Compositional and structural analysis of engineered stones and inorganic particles in silicotic nodules of exposed workers

Abstract

Background Engineered stone silicosis is an emerging disease in many countries worldwide produced by the inhalation of respirable dust of engineered stone. This silicosis has a high incidence among young workers, with a short latency period and greater aggressiveness than silicosis caused by natural materials. Although the silica content is very high and this is the key factor, it has been postulated that other constituents in engineered stones can influence the aggressiveness of the disease. Different samples of engineered stone countertops (fabricated by workers during the years prior to their diagnoses), as well as seven lung samples from exposed patients, were analyzed by multiple techniques. Results The different countertops were composed of SiO2 in percentages between 87.9 and 99.6%, with variable relationships of quartz and cristobalite depending on the sample. The most abundant metals were Al, Na, Fe, Ca and Ti. The most frequent volatile organic compounds were styrene, toluene and m-xylene, and among the polycyclic aromatic hydrocarbons, phenanthrene and naphthalene were detected in all samples. Patients were all males, between 26 and 46 years-old (average age: 36) at the moment of the diagnosis. They were exposed to the engineered stone an average time of 14 years. At diagnosis, only one patient had progressive massive fibrosis. After a follow-up period of 8 ± 3 years, four patients presented progressive massive fibrosis. Samples obtained from lung biopsies most frequently showed well or ill-defined nodules, composed of histiocytic cells and fibroblasts without central hyalinization. All tissue samples showed high proportion of Si and Al at the center of the nodules, becoming sparser at the periphery. Al to Si content ratios turned out to be higher than 1 in two of the studied cases. Correlation between Si and Al was very high (r = 0.93). Conclusion Some of the volatile organic compounds, polycyclic aromatic hydrocarbons and metals detected in the studied countertop samples have been described as causative of lung inflammation and respiratory disease. Among inorganic constituents, aluminum has been a relevant component within the silicotic nodule, reaching atomic concentrations even higher than silicon in some cases. Such concentrations, both for silicon and aluminum showed a decreasing tendency from the center of the nodule towards its frontier.

Demographic, exposure and clinical characteristics in a multinational registry of engineered stone workers with silicosis

“…In contrast, a study of sandblasters found that silicosis was linked to both exposure concentration and duration 32. Our findings suggest that other exposure factors besides work tenure alone, including RCS concentration, particle size and mineralogical characteristics, and chemical composition of particulate matter retained in workers’ lungs, may be important in risk for disease from ES dust 33 34. Pavan et al hypothesise that enhanced free radical production from ES dust containing greater quantities of transition metal ions may augment the pulmonary fibrogenic response compared with quartz alone 35.…”

“… 32 Our findings suggest that other exposure factors besides work tenure alone, including RCS concentration, particle size and mineralogical characteristics, and chemical composition of particulate matter retained in workers’ lungs, may be important in risk for disease from ES dust. 33 34 Pavan et al hypothesise that enhanced free radical production from ES dust containing greater quantities of transition metal ions may augment the pulmonary fibrogenic response compared with quartz alone. 35 Investigation of ES dust mineralogy using animal models and in situ techniques may provide additional insights into disease pathogenesis.…”

Engineered Stone Fabrication Work Releases Volatile Organic Compounds Classified as Lung Irritants

“…Phthalic anhydride and styrene were two of the most common compounds, together making up 31–88% of the total organic composition of the emissions by PY-GC-MS. Similar organic species were observed when León-Jiménez et al (2021) and Hall et al (2021) pyrolyzed small pieces of engineered stone samples. Given the role of styrene and phthalic anhydride in the manufacture of polymer and epoxy resins, their presence in the resin-containing engineered stones is perhaps not surprising ( WHO, 1999 ; Tustin et al , 2022 ).…”

“…However, little information is available on the organic nature of the dust emitted from engineered stone fabrication work, which could be contributing to the aetiology of lung disease in this occupational group. There appear to be two published works which have explored the organic composition of bulk engineered stone material, but the speciation of organics released during active machining, which could have health implications, is relatively unexplored ( Hall et al , 2021 ; León-Jiménez et al , 2021 ).…”

Inflammatory indices obtained from routine blood tests show an inflammatory state associated with disease progression in engineered stone silicosis patients

“…Engineered Stone is a composite material fabricated with finely crushed natural rocks with high content in silica, assembled with polymeric resins as a binder, and in general, adding different pigments like metals. Usually, ES is composed of 10–15% of resins and the rest is silica, cristobalite or quartz in different concentrations 3 . Reports of a significant number of affected workers initially came from Israel 4 and Spain 5 .…”