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Naturally Occurring Asbestos

Where is Asbestos Found?

Asbestos is a commercial and industrial term describing a group of specific silicate minerals that forms bundles of long, very thin mineral fibers. The form and structure of these fibers is called asbestiform. In addition to asbestos, there are additional minerals that are asbestiform including winchite and richterite that are not technically considered asbestos. The definition and description of asbestos and asbestiform minerals are complex and discussed elsewhere (see bibliography). From a public health perspective, some asbestiform minerals are known to cause health effects while the health concerns of other asbestiform minerals are subject to unresolved scientific questions. All asbestiform minerals are referred to here as asbestos.

Asbestos is most commonly found in three rock types: serpentinites, altered ultramafic rocks, and some mafic rocks. Other rock types known to host asbestos include metamorphosed dolostones, metamorphosed iron formations, carbonatites, and alkalic intrusions. Contributing to asbestos formation is the faulting and fracturing of these rocks with increased temperatures, pressures, and the presence of water. The amount of asbestos or asbestiform minerals in these rocks can range in size from commercial-grade ore bodies to thin impure veinlets or low-grade occurrences.

Asbestos can be released from these rocks if the rocks are broken or crushed. Asbestos can also be released from asbestos containing soils that are stirred up. The presence and prevalence of asbestos fibers in soils overlaying rocks containing asbestos is not known and needs to be evaluated.

What are the known locations of Naturally Occurring Asbestos?

The history of asbestos discovery and usage is at least 5,000 years old. In the United States, the prospecting and identification of asbestos began in the mid to late 1800s. The US Geological Survey, in 2006 and 2007, completed literature reviews of the known locations of naturally occurring asbestos in the Eastern US , Central US , and Rocky Mountain US States . Information about the western US States is available at USGS at (Mineral Resources On-line Spatial Data ).

ATSDR combined these data sets into two single maps, which can be viewed below:
  • US [PDF - 1.28 MB]
    This map highlights the top 100 fastest growing counties within the contiguous United States and Alaska and the location of naturally occurring asbestos.
  • Georgia [PDF - 1.83 MB]
    This map depicts the 100 fastest growing US counties in north Georgia in relation to the locations of naturally occurring asbestos and ultramafic rocks which are known to host asbestos.

Can Naturally Occurring Asbestos become a Health Problem?

Naturally occurring asbestos is only a health problem if it is disturbed. Asbestos is made up of fibers that are so small you cannot see them. If asbestos fibers are in the air you breathe, you might get asbestos fibers in your lungs. Breathing in the fibers is the primary way that people are exposed to asbestos.

The US [PDF - 1.28 MB] and Georgia  [PDF - 1.83 MB] maps show the known locations of naturally occurring asbestos in the United States and provide an indicator of areas that may be more prone to surface soil disturbance.

The two indicators these maps define are listed below:
  • Increase in the number of homes by housing starts
  • Increase in population by the 100 fastest growing counties

More information about asbestos and health and limiting exposures to naturally occurring asbestos is found at basic information about naturally occurring asbestos. Fairfax County, Virginia has developed procedures for maintaining safe working conditions on construction sites in areas of naturally occurring asbestos and to prevent migration of asbestos laden dust off these sites (naturally occurring asbestos in Fairfax County).


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