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Naturally Occurring Asbestos

Asbestos is the name for six different fibrous minerals that occur naturally in some rocks.

Some asbestos fibers are too small to be seen by the naked eye. These fibers don’t dissolve in water or evaporate. They don’t break down easily with heat, fire, chemicals or biological processes. Because of its durability and heat resistance, it is still used in some commercial products.

Human exposure to commercially mined asbestos fibers has caused mesothelioma, lung cancer, and asbestosis. The information below is specific to asbestos found in its natural state in the environment.

Where is naturally occurring asbestos found in the environment?

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 percent up to more than 25 percent.

Can be released if the rock that contains it is broken or crushed.

In rock formations across the country, including in areas of Washington. It has been documented in some areas of Skagit and Whatcom counties. The most well-known location is the Sumas Mountain slide zone in Whatcom County. Evidence of naturally occurring asbestos has also been found in rocks from the north side of Burlington Hill and to the south of Beaver Lake in Skagit County.

Are there any maps that show where asbestos has been found?

Washington State Department of Natural Resources map of potential zones of naturally occurring asbestos, based on available historical geologic information. Naturally occurring asbestos likely is present in more locations in northwest Washington.

What protective measures do I need to take when I’m developing or using my property?

Leave it alone: If rock containing naturally occurring asbestos is intact and undisturbed, your risk of exposure is low. Don’t blast it, crush it, or grind it up.

Have a plan: Before you disturb rock or soil that is likely to contain asbestos make sure you have an adequate plan to control and contain the dust.

Keep it wet and cap it: If the rock or dirt contains naturally occurring asbestos, keep it wet while you’re working, and seal it under a layer of clean soil and a layer of pavement, turf, or clean gravel, when you’re finished.

Are there already established best practices?

El Dorado County in California and the California Air Resources Board have tools and information for evaluating sites for asbestos and developing mitigation plans if needed. In particular, the El Dorado County website has an asbestos dust mitigation plan application that can serve as a template to develop a mitigation plan.

How do I evaluate a property to determine if it contains naturally occurring asbestos?

If you want to evaluate your property or a property you are working on for the presence of naturally occurring asbestos, you can:

Sumas Mountain asbestos and Swift Creek, Whatcom County

The Sumas Mountain landslide contains deposits of naturally occurring asbestos, which can be dangerous to your health.

For more information on naturally occurring asbestos, what agencies are doing to minimize the health risks from the Sumas Mountain landslide, and how you can protect your home and family, please review the following materials: