Surface reactivity of amphibole asbestos: a comparison between crocidolite and tremolite

Abstract

Among asbestos minerals, fibrous riebeckite (crocidolite) and tremolite share the amphibole structure but largely differ in terms of their iron content and oxidation state. In asbestos toxicology, iron-generated free radicals are largely held as one of the causes of asbestos malignant effect. With the aim of clarifying i) the relationship between Fe occurrence and asbestos surface reactivity, and ii) how free-radical generation is modulated by surface modifications of the minerals, UICC crocidolite and fibrous tremolite from Maryland were leached from 1 day to 1 month in an oxidative medium buffered at pH 7.4 to induce redox alterations and surface rearrangements that may occur in body fluids. Structural and chemical modifications and free radical generation were monitored by HR-TEM/EDS and spin trapping/EPR spectroscopy, respectively. Free radical yield resulted to be dependent on few specific Fe2+ and Fe3+ surface sites rather than total Fe content. The evolution of reactivity with time highlighted that low-coordinated Fe ions primarily contribute to the overall reactivity of the fibre. Current findings contribute to explain the causes of the severe asbestos-induced oxidative stress at molecular level also for iron-poor amphiboles, and demonstrate that asbestos have a sustained surface radical activity even when highly altered by oxidative leaching.

Assessment of the physicochemical properties of chrysotile-containing brake debris pertaining to toxicity

“…Within this study we also sought if incubation in simulated biological fluids could cause modifications in free radical generation. Such an evolution over time has been reported previously in relation to amphiboles (Andreozzi et al 2017). Analysis of intrinsic ROS production by EPR showed no significant increase over vehicle control for any of the test samples indicating, that for the spin-trap Tempone-H at least, reactivity is minimal.…”

Laser ablation inductively coupled plasma mass spectrometry as a novel clinical imaging tool to detect asbestos fibres in malignant mesothelioma

“…By geological classification, asbestos fibres are defined as having aspect ratio ≥3:1, length ≥5 μm, and width <0.25 μm. 6 This does not account for cleavage fragments, or high potency shorter fibres. 9 This asbestos classification was created to facilitate the counting of the MF using standard microscopy methods and was not based on the potency of these segments or shorter fibres to induce ARD.…”

“…By geological classification, asbestos fibres are defined as having aspect ratio ≥3:1, length ≥5 μm, and width <0.25 μm 6 . This does not account for cleavage fragments, or high potency shorter fibres 9 .…”

Towards a detailed comprehension of the inertisation processes of amphibole asbestos:in situhigh-temperature behaviour of fibrous tremolite

“…Accordingly, a recent study performed by our group on the pathogenic-related fibre surface reactivity of riebeckite and tremolite showed that both fibrous amphiboles have sustained radical production, even when highly altered by oxidative leaching. In particular, tremolite exhibited a significant radical production from both pristine and altered fibres (Andreozzi et al, 2017). Differently from riebeckite, the generally small iron content of tremolite makes potentially difficult a detailed analysis of subtle modifications of the iron site allocation and variation of its oxidation state.…”