Abstract
Once penetrated into the lungs of exposed people, asbestos induces an in vivo biomineralisation process that leads to the formation of a ferruginous coating embedding the fibres. The ensemble of the fibre and the coating is referred to as asbestos body and is believed to be responsible for the high toxicological outcome of asbestos. Lung tissue of two individuals subjected to prolonged occupational exposure to crocidolite asbestos was investigated using synchrotron radiation micro-probe tools. The distribution of K and of elements heavier than Fe (Zn, Cu, As, and Ba) in the asbestos bodies was observed for the first time. Elemental quantification, also reported for the first time, confirmed that the coating is highly enriched in Fe (~20% w/w), and x-ray absorption spectroscopy indicated that Fe is in the 3+ oxidation state and that it is present in the form of ferritin or hemosiderin. Comparison of the results obtained studying the asbestos bodies upon removing the biological tissue by chemical digestion and those embedded in histological sections, allowed unambiguously distinguishing the composition of the asbestos bodies, and understanding to what extent the digestion procedure altered their chemical composition. A speculative model is proposed to explain the observed distribution of Fe.
Highlights
Properties of asbestos by favouring the generation of reactive oxygen species[10,11]
According to previous studies[7,10], both optical microscopy (OM) and Scanning Electron Microscopy (SEM) images confirmed the typical features of the AB: their coating was often segmented along the fibre length into spaced spherical or ellipsoidal units, and often knobbed at the extremities[7,16]
The diameter of the fibres was measured to fall in the range between 0.3–0.4 μm, in agreement with that reported for crocidolite fibres[18]
Summary
Properties of asbestos by favouring the generation of reactive oxygen species[10,11]. A pioneer study exploiting transmission electron microscopy (TEM)[7], indicated that the fibres’ coating contains crystalline particles of the same order of size of the inorganic iron core of the ferritin molecule. On this basis, it was hypothesized that the crystalline material comprising the major part of the AB is composed of ferritin. Synchrotron radiation micro-probe techniques[14,15] are among the few tools with the resolution and sensitivity required to study the composition of micrometric AB in situ (i.e. embedded in the original biological tissue). With respect to the previous works exploiting similar synchrotron based techniques for this topic[16,17], this work focuses on elements heavier than Fe, and on the comparison between the composition of the AB isolated by the digestion of the biological tissue and those embedded in the original lung tissue
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