This EPA weblink (here) indicates that any type of rock could contain naturally occurring radioactive elements, such as radon.
- Some types of granite may contain more of these elements than others.
- The link indicates that there are no generally accepted testing methods for radon in granite counter tops.
- The EPA also discusses the length of time for radon to degrade and the types of home tests available - which may be a good idea for anyone to know, given the potential health risks associated with radon.
This EPA link outlines the health risks of radon and can a be a good starting point to learn and provide guidance toward mitigating radon.
For more information:
Read "Where can I find radon testing equipment for granite countertops? And what are safe levels?" a Q&A answered by Bill Bradbury.