Chemical variability of artificial stone powders in relation to their health effects

Abstract

The occurrence of highly severe silica-related diseases among the resin- and silica-based artificial stone workers was claimed, associated to an extremely short latency. High levels of exposure and intrinsic properties of AS are thought to modulate the development of silicosis and auto-immune diseases. This study compares parent materials and processed dusts, to shed light on changes of AS occurring in the manufacturing process, through an XRF, EPR and XAS investigation. We point out the extremely wide variability of the materials, the occurrence of chemical signatures impressed by the processing techniques, and the unprecedented generation of stable radicals associated to the lysis of the Si-O chemical bond inside the resin coated respirable crystalline silica. These results suggest that the AS processing in industrial stone workshops can create respirable dusts with peculiar physical and chemical properties, to be correlated to the observed clinical evidences.

A study of radicals in industrial raw cristobalite powders

“…The specificity of this formation of radicals and their intrinsic stability provide a peculiar case in the field of the studies of radicals associated with crystalline silica. Indeed, their presence was never described in previous studies concerning industrial raw materials (Romanelli et al 2012;Di Benedetto et al 2019). This fact and the long endurance of the superoxide radical population are unlikely a general property of radicals associated with crystalline silica materials used in industrial settings.…”

“…These mixtures are modelled in various shapes (essentially for countertop and bathroom furniture's production), the resins are let harden, and the final object is polished as a natural stone. The seldom presence of cristobalite, in spite of quartz, in the production of silica-based artificial stone has been firstly described by Di Benedetto et al (2019).…”

“…Nonetheless, the TLV fixed by EU directive seems only partially adequate to the carcinogenic power of crystalline silica, and to the risk associated to exposure, even at low doses, to cristobalite. Clusters of workers exhibiting silicosis have been found, in the last years, in the production of microcasted gold (Murgia et al 2007;Romanelli et al 2012) and of artificial stone (Di Benedetto et al 2019;Leso et al 2019) and among the dental technologists (Barbieri et al 2020).…”

“…The main industrial applications of cristobalite conventionally span from abrasives to pigments, to metal casting, to the production of chemicals. Recently, cristobalite was described also in some products belonging to the so-called artificial stone composite materials, which are mixtures of silica minerals and polyester or acrylic resins (Di Benedetto et al 2019). Besides its use as the main constituent of a material, cristobalite is virtually present in almost all quartz-bearing production, due to its mineralogical affinity in some natural settings (most of the industrial silica has a natural origin, USGS 2016), although in concentrations rarely exceeding 1 wt% (IARC 2012).…”

Silica‐related diseases in the modern world

“…It is likely several factors impact on the development of disease in any one individual, including not only the length, but also the intensity of exposure, which may overwhelm usual AM clearance mechanisms, as well as the composition of the product generating respirable crystalline silica. It could be that resins and other materials used in the manufacture of some products may lead to the generation of unexpected compounds, which effectively act as adjuvants to intensify the inflammatory response 39. Finally, silicosis pathogenesis should be viewed through a lens of gene‐environment interactions, with early reports confirming susceptibility to silicosis in carriers of polymorphisms in the TNF‐α and FAM13A genes 40…”