Some granite countertops contain radioactive uranium as part of the matrix. Uranium and many of its daughter products emit gamma radiation. Those granites also emit some radioactive radon gas.
There is a lot of confusion about radiation versus radon. Let's look at the two and how they are different.
Gamma radiation is also called penetrating radiation. Gamma is the type of radiation that travels through the body and can cause damage to DNA in its path. Particular types of DNA damage can initiate cancer.
Small amounts of gamma radiation are everywhere. Some gamma comes from the sun, and smaller amounts come from the soil. On a cross-county plane flight, my gamma dosimeter read 37 µR/hr. Typical background in the Bay Area is generally 5-10 µR/hr. Compare those numbers with the 520 µR/hr in the photo.
Radon is a radioactive gas. Radon is a decay product of uranium, and small amounts of radon gas will be emitted from any granite that contains uranium. The amount of radon released from granite will depend on the uranium concentration and the porosity of the stone. Research from Dr. Daniel Steck indicates that porous granites release more radon that denser granites.
The hazard associated with radon gas is alpha radiation emitted inside the lung. Alpha particles cannot penetrate skin, so alpha outside the body is not a concern. However, alpha radiation inside the lung is a very different story. Although alpha particles cannot travel far, they are large and very damaging to delicate tissue inside the lung. Exposure to radon gas is the leading cause of lung cancer in non-smokers.
Radon gas is the only decay product of uranium that is a gas. All of uranium's other decay products are solids, and they remain bound within the matrix of the granite. Radon gas is a hazard because it migrates out of the granite and into the air we breathe.
A client's radioactive Jupurana Bordeaux emitted radon at a rate of 350 pCi/square foot each hour. Radon concentration in her kitchen was three times higher than in the rest of her home.
Gamma radiation and radon gas are measured completely differently. Measure gamma radiation with a gamma dosimeter, a Micro-R meter, or a Geiger counter that is well-shielded with Plexiglas. Test for radon in air using a radon test kit approved by EPA.
Unfortunately, there are no electronic radon meters produced for consumers that are approved by EPA. Although radon meters are fun toys, consumers should not rely overly on the readings they produce.
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