Radon in granite

Radon is not added to granite; it forms inside it. EPA's What is Radon? page says radon is a radioactive gas that forms naturally when uranium, thorium, or radium, which are radioactive metals, break down in rocks, soil and groundwater. EPA's Radionuclide Basics page says radon comes from the natural decay of uranium and radium found in nearly all rocks and soils.

EPA's granite page applies this to the stone and lists what those elements give off. They can emit radiation and produce radon gas, a source of alpha and beta particles and gamma rays. Some types of granite may emit gamma radiation above typical background levels, and some granite used for countertops may contribute variably to indoor radon levels.

Why some granites differ

EPA's page for granite workplaces gives the reason one slab can differ from another: some granites are more radioactive than others, depending on the composition of the molten rock from which they formed. EPA's countertop page adds that while radiation levels are not typically high, measurement of specific samples may reveal higher than expected levels on a case-by-case basis. Neither page names a type, color or quarry to avoid.

Granite is not the only building material with natural radioactivity. EPA's RadTown page on building materials says some building materials, such as granite, brick, marble and other items, contain natural radioactivity, and that the amount depends on the type of material, but the amount of radiation released from these materials is typically very, very low.

The radon link is the same for each. RadTown says that when the natural radioactivity found in building materials decays, it releases the radioactive gas radon, which may contribute to elevated radon levels in homes and buildings, and that indoor radon is a more common and a far larger public health risk than radiation from building materials. RadTown's advice for every material is to test your home for radon and to correct elevated levels.

EPA has a second granite page, under its radiation program, that looks at the stone itself. It says granite, like any other stone, may contain veins of naturally occurring radioactive elements like uranium, thorium, and their radioactive decay products, and that these trace concentrations may vary from stone to stone, or even within a single slab of granite. It says radon released from granite building materials can be released over the lifetime of use but typically will be diluted by ventilation.

The radiation page also says that, in addition to radon, naturally occurring radioactive elements in the granite can emit small amounts of beta and gamma radiation, and that any radiation present would decrease quickly with increasing distance from the source. For anyone who wants a countertop measured anyway, it points to each state's radiation protection program, listed through the Conference of Radiation Control Program Directors (CRCPD).

Radon in granite countertops: EPA's answers

EPA answers the countertop question in several parts. On danger, it says that while radon gas and radiation emission levels attributable to granite are not typically high, there are simply too many variables to generalize about the potential health risks inside a particular home that has granite countertops, and that it is prudent to limit your family's exposure to radon whenever possible. On research, EPA says it is aware of a few studies that have conducted limited research on radon in granite countertops and will continue to review this research. On rules, it says there are currently no regulations concerning granite countertops radon gas or radiation emissions.

EPA also says it will continue to monitor and analyze the evolving research on radiation and granite countertops and will update its recommendations as appropriate. In the meantime, its advice to consumers who have granite countertops starts with the air, not the stone: to reduce the radon risk you should first test the air in your home to determine the radon level.

Radon gas and granite countertops in a kitchen

A countertop sits in a kitchen, and a kitchen is not where EPA says to measure a home's radon. The Citizen's Guide says to put a test kit in the lowest lived-in level of the home, in a room that is used regularly, but not your kitchen or bathroom. That test measures what matters for the people in the house, whatever the source. Testing is the only way to know the radon level in a specific building.

Every EPA guide cited here ranks the soil first. EPA's granite page says EPA believes the principal source of radon in homes is from the soil in contact with basement floors and walls. The Consumer's Guide says that in the United States, radon gas in soils is the principal source of elevated radon levels in homes. The Citizen's Guide says radon from soil gas is the main cause of radon problems, and that building materials rarely cause radon problems by themselves.

How EPA sees granite radon next to soil gas

WHO lists the factors that set the radon concentration in a building, and building materials are one of them: the local geology, including the uranium content and permeability of the underlying rocks and soils; the routes available for radon to pass from the soil into the building; the radon exhalation from building materials; and the rate of exchange between indoor and outdoor air. EPA's granite page makes the comparison directly: while natural rocks such as granite may emit radiation and radon gas, the levels attributable to such sources are not typically high.

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1. 1Cracks in solid floors
2. 2Construction joints
3. 3Cracks in walls
4. 4Gaps in suspended floors
5. 5Gaps around service pipes
6. 6Cavities inside walls
7. 7The water supply

The ground under a house is where EPA's guides say radon enters. EPA's Radionuclide Basics page says radon can move up from the ground into buildings through openings in floors or walls that are in contact with the ground, and that it can accumulate in buildings and, over time, can pose a serious health hazard. The Citizen's Guide says it moves up through the ground to the air above and into your home through cracks and other holes in the foundation, and that your home traps radon inside, where it can build up.

The EPA guides cited here do not say that homes on granite bedrock have higher radon than others, and the rock under a lot is not a reading for the house on it. The Citizen's Guide says local geology, construction materials and how the home was built are among the factors that can affect radon levels in homes, and that radon levels can vary greatly from home to home. EPA's Map of Radon Zones identifies areas with the greatest potential for elevated indoor radon levels, but EPA says it should not be used to determine if individual homes need to be tested. See the radon map for your county's zone.

Measuring granite countertops radon and radiation

Not in any standard way. EPA says that at this time a generally accepted radiation testing protocol for countertops does not exist, and neither imported nor domestic granite products require radiation testing. Radiation concentrations can only be measured using sophisticated portable instruments, or with laboratory equipment, and those instruments require a knowledgeable and trained user and proper instrument calibration. For local radiation experts, EPA points to each state's radiation protection program, through the Conference of Radiation Control Program Directors (CRCPD).

EPA notes that do-it-yourself radon test kits are not specifically designed or intended for measuring radon emissions from countertops. If you are concerned about the radon level in your home, EPA's advice is to purchase a test kit and use it as instructed. A specially trained and qualified radiation professional may be equipped to test for other radon sources, such as granite or diffusion from drinking water, when diagnosing the nature and source of a home's radon problem.

What EPA says to do instead

1. 1

   Test the air in your home

   EPA says to first test the air in your home to determine the radon level. Place the kit in the lowest lived-in level, in a room used regularly but not the kitchen or bathroom. Compare kits on the radon test kits page.

2. 2

   Follow up a high short-term result

   EPA's Citizen's Guide says that if a short-term result is 4 pCi/L or more, take a follow-up test to be sure, either a long-term test or a second short-term test.

3. 3

   Fix the home if the level calls for it

   EPA recommends fixing a home when the radon level is 4 pCi/L or higher. EPA's granite page says to hire a qualified radon professional to fix or mitigate your home, and to contact your state radon office for assistance. Find one in the radon professionals directory.

4. 4

   Ask about other sources only if the fix falls short

   EPA says a qualified radiation professional may be able to test for sources such as granite when diagnosing a home's radon problem. Commonly employed mitigation techniques, EPA says, can reduce the radon level coming from soil beneath your home to 2 pCi/L or less in most homes.

A high result in a home with granite does not point to the countertop. EPA's radiation page says that if elevated levels are measured, the most effective action may be to install a device that removes radon from the air in the home, rather than to remove granite countertops. EPA's countertop page says to hire a qualified radon professional to fix or mitigate your home, and that commonly employed mitigation techniques can reduce the radon level coming from soil beneath your home to 2 pCi/L or less in most homes.

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1. 1Soil gas drawn from beneath the slab
2. 2Suction point through the slab
3. 3Vent pipe
4. 4Fan, outside the living space
5. 5Discharge above the roofline

The Consumer's Guide to Radon Reduction says EPA generally recommends methods that prevent the entry of radon, and describes soil suction as drawing the radon from below the home and venting it through a pipe, or pipes, to the air above the home where it is quickly diluted. For any type of home it also lists ventilation: a heat recovery ventilator can be installed to increase ventilation, which will help reduce the radon levels in your home. Whatever is installed, the guide says a post-mitigation radon test should be done within 30 days of system installation. More in radon mitigation.

EPA has a separate page for people who work with the stone. It says that, 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. It also says that, to date, the Occupational Safety and Health Administration (OSHA) has not performed any testing for radon in the workplace where granite is fabricated or finished.

Because some granites are more radioactive than others, EPA says it is possible that radon is present in a granite workplace at levels exceeding background radon concentrations, and that the only way to know for sure is for your employer to test your workplace. Radon is covered by the OSHA standard for ionizing radiation exposure in the workplace, which also requires employers to survey the workplace as necessary, including measurements of levels of radiation or concentrations of radioactive material present.