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fabricating AS, exposures during dry or semi-dry tasks reached hundreds of µ g / m ³. 37 This is most notable in data from China, where 94 % of silicosis cases occurred in workers from unlicensed workshops. Although stateowned factories in China are subject to stringent government oversight of dust control measures and health monitoring, unlicensed workshops operate entirely outside the scope of government regulation. Under these precarious working conditions, where dry cutting was predominantly used, silica dust concentrations at some processing and installation sites reached 351,000 ± 30,760 µ g / m 3 and 127,600 ± 17,360 µ g / m ³ during shortterm( 15-minute) sampling, far exceeding the Chinese OEL of 200 µ g / m 3 averaged over 8 hours. 7 These data demonstrate that dry cutting, especially when conducted without adequate dust suppression and ventilation, results in respirable crystalline silica exposures that exceed regulatory limits by several orders of magnitude and constitute an extreme occupational hazard.
Even when engineering controls, such as wet methods and exhaust ventilation, are employed, workers’ exposures to silica routinely exceed OELs. 28, 29, 56, 58, 59, 62, 63 For example, an examination of silica exposure among stone countertop fabricators in Georgia, USA, found that for the 63 employees who exclusively used wet methods, 51 % had exposures at or above the Occupational Safety and Health Administration( OSHA) Permissible Exposure Limit( PEL) of 50 µ g / m 3, reaching as high as 370 µ g / m 3, and 70 % had exposures above the Action Limit( AL) of 25 µ g / m 3. 56 Overexposures occurred at both small( 24 or fewer workers) and larger( 25 or more workers) companies. 56 The failure of wet methods to fully control exposures may in part reflect the small size of the particles generated. When AS dust was mixed with water and observed for 24 hours, the ultrafine particulate fraction floated on the surface and did not settle over time, indicating potential for persistence in the air during slab processing despite the use of water. 39
In Australia, surveys reveal persistent overexposures in the industry. In New South Wales, 85 % of workers performing dry tasks and 71 % using water-fed tools exceeded the workplace exposure standard( 100 µ g / m 3), with handheld dry cutting exceeding the limit by 7 – 14 times. 59 Even after five years of implementing a compliance program, exposures still exceeded the OEL in over half of the workshops monitored. 62 In Victoria, prior to 2020, 86 % of 544 stone benchtop workers had worked in shops where dry cutting was performed. 8 Similarly, in a recent industry-supported survey of US and Canadian countertop fabrication shops, 257( 23 %) shops agreed to participate. Of these, 120 shops reported sampling for silica, and 46 provided usable results. 9.2 % of 292 personal samples exceeded the OSHA PEL, and nearly half of the shops had at least one sample above the AL, demonstrating that elevated exposures occur even in self-selected facilities that are more likely to be safety-conscious and that current engineering controls cannot consistently maintain exposures below regulatory limits. 29 These findings show that regulatory standards, awareness, and training alone have not eliminated hazardous exposures.
Given that wet methods alone do not consistently reduce silica exposures below recommended limits, fabricators should be provided with effective, properly fitted respiratory protection, regardless of other controls in place. 56 However, to date, no studies have evaluated the performance of respirator filters and cartridges against the complex mixture of airborne contaminants generated during artificial stone fabrication, including RCS with distinctive particle size, surface area, and morphology; volatile organic vapors; trace metals; and moisture or water droplets associated with wet cutting methods. 33 Filter performance and particle penetration depend on particle size, the presence of water, dust accumulation on the mask surface, and variations in workers ' minute ventilation. 64 For workers who wear a tight-fitting, negative-pressure elastomeric respirator or a filtering facepiece respirator( N95), there is potential for facepiece leak paths due to particle penetration and gaps around the facepiece perimeter, leading to significant variability and uncertainty in workplace protection factor values. 65 Moreover, studies on respirator performance demonstrate that protection factors vary substantially under workplace conditions, often falling below assigned values due to leakage, improper fit, or particle characteristics that affect filter penetration. 65
The abrasive blasting industry provides a clear example of another sector facing substantial challenges in protecting workers from high levels of RCS exposure comparable to those observed in AS fabrication. In this setting, the use of supplied-air respirators, respirators with hoods or helmets, and adequate positive pressure has
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