Radon, a radioactive gas, is a widespread geohazard across the state of Colorado.


Geology plays an important role in water and air quality. Naturally occurring radioactive elements such as radium, uranium, and thorium are found in small amounts in most rocks, soils, and groundwater. One of the most common hazards from the presence of these natural elements is radon gas, a colorless, odorless gas, a natural element, that is the byproduct of the radioactive decay/breakdown of uranium, thorium, and radium.

Radon gas is the second leading cause of lung cancer in the United States after smoking cigarettes, and the leading cause of lung cancer for non-smokers. If rocks, soil, or groundwater with greater than normal concentrations of these elements are present around a home or building, the water or air inside may contain high levels of radioactivity, posing a significant health hazard. Radon gas has been found in all parts of Colorado and about half of homes in Colorado have radon levels of concern. The CGS has found that radon levels in homes are strongly influenced by local geology, emphasizing the importance of the research that the CGS does, studying the geologic setting of areas where people live and work.

How to test for radon in a home

Radon gas can enter a home or building through cracks or gaps in the foundation, floors, walls, and construction joints or around pumps, wires, and pipes. It may also come from water that is drawn from groundwater through a well. The Environmental Protection Agency (EPA) has established the maximum safe levels of this radioactive gas, and simple, inexpensive testing can determine if it is an issue in your home or business. Colorado’s Department of Public Health & Environment (CDPHE) has a number of resources for homeowners and renters to learn how to test and mitigate their homes for radon: .