Evaluation of on-tool dust control measures for processing engineered stone

Abstract

The use of engineered stone materials for benchtops in domestic and commercial premises has increased in the last 10 -15 years. Natural stone products such as granite may contain up to 40% crystalline silica (as quartz), but the new engineered or artificial stone products often contain >90% w/w quartz bonded with resin. The proportionally higher quartz content is likely to have increased exposure to respirable crystalline silica (RCS) dust for workers fabricating the benchtops by cutting, grinding, drilling or polishing. This is particularly concerning where much of the industry is small scale and has not increased dust controls proportionally with silica exposure risk. The new and prima facie evidence of accelerated silicosis cases amongst engineered stone workers suggests that it is more than just a higher proportion of crystalline silica in the bulk material (Phillips et al., 2013; Zwack et al., 2016). The quartz in benchtop slabs is bound by polymer resins often polyester based (usually also containing some pigment and titanium dioxide or iron oxides), and adhesives used to join slabs are acrylic-based and may include methyl methacrylate. Intense and/or prolonged inhalation of fine dust can lead to irreversible lung disease, and research (Vacek et al., 2011; Kirby, 2019; Leso et al., 2019; Ronsmans et al., 2019) has shown this to be an issue of concern for industry and regulators. In Australia, cases of lung disease in engineered stone fabricators have been reported by respiratory specialists (Hoy et al., 2018; Hoy & Yates, 2018). The condition is occurring in relatively young workers, following a shorter exposure time and a shorter latency period than expected in industries associated with silica dust such as mining. Dust control measures in the engineered stone industry can include water assisted dust suppression, on-tool dust extraction, local exhaust ventilation (LEV), and combinations thereof. A summary of available literature on exposure control measures evaluated in engineered stone and related industry settings, is presented in Table 4. Local Exhaust Ventilation (LEV), particularly on-tool LEV, has been shown to be effective in respirable dust control in concrete grinding and polishing (Croteau et al., 2004; Akbar-Khanzadeh et al., 2010; Healy et al., 2014), but the effectiveness of LEV in engineered stone benchtop fabrication (with or without wet methods) is largely uncharacterised. Furthermore, there is currently no consensus on ‘best practice’ for effective wet methods for dust control or local exhaust ventilation to allow for the capture of dust at the source. This study sought to address this current knowledge gap by evaluating commercially available tools and dust control measures for the processing of engineered stone materials using hand-held tools.