An XAS and EPR study of industrial quartz-resin composites: preliminary results and health survey in Tuscany

In the Empoli area of Tuscany, 8 companies are active in working stone and quartz-resin composite materials. Workers' exposure during finishing of artificial stones is associated with severe cases of silicosis arising in young subjects with relatively short seniority, often leading to lung transplantation. The fate of respirable dust produced by this unhealthy activity (mechanical finishing of the artificial stone) is investigated through continuous-wave EPR, pulsed EPR and XAS spectroscopy, together with SEM-EDS microanalysis, and X-ray diffraction. The preliminary results show that that artificial stones, in spite of consisting almost exclusively of quartz and amorphous silica, are variably tinged with minute amounts of different mineral species. A variable speciation of numerous transition metal ions is also observed, coupled with the presence of a drastic change in the inorganic radical population. In contrast, no evidence of the presence of organic radical species was observed. Radical species consist of the Al defects in quartz in the raw samples, and frequent association with Si species is evidenced in manufactured materials. Moreover, the Fe speciation is completely changed from the raw to the manufactured materials, indicating the rare presence of metallic Fe contamination. Correlations with the manufacturing process, in particular comparing the dry and wet finishing steps, are proposed.