Introduction

Asbestos, actually a generic term, is defined as the fibrous or asbestiform variety of several specific naturally occurring hydrated magnesia silicate minerals. Within the context of this presentation, it is correct to say that all asbestos minerals are fibrous (but not all minerals that are fibrous are asbestos), e.g., tremolite asbestos means fibrous tremolite.

Asbestos, in the earth's crust, is a relatively common material. The U.S., U.K., Canada, France, Germany, Italy, Russia, Turkey, and Greece are some of the countries that have dealt with the issue of naturally occurring asbestos contamination in the mining industry. Germany has specific guidelines to certify products that come from asbestos contaminated quarries as "asbestos free" if the analytical air procedures followed result in what the U.S. often calls "trace" amounts. (Kolmsee et al., 2001)

Asbestos is a known carcinogen and accounts for illnesses in a large number of people who inhaled excessive amounts of the airborne fibers of the mineral. In the past, asbestos was purposely mined in the U.S. (and in some countries today) and used in various commercial applications, including fire proofing and insulation. Today, most countries, including the U.S., do not mine for asbestos but still nevertheless must deal with the consequences of accidentally disturbing it while extracting another mineral resource or during construction activities. Release episodes can also occur from the disturbance of old commercial-industrial applications. While limited need exists for new asbestos, such as in specialized aerospace applications, asbestos is otherwise undesirable in the industrialized world.

For the mining industry, avoidance is the key. Exploratory geological surveys that discover asbestos in advance of excavation or start of mineral extraction operations can prevent future problems, including disabled workers, public embarrassment, tort actions and liability. The best approach is to take preventive measures beforehand rather than reactive measures after the fact. Planning and testing is a more cost-effective strategy in the long run than the potential consequences of not doing so. From time-to-time, however, problems can arise for some mine operators. Geological surveys are not always perfect and following ore or good stone into unexplored territory can inadvertently expose asbestos deposits. Regulators have a duty to protect miners and the public from exposure in these cases, and they have broad authorities available to them to accomplish this mission. The prevention of contact with asbestos is the preferred proactive course of action. Application of standard engineering dust control measures are generally adequate to minimize any fiber exposure and simultaneously keep respirable silica dust exposures to airborne concentration levels that are well below the exposure limit values. The use of respiratory protection by miners is not an optimal method of exposure control. When workers may be exposed to asbestos, special occupational medical surveillance measures may be considered.

Biology of Asbestos Fiber Exposure

Most mining workplace exposures to asbestos occur over a period of many years, and there is a latency period before adverse health effects manifest themselves.

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