucleus, (e.g. homeobox genes), ATP-binding function and extracellular region (e.g. WNT-group of genes). These differentially methylated genes might contribute to asbestos-related diseases in bronchial cells. [ABSTRACT FROM AUTHOR]

The southern Sinai Peninsula, underlain by the northernmost extension of the Arabian-Nubian Shield, exposes post-collisional calc-alkaline and alkaline granites that represent the youngest phase of late Neoproterozoic igneous activity. We report a petrographic, mineralogical and geochemical investigation of post-collisional plutons of alkaline and, in some cases, peralkaline granite. These granites intrude metamorphosed country rocks as well as syn- and post-collisional calc-alkaline granitoids. The alkaline and peralkaline granites of the southern tip of Sinai divide into three subgroups: syenogranite, alkali feldspar granite and riebeckite granite. The rocks of these subgroups essentially consist of alkali feldspar and quartz with variable amounts of plagioclase and mafic minerals. The syenogranite and alkali feldspar granite contain small amounts of calcic amphibole and biotite, often less than 3%, while the riebeckite granite is distinguished by sodic amphibole (5-10%). These plutons have geochemical signatures typical of post-collisional A-type granites and were most likely emplaced during a transition between orogenic and anorogenic settings. The parental mafic magma may be linked to lithospheric delamination and upwelling of asthenospheric mantle material. Differentiation of the underplated basaltic magma with contributions from the juvenile crust eventually yielded the post-collisional alkaline granites. Petrogenetic modelling of the studied granitic suite shows that pure fractional crystallization cannot quantitatively explain chemical variations with the observed suite, with both major oxides and several trace elements displaying trends opposite to those required by the equilibrium phase assemblage. Instead, we show that compositional variation from syenogranite through alkali feldspar granite to riebeckite granite is dominated by mixing between a low-SiO2 liquid as primitive or more primitive than the lowest-SiO2 syenogranite and an evolved, high-SiO2 liquid that might be a high-degree partial melt of lower crust. [ABSTRACT FROM AUTHOR]

Occupational and environmental asbestos exposure is the main determinant of malignant pleural mesothelioma (MPM), however, the mechanisms by which its fibres contribute to cell toxicity and transformation are not completely clear. Aberrant DNA methylation is a common event in cancer but epigenetic modifications involved specifically in MPM carcinogenesis need to be better clarified. To investigate asbestos-induced DNA methylation and gene expression changes, we treated Met5A mesothelial cells with different concentrations of crocidolite and chrysotile asbestos (0.5 ÷ 5.0 µg/cm2, 72 h incubation). Overall, we observed 243 and 302 differentially methylated CpGs (≥ 10%) between the asbestos dose at 5 µg/cm2 and untreated control, in chrysotile and crocidolite treatment, respectively. To examine the dose-response effect, Spearman’s correlation test was performed and significant CpGs located in genes involved in migration/cell adhesion processes were identified in both treatments. Moreover, we found that both crocidolite and chrysotile exposure induced a significant up-regulation of CA9 and SRGN (log2 fold change > 1.5), previously reported as associated with a more aggressive MPM phenotype. However, we found no correlation between methylation and gene expression changes, except for a moderate significant inverse correlation at the promoter region of DKK1 (Spearman rho = − 1, P value = 0.02) after chrysotile exposure. These results describe for the first time the relationship between DNA methylation modifications and asbestos exposure. Our findings provide a basis to further explore and validate asbestos-induced DNA methylation changes, that could influence MPM carcinogenesis and possibly identifying new chemopreventive target. [ABSTRACT FROM AUTHOR]

In this work, hyperspectral imaging in the short wave infrared range (SWIR: 1000–2500 nm) coupled with chemometric techniques was evaluated as an analytical tool to detect and classify different asbestos minerals, such as amosite ((Fe 2+ ) 2 (Fe 2+ ,Mg) 5 Si 8 O 22 (OH) 2 )), crocidolite (Na 2 (Mg,Fe) 6 Si 8 O 22 (OH) 2 ) and chrysotile (Mg 3 (Si 2 O 5 )(OH) 4 ), contained in cement matrices. Principal Component Analysis (PCA) was used for data exploration and Soft Independent Modeling of Class Analogies (SIMCA) for sample classification. The classification model was built using spectral characteristics of reference asbestos samples and then applied to the asbestos containing materials. Results showed that identification and classification of amosite, crocidolite and chrysotile was obtained based on their different spectral signatures, mainly related to absorptions detected in the hydroxyl combination bands, such as Mg-OH (2300 nm) and Fe-OH (from 2280 to 2343 nm). The developed SIMCA model showed very good specificity and sensitivity values (from 0.89 to 1.00). The correctness of classification results was confirmed by stereomicroscopic investigations, based on different color, morphological and morphometrical characteristics of asbestos minerals, and by micro X-ray fluorescence maps, through iron (Fe) and magnesium (Mg) distribution assessment on asbestos fibers. The developed innovative approach could represent an important step forward to detect asbestos in building materials and demolition waste. [ABSTRACT FROM AUTHOR]

Geological, geochemical, and geochronological studies of rocks have been performed at the Okunyovo rare-metal ore magmatic complex (Western Sayan Mountains) composed of alkali granites and related F-Be mineralization. The geological data obtained and the features of the geochemical similarity of granite and ore mineralization identified are indicative of their genetic relation. Riebeckite from two granite samples has been subjected to Ar/Ar analyses. The estimated age values of 481.5 ± 2.7 Ma and 486.5 ± 5.8 Ma are consistent within the limits of error and determine the age of Okunyovo alkali granite within 481-486 Ma ago. These data have made it possible to relate the studied rock and ore formation to the development of the Early Paleozoic ASFR controlled by the mantle plume. Along with the Okunyovo rare-metal granite massif, within the Sayan Region of the magmatic province, there are a number of Early Paleozoic alkali massifs related to the Aryskan, Raduga, and Kazyr rare-metal deposits. They are located in the conjugation area of the Western and Eastern Sayan ridges, in the Early Paleozoic Eastern Sayan rare-metal magmatism zone specialized in Be, W, Mo, Zr, Nb, and REEs. [ABSTRACT FROM AUTHOR]

Magnesio-riebeckite from the dumps of the abandoned mine of Varenche (45°47'22" N, 7°29'17" E), Saint-Barthélemy, Nus, Aosta Valley (Italy), was studied to provide the complete mineral description (including crystal structure) and insights into the crystal-chemistry of riebeckite. The empirical formula derived from electron microprobe analysis and single-crystal structure refinement is A(Na0.09K0.01)Σ=0.10 B(Na1.77Ca0.11Mg0.08Mn0.042+)Σ=2.00 C(Mg2.93Mn0.132+Fe0.072+Zn0.01Ni0.12Fe1.253+Al0.48Ti0.01)Σ=5.00 T(Si7.92Al0.08)Σ=8.00 O22 W(OH1.88F0.12)Σ=2.00. Magnesio-riebeckite is biaxial (+), with α = 1.678(2), β = 1.682(2), γ = 1.688(2) and 2V (meas.) = 80.2(1.7)°, 2V (calc.) = 78.7°. The unit-cell parameters are a = 9.6481(14), b = 17.873(3), c = 5.3013(7) Å, β = 103.630(2)°, V = 888.4 (2)ų, Z = 2, space group C2/m. The strongest ten reflections in the powder X-ray pattern [d values (in Å), I, (hkl)] are: 2.701, 100, (151); 8.303, 83, (110); 3.079, 62, (310); 3.391, 53, (131); 4.467, 50, (040,021); 2.522, 50, (202); 2.578, 35, (061); 2.155, 30, (261), 4.855, 30, (111), 2.300, 29, (351). [ABSTRACT FROM AUTHOR]

Asbestos may cause adverse effects, but relationship between mineralogy and texture of fibres versus toxicity is still lacking. Toxicological studies can be interpreted and compared only if quantitative features of fibres are determined. Here, riebeckitic (“crocidolite”) amphibole fibres were analysed by XRPD, FTIR, SEM-EDS and EMP-WDS; only crystals with stochiometry A□B Na 2 C (Fe 2+ 2.5 Mg 0.5 ) C Fe 3+ 2 T Si 8 O 22 W (OH) 2 are present in the starting material used for the experiments. Fibres deposited from solutions of 0.1, 1, 10, 25, 50, 75 and 100 mg/L were counted by image analysis using SEM images. At 0.1 and 1 mg/L the fibres are well separated, whereas between 1 and 10 mg/L they start to agglomerate. In-vitro tests performed on fibres deposited at the same mg/L concentrations show that the toxic potential follows a curvilinear increasing trend with a decreasing rate. Since the range of sizes of single fibres and their mineralogy are constant, this decreasing rate can be only attributed to the increasing amount of agglomerated fibres. Hence, single versus agglomerated fibre population is a factor that cannot be neglected in defining the final adverse effects of asbestos. The analytical protocol proposed here is valuable for any aero-dispersed dust, in polluted environments, as well as in the interpretation of experimental studies. [ABSTRACT FROM AUTHOR]

Although industrial uses of asbestos have declined since the 1970s, in recent years there has been a renewed interest in para-occupational (“take-home”) exposure to these fibers. The aim of this study was to quantify the release of asbestos fibers, if any, during the shaking out of crocidolite- and chrysotile-contaminated clothing in a simulated at-home setting. An exposure study was conducted in which personal and area air samples were collected during the handling (i.e. shake-out) of work clothing (shirt and pants) previously worn by an operator who had cut asbestos-containing cement pipe. During eight “loading” events, the operator cut a historically representative asbestos-containing cement pipe (10% crocidolite and 25% chrysotile) using a powered abrasive saw. Subsequently, 30-minute air samples were collected during four “shake-out” events, each of which consisted of the handling of two complete sets of contaminated work clothes. Samples were analyzed in accordance with NIOSH methods 7400 and 7402. The mean phase contrast microscopy equivalent (PCME) airborne concentrations were 0.52 f/cc (SD = 0.34 f/cc) for total asbestos fibers, 0.36 f/cc (SD = 0.26 f/cc) for chrysotile and 0.17 f/cc (SD = 0.096 f/cc) for crocidolite. Based on likely estimates of the frequency of laundering activities, and assuming that the dusty clothing (1) is not blown off in the occupational setting using compressed air and (2) is not shaken out before entering the home, a family member handling the clothing could potentially have a lifetime cumulative exposure to chrysotile and crocidolite of approximately 0.20 f/cc-year and 0.096 f/cc-year, respectively. [ABSTRACT FROM AUTHOR]

Anomalous high-conductivity layers are typical of subduction zones, the largest recycling systems of the Earth. Understanding the mineral physics underlying the high conductivity of rocks has paramount implications for several planetary-scale processes, including global water cycling, earthquake activity, and arc magmatism. Here, by using in situ polarized Raman spectroscopy, we provide a direct proof for the development of anisotropic electron-phonon excitations (polarons) and delocalized H+ in riebeckite, a Fe-bearing sodic amphibole typical of blue-schist metamorphic facies. The activation of polarons starts at 500 K (227 °C) and is complete at 650 K (377 °C) under both reducing and oxidizing conditions. At higher temperatures external oxygen triggers the expulsion of H+ and e − from the crystal bulk. The temperature range observed for the development of charge carriers is in excellent agreement with the conductivity trends measured for riebeckite in previous studies, and nicely fits the temperatures for the development of high-conductivity layers in warm and cold subduction zones. The study directly demonstrates the activation of polarons at temperatures characteristic of convergent plate margins provides the atomic-scale picture whose macroscopic-scale expression is the anomalous conductivity measured in subduction zones. [Display omitted] [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Although every year, thousands of people die from asbestos-related diseases, many people disregard things that are past. Meanwhile, a lot of people, in particular, in many Asia countries that have no guideline values for waterborne asbestos are currently in a fever of anxiety about the possibility of its health hazards. This study focused on a grasping the actual situation of asbestos in household tap water. An intensive collection of the tract drinking-water was conducted in Iksan, Korea (at six homes), and Fukuoka, Japan (at nine homes). After pretreatment, both morphological observation and elemental analysis were simultaneously carried out using a scanning electron microscopy (SEM) with an energy dispersive X-ray spectrometer (EDX). The concentrations of waterborne asbestos fiber varied from place to place in both local cities. Their average concentrations at all sites in Iksan and Fukuoka were 213.3 and 181.1 f/L, respectively. Although the measured values in this study were the sum of chrysotile, amosite, and crocidolite fibers with a high risk of cancer, they were found to be consistently below the MCL (the Maximum Contaminant Level recommended by the U.S. toxicological profile for Asbestos). A significant link was found between open water supply channels and waterborne asbestos. The backward wind trajectory projections indicated that the present water sampling sites might be affected by the airborne asbestos fiber in the upwind atmosphere. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A range of fibrous materials, including several types of asbestos and carbon fibres with nano scale diameters that had reported positive genotoxicity data (predominantly clastogenicity), were tested in the in vitro micronucleus test (OECD 487) in GLP-compliant studies in Chinese Hamster Ovary cells. Out of eight materials tested, only one (crocidolite, an asbestos fibre) gave a positive response either in the presence or absence of metabolic activation (S9) and at short (3 h) or extended (24 h) exposure times (p ≤ 0.001). Our data suggest that the commonly used tests for clastogenicity in mammalian cells require extensive modification before fibrous materials are detected as positive, raising questions about the validity of these tests for detecting clastogenic and aneugenic fibrous materials. [ABSTRACT FROM AUTHOR]

Australia is known to have had the highest per-capita asbestos consumption level of any nation, reaching a peak in the 1970s. Although crocidolite was effectively banned in the late 1960s, and amosite use ceased in the mid 1980s, a complete asbestos ban was not implemented until 2003. This resulted in an epidemic of asbestos-related disease, which has only now reached its peak. Between 1982 and 2011, 13,036 individuals were newly diagnosed with malignant mesothelioma, with 690 diagnosed in 2011. A further 778 cases were identified between 1945 and 1981 from retrospective searches and the first 2 years of the Australian Mesothelioma Program. The age-standardized malignant mesothelioma incidence rate has leveled off in the last 10 years (2.8 per 100,000 in 2011). There has been a marked increase over time in the age-specific incidence rates for individuals aged 75 years or older. Data from the current Australian Mesothelioma Registry on asbestos exposure history in Australia is available for 449 subjects diagnosed between July 1, 2010, and April 1, 2015. This asbestos exposure history data show that 60% (n = 268) of cases had probable or possible occupational asbestos exposure, with trade-based jobs being the most frequent sources of occupational asbestos exposure. In addition, out of the 449 cases, 377 were recorded as having probable or possible nonoccupational asbestos exposure. Continuous vigilance toward changes over time in the settings in which people are exposed to asbestos and in the descriptive epidemiology of malignant mesothelioma is recommended to enable a comprehensive understanding of the current and future impact of asbestos-related diseases in Australia. [ABSTRACT FROM PUBLISHER]

Pulmonary exposure to multiwalled carbon nanotubes (MWCNT) induces an inflammatory and rapid fibrotic response, although the long-term signaling mechanisms are unknown. The aim of this study was to examine the effects of 1, 10, 40, or 80 μg MWCNT administered by pharyngeal aspiration on bronchoalveolar lavage (BAL) fluid for polymorphonuclear cell (PMN) infiltration, lactate dehydrogenase (LDH) activity, and lung histopathology for inflammatory and fibrotic responses in mouse lungs 1 mo, 6 mo, and 1 yr postexposure. Further, a 120-μg crocidolite asbestos group was incorporated as a positive control for comparative purposes. Results showed that MWCNT increased BAL fluid LDH activity and PMN infiltration in a dose-dependent manner at all three postexposure times. Asbestos exposure elevated LDH activity at all 3 postexposure times and PMN infiltration at 1 mo and 6 mo postexposure. Pathological changes in the lung, the presence of MWCNT or asbestos, and fibrosis were noted at 40 and 80 μg MWCNT and in asbestos-exposed mice at 1 yr postexposure. To determine potential signaling pathways involved with MWCNT-associated pathological changes in comparison to asbestos, up- and down-regulated gene expression was determined in lung tissue at 1 yr postexposure. Exposure to MWCNT tended to favor those pathways involved in immune responses, specifically T-cell responses, whereas exposure to asbestos tended to favor pathways involved in oxygen species production, electron transport, and cancer. Data indicate that MWCNT are biopersistent in the lung and induce inflammatory and fibrotic pathological alterations similar to those of crocidolite asbestos, but may reach these endpoints by different mechanisms. [ABSTRACT FROM AUTHOR]

This work presents a comparative FEG–SEM study of the morphological and chemical characteristics of both asbestos bodies and fibres found in the tissues of Sprague–Dawley rats subjected to intraperitoneal or intrapleural injection of UICC chrysotile, UICC crocidolite and erionite from Jersey, Nevada (USA), with monitoring up to 3 years after exposure. Due to unequal dosing based on number of fibres per mass for chrysotile with respect to crocidolite and erionite, excessive fibre burden and fibre aggregation during injection that especially for chrysotile would likely not represent what humans would be exposed to, caution must be taken in extrapolating our results based on instillation in experimental animals to human inhalation. Notwithstanding, the results of this study may help to better understand the mechanism of formation of asbestos bodies. For chrysotile and crocidolite, asbestos bodies are systematically formed on long asbestos fibres. The number of coated fibres is only 3.3% in chrysotile inoculated tissues. In UICC crocidolite, Mg, Si, and Fe are associated with the fibres whereas Fe, P and Ca are associated with the coating. Even for crocidolite, most of the observed fibres are uncoated as coated fibres are about 5.7%. Asbestos bodies do not form on erionite fibres. The crystal habit, crystallinity and chemistry of all fibre species do not change with contact time, with the exception of chrysotile which shows signs of leaching of Mg. A model for the formation of asbestos bodies from mineral fibres is postulated. Because the three fibre species show limited signs of dissolution in the tissue, they cannot act as source of elements (primarily Fe, P and Ca) promoting nucleation and growth of asbestos bodies. Hence, the limited number of coated fibres should be due to the lack of nutrients or organic nature. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2) nanofibres are a novel fibrous nanomaterial with increasing applications in a variety of fields. While the biological effects of TiO2 nanoparticles have been extensively studied, the toxicological characterization of TiO2 nanofibres is far from being complete. In this study, we evaluated the toxicity of commercially available anatase TiO2 nanofibres using TiO2 nanoparticles (NP) and crocidolite asbestos as non-fibrous or fibrous benchmark materials. The evaluated endpoints were cell viability, haemolysis, macrophage activation, trans-epithelial electrical resistance (an indicator of the epithelial barrier competence), ROS production and oxidative stress as well as the morphology of exposed cells. The results showed that TiO2 nanofibres caused a cell-specific, dose-dependent decrease of cell viability, with larger effects on alveolar epithelial cells than on macrophages. The observed effects were comparable to those of crocidolite, while TiO2 NP did not decrease cell viability. TiO2 nanofibres were also found endowed with a marked haemolytic activity, at levels significantly higher than those observed with TiO2 nanoparticles or crocidolite. Moreover, TiO2 nanofibres and crocidolite, but not TiO2 nanoparticles, caused a significant decrease of the trans-epithelial electrical resistance of airway cell monolayers. SEM images demonstrated that the interaction with nanofibres and crocidolite caused cell shape perturbation with the longest fibres incompletely or not phagocytosed. The expression of several pro-inflammatory markers, such as NO production and the induction of Nos2 and Ptgs2, was significantly increased by TiO2 nanofibres, as well as by TiO2 nanoparticles and crocidolite. This study indicates that TiO2 nanofibres had significant toxic effects and, for most endpoints with the exception of pro-inflammatory changes, are more bio-active than TiO2 nanoparticles, showing the relevance of shape in determining the toxicity of nanomaterials. Given that several toxic effects of TiO2 nanofibres appear comparable to those observed with crocidolite, the possibility that they exert length dependent toxicity in vivo seems worthy of further investigation. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) are emerging as important occupational and environmental toxicants owing to their increasing prevalence and potential to be inhaled as airborne particles. CNTs are a concern because of their similarities to asbestos, which include fibrous morphology, high aspect ratio, and biopersistence. Limitations in research models have made it difficult to experimentally ascertain the risk of CNT exposures to humans and whether these may lead to lung diseases classically associated with asbestos, such as mesothelioma and fibrosis. In this study, we sought to comprehensively compare profiles of lung pathology in mice following repeated exposures to multiwall CNTs or crocidolite asbestos (CA). We show that both exposures resulted in granulomatous inflammation and increased interstitial collagen; CA exposures caused predominantly bronchoalveolar hyperplasia, whereas CNT exposures caused alveolar hyperplasia of type II pneumocytes (T2Ps). T2Ps isolated from CNT-exposed lungs were found to have upregulated proinflammatory genes, including interleukin 1ß (IL-1ß), in contrast to those from CA exposed. Immunostaining in tissue showed that while both toxicants increased IL-1ß protein expression in lung cells, T2P-specific IL-1ß increases were greater following CNT exposure. These results suggest related but distinct mechanisms of action by CNTs versus asbestos which may lead to different outcomes in the 2 exposure types. [ABSTRACT FROM AUTHOR]

Human exposure to asbestos can cause a wide variety of lung diseases that are still a current major health concern, even if asbestos has been banned in many countries. It has been shown in many studies that asbestos fibers, ingested by alveolar macrophages, disrupt lung iron homeostasis by sequestering iron. Calcium can also be deposited on the fibers. The pathways along which iron and above all calcium interact with fibers are still unknown. Our aim was that of investigating if the iron accumulation induced by the inhaled asbestos fibers also involves calcium ions accumulation. Lung sections of asbestos-exposed mice were analyzed using an extremely sensitive procedure available at the synchrotron facilities, that provides morphological and chemical information based on X-ray fluorescence microspectroscopy (μ-XRF). In this study we show that (1) where conventional histochemical procedures revealed only weak deposits of iron and calcium, μ-XRF analysis is able to detect significant deposits of both iron and calcium on the inhaled asbestos fibers; (2) the extent of the deposition of these ions is proportionally directly related and (3) iron and calcium deposition on inhaled asbestos fibers is concomitant with the appearance of inflammatory and hyperplastic reactions. [ABSTRACT FROM AUTHOR]

The thermal behaviour of two crocidolite asbestos samples was characterized. Infrared spectroscopy (FT-IR), powder X-ray diffraction, scanning electron microscopy and thermal analysis (DTA and TG) with evolved gas analysis were carried out on samples of crocidolite asbestos as received and after heating in order to observe their structural changes and dehydroxylation process. The results show that the dehydroxylation process of crocidolite asbestos occurs at different temperatures and is in the range 400-650 °C. This temperature is dependent on the origin of asbestos samples and may be associated with an increased amount of magnesium in the structure of asbestos. For the sample which comes from the Republic of South Africa, the dehydroxylation process occurs at lower temperature in contrast to Russian crocidolite asbestos sample from cement-asbestos material. However, this temperature range is lower than those reported by some authors, who state that the decomposition temperature of crocidolite should be at least 900 °C. This finding may have a significant influence on thermal utilization of asbestos materials, e.g. cement-asbestos, because the temperature of the heat treatment in the utilization process should be as low as possible. [ABSTRACT FROM AUTHOR]

The interleukin-1 (IL-1) family has been implicated in cellular responses to nanoparticles including carbon nanotubes (CNTs). IL-1α and β are key proinflammatory cytokines important in inflammatory and oxidative stress responses. The aim of this study was to characterize the role of IL-1 in cellular responses of CNTs in cells from IL-1α/β wild type (IL1-WT) mice and cells with reduced inflammatory potential from IL-1α/β deficient (IL1-KO) mice. Two multi-walled CNTs, CNT-1 containing long and thick fibers and CNT-2 containing short and thin fibers, were compared to UICC crocidolite asbestos fibers. Upon CNT exposure toxicity and apoptosis were affected differently in IL1-WT and IL1-KO cells. Upregulation of TNFα and IL-1α mRNA expression in IL1-WT cells was dependent on the type of CNT. On the contrary precursor IL-1α protein was downregulated after 24 h. The mitogen-activated protein kinase (MAPK) c-Jun N-terminal kinase (JNK) was activated in IL1-KO cells and regulated by CNTs, whereas no significant changes of extracellular regulated kinase (ERK) were observed when comparing IL1-WT and IL1-KO cells. In summary, the results presented here indicate that IL-1 contributes to the cellular and molecular effects of CNT exposure and that the type of CNT has an important effect on the cellular response. [ABSTRACT FROM AUTHOR]

The Siuna Serpentinite Mélange (SSM) is a subduction-zone-related complex that contains diverse blocks of igneous and sedimentary origin, overprinted by various metamorphic conditions. The SSM is located at the southern border of the Chortís block and marks the boundary between continental and oceanic crusts in the western margin of the Caribbean Plate. The serpentinite matrix mainly consists of lizardite/chrysotile, Cr-rich spinel, and relict orthopyroxene that suggest a harzburgitic protolith and an upper mantle supra-subduction zone origin. Blocks within the southern and central regions range from Jurassic pelagic sediments to mafic/intermediate igneous rocks that are metamorphosed to various degrees, ranging from prehnite-pumpellyite/greenschist to likely blueschist facies (e.g. riebeckite-bearing metashale) conditions. In contrast, the northern section encloses almost exclusively epidote-amphibolite facies metabasite blocks, and minor mica- and chlorite-rich rocks of metasomatic origin, respectively. Some of the epidote-amphibolite blocks contain relic garnet-rich zones embedded in an amphibole-rich matrix. The garnets appear to record two generations of growth and contain mineral inclusions such as amphibole, apatite, titanite, aegirine-augite, and quartz. Thermobarometric estimates for the garnet-rich zones and epidote-amphibolite-rich matrix suggest a prograde blueschist facies at ~1.2 GPa and 400–450°C, an eclogite facies metamorphic peak at 1.5–1.7 GPa and 565–614°C, and a post-peak epidote-amphibolite facies metamorphism. These pressure and temperature estimates indicate a classical clockwisePTpath that has been observed in many palaeo-subduction zone environments worldwide. Phengite Ar–Ar dating of mica-rich rock yields 140 Ma and suggests an Early Cretaceous exhumation along the southern edge of the continental Chortís block. [ABSTRACT FROM AUTHOR]