Quantitative measurement of relative flexibility have been made on amphibole fibres based on calculation of bending strain of maximally bent fibre segments. Enhanced flexibility was found to be an inverse function of fibre diameter. Asbestos is therefore a morphological entity. These conclusions are supported by consistent observations of fibre diameter/flexibility relationships in amphiboles, serpentine, and rutile. Flexibility may arise from growth of thin crystals (primary flexibility), or from crystal diameter reduction (secondary flexibility). Mechanisms for secondary flexibility in amphiboles include splitting and solution along cleavage planes. Gross morphological characteristics are a poor indicator of microscopic habit, since coarsely fibrous minerals such as picrolite antigorite may not be fibrous after particle width reduction, and secondary asbestiform fibres are often derived from minerals with a non-fibrous morphology on gross examination.

The structure of chrysotile, an important asbestos mineral, consists of layers curled concentrically or spirally into tubes. Published transmission electron microscope (TEM) images suggest that successive layers are generally stacked out of register with one another. However, a lattice model can be constructed in such a way that each layer can be stacked in register with the next, five times around the circumference, so that the structure exhibits a global 5-fold symmetry. We report here TEM observations confirming that chrysotile asbestos can form crystals with this structure, the first observation of five-fold symmetry in a natural crystalline material.

A chrysotile disc is proposed as the fundamental seed structure for the formation of chrysotile asbestos fibres, polygonal serpentine fibres and polyhedral lizardite spheres. The curvature, fivefold symmetry and hydrogen-bonding alignment of the layers in the seed disc control the formation of the 15 or 30 sectors in polygonal serpentine and the orientations of the planar arrays of 15 or 30 radial crystals in polyhedral serpentine. A polygonized disc precursor to polygonal fibre formation has been observed at an arrested stage of growth in a synthesis experiment.

Raman spectroscopy was assessed for its ability to rapidly identify asbestos phases by submitting the amphiboles anthophyllite, amosite, crocidolite and tremolite to spectroscopic analysis. All the phases were characterized by using XRD, SEM, TEM (CTEM, SAED), AEM and EDS techniques. This study demonstrates that accurate identification of the mineralogical phase can be attained by analysing the position in the Raman spectrum of the bands corresponding to the symmetric stretching modes (vs) and to the antisymmetric stretching modes (vas) of the different Si—O linkages. Raman spectroscopy thus proves to be an effective technique for rapidly distinguishing the different fibrous minerals examined.

Asbestos bodies are the histological hallmarks of asbestos exposure. Both conventional and advanced techniques are used to evaluate abundance and composition in histological samples. We previously reported the possibility of using synchrotron X-ray fluorescence microscopy (XFM) for analyzing the chemical composition of asbestos bodies directly in lung tissue samples. Here we applied a high-performance synchrotron X-ray fluorescence (XRF) set-up that could allow new protocols for fast monitoring of the occurrence of asbestos bodies in large histological sections, improving investigation of the related chemical changes. A combination of synchrotron X-ray transmission and fluorescence microscopy techniques at different energies at three distinct synchrotrons was used to characterize asbestos in paraffinated lung tissues. The fast chemical imaging of the XFM beamline (Australian Synchrotron) demonstrates that asbestos bodies can be rapidly and efficiently identified as co-localization of high calcium and iron, the most abundant elements of these formations inside tissues (Fe up to 10% w/w; Ca up to 1%). By following iron presence, we were also able to hint at small asbestos fibers in pleural spaces. XRF at lower energy and at higher spatial resolution was afterwards performed to better define small fibers. These analyses may predispose for future protocols to be set with laboratory instruments.

Since 1972, when the US Occupational Health and Safety Administration established the first limits on occupational exposure to asbestos fibers, numerous analytical methods employing several microscopy techniques have been developed to identify a group of minerals defined by legislation as asbestos. While transmission electron microscopy (TEM) is implemented in standardized analytical methods, these methods specify the use of selected area electron diffraction. Because of this constraint, the diffraction data a TEM can provide are often underutilized due to challenges associated with collecting and interpreting individual diffraction patterns. It has been shown that transmission electron backscatter diffraction (tEBSD) produces diffraction patterns nearly identical to electron backscatter diffraction, but from smaller crystal domains. This paper explores the utility of tEBSD for characterization of asbestiform particles from reference asbestos materials, a suite of amphibole minerals of varying morphologies to determine if there is a correlation between mineral habit (i.e., crystal form), microscopic particle shape preferred orientation, and mineral specimens from an industrial talc deposit to provide a case study of the utility and limitations of the technique.

Ferruginous bodies observed in lungs of patients affected by mesothelioma, asbestosis, and pulmonary carcinoma are important to relate the illness to exposure, environmental or occupational, to asbestos. Identification of the inorganic phase constituting the core of the ferruginous bodies, formed around asbestos but also around phases different from asbestos, is essential for legal purposes. Environmental scanning electron microscopy/energy dispersive spectroscopy was used to identify the fibrous mineral phase in the core of ferruginous bodies observed directly in thin sections of tissue, without digestion of the biological matrix. Spectra were taken with sequential analyses along a line crossing the core of the ferruginous bodies. By comparing the spectra taken near to and far from the core, the chemical elements that make up the core could be identified.

As is well known from literature, the grinding process, which is an unavoidable step in sample preparation, may strongly modify the physical properties of chrysotile through amorphisation. The aim of this work is to establish the proper milling time to apply to the samples before an accurate X-ray powder diffraction quantitative analysis. We have used the RIR (reference intensity ratio) analytical method, based on the measurement of the ratio I/Is between the intensity of the strongest line of an analyte and the intensity of the analytical peak of a standard material, when they are thoroughly mixed 50:50 by weight. We have studied how the RIR value changes as a function of the milling time of the sample and how the accuracy of this quantitative method is affected.

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

Time-resolved synchrotron powder diffraction was used to follow the thermal transformation of cement-asbestos. Thermal transformation of asbestos fibers into nonfibrous crystalline phases is a promising solution for the elimination of these hazardous minerals. Time resolution offered by the use of an imaging plate detector with a high-brightness X-ray source allowed for the observation of metastable phases, commonly not detectable with conventional instrumentation. In addition, the use of a closed capillary as a sample holder mimicked the real, novel industrial reactor where cement-asbestos slates are sealed in a tunnel kiln. The changing gas atmosphere in the closed system was shown to affect the final composition of the recrystallized product. This study demonstrates the importance of advanced powder diffraction techniques in this field of applied research.

Lungs exposed to occupational dust may be especially vulnerable to fatal infections. We followed up asbestos-exposed workers (n=590) originally screened for lung cancer with computed tomography and scored for pleuropulmonary fibrosis. We checked these workers' influenza and pneumonia mortality data (ICD-10 codes J10–J18) in the national register. In total, 191 deaths, including 43 deaths from infectious pneumonia, occurred in 6158 person-years of follow-up (mean follow-up time 10·44 years). ‘Some interstitial fibrosis’ [hazard ratio (HR) 2·26, 95% confidence interval (CI) 0·98–5·19, P=0·06] and ‘definite interstitial fibrosis’ (HR 3·70, 95% CI 1·22–11·23, P=0·02) were associated with an increased risk of death from pneumonia compared to no fibrosis. Asbestosis patients, i.e. those with both asbestos exposure and lung fibrosis, therefore appear to be particularly at risk for death from pneumonia. These patients should be vaccinated against influenza and Pneumococcus.

Cell culture systems have been developed to assess the potential pathogenicity of mineral dusts. The in vitro cytotoxicities of a variety of dusts towards mouse peritoneal macrophages, Chinese hamster lung cells (V79 cell line) and human alveolar type II cells (A549 cell line) were investigated.

Non-pathogenic dusts were found to be inert in vitro. Fibrogenic non-fibrous dusts such as silica were only cytotoxic towards macrophages. Fibrous dusts which are both fibrogenic and carcinogenic in vivo are cytotoxic towards all three cell types, their cytotoxicity being dependent on fibre size. The size range important for the observed biological effect is longer than about 8 μm and thinner than about 1·5 μm.