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This page contains information from the American Association of Radon Scientists and Technologists (AARST), the Conference of Radiation Control Program Directors (CRCPD), and the Health Physics Society (HPS).
The following is the Position Statement on Granite Countertops and Radon Gas from the Technical and Science Committee of the American Association of Radon Scientists and Technologists (AARST):
Radon Risk:
The primary concern about indoor radon gas is the increased risk of lung cancer that exists from breathing radon and its byproducts. The magnitude of the risk depends on the radon concentration in the air you breathe and how long you are breathing it. Radon gas is a serious national concern. The risk of radon-related lung cancer increases the longer you are exposed, although any exposure to radon poses some risk.
Testing for radon in the air you breathe should be a high priority and the first step for anyone concerned about radon gas. The U.S. Surgeon General, U.S. EPA, AARST, and the American Lung Association recommend that all homes be tested for radon gas.
At this time, the EPA does not believe sufficient data exists to conclude that the types of granite commonly used in countertops are significantly increasing indoor radon levels.
Radon Sources Including Granite:
Soil, sand, and rock underneath the home are the primary sources of indoor radon gas. The soil under a house always contains traces of uranium that eventually decay into radium, that then decays directly into radon. This soil constitutes an enormous surface area for release of radon gas into the air and into buildings. Materials inside a building such as concrete, granite, slate, marble, sand, shale and other stones can also contain traces of radium that release radon with varying intensities. While natural rocks, such as granite, may emit some radon gas, the subsequent levels of radon in the building that are attributable to such sources are not typically high. The contribution from building materials to the indoor radon concentration is very dependent upon the building ventilation rate.
Appropriate Radon Testing Methods:
Direct measurements in a building of the gamma radiation or radon emanation from a material, such as granite, is not a reliable indicator of radon concentrations that will be in the air you breathe. Attempts to use such measurements for estimating risk are subject to large errors due to the :
a) wide variability of radon emanation rates across the surface of granite
b) significant variability in ventilation rates from home to home and room to room
c) volume of space that the building material is contained in
This position statement does not address the risk, if any, of gamma radiation from indoor building materials.
Practical Diagnostic Test:
Diagnostic measurements of the radon in the air you breathe can provide better risk estimates.
Perform a radon measurement according to testing protocols (specified by EPA or AARST as noted below) in the lowest level (or lived-in level) of your home.
At the same time, perform another test in the room where the granite countertop or other suspect building material exists. You may also want to test in a highly occupied room, like your bedroom. (Use different rooms if these locations are on the same floor.)
Place the test devices at least 20 inches off the floor according to testing protocols and at least 20 inches away from the countertop or suspect material. Carefully follow all manufacturers' test kit instructions.
You may also contact a State licensed or nationally certified radon measurement professional to conduct the measurements for you.
If any of the test results are at, or above, the EPA recommended action levels, retest these areas to confirm the initial results.
Interpreting Radon Test Results:
For guidance on test results and protocols for measurements of radon in the air, see documents such as EPA's Citizens Guide to Radon or other EPA publications at http://www.epa.gov/radon/pubs. Other information and publications for measuring radon in the air for home and multi-family dwellings can also be found at http://www.aarst.org.
If confirmed measurements are at, or above, the EPA recommended action levels, contact a State licensed or nationally certified mitigation professional to reduce the radon levels in the home.
Reducing Radon Concentrations:
The best approach to reduce radon in the home is to install an active soil depressurization system (ASD) and reduce the entry of radon coming from the soil. In some cases, increasing the entry of outdoor air to the home is an appropriate method to reduce radon levels by dilution and improve indoor air quality. Both of these methods require a qualified radon mitigation professional to design and install the appropriate radon reduction system. Only in extreme cases would removal of the granite be necessary to reduce the radon concentration, assuming appropriate measurements confirm it as the significant sources.
In Conclusion:
Testing the air you breathe is the best method to determine your risk from radon, whether the source of the radon is from the soil or from a material inside the building.
We support peer-reviewed research to identify and quantify the contributions of various building materials to indoor radon concentration.
This statement was provided by the Science and Technical Committee of the American Association of Radon Scientists and Technologists (AARST)
This statement was prepared by AARST professionals with no external funding or other support. The sole purpose of this statement is educational and to reduce lung cancer deaths from elevated concentrations of indoor radon.
For More Information Contact:
Peter Hendrick, Executive Director
AARST
14 Pratt Road
Alstead, NH 03602
603-756-9259
director@aarst.org
The following information is from the Conference of Radiation Control Program Directors (CRCPD):
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 compositon 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 a 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 distrinct 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 claim 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.
The following information is from the Health Physics Society (HPS):
Radiation from Granite Countertops
Summary: Assuming a relatively tight house with an air change rate of 0.5/hr and using average measured dose rates from granite countertop slabs, the estimated radon concentration in kitchen air would be 0.13 pCi/L. This concentration is less than one-eighth the average radon gas concentration in U.S. homes and is well below the Enfironmental Protection Agency (EPA) guideline of 4.0 pCi/L.
It isn't a surprise that granite emits radiation. So do other items in our households. The amount of radiation emitted from granite can vary depending on the amount of natural uranium and/or thorium concentration.
The surprise is that, in the New York Times article, "What's Lurking in Your Countertop?" (Home, July 24, 2008), a radon measurement contractor stated that exposure rates from granite countertops in the kitchen of a summer home in upstate New York were ten times higher than in other areas of the residence. He attributed the elevated exposure rate to uranium in the granite countertops. The article reports that radon levels in the kitchen (of this home) were reported to be 100 pCi/L compared to basement levels of 6 pCi/L.
There are some alerting factors when we see measurements and statements like this. First, investigation determined that the measurement procedure was not valid. The procedure used by the contractor was not appropriate (as per Environmental Protection Agency radon measurement methods) and did not provide a real idea of the amount of radon in the ambient kitchen air. Second, even if the measurement had been valid, one measurement result based on one type of granite countertop in one particular home is not an indication of radon exposure in any other kitchen with a granite countertop. What is needed is to measure many types of granite. So some members of the Health Physics Society did.
The bottom line: No action needs to be taken to remove granite countertops in existing homes. If there are concerns by the homeowners, appropriate radon concentration monitor should be conducted in th living areas of the home (per EPA protocols). If the granite countertop is determined to be a cause of concern, the most risk-reducing and cost-effective action to take would be to remove radon from the air throughout the home rather than remove the granite countertop.
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