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Granite & Radon Information
Category: Industry News
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."
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 (K40). 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 K40, the black biotites and horn-blendes contain K40, U and Th, and the small inclusions of minerals such as zircon, apatite, sphene, etc. contain the most U and Th.
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.
Additional Radon Information
The U.S. Surgeon General and EPA recommend all homes be tested and fixed if the radon level is 4 pCi/L or more.
Find links to qualified testing and mitigation professionals in your state at the EPA website and via the National Environmental Health Association or the National Radon Safety Board. The latter two groups offer proficiency listing/accreditation/certification in testing and mitigation.
Inexpensive, easy-to-use radon test kits can be purchased in stores and online at sources such as www.radon.com.
Studies about radon's health effects can be found through the nonprofit American Association of Radon Scientists and Technologists (www.aarst.org), the World Health Organization (www.who.int), and many other locations.
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.