of engineered stone into countertops and other products. Laboratory studies with human lung cells have shown that engineered stone dust causes significantly more inflammation and cell death compared to natural stone, with other non-silica ingredients independently associated with toxicity. Particle surface features may also be responsible for the unique toxicity of engineered stone on lung cells, with membrane destabilization and lysis, and the generation of reactive oxygen species that can add to lung injury. 6
4. The number of fabrication workers with silicosis is going to increase. In early 2025, Cal / OSHA estimated there were approximately 800 fabrication shops that employed about 4,000 workers in California, and that the global rate of silicosis among workers in this industry was as high as 21 %. At the time of Cal / OSHA’ s briefing to the Board in August 2025, CDPH had reported 364 cases of silicosis caused by engineered stone. Cal / OSHA staff reported that the expected number of cases of silicosis among these 4,000 workers was 680, based on a case rate of only 17 %, and that the expected number of silicosis deaths among these 680 cases was 130( 19 %), well above the 364 cases and 24 deaths CDPH had identified at that time through passive reporting channels. In their August briefing, Cal / OSHA updated the number of shops to 920 and the number of workers to 4,600, noting that“ the projected case and fatality rates will be proportionately higher,” and that“ both the current conditions and the projections are alarming.” 7 As long as exposure to crystalline silica dust from engineered stone continues, the total number of cases and deaths beyond these estimates will continue to grow.
5. Airborne concentrations of respirable crystalline silica dust are above the Cal / OSHA limit in many fabrication shops. After the first cases of silicosis were reported by CDPH in 2019, Cal / OSHA initiated a targeted inspection program of fabrication shops in California. An analysis of airborne silica dust concentrations during these inspections showed that over 50 % of these workplaces had levels above the allowable OSHA Action Limit( 25 ug / m 3) for respirable crystalline silica dust. 8 Similarly, a national survey of
6 Ramkissoon C, Gaskin S, Hall T, Pisaniello D, Zosky G. Engineered Stone Fabrication Work Releases
Volatile Organic Compounds Classified as Lung Irritants. Ann Work Expo Health. 2023 Feb 13; 67( 2): 288- 293; Ramkissoon C, Song Y, Yen S, et al. Understanding the pathogenesis of engineered stone-associated silicosis: The effect of particle chemistry on the lung cell response. Respirology. 2024; 29( 3); Rishi K, Ku BK, Qi C, Thompson D, Wang C, Dozier A, Vogiazi V, Zervaki O, Kulkarni P. Release of Crystalline Silica Nanoparticles during Engineered Stone Fabrication. ACS Omega. 2024 Dec 10; 9( 51): 50308-5031; Mandler WK, Knepp AK, Leonard SS, McKinney W, Keeley S, Qian Y. Characterization of engineered stone dust-induced reactive oxygen species generation and cytotoxicity in vitro. J Toxicol Environ Health A. 2025 Oct 10:1-11; Ophir N, Fireman E, Kramer MR, Korenstein R. Artificial stone dust affects oxidative stress and epithelial barrier in CALU 3 cells. Exp Lung Res. 2025; 51( 1): 81-90; Pavan C, Fimiani M, Cananà S, Diana A, Marafante M, Bertinetti S, Escolano-Casado G, Mino L, Pisaniello D, Leinardi R, Tomatis M, Turci F. The Combined Role of Silanols and Oxidative Stress in Determining Engineered Stone Dust Toxicity. ACS Organic & Inorganic Au. November 5, 2025. DOI: 10.1021 / acsorginorgau. 5c00089.
7
Cal / OSHA Update. Silicosis among artificial stone fabrication workers. Occupational Safety and Health Standards Board, August 21, 2025. Presented by Mike Wilson, Eric Berg and Betsey Noth, Cal / OSHA Research and Standards.
8
Surasi K, Ballen B, Weinberg JL, Materna BL, Harrison R, Cummings KJ, Heinzerling A. Elevated exposures to respirable crystalline silica among engineered stone fabrication workers in California, January 2019-February 2020. Am J Ind Med. 2022 Sep; 65( 9): 701-707.
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