Nattrass C, Horwell C J, Damby D E, Brown D, Stone V
Institute of Hazard, Risk & Resilience, Department of Earth Sciences, Durham University, Durham DH1 3LE, UK.
Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universitaet Muenchen, Munich 80333, Germany; United States Geological Survey, Menlo Park, California 94025, USA.
Environ Res. 2017 Nov;159:164-175. doi: 10.1016/j.envres.2017.07.054. Epub 2017 Sep 18.
Exposure to crystalline silica (SiO), in the form of quartz, tridymite or cristobalite, can cause respiratory diseases, such as silicosis. However, the observed toxicity and pathogenicity of crystalline silica is highly variable. This has been attributed to a number of inherent and external factors, including the presence of impurities. In cristobalite-rich dusts, substitutions of aluminium (Al) for silicon (Si) in the cristobalite structure, and impurities occluding the silica surface, have been hypothesised to decrease its toxicity. This hypothesis is tested here through the characterisation and in vitro toxicological study of synthesised cristobalite with incremental amounts of Al and sodium (Na) dopants.
Samples of synthetic cristobalite with incremental amounts of Al and Na impurities, and tridymite, were produced through heating of a silica sol-gel. Samples were characterised for mineralogy, cristobalite purity and abundance, particle size, surface area and surface charge. In vitro assays assessed the ability of the samples to induce cytotoxicity and TNF-α production in J774 macrophages, and haemolysis of red blood cells.
Al-only doped or Al+Na co-doped cristobalite contained between 1 and 4 oxide wt% Al and Na within its structure. Co-doped samples also contained Al- and Na-rich phases, such as albite. Doping reduced cytotoxicity to J774 macrophages and haemolytic capacity compared to non-doped samples. Al-only doping was more effective at decreasing cristobalite reactivity than Al+Na co-doping. The reduction in the reactivity of cristobalite is attributed to both structural impurities and a lower abundance of crystalline silica in doped samples. Neither non-doped nor doped crystalline silica induced production of the pro-inflammatory cytokine TNF-α in J774 macrophages.
Impurities can reduce the toxic potential of cristobalite and may help explain the low reactivity of some cristobalite-rich dusts. Whilst further work is required to determine if these effects translate to altered pathogenesis, the results have potential implications for the regulation of crystalline silica exposures.
接触石英、鳞石英或方石英形式的结晶二氧化硅（SiO）可导致呼吸系统疾病，如矽肺病。然而，观察到的结晶二氧化硅的毒性和致病性差异很大。这归因于许多内在和外在因素，包括杂质的存在。在富含方石英的粉尘中，有人推测方石英结构中铝（Al）取代硅（Si）以及覆盖二氧化硅表面的杂质会降低其毒性。本文通过对添加不同量铝和钠（Na）掺杂剂的合成方石英进行表征和体外毒理学研究来验证这一假设。
通过加热硅溶胶 - 凝胶制备含有不同量铝和钠杂质的合成方石英样品以及鳞石英样品。对样品进行矿物学、方石英纯度和丰度、粒径、表面积和表面电荷的表征。体外试验评估样品在J774巨噬细胞中诱导细胞毒性和肿瘤坏死因子 -α（TNF-α）产生的能力以及对红细胞的溶血作用。
仅铝掺杂或铝 + 钠共掺杂的方石英结构中含有1至4氧化物重量百分比的铝和钠。共掺杂样品还含有富含铝和钠的相，如钠长石。与未掺杂样品相比，掺杂降低了对J774巨噬细胞的细胞毒性和溶血能力。仅铝掺杂在降低方石英反应性方面比铝 + 钠共掺杂更有效。方石英反应性的降低归因于结构杂质和掺杂样品中结晶二氧化硅丰度较低。未掺杂和掺杂的结晶二氧化硅均未在J774巨噬细胞中诱导促炎细胞因子TNF-α的产生。
杂质可降低方石英的潜在毒性，并可能有助于解释一些富含方石英粉尘的低反应性。虽然需要进一步研究以确定这些效应是否转化为发病机制的改变，但这些结果对结晶二氧化硅暴露的监管具有潜在意义。
