Radon is produced during the radioactive decay process of uranium that has been in the earth's crust since the earth was formed. A picocurie is 0.037 radioactive disintegrations per second.
Concentrations vary widely in North Carolina groundwater.
Public groundwater supplies seem to have the highest radon levels where the water moves through granites in the piedmont. A high concentration of radon in the groundwater in your area does not necessarily mean that there will be a high concentration of radon in your drinking water. Radon escapes harm- lessly into the air when water is being treated for use in a municipal system. Also, radon decays into other substances over time while the water is being stored. Municipal systems that use surface water a lake or a river instead of groundwater will probably have low waterborne radon levels.