EPA What information do you have about radiation in granite countertops? 8/08/2008

Question
What information do you have about radiation in granite countertops?


Answer
Are granite countertops radioactive?

Based on existing studies, most types of granite used in countertops and other aspects of home construction are not typically known to be major contributors of radiation and radon in the average home.


Granite is an igneous rock, meaning that it was formed by the cooling of molten rock. As it cooled, minerals in the rock formed crystals. Uranium, radium, and thorium occur naturally in a wide number of minerals that appear as crystals in granites from around the world. Some granites are more radioactive than others, depending on the composition of the molten rock from which they formed.

The radium and thorium in the granite can decay into radon, a colorless, odorless, radioactive gas, which may be released from the granite over time. However, since the matrix of the granite is generally not very porous, the radon is less likely to escape from the granite than from a more porous stone such as sandstone.

(We are not aware of any radiation associated with soapstone, which is a metamorphic rock [igneous or sedimentary rock that has been altered by heat and temperature: marble is another kind of metamorphic rock, which originally was limestone.])

Can I test my granite countertops for radiation?

At this time, a generally accepted testing protocol does not exist.


Radiation can only be measured using expensive and sophisticated portable instruments, or with laboratory equipment. These instruments and equipment require a knowledgeable and trained user and proper instrument calibration.


The Conference of Radiation Control Program Directors (CRCPD) maintains a web page where you can find contact information for each state's radiation protection program. Please visit this web page, http://www.crcpd.org/Map/map.asp , to find information for your state.


What dose would people receive from granite countertops?

Based on existing studies, most types of granite used in countertops and other aspects of home construction are not typically known to be major contributors of radiation and radon in the average home.

As with all radiation sources, the dose of radiation that a person would receive depends on a wide variety of factors:

· type of radiation

· amount of time spent near the source

· distance from the source

· other factors.

Does enough uranium occur in granite deposits to be mined?

Some granitic deposits in the United States, Canada, and elsewhere in the world, contain enough uranium that mining them is profitable. Mining and extracting uranium ore from granites is expensive enough that miners searching for uranium in granitic rock look for pockets of concentrated uranium ore in veins or pegmatites (very coarse grained rock in which the uranium bearing crystals would tend to concentrate). Granite containing these pockets of uranium ore looks different from the surrounding "country rock" granite. It also tends to occur in distinct areas, which are separate from the country rock granite. It is possible that higher concentrations of uranium ore could be found where granite is quarried for countertops ( i.e., outside the mining area). However, most mines will include a large enough area in their claims that any pockets of uranium ore outside the main mining area will be captured.

Are there regulations about radiation in granite countertops?

There are currently no regulations concerning radiation levels in countertops.

Is granite from other countries tested for radioactivity levels?

Radiological testing of imported, or domestic, granite is not usually done.


For More Information Visit:
www.epa.gov/radon