Scientific Reports 12권, 기사 번호: 4351(2022) 이 기사 인용
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엔지니어드 스톤은 최근 석공 산업 종사자들 사이에서 규폐증 사례가 급증하는 것과 관련된 새로운 건축 자재입니다. 석공의 짧은 잠복기에 따른 폐질환의 위험성을 이해하기 위해 통제된 조건에서 공학석을 건식 가공하여 실시간 먼지 노출 시나리오를 시뮬레이션하고, 생성된 호흡성 먼지를 물리적, 화학적 특성으로 포착 및 분석했습니다. 비교를 위해 천연 화강암과 대리석이 포함되었습니다. 가공된 돌을 절단하면 호흡 가능한 결정질 실리카 함량이 80% 이상인 석영과 크리스토발라이트 형태의 고농도의 매우 미세한 입자(< 1 µm)가 생성되었습니다. 엔지니어드 스톤에는 또한 수지 8~20%와 금속 성분 1~8%가 포함되어 있습니다. 이에 비해 천연석은 호흡 가능한 결정질 실리카(4~30%)가 훨씬 낮고 금속 함량이 29~37%로 훨씬 높습니다. 자연석 먼지 배출은 공학석보다 표면적이 더 작을 뿐만 아니라 표면 전하도 더 낮았습니다. 이 연구는 공학석 유형 내에서뿐만 아니라 공학석과 자연석 사이의 물리적, 화학적 변동성을 강조했습니다. 이 정보는 궁극적으로 공학석 제조 작업으로 인한 고유한 위험을 이해하는 데 도움이 될 것이며 호흡 가능한 결정질 실리카에 대한 노출을 낮추는 것을 목표로 하는 특정 공학적 통제 조치의 개발을 안내하는 데 도움이 될 것입니다.
규폐증은 건설, 야금, 석탄, 금속 채굴/채석 등의 산업에서 흔히 발견되는 직업성 폐질환입니다. 이는 석영, 삼중석 또는 크리스토발석 형태의 호흡성 결정질 실리카(RCS)를 흡입함으로써 발생합니다1. 지각에서 가장 풍부한 광물인 석영은 특히 석영 함유 물질의 기계적 처리와 관련된 직업 환경에서 다른 다형체보다 더 자주 발견됩니다2. 크리스토발석에 대한 직업적 노출은 세라믹 산업에서도 용광로의 석영 변환 결과로 발생할 수 있으며, 85% 이상의 크리스토발석을 함유한 샘플을 처리하는 규조토 산업에서도 발생할 수 있습니다1,3. 코에사이트(coesite) 및 스티쇼바이트(stishovite)와 같은 결정질 실리카의 다른 다형성에 노출되는 경우는 드뭅니다4.
인공석이라고도 불리는 엔지니어드 스톤은 주방 및 욕실 조리대, 바닥 및 외관 타일 제작에 일반적으로 사용되는 새로운 건축 자재입니다. 내구성, 미적 매력, 다양성 및 경제성으로 인해 인기가 높습니다. 그들의 판매는 둔화될 조짐을 보이지 않습니다. 실제로 미국 시장 점유율은 매년 7.4%씩 증가할 것으로 추산됩니다5. 불행하게도 이러한 신소재의 인기 증가는 업계 근로자들 사이에서 '가속성 규폐증'의 출현과 관련이 있습니다6. 비극적이게도 규폐증의 발병은 전통적으로 관찰된 것보다 더 짧은 노출 기간과 더 짧은 잠복 기간 후에 발생했습니다2. 스페인의 한 연구에서는 2007년에서 20117년 사이에 규폐증 사례가 61% 증가했다고 보고했는데, 이는 짧은 기간 내에 중요한 클러스터였습니다. 규폐증 진단을 받은 근로자의 평균 연령은 33세였으며, 인공 돌가루에 노출된 평균 연령은 11세였습니다. 이스라엘, 미국 및 호주에서도 근로자들 사이에서 규폐증 발생률이 비슷하게 증가한 것으로 보고되었습니다5,6,8.
엔지니어드 스톤 작업자의 건강에 대한 우려는 엔지니어드 스톤이 일반적으로 안료 및 고분자 수지와 매트릭스로 결합된 90% 이상의 석영을 함유하고 있다는 사실에서 비롯됩니다9. 이에 비해 천연석은 인공 제품보다 실리카 함량이 훨씬 낮습니다. 대리석과 화강암은 각각 3%와 40%의 실리카를 함유한 두 가지 천연석입니다. 따라서 공학석의 절단, 드릴링 및 연마와 같은 제조 공정에서는 석영 함유 먼지의 대기 농도가 높아질 수 있습니다10. 흥미롭게도 이러한 기계 공정은 먼지 노출을 줄이기 위해 물을 공급하는 공압식 그라인더 및 폴리셔를 사용하여 산업계의 습한 조건에서 수행되는 경우가 점점 더 늘어나고 있습니다. 그럼에도 불구하고 마무리 작업은 수분 억제 없이 수동으로 끝나는 경우가 많으므로 결정질 실리카11에 노출될 가능성이 높습니다.
80% crystalline silica, often as a combination of quartz and cristobalite. Two engineered stones had only quartz in their composition (> 90%), while the majority of the other samples contained between 42 and 88% quartz. In engineered stone samples with relatively low (< 25%) quartz, such as ES6 and ES12, cristobalite accounted for the rest of the mineralogical composition (Table 1). Cristobalite was present in several other samples, albeit in lower concentrations than ES6 or ES12. It was present in moderate levels (36 ± 4.1%) in ES2, ES3 and ES11 and in low levels (< 5%) in ES1 and ES4 (Table 1). Compared to crystalline silica minerals, albite and rutile were less commonly found in respirable engineered stone dust. When present, they were observed in very low amounts, typically < 5% (Table 1). The only exception was ES4 which had a varied mineralogical composition, including 13% rutile (Table 1). No muscovite was observed in engineered stones./p> white marble (11%) > white granite (3.6%). The natural stones comprised several other minerals for example, albite, a feldspar mineral commonly found in igneous rocks such as black granite. White marble contained predominantly calcite (66%) and dolomite (22%) and white granite contained mostly dolomite (91%)./p> 16%) (Table 1). Sample weight loss, as shown by a derivative thermogravimetric graph (DTG) (Supplementary Fig. S1), occurred in three stages: a small weight loss was observed while the sample was heated to up to ~ 300\(^\circ\)C, attributed to the desorption of water9; the second, and maximum, weight loss occurred at around 450\(^\circ\)C for all respirable engineered stone dust samples and was attributed to the loss of polymeric resin from the material. The third weight loss was observed at higher temperatures (~ 600\(^\circ\)C), but was considered minimal in comparison to the other two losses (Supplementary Fig. S1)./p> 90% of the dust particles had diameters in the size range of 190 nm to 825 nm (Fig. 1). The respirable dust emissions from cutting most engineered stones were similar in diameter, except for ES10 which had significantly finer dust, with particle diameter range of 142–295 nm (average 218 nm); in comparison, ES8 had the largest dust size with a particle diameter range of 459–1106 nm (average of 715 ± 91 nm) (Table 1, Fig. 1). Among all three natural stones, the black granite had a lower average particle size (503 nm) than the other two (534 and 675 nm respectively) (Table 1), but all three natural stones had particle size distributions comparable to those of engineered stones (Fig. 1)./p> 90%) content, such as ES8 (Table 1)./p> 2.50 ± 0.13 m2/g surface area, while the rest averaged 1.72 ± 0.11 m2/g in surface area. In comparison, the specific surface area of the natural stones (range of 0.439 – 0.878 m2/g) was lower than the engineered stones (Supplementary Information Table S1)./p> 6% by weight elemental content (Fig. 3a)./p> 1% wt.) elements, it was observed that the following elements were in trace amounts in engineered stones: Cu, P, S, Ni, Co, Cr, Sn, Zr and Cl (Fig. 3a). Elements Fe, Ca, Mg, and K were predominantly in minor distributions. Certain elements such as Ca, Mg, Na and Ti had a range of concentrations from minor to major elemental fields./p> 80% by weight crystalline silica and 8–20% resin21. Further characterisation of the RCS was undertaken on the basis that the crystalline structure of the minerals may exert an influence on their toxicity22. In our study, 9 out of 12 engineered stone respirable dust samples had a combination of quartz and cristobalite structures, although quartz was still the dominant structure, forming > 55% of the total mineralogy. Cristobalite was the second most common mineral, while albite and rutile were detected in smaller amounts. Quartz and cristobalite differ from one another in their mineralogy, surface characteristics and natural association with other elements23. Early studies comparing the dose response of quartz and cristobalite on pulmonary function in rats showed that both structures were similarly detrimental to the lungs, although cristobalite elicited a slightly faster response than quartz24. However, subsequent animal experiments and epidemiological studies discounted these findings, by showing no evidence for differences in the inflammatory and fibrogenic potentials of quartz and cristobalite23. Horwell et al.4 even showed that cristobalite-rich volcanic ash was less toxic than expected and posed less of a respiratory health hazard than quartz. They attributed this finding to the relative open structure of cristobalite compared to quartz, which allows the substitution of cations such as aluminium (Al3+) and sodium (Na+) in the Si tetrahedral, hence affecting cristobalite toxicity1,4. Taken together, these studies show insufficient evidence that either mineral is more toxic than the other. Nonetheless, the high concentration of crystalline silica in the respirable dust from engineered stones may be cause for concern as quartz and cristobalite are the only crystalline silica minerals recognised as Group 1 carcinogens—“carcinogenic to humans”—by the International Agency for Research on Cancer25./p> 85% quartz) had a bimodal distribution, with one mode in the same range as in this study (~ 500 nm), whereas the other was in the ultrafine particle (UFP) range, commonly defined as particles < 100 nm29. Although visually observed, UFPs were not measured in the present study, likely due to the limitations of the air sampling or particle size analysis techniques. We are currently exploring some real-time measurement of UFP using direct reading instrumentation for more precise dust exposure assessment during engineered stone fabrication tasks./p> 0.7) and particle imaging by SEM, the dust particles in our study were, in fact, heterogenous in shape, size and structure. Apart from particle size and morphology, the surface properties of quartz have been reported to also play an important role in cytotoxicity, suggesting that the specific surface area of engineered stones may be a useful parameter for characterisation and differentiation between engineered and natural stones26,31,32./p> 1%) quantities in the samples studied, possibly originating from the pigments and resins37,38. Although generally considered non-toxic, Ti (titanium dioxide, TiO2) has been shown to be an aetiological agent for lung inflammation, especially in the ultrafine fraction39,40. The possible role of metals in the toxicity of silica has been elicited before. For example, Clouter et al.41 (and references therein) suggested that the toxicity of quartz involves Fe. While the presence of Fe and Al has been considered for the potential reason for the differing zeta potentials of black granite and other natural stones, this could not explain the greater negative zeta potential of engineered stone compared to the black granite, since the concentration of Fe and Al is much lower in engineered stone. Several other elements not found in the natural stone samples were detected in the engineered stone ones, but only in trace quantities. Therefore, while we cannot exclude any role of metal ions in silica toxicity, it is unlikely that any such effect is mediated though the pathway linked with the generation of zeta potential./p>
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