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Pacific Southwest, Region 9

Serving: Arizona, California, Hawaii, Nevada, Pacific Islands, Tribal Nations

Naturally Occurring Asbestos

Related Information

Naturally Occuring Asbestos Fact Sheet (PDF) (7 pp, 85K)

The EPA Region 9 office is working in areas of California to address concerns about potential effects of naturally occurring asbestos. Asbestiform minerals occur naturally in rock and soil as the result of natural geologic processes, often in veins near earthquake faults in the coastal ranges and the foothills of the Sierra Nevada mountains. Naturally occurring asbestos is also found in other areas of the country.

Naturally occurring asbestos (NOA) can take the form of long, thin, separable fibers. Natural weathering or human disturbance can break NOA down to microscopic fibers, easily suspended in air.

There is no health threat if asbestos fibers in soil remain undisturbed and do not become airborne. When inhaled, these thin fibers irritate tissues and resist the body's natural defenses. Asbestos, a known carcinogen, causes cancers of the lung and the lining of internal organs, as well as asbestosis and other diseases that inhibit lung function.

EPA Region 9 has conducted assessments of airborne asbestos exposure in the Clear Creek Management Area and El Dorado Hills in California.

Clear Creek Management Area (CCMA)

Enduro rider

The EPA has also conducted a study at the Clear Creek Management Area (CCMA), which is a popular area for off-road vehicle use, as well as other activities such as hiking and camping. These recreational activities create airborne asbestos exposures. For more information on this study, visit the CCMA Web page.

El Dorado Hills

Photo of:  recently paved road near Oak Ridge High School
Paving dirt roads and covering bare soil around Oak Ridge High School in El Dorado Hills, CA is preventing naturally occurring asbestos in the soil from becoming airborne dust, which can be inhaled.

The EPA recently completed a comprehensive investigation to assess the potential for exposure from naturally occurring asbestos in El Dorado County, California. The reason for this investigation as well as sampling results and continuing plans are detailed on Region 9's El Dorado Web page.

El Dorado Hills Naturally Occurring Asbestos Multimedia Exposure Preliminary Assessment and Site Inspection Report Interim Final Web version | PDF version (PDF 163 pages 1.3 MB) Note: See the web version for accompanying photos, figures and tables. They were removed from the PDF to reduce its size.

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