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TENORM
Naturally-Occurring Radiation: 

Granite Countertops and Radiation

TENORM

This page contains information about granite and radioactivity in granite.

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Granite Overview

Granite is an igneous rock, having been formed as lava or molten rock cooled and solidified over thousands, or even millions of years. Since granite forms so slowly, minerals have a long time to grow into the crystals that give it its distinctive patterns. Granite comes in a wide range of colors that vary with the elements in it. Granite’s durability and decorative appearance make it a popular building material in homes and buildings.

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Radiation From Granite

Any type of rock could contain naturally occurring radioactive elements like radium, uranium and thorium. Some pieces of granite contain more of these elements than others, depending on the composition of the molten rock from which they formed.

If present, these radioactive elements will decay into radon, a colorless, odorless, radioactive gas which may be released from the granite over time. You can see in the diagram below how the decay of Uranium-238 (a radioactive element) produces Radon-222 gas:

Graphical diagram of how decay of uranium-238 produces radon gas


To learn more about radioactive decay and radioactive half lives, see our half-life page.

However, since granite is generally not very porous, less radon is likely to escape from it than from a more porous stone such as sandstone. It’s important to know that radon originating in the soil beneath homes is a more common problem and a far larger public health risk than radon from granite building materials. Also, any radon from granite countertops in kitchens or bathrooms is likely to be diluted in the typical home since those rooms are usually well ventilated.

In addition to radon, the other natural radioactive material in the granite can emit radiation. However, it is extremely unlikely that granite countertops in homes could increase the radiation dose above that the normal, natural background dose that comes from soil and rocks.

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Testing

To reduce your risk of lung cancer from exposure to radon you should test the air in your home. There are many inexpensive do-it-yourself home radon test kits available at the retail level, on-line, or from 1-800-SOS-RADON (767-7236).
Identifying the presence and concentration of radioactive elements in granite requires expensive and sophisticated portable instruments or laboratory equipment. These instruments and equipment require proper calibration, and interpretation of their readings requires a knowledgeable and trained user. At this time, there is no generally accepted home testing protocol for radiation in granite countertops.

If you have questions about testing your countertops, you can get information from your state’s radiation protection program. The Conference of Radiation Control Program Directors (CRCPD) Exit EPA Disclaimerlists contacts for each state.

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