Exploring the link between surface structures and toxicity in mineral particles: Case study of induced and intrinsic toxicity in quartz

吸入的粉尘中有一部分是由小到可以深入肺部的颗粒组成的。大多数微粒是相对无害的，一旦被识别为异物，就会通过特殊的机制从肺中清除。偶尔，颗粒物会抵抗去除，并会产生毒性反应。也许最广为人知的案例是石棉纤维，它最终会导致肺部疾病、石棉肺和肺癌间皮瘤。在柴油油烟中还发现了其他有害颗粒。采矿、采石和喷砂等行业产生的粉尘也与矽肺和肺癌等肺部疾病有关。在这种情况下，罪魁祸首通常是石英，这是环境中第二常见的矿物，除非大量吸入，否则通常相对无害。对这个项目来说，重要的特点是石英的毒性是多种多样的。石英尘有剧毒的例子，也有毒性相对较低的例子。毒性也可以通过机械破碎石英颗粒来诱导，例如在破碎岩石进行采矿的过程中或在喷砂过程中在高压下撞击时发生的情况。这种毒性是短暂的，在几个小时到一到两天内迅速腐烂。这可以证明，至少对于石英来说，导致毒性反应(如炎症)的过程始于颗粒的表面。在表面涂上涂层可以减少或消除毒性，当涂层被移除时，毒性可以恢复。这表明，毒性最强的石英样品的表面与毒性最小的样品的表面将以某种可检测的方式不同。该项目将通过检查已知具有一系列不同毒性的石英颗粒来定位任何此类差异。已经提出了几个特征，包括与表面的水分子反应，表面位置上存在铝或铁杂质，以及表面自由基的存在。到目前为止，自由基已经成功地与破碎石英的瞬时毒性相关，但与毒性的长期内在差异无关，这表明石英表面的其他特征可能是重要的。该项目将涉及应用表面化学方法来检测不同石英样品表面的元素和分子结构，并在分析之前通过加热从表面解吸分子。同样的样品也将用原子力显微镜在原子水平上进行表征，在原子力显微镜下，表面的图像可能会揭示表面地形的差异。将进行实验，以测试是否可以在本征毒性已经很高的石英样品中诱导出额外的毒性。到目前为止，还没有进行过这样的实验。研究的结果应该是更好地了解所涉及的机制，从而为环境和职业接触粉尘领域的监管者和决策者提供更好的信息。

A proportion of dust that is inhaled consists of particles that are small enough to penetrate deep into the lungs. Most particles are relatively harmless and on being recognised as foreign are removed from the lung by specialised mechanisms. Occasionally particles are resistant to removal and can set up toxic reactions. Perhaps the best known case is that of asbestos fibres that can ultimately lead to the lung disease asbestosis and the lung cancer mesothelioma. Other harmful particulates are found in diesel fumes. Dust created by industries such as mining, quarrying and sandblasting is also associated with lung disease including silicosis and lung cancer. In this case the culprit is usually quartz, the second most common mineral in the environment and normally relatively harmless unless inhaled in large doses. The feature of importance to this project is that quartz is variable in its toxicity. There are examples of quartz dust that are highly toxic and others with relatively low toxicity. Toxicity can also be induced by mechanically fracturing quartz grains, as happens in the process of breaking rocks for mining or impacting at high pressure during sandblasting. This toxicity is transient and decays rapidly over a few hours to one or two days. It can be shown that for quartz, at least, the process leading to a toxic response such as inflammation begins at the surface of the particle. Coating the surface can reduce or eliminate the toxicity which can then be restored when the coating is removed. This suggests that the surfaces of the most toxic samples of quartz will differ in some detectable way from the surface of the least toxic samples. This project will seek to locate any such differences by examining quartz particles known to have a range of different toxicities. Several features have been suggested including reaction with water molecules at the surface, the presence of aluminium or iron impurities on surface sites, and the presence of surface free radicals. Hitherto free radicals have been successfully correlated with the transient toxicity of fractured quartz but not with the long term inherent differences in toxicity suggesting that other characteristics of the quartz surface are likely to be important. The project will involve applying the methodologies of surface chemistry to detecting elemental and molecular structures on the surface of different samples of quartz, and by desorbing molecules from the surface by heating prior to analysis. The same samples will also be characterised at the atomic level using atomic force microscopy in which images of the surface may reveal differences in surface topography. Experiments will be conducted to test whether additional toxicity can be induced in quartz samples with already high intrinsic toxicity. To date such experiments have not been conducted. The outcome of the research should be a better understanding of the mechanisms involved and thus better information for regulators and policy makers in the field of environmental and occupational exposure to dusts.