General Radon Information

North Carolina specific radon and radon level information can be found throughout this site. You will be able to find information about certified radon inspectors in North Carolina, as well as detailed radon level information for every county in North Carolina.

Radon is an odorless, tasteless colorless Noble gas that is inert (non-reactive) that is found throughout the world in varying concentrations. The amount of radon in the soil depends on soil chemistry, which varies from one house to the next. Radon levels in the soil range from a few hundred to several thousands of pCi/L. Radon occurs naturally from the radioactive decay of Uranium-238 and its decay products (daughters), which include Radium-226 and Radon-222.

Radon enters building structures as a soil gas that utilizes existing cracks in concrete floors or walls, open soil in crawl spaces, improperly or poorly sealed floor drains or pipe entry points in floor slabs. Without significant ventilation and air exchange in crawl spaces and under the floor slab (sub slab ventilation), Radon builds up and enters the living spaces of homes and other structures.

Radon can move easily through soil and tiny cracks in rock. When it reaches the surface of the soil, it disperses and is diluted to very low levels in the outdoor environment. However, when the gas moves upward through soil beneath a home, it may enter through cracks or other openings in the foundation and build up to unacceptable levels.

The lead agency for radon activities in North Carolina is NC Radiation Protection (NCRP) a section of the Division of Environmental Health (DEH) of the Department of Environmental and Natural Resources (DENR). This agency is the main point of contact for radon activities to the citizens of North Carolina.

The geology of the state of North Carolina suggests certain areas of the state in the Piedmont and Blue Ridge Mountain regions could have elevated indoor radon levels. A State Geological Society survey map of North Carolina identifies areas that contain gneiss, schist and granite rocks underlying the soils. These are the rock types which contain higher concentrations of uranium and radium, the parent radionuclides of radon gas.

The most important characteristics of soil that determine how much radon is emitted and how far it can travel are the soil's radium content, the moisture in the soil and how easily the gas can travel through the soil (permeability). The moisture in the soil and permeability depend on the age and composition of the soil. EPA and USGS included all of these characteristics in their production of the Map of Radon Zones, along with survey data on uranium in soil, house architecture information and actual radon measurements. Based on the results from the Map of Radon Zones, there are eight North Carolina counties that qualify as Zone One counties. The following counties are projected to have average radon in air levels greater than 4 pCi/L on average: Watauga, Alleghany, Mitchell, Buncombe, Henderson, Transylvania, Cherokee, and Rockingham.

The EPA Map of Radon Zones shows the general trend of radon levels in the state. The levels tend to be lower in the Coastal Plain, then increase in the middle area of the state - the Piedmont, and increase more in the mountains. There are exceptions to this general such as Rockingham County, a Zone One county amidst generally Zone Two counties. Other exceptions are Wake County, Warren County and Franklin County, which are Zone Two counties with Zone Three counties nearby. These exceptions are often due to the different types of rock formations and geological features in the area.

The U.S. Environmental Protection Agency (EPA, 1992) estimated that between 7,000 and 30,000 lung cancer deaths in the United States each year are caused by breathing radon gas. In fact, radon is believed to be second only to smoking as the major cause of lung cancer in the United States. Although the EPA and the Surgeon General warn that smokers have a higher risk of developing lung cancer from radon exposure than non-smokers, the radon levels in all homes can be reduced.

As a means of prevention, EPA and the Office of the Surgeon General recommend that all homes below the third floor be tested for Radon. Because Radon is invisible and odorless, a simple test is the only way to determine if a home has high Radon levels. EPA recommends mitigating homes with Radon levels 4.0 picocuries per liter or greater. There are straightforward reduction techniques that will work in virtually any home.