Marble Institute of America Consumer Information

Granite and Radon Information

In the past few days, a television video has circulated online that has created widespread consumer confusion and concern about radiation levels occurring in natural granites used for residential countertops. The report suggests some countertops may pose health risks, ignoring years of legitimate and independent scientific research that has concluded that natural stone is perfectly safe to use in homes.

It’s misleading to even hint that we would knowingly sell a product that might harm consumers! The report was prompted by a group that claims to be independent, but is actually funded by two companies that manufacture synthetic stone countertops made of quartz gravel, resins, coloring agents and other chemicals.

Unlike these competing synthetic products, granite is not manufactured in a plant by combining quartz gravel, resins, coloring agents and other chemicals. Throughout the years, consumers have been drawn to natural stone’s beauty, durability, cleanliness and safety.

It’s outrageous that manufacturers of synthetic stone countertops would use a front group like this to scare consumers. It is also alarming that manufacturers of a competing product feel they can only compete by groundlessly creating fear about natural stone, which is safe, beautiful and superior.

How does radon get into a building?
(from the National Safety Council)

"Most indoor radon comes into the building from the soil or rock beneath it. Radon and other gases rise through the soil and get trapped under the building. The trapped gases build up pressure. Air pressure inside homes is usually lower than the pressure in the soil. Therefore, the higher pressure under the building forces gases though floors and walls and into the building. Most of the gas moves through cracks and other openings. Once inside, the radon can become trapped and concentrated.

"Openings which commonly allow easy flow of the gases in include the following:

Cracks in floors and walls
Gaps in suspended floors
Openings around sump pumps and drains
Cavities in walls
Joints in construction materials
Gaps around utility penetrations (pipes and wires)
Crawl spaces that open directly into the building

"Radon may also be dissolved in water, particularly well water. After coming from a faucet, about one ten thousandth of the radon in water is typically released into the air. The more radon there is in the water, the more it can contribute to the indoor radon level.

"Trace amounts of uranium are sometimes incorporated into materials used in construction. These include, but are not limited to concrete, brick, granite, and drywall. Though these materials have the potential to produce radon, they are rarely the main cause of an elevated radon level in a building." (http://www.nsc.org/library/facts/radon.htm)

The truth of the matter is that granite is a safe product. It's been used for thousands of years and the relationship between granite and radon has been studied for years and years. How safe is granite? There have been mathematical models developed that show that one could live in an all-granite home or building, including sleeping on granite, for an entire year and still be within very safe levels of exposure. Nonetheless, the Marble Institute of America has produced a brochure to help you understand granites, radioactivity and natural stone.

Radioactivity in Granite: It’s Natural

All rocks have a small amount of radioactivity in them due to the presence of minerals that contain radioactive elements uranium (U), thorium (Th) and potassium-40 (40K). Because granite typically contains more of these elements than most other rocks, it will be more radioactive than a slate or marble. All of the minerals in granite contain some radioelements; the white or pink feldspars contain 40K, the black biotites and horn-blendes contain 40K, U and Th, and the small inclusions of minerals such as zircon, apatite, sphene, etc. contain the most U and Th.

Some Frequently Asked
Questions and the Answers

Q. What is radiation?

A. Radiation is energy that is transported as waves or particles. This includes visible light, infrared, ultraviolet and microwaves.

Q. What are the sources of nuclear radiation?

A. There are natural and man-made forms of radiation. Natural radiation includes cosmic radiation and emissions from radioactive elements in the earth, radon gas in your home, some foods and well water. Man-made radiation comes from dental x-rays, medical diagnostics and treatment, the remains of nuclear bomb testing, emissions from nuclear reactors, radioactive elements in drywall and concrete and cigarette smoke. The pie chart included in this brochure shows the approximate contribution of each of these to your annual radiation dose.

Q. What about food that is prepared directly on the granite surface? Is there a chance that it could absorb radioactive energy, which later would be ingested by those eating the food?

A. The only way that radioactive elements such as uranium can get into the food is if they became dissolved in water and absorbed in the food. However, granite is one of the most insoluble materials known to man and the amount that could be dissolved is miniscule in comparison to the radioactive elements that are already in the food (in meat or from uptake by soil or air-born particles during growth). Radioactive energy given off at the granite surface will enter food that is directly in contact with the surface but, like all energetic rays, it changes into heat and/or non-radioactive particles. These processes happen quickly so the radiation does not remain in the food.

Radiation: It’s All Around Us

It's in the air we breathe, in the water we drink, in the soil and rock we stand on, and in the sun's rays we like to bask in! Added to this is the radiation we get from man-made sources, such as x-rays, medical treatments, building materials, etc.

Radiation in Granite is Not Dangerous

From what we know, there are two ways in which countertops, tiles and other finishes made of granite might emit any level of radiation. The first is by the release of tiny amounts of the radioactive gas radon which can be inhaled. The second is by direct radiation from the surface itself to the homeowner. In both cases, the radiation emitted is from the same process - natural radioactive decay of one element into another. Compared to other radiation sources in the home and outside, the risk to the homeowner from radioactivity emitted from a granite countertop or tiles is practically non-existent. In fact, the amount of radon gas emitted by a granite countertop is less than one millionth of that already present in the household air from other sources.

Typical Contributions to
Radon Content of Indoor Air (pCi/L)

If you have further questions about radon and granite, contact the Marble Institute of America at 440-250-9222, send an email to miainfo@marble-institute.com, or visit www.marble-institute.com

About the Marble Institute of America
For over 60 years the Marble Institute of America (MIA) has been the world's leading information resource and advocate for the natural stone industry. MIA members include marble, granite, limestone, sandstone and other natural stone producers and quarriers, fabricators, installers, distributors and contractors around the world.