Naturally Occurring Asbestos & Exposure Risks

Author: Paul Cochrane
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Asbestos is the name given to a group of six different fibrous minerals that occur naturally in the environment. Asbestos fibers are too small to be seen by the naked eye. They do not dissolve in water or evaporate. They are resistant to heat, fire, and chemical or biological degradation. Prolonged inhalation exposure to asbestos fibers can cause mesothelioma, asbestosis and lung cancer. The term “naturally occurring asbestos” or NOA, refers to the mineral as a natural component of soils or rocks as opposed to asbestos in commercial products, mining or processing operations. Naturally occurring asbestos can be released from rocks or soils by routine human activities or natural weathering processes. If naturally occurring asbestos is not disturbed and fibers are not released into the air, then it is not a health risk. According to the Agency for Toxic Substances and Disease Registry (ATSDR), “Asbestos is commonly found in ultramafic rock, including serpentine rock, and near fault zones. The amount of asbestos typically present in these rocks ranges from less than 1% up to about 25%, and sometimes more. Asbestos can be released from ultramafic and serpentine rock if the rock is broken or crushed.” People can be exposed to naturally occurring asbestos through routine activities that crush asbestos-containing rock or stir up dust in soils that contain asbestos fibers. The following are a few examples of these activities in areas with naturally occurring asbestos: • Working in a yard or garden • Digging or shoveling dirt • Riding bicycles, off-road vehicles or driving on unpaved surfaces • Running and hiking on unpaved surfaces Workers can also be exposed to naturally occurring asbestos during activities, such as construction, that disturb the ground. Fortunately, environmental testing can determine if asbestos is present and there are management approaches to help mitigate these types of exposure risks. These are just a few things to know about naturally occurring asbestos. To learn more about this or other environmental, indoor air quality, occupational, health or safety issues, please visit the websites shown below. Clark Seif Clark EMSL Analytical, Inc. Indoor Environmental Consultants, Inc. LA Testing Zimmetry Environmental Healthy Indoors Magazine Hudson Douglas Public Adjusters


  1. I thought the USGS maps showing locations of naturally occurring asbestos were a great resource.  One interesting note of the 48 lower states there were three states not included:  California, Oregon and Washington.  Wonder why, since there are over two dozen locations in death valley where there is naturally occurring asbestos documented.  Then I saw some thing interesting from Texas.  I have a talc sample from the old rail bed going through Lano TX.  The talc mine there is listed for having naturally occurring asbestos, with a photo detailing the structure of the talc under magnification.  Interesting what you pick up during geology field trips in college.