天然石棉矿床地质学及其在公共卫生政策中的应用(英文)

20世纪,越来越多的证据使人们意识到,吸入含石棉的灰尘会使从事与石棉有关的几种职业(如石棉采矿、造船和石棉产品组装)的工人患上几种严重的呼吸道疾病(石棉沉着病,肺癌和mesotheliuma)。为此已经制定了若干规定,以控制工人们在特殊的制造、采矿和其他工作地点与石棉尘埃的接触。比较间接的是控制和管理"天然产生的石棉"(NOA),这一问题近年来也引起了管理机构、健康机构和居民团体的注意。NOA包括在自然状态下原地找到的被描述为石棉的矿物,例如在基岩或土壤中的这种矿物。NOA之所以引起关注,是因为如果含石棉的岩石受到自然侵蚀或人类活动(例如修路、城市开挖、农业、采矿、压碎和碾磨)的影响,就有可能暴露并变成空中尘埃的微小纤维。天然石棉矿床的规模差异很大,从薄的四散的细脉一直到大的矿体。它们的地理分布与地质条件直接有关。石棉产出的地质背景是含镁丰富的主岩,这些岩石受到低压低温的变质作用蚀变而成。已知的容矿主岩包括变质的和已被交代的超基性岩(尤其是蛇纹岩)、一些基性火成岩、变质白云岩和变质的铁建造。石棉形状的角闪石在几种热液蚀变型的碱性火成侵入体中也能作为副矿物存在。石棉形成于可预见和可鉴别的地质环境。这种认识是一种信息,而这种信息使公众健康机构可以执行有情报根据的屏蔽和管理规划。第一步是在区域的或国家规模的尺度上确定和描述已知的(报道过的)石棉矿床。第二步是对容纳已知石棉矿的单位进行填图,以划定可能的其他石棉矿化的范围。这种地质研究使有关机构对遇到石棉的可能性做出规划,而尽量节省在不太可能遇到石棉矿的地区的管理费用。对石棉地质条件的认识可以事先应用于岩石和土壤的挖掘项目,而不管挖掘的规模有多大。这种对石棉管理的科学探索能有助于缓解对挖掘所发现的自然石棉矿床的连续不断地做出反应。因此,通过对很可能含有石棉矿床的地区做填图,规划者可开发出一些控制尘埃的程序,这些程序适用于工人和附近居民最容易暴露于空气携带的石棉的地区。

The geology of natural asbestos deposits and its application to public health policy

A growing body of evidence in the 20th century led to the realization that inhalation of asbestos-bearing dusts was the cause of several serious respiratory diseases(asbestosis,lung cancer,and mesothelioma)among workers of asbestos-related occupations,such as asbestos mining,shipbuilding,and asbestos product fabrication.As a result,a number of regulations were developed to govern asbestos dust exposures in specific manufacturing,mining,and other occupational sites.Less straightforward is the regulation and management of"naturally occurring asbestos"(NOA),which has recently gained the attention of regulatory agencies,health agencies,and citizen groups.NOA includes minerals described as asbestos that are found in-place in their natural state,such as in bedrock or soils.NOA is of concern due to potential exposures to microscopic fibers that can become airborne if asbestos-bearing rocks are disturbed by natural erosion or human activities(road building,urban excavations,agriculture,mining,crushing,and milling,as just a few examples).Natural asbestos deposits range widely in size,from thin,scattered veinlets to large ore bodies.Their geographic distribution is directly linked to geology.The geologic settings in which asbestos occur are Mg-rich host rocks altered by relatively low pressure and temperature metamorphism.Specifically,the rock types known to host asbestos include metamorphosed and metasomatized ultramafic rocks(particularly serpentinite)and some mafic igneous rocks,metadolostones,and metamorphosed iron formations.Asbestiform amphiboles can also occur as accessory minerals in several hydrothermally altered types of alkaline igneous intrusions.Recognizing that asbestos forms in predictable and identifiable geologic environments is information that allows public health agencies to conduct an informed asbestos screening and management program.The first steps involve locating and describing the known(reported)asbestos deposits,at a regional or national scale.Next,the geologic units that host known asbestos are mapped,which delineates the extent of possible additional asbestos mineralization.This geological approach allows agencies to plan for the possibility of encountering asbestos where appropriate,while also sparing the unneeded expense of asbestos regulation in regions that are unlikely to contain asbestos deposits.A basic understanding of the geology of asbestos can be applied beforehand at any rock and soil excavation project,regardless of scale.This scientific approach to asbestos management will help alleviate the need to continually respond to surprise discoveries of natural asbestos deposits uncovered by excavation projects.Thus,by mapping the terrains most likely to host asbestos mineral deposits,planners can develop dust-control procedures appropriate for the regions where workers and nearby residents are most likely to be exposed to airborne asbestos.