Artificial stone countertops contain natural stone, quartz, resins, and Portland cement. The combination of these materials can contain more than 90% silica.1 In contrast, natural stone contains 50% or less silica.2 Artificial stone is desirable because it is lighter and thinner than natural stone, non-porous, and has strong mechanical resistance.3 Manufacturers also market the new material as stain and scratch proof, acid and fire resistant, environmentally friendly, and non-toxic while claiming these materials are indistinguishable from natural stone. Because of its desirable properties, artificial stone is a preferred choice in homes for kitchen or bathroom countertops and in retail and hospitality establishments. Cases of silicosis have recently been associated with the manufacture of artificial stone products, and a discussion of the industry practices leading to these occupational injuries is provided here.
What is silicosis?
Silicosis refers to a spectrum of pulmonary diseases caused by inhalation of free crystalline silica and is marked by scarring and thickening of the lung tissue which can progress to respiratory failure and death.4 Silica inhalation is the main cause of occupational respiratory disease worldwide,5 and differences in exposure can result in different forms of the pulmonary disease which include acute silicosis, accelerated silicosis, chronic silicosis, and progressive massive fibrosis.6 For example, high-intensity silica exposure is associated with acute and accelerated silicosis with acute silicosis developing within a few weeks to less than 5 years of high-intensity exposure7,8 and accelerated silicosis developing within 10 years of moderate – high levels of exposure.4 Chronic silicosis can develop following decades of exposure to silica dust and even progress after exposure has ceased.4
Silica, also known as silicon dioxide, exists as different forms with quartz being the most common form and a major component of granite (~30% free silica), slate (40% free silica), and sandstone (almost pure silica).9 Other forms of silica include tridymite, cristobalite, coesite, and stishovite.10-12 Although all these forms are biologically toxic, quartz is the predominant form involved in occupational exposures12 and pulmonary disease.9 The toxicity of silica results from the ability of silica surfaces to interact with water to form reactive silanol groups12 and to generate oxygen radicals.13-16 These reactive groups are capable of injuring target pulmonary cells which culminate in inflammation and fibrosis.17
Silica is found in more than 95% of rocks and present in many construction materials such as concrete, sand, mortar, and stone.18 Respirable silica (particles with diameters smaller than 10 microns) is created during the cutting, grinding, polishing, and crushing of these construction materials for the fabrication of consumer products.7 Historically, industries that generate respirable silica include mining, quarrying, sandblasting, masonry, stone cutting, foundry work, and ceramics4,19 Although the overall mortality to silicosis has decreased in the United States from 1969 to 2010 due to improved workplace protection and occupational health surveillance,20-22 up to 200,000 miners and 1.7 million non-mining workers in the United States still experience occupational exposures to inhaled silica, and new cases of silicosis are recognized worldwide every year.23-25
Silica exposure in the artificial stone industry
Consistent with this trend, hazardous silica exposures have increased22 with cases of silicosis being associated with the manufacture of artificial stone.26-34 Initial cases were reported in Spain in 2010 (26,35,36), followed by Israel in 2012,27 and then other countries including Italy,1,30 the United States,28,37 Australia,33,38 and Belgium.32 Studies of these outbreaks documented a prevalence of 25% among workers in Italy,1 54% in Spain,26 and 12% in Australia.38 Moreover, these cases progressed rapidly, suggesting that silicosis associated with artificial stone is more aggressive than classic silicosis,39 and occurs in young workers, with a median age of 29 years.40
Because of the widespread use of artificial stone, current efforts attempt to identify at risk workers and implement controls to limit silica exposure.41 Artificial stone is composed of ﬁnely crushed rock and synthetic resins with a high silica content (~90%),1,42 whereas natural stone contains 50% or less.2 Fabrication of artificial stone for use in countertops generates respiratory crystalline silica during cutting and grinding, and controlled studies show that aerosolized particles from cut or ground artificial stone have 3 times higher silica content compared to manipulated granite.43 These manipulations potentially expose workers to higher amounts of respirable silica compared to working with natural stone44 and pose a substantial risk for developing more severe forms of silicosis.26,28,33
Safety controls for the artificial stone industry
Although silicosis afflicts far fewer people in the United States than in the past,22 studies examining the sources of respirable silica during the fabrication of artificial stone suggest that standard control measures and use of personal protective equipment should be reevaluated.43,45 While wet cutting and use of respirators are effective when properly implemented, the amount of dust generated during grinding and polishing creates a layer of dust covering all surfaces, and these deposited particles are subject to resuspension.43 Studies have recommended that power tools for cutting, grinding, and polishing of artificial stone countertops include dust suppression.43,45,46 Furthermore, aggressive engineering controls should be implemented to keep dust levels at a minimum, avoid exposure during the manipulation process, and prevent dust resuspension.46 Additional controls would include floor drainage systems for cleaning, respiratory protection, and ventilation of confined spaces when cutting and grinding artificial stone.43
Collectively, silicosis associated with artificial stone fabrication progresses rapidly with patients developing respiratory failure. Silicosis is preventable if exposures to airborne silica can be controlled. Therefore, a need exists to identify at risk artificial stone fabrication workers in order to prevent the potential for excess exposure to silica dust and protect workers from increasing their risk for developing this pulmonary disease.
- Bartoli, D.; Banchi B, Di Benedetto F, Farina GA, Iaia TE, Poli C, Romanelli M, Scancarello G, and Tarchi M. (2012) Silicosis in employees in the processing of kitchen, bar and shop countertops made from quartz resin composite. Provisional results of the environmental and health survey conducted within the territory of USL 11 of Empoli in Tuscany among employees in the processing of quertz resing compositre materials and review of the literature. Ital. J. Occup. Environ. Hyg. 3:138.
- Esswein EJ, Breitenstein M, Snawder J, Kiefer M, and Sieber WK. (2013) Occupational exposures to respirable crystalline silica during hydraulic fracturing. J. Occup. Environ. Hyg. 10:347.
- Li Y and Ren S. (2011) Building Decorative Materials. Cambridge, UK: Elsevier.
- National Institute for Occupational Safety and Health (NIOSH). (2002) NIOSH hazard review. Health effects of occupational exposure to respirable crystalline silica. Washington, DC: US Department of Health and Human Services, CDC, National Institute for Occupational Safety and Health; 2002. DHHS (NIOSH) publication no. 2002-129, http://www.cdc.gov/niosh/docs/2002-129/default.html.
- Cullinan P, Mutioz X, Suojalehto H, et al. (2017) Occupational lung diseases: from old and novel exposures to effective preventive strategies. Lancet Respir Med. 5(5):445.
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- Barnes H, Goh NSL, Leong TL, and Hoy, R. (2019) Silica-associated lung disease: An old-world exposure in modern industries. Respirology 24:1165.
- Seaton A, Cherrie JW. (1998) Quartz exposures and severe silicosis: A role for the hilar nodes. Occup. Environ. Med. 55:383.
- Lapp NL. (1981) Lung disease secondary to inhalation of nonfibrous minerals. Clin Chest Med 2:219.
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- Castranova V, Vallyathan V, Wallace WE, eds. (1996) Silica and Silica-Induced Lung Diseases. Boca Raton, FL: CRC Press.
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- Castranova V. (1998) Particulates and the airways: basic biological mechanisms of pulmonary pathogenicity. Appl Occup Environ Hyg 13:613.
- Lapp NL and Castranova V. (1993) How silicosis and coal workers' pneumoconiosis develop-a cellular assessment. Occup Med: State of the Art Rev 8:35.
- Vallyathan V, Shi X, Dalal NS, Irr W, and Castranova V. (1988) Generation of free radicals from freshly fractured silica dust: potential role in acute silica-induced lung injury. Am Rev Respir Dis 138: 1213.
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- Occupational Safety and Health Administration (OSHA). (2017) Small Entity Compliance Guide for the Respirable Crystalline Silica Standard for General Industry and Maritime. OSHA 3911-07. Https://www.osha.gov/Publications/OSHA3911.pdf.
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- Centers for Disease Control and Prevention (CDC). (2008) Silicosis-related years of potential life lost before age 65 years--United States, 1968-2005. MMWR Morb Mortal Wkly Rep 57:771.
- Bang KM, Mazurek JM, Wood JM, et al. (2015) Silicosis mortality trends and new exposures to respirable crystalline silica - United States, 2001-2010. MMWR Morb Mortal Wkly Rep 64:117.
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- Blackley DJ, Crum JB, Halldin CN, et al. (2016) Resurgence of Progressive Massive Fibrosis in Coal Miners - Eastern Kentucky, 2016. MMWR Morb Mortal Wkly Rep 65:1385.
- Perez-Alonso A, Cordoba-Dona JA, Millares-Lorenzo JL, Figueroa-Murillo E, Garcia-Vadillo C, and Romero-Morillos J. (2014) Outbreak of silicosis in Spanish quartz conglomerate workers. Int J Occup Environ Health. 20(1):26.
- Kramer MR, Blanc PD, Fireman E, Amital A, Guber A, Rhahman NA, and Shitrit D. (2012) Artificial stone silicosis: Disease resurgence among artificial stone workers. Chest 142:419.
- Friedman GK, Harrison R, Bojes H, Worthington K, and Filios M. (2015) Notes from the field: silicosis in a countertop fabricator-Texas, 2014. MMWR Morb Mortal Wkly Rep. 64(5):129.
- Mazurek JM, Schleiff PL, Wood JM, Hendricks SA, and Weston A. (2015) Update: Silicosis Mortality—United States, 1999–2013. Mmwr. Morb. Mortal. Wkly. Rep. 64:653.
- Paolucci V, Romeo R, Sisinni AG, Bartoli D, Mazzei MA, and Sartorelli P. (2015) Silicosis in workers exposed to artificial quartz conglomerates: does it differ from chronic simple silicosis? Arch Bronconeumol. 51(12):e57.
- Grubstein A, Shtraichman O, Fireman E, Bachar GN, Noach-Ophir N, and Kramer MR. (2016) Radiological evaluation of artificial stone silicosis outbreak: Emphasizing findings in lung transplant recipients. J. Comput. Assist. Tomogr. 40:923.
- Ronsmans S, Decoster L, Keirsbilck 5, Verbeken EK, and Nemery B. (2019) Artificial stone-associated silicosis in Belgium. Occup Environ Med. 76(2):133.
- Hoy RF, Baird T, Hammerschlag G, et al. (2018) Artificial stone-associated silicosis: a rapidly emerging occupational lung disease. Occup Environ Med. 75(1):3.
- Pascual Del Pobil y Ferré MA, Sevila RG, Rodenas MG, Medel EB, Reos EF, and Carbonell JG. (2019) Silicosis: A former occupational disease with new occupational exposure scenarios. Rev. Clín. Española 219:26.
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- Kirby T. (2019) Australia reports on audit of silicosis for stonecutters. Lancet 393:861.
- León-Jiménez A, Hidalgo-Molina A, Conde-Sánchez MÁ, Pérez-Alonso A, Morales-Morales JM, García-Gámez EM, Córdoba-Doña JA. (2020) Artificial Stone Silicosis: Rapid Progression Following Exposure Cessation. Chest. 158(3):1060.
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- Rose C, Heinzerling A, Patel K, et al. (2019) Severe Silicosis in Engineered Stone Fabrication Workers - California, Colorado, Texas, and Washington, 2017-2019. MMWR Morb Mortal Wkly Rep 68:813.
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- Carrieri M, Guzzardo C, Farcas D, Cena LG. (2020) Characterization of Silica Exposure during Manufacturing of Artificial Stone Countertops. Int J Environ Res Public Health. 17(12):4489.
- Centers for Disease Control and Prevention (CDC). (2015) Hazard alert: worker exposure to silica during countertop manufacturing, finishing, and installation. Available at: https://www.osha.gov/Publications/OSHA3768.pdf
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- Johnson DL, Phillips ML, Qi C, Van AT, Hawley DA. (2017) Experimental Evaluation of Respirable Dust and Crystalline Silica Controls During Simulated Performance of Stone Countertop Fabrication Tasks With Powered Hand Tools. Ann Work Expo Health. 61(6):711.