Continuous-wave and pulse EPR study of radical species in industrial quartz resin composites: preliminary results and health survey in Tuscany

In the territory of USL 11 Empoli (Tuscany), 8 companies are active in working stone and quartz resin composite materials, sometimes labelled as “artificial stones”, mainly used to produce kitchen, bar and shop countertops. These composites commonly contain more than 90% of quartz and are processed in the same manner as natural materials. However, workers' exposure associated to the finishing of artificial stones is associated to severe cases of silicosis arising in young subjects with relatively short seniority and that often lead to lung transplantation. The origin of this unhealthy activity by the respirable dusts produced during the mechanical finishing of the artificial stone countertops is the object of the present study, carried out through both continuous-wave and pulsed EPR spectroscopy. This study is aimed to highlight changes in the type and amount of radical species present in the bulk and at the surface of artificial stone materials before and after the industrial processing. The obtained results will be interpreted under the light of a thorough minero-chemical characterisation, carried out through SEM-EDS microanalysis, and X-ray Diffraction. The preliminary results point out that artificial stones, in spite of consisting almost exclusively of quartz and amorphous silica, are variably doped with very subordinate amounts of different mineralogical species (mixed to control the final aesthetic features of the countertop). A variegate and variable speciation of numerous transition metal ions is also observed, coupled to the presence of a drastic change in the inorganic radical population. In contrast, no evidence of the presence of organic radical species was observed.