North Carolina Radon Potential Map

The indoor level of radon and other radionuclides in a building is due to the presence of radioactive elements either in the ground or in the building's materials. But the presence of radon and other radionuclides in private well water is due to the geology surrounding the water source.

Since both the geology under buildings and building materials may have radioactive elements, the North Carolina Radon Program suggests that all buildings, particularly residences, be tested for indoor air radon levels.

This map and the data within is intended to assist North Carolinians with understanding when and where they may want to test their private well water. Elevated levels of radionuclides (e.g. radon, uranium, gross alpha, gross beta) are most likely to be in specific geologic units identified in this map.

Radon, measured in picocuries per liter (pCi/L), is a radioactive gas that forms naturally when the radioactive metals uranium, thorium, or radium break down in rocks, soil, and groundwater.

Radon is colorless, tasteless, and odorless. Common uranium-bearing, high radon potential rock types in North Carolina include metamorphosed rocks with granitic composition, graphitic schists, and generally well-fractured rocks (which create pathways for radon to easily flow).

Researchers from the  North Carolina Geological Survey (NCGS)  used data collected by the  Department of Health and Human Services (DHHS)  -  Radon Program  from over 78,000 home radon test kit (air) results. These radon data points were linked to the digitized  Geologic Map of North Carolina  from 1985, in order to produce a detailed and interactive statewide radon-potential map. For the NCGS, this is an effort for a more complete picture of radon from its geologic source.  Initial agency research in 2014 linked radon data to the state-wide geology broadly from groundwater data .

The 1985 North Carolina Geologic statewide map was produced at a broad-scale and therefore lacks the geologic detail that is preferred in some areas. Also, since 1985, ideas and practices regarding North Carolina's geologic units have changed some over time. Mapping North Carolina's geology in more detail, together with these evolving geologic concepts, is an on-going effort that continues to this day.

Only the radon emitting potential of the geologic units is considered in the analysis. Other factors which could increase radon hazard, such as faulting and rock fracture networks -which could increase the radon mobility potential of any rock unit - is not built into the analysis. Although we trust that this map represents a good approximation of the radon potential in North Carolina, it is encouraged to use the map as a "first pass" approximation of the radon potential of an area of interest.

The purpose of the North Carolina Radon Program is to:

• Increase awareness of the source and health impacts of radon exposure
• Provide resources that assist North Carolinians with testing indoor radon levels
• Empower North Carolinians on how to lower radon levels

The mission of the North Carolina Geological Survey is to provide unbiased and technically accurate applied earth science information to address societal needs. This includes geologic maps, mineral resource and geochemical information, topographic maps and digital products, and earth science education initiatives. The agency examines, surveys and maps the geology, mineral resources and topography of the state, while encouraging the wise conservation and use of geologic resources by industry, commerce, agriculture and government for the general welfare of the citizens of North Carolina.