Environmental Health

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Environmental Health

Director: Jennifer Johnson
Geologic Hazards – Radon, Naturally Occurring Asbestos, and Arsenic


What is radon?

Radon is a naturally occurring radioactive gas that is invisible, odorless, and tasteless. It comes from the radioactive decay of radium, an element found in most rocks and soils. Radon can enter a building from the ground underneath it, and concentrate to tens or even hundreds of times the level in outdoor air.  Radon is the leading cause of lung cancer among non-smokers.  Radon has been detected in homes in Skagit County.  Learn more about radon risks, how to test your home, and how to limit your exposure.

Naturally Occurring Asbestos

What is asbestos?

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.   Asbestos is still used in some commercial products.  Human exposure to commercially mined asbestos fibers has caused mesothelioma, lung cancer, and asbestosis. The information below deals with asbestos found in its natural state in the environment.

Naturally occurring asbestos
refers to those fibrous minerals that are found in the rocks or soil in an area and released into the air by routine human activities or rock weathering.

Where asbestos is found in your environment

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. 

Ultramafic and serpentine rock formations are found in areas of Washington.  Naturally occurring asbestos 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.  The Environmental Protection Agency also recently found evidence of naturally occurring asbestos in rocks from the north side of Burlington Hill in Skagit County. 

Washington State Department of Natural Resources has mapped potential zones of naturally occurring asbestos.

These maps are based on available historical geologic information.  Naturally occurring asbestos can likely be found in additional locations in Washington and Skagit County.  If you live or work on a property with exposed ultramafic or serpentine rock and want to evaluate your property for the presence of naturally occurring asbestos the information below may be helpful to you.

Naturally Occurring Asbestos Fact Sheets can provide you with more information about asbestos and good guidance for steps you can take to keep naturally occurring asbestos out of your home:


Arsenic is a naturally occurring element that is normally present throughout our environment in water, soil, dust, air, and food. Levels of arsenic can vary from place to place due to farming and industrial activity as well as natural geological processes.  Arsenic is toxic to humans and can cause many different health impacts depending on exposure levels and individual sensitivities. 

Arsenic can get into drinking water when well water is drawn from an aquifer that passes through arsenic containing rock formations.  Arsenic has been detected at levels of public health concern in wells in Skagit County.  The Arsenic in Drinking Water Wells Map provides approximate locations of elevated arsenic in Skagit County wells.

Washington State Department of Health provides additional information on arsenic and health.