Page 12 of 50
Biological Impacts
In vitro studies using human lung cells have shown that AS dusts induce significantly stronger inflammatory and cytotoxic responses than NS dusts. The degree of macrophage inflammation was associated with AS quartz content, supporting its key role in disease pathogenesis. However, metals like Al and Co were also independently associated with toxicity, suggesting that other physiochemical properties of AS dust may be important drivers of dysregulated cellular response. 49 Even low-silica AS formulations induced inflammation, further highlighting the role of non-silica components in AS and suggesting they may play a significant role in disease pathogenesis in this occupational group. 32 Moreover, in an experimental model using Calu-3 lung epithelial cells, AS exposure increased oxidative stress and induced heme oxygenase-1 expression. This was accompanied by a decrease in transepithelial electrical resistance( TEER), indicating increased permeability and a potential for rapid translocation of particles into the systemic circulation, possibly contributing to the autoimmune diseases observed in exposed workers.
53, 54
Silica Exposure and Control During Fabrication
Countertop fabrication involves processing and manipulating an AS slab by performing a variety of tasks, including but not limited to polishing, cutting, and bevelling. The tools employed range in sophistication from hand tools to complete robotic and computer numerical control( CNC) machinery, such as saws, water laser jets, and polishing machines. 2
One of the tenets of occupational exposure science is the“ Hierarchy of Controls,” promoted by occupational health and safety agencies worldwide, including the US National Institute for Occupational Safety and Health( NIOSH), as illustrated in Figure 4. 55 The Hierarchy is a standard approach to reducing hazardous exposures in the workplace, with elimination of the toxic exposure being the most effective and personal protective equipment being the least effective. In AS fabrication, engineering controls include wet methods to limit dust generation and general and local exhaust ventilation to remove dust from the atmosphere. 56 Administrative controls are policies and procedures, such as restricted access zones, hazard communication training, and housekeeping practices. Respirators are a form of personal protective equipment and are effective only when appropriately selected, correctly used, and properly maintained. For tight-fitting respirators, effective use requires fit testing to ensure an adequate seal to the face to prevent leakage, and workers must be cleanshaven in areas where the respirator seals to the skin. Powered air-purifying( positive-pressure) respirators are generally less prone to face-seal leakage and may reduce breathing resistance; however, their use can be associated with limitations, including impaired communication, reduced visibility, and the need for further training and maintenance. 57
Countertop fabrication workers perform a variety of tasks, each with different exposure characteristics. To better understand the level of exposure and inform the selection of controls, such as respirators, fabrication workers can be grouped by task type into one or more of the following five similar exposure group( SEG) categories: automated tool operators, small tool operators, lamination workers, support workers, and installers. 2, 56, 58 – 60 Job tasks and exposure considerations are found in Table 2.
Downloaded from academic. oup. com / annalsats / advance-article / doi / 10.1093 / annalsats / aaoag176 / 8719399 by guest on 10 November 2026
Limitations of Engineering Controls in AS Fabrication
Dry cutting of AS frequently yields RCS levels far in excess of OELs. 6, 34, 35 In a controlled study of dry machining of AS slabs, very fine particles(< 1 µ m) were generated, with > 80 % of the respirable dust composed of crystalline silica. 61 A review of fabrication-shop exposures reported that dry-finishing tasks produced ambient dust concentrations ranging from 215 to 519 µ g / m ³, and that in operations where dry hand-tool finishing was used, exposures“ increased up to 3,880 µ g / m ³”. 62 In field inspections of modern workshops