Investigating the composition of asbestos bodies from occupationally exposed individuals via X-ray Absorption Spectroscopy

Asbestos bodies (AB) are iron-rich coatings that form in vivo around inhaled asbestos fibres within lung tissue. Since the Fe-rich coating represents the actual interface between asbestos fibres and lung tissue, determining the chemical form of iron is crucial to understanding its role in the pathogenesis of asbestos related diseases. Nevertheless, the speciation of Fe in AB remains debated. Ferrihydrite, the mineral phase storing Fe in the ferritin and hemosiderin core, is metastable and can transform into more crystalline phases such as goethite or hematite under specific environmental conditions (Bardelli et al., 2023). This study investigates the iron speciation in AB to assess whether their composition is consistent across different samples, with the aim of gaining insight into possible patterns in their formation and associated toxicity. The samples consist of non-neoplastic lung tissue fragments of former workers of a steel plant, an asbestos mine, and a textile mill. These individuals experienced prolonged exposure to different types of asbestos (primarily chrysotile, but also crocidolite and amosite) and developed asbestosis and/or pleural mesothelioma. We investigated the iron species constituting the AB using X-ray absorption spectroscopy (XAS) at the Fe K-edge, performed with synchrotron radiation. This technique allowed the detection of poorly crystalline phases such as ferrihydrite and enabled in situ analysis with high resolution. To explore compositional trends among the samples, we first applied principal component analysis (PCA), followed by linear combination fitting (LCF) to identify the iron phases. The results indicate possible variability in AB composition, with differing amounts of iron oxides and oxyhydroxides (ferrihydrite, goethite, and hematite). Synchrotron-based X-ray diffraction analyses on single AB are planned to confirm XAS results. Bardelli F. et al. (2023) - Closing the knowledge gap on the composition of the asbestos bodies. Environ. Geochem. Health, 45(7), 5039-51.