Radon is a colorless, odorless, and tasteless radioactive gas that comes from the natural decay of uranium. It can be released into the air from rock, soil, and groundwater, and it can build up in dangerous concentrations in enclosed spaces. Radon is one of Wyoming’s most widespread geologic hazards, with test results showing that there are homes and buildings with elevated radon levels in all 23 counties.


Indoor radon concentrations are affected by geologic conditions and building construction, and they can vary widely between structures due to local factors. Geologic factors that affect radon potential include the uranium content of nearby bedrock, the permeability of surrounding rock or soil, and soil moisture conditions. Radon gas can most readily move through dry, porous, and permeable materials, such as fractured bedrock or well-drained gravel. Radon is also easily dissolved in and transported through the movement of groundwater. Elements of building construction that can lead to elevated indoor radon levels include cracks or openings in the foundation, air pressure that is lower inside the building than in the ground surrounding it, and the presence of porous and permeable fill material surrounding the foundation.


Exposure to radon over time can cause lung cancer, and it is the second leading cause of the disease in the United States. There is no safe level of exposure to radon. The U.S. Environmental Protection Agency (EPA) recommends building owners mitigate indoor radon concentrations that have tested at or above 4.0 picocuries per liter (pCi/L) and to consider mitigation for concentrations between 2.0 and 4.0 pCi/L. The World Health Organization action level for indoor radon concentration is 2.7 pCi/L.


Site-specific radon testing and monitoring is the definitive way to evaluate a building’s indoor radon concentration and is recommended for all homes. Testing can be conducted through professional contractors or do-it-yourself test kits. The Wyoming Department of Health offers free and discounted at-home radon test kits for Wyoming residents. Visit the Wyoming Radon Program webpage at health.wyo.gov/radon for more information.

How radon enters a home. [Credit: Environmental Protection Agency] 


James Mauch, james.mauch@wyo.gov