In what seems to be a genuine concern of the effects of radon emissions in residential homes, a certain website from a non-profit organization out of Houston has made it a point to imply without scientific proof, that natural stone could be a major contributor of radon in a household.
The allusion that seems to be made, that natural stone installed in your home is dangerous to your health is raised repeatedly on the website and in a recent local Houston TV news program.
It’s interesting to note that the two major contributors of this non-profit organization are manufacturers of engineered stone. One of those contributing manufacturers has a marketing executive on the board of directors of this particular organization.
From what may be perceived on the surface as perhaps another “going green” ad campaign, seems to be a different slant on the ongoing battle of the engineered stone manufacturers against natural stone.
Keep in mind that granite as does most natural components found in building material, allows vapors to pass through them that might contain trace amounts of radon. There are very small amounts of uranium found in trace minerals such as biotite in some natural stones. When quarried if a large cluster of biotite is exposed the result initially would be a radon reading. However, once a piece of granite or natural stone exposed to a large amount of uranium rich mineral in the ground is removed from the source and exposed to the air, the radon vapor transmission would weaken drastically and then dissipate. Simply put, think of natural stone as a very dense sponge that allows water, air and yes radon to pass through the stone. Once the stone is removed from the source of radon (the earth) the stone has no radon to filter through it.
We do endorse Radon testing but to allude that natural stone is a main contributor seems ludicrous.
Here are some facts about Radon:
WHERE DOES RADON COME FROM?
“Radon comes from the natural radioactive decay of radium and uranium found in the soil beneath the house. The amount of radon in the soil depends on complex soil chemistry, which varies from one house to the next. Radon levels in the soil range from a few hundred to several thousands of pCi/L. The amount of radon that escapes from the soil to enter the house depends on the weather, soil porosity, soil moisture, and the suction within the house”.
HOW DOES RADON GET INTO THE HOUSE?
“Houses act like large chimneys. As the air in the house warms, it rises to leak out the attic openings and around the upper floor windows. This creates a small suction at the lowest level of the house, pulling the radon out of the soil and into the house. (Just as natural stone filters radon emission as mentioned before.) You can test this on a cold day by opening a top floor window an inch. You will notice warm air from the house rushing out that opening; yet, if you open a basement window an inch, you will feel the cold outside air rushing in. This suction is what pulls the radon out of the soil and into the house. You might think caulking the cracks and the openings in the basement floor will stop the radon from entering the house. However, scientific studies show, it only takes enough unsealed cracks or pin holes in the caulking to equal a hole 1/2" in diameter to let all the radon in. It is unlikely that caulking the accessible cracks and joints will permanently seal the openings radon needs to enter the house. The radon levels will still likely remain unchanged.
Fortunately, there are other extremely effective means of keeping radon out of your home. Throughout the country, several million people have already tested for radon. Some houses tested as high as 2,000-3,000 pCi/L; yet, there hasn't been one house that could not mitigate to an acceptable level. The difference in reference to natural stone is that one the stone slab is removed from the source and exposed to the atmosphere the radon is vented in the same way ventilation of a house mitigates the radon emissions in the soil.
Levels of radiation from granite products, which technically are measurable, are in fact, small fractional values of established thresholds for environmental safety. 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.
Calculations show that, if an average countertop, traps an average uranium concentration of four ppm (parts per million), the concentration of radon that is given off by the countertop into the household air would be 270,000 times less than the level of radon in the outside air. The maximum contact level that you would receive over one year if you were to sit on a countertop all of the time would be about one quarter of the annual radiation from all sources. If you were just a few inches away from the granite (such as when doing the dishes), the dose would be too low to measure.
To Quote Donald Langmuir, PhD, Professor Emeritus of Geochemistry, Colorado School of Mines, & President, Hydrochem Systems Corp.
”To show how laughable are the concerns of radon emitted from natural stone, the typical granite countertop in our example will release 7.4 x 10 -7 pCi/L of air. This corresponds to 2.7 x 10 -8 atom decays per second (dps). This represents 0.85 decays per year. In other words, less than one atom of radon is produced by the countertop in one year. This is hardly worth getting excited about. I would suggest that a good way to reduce our exposure to the radon present in outdoor air would be to build an air-tight house out of granite countertops! There are certain properties of rocks that can increase their radon emanation efficiency, or in other words increase the release of radon from a given weight of rock. These are rock properties that maximize the exposure of internal or external rock surfaces to water or air, allowing any radon gas to escape. The author of 'Granite and Radon' argues that such properties, which include rock porosity, fissuring and mylonitization, will increase radon releases. This is probably true, however, a granite with such properties would be too brittle to make into a countertop, and too open to take a polish, and so would not be marketable as a countertop - unless the rock pores were first filled with a chemical sealant. Such sealing would also eliminate any possible radon release problems.”
In a more recent study that was conducted by L. L. Chyi, a Ph.D. and professor of Geochemistry and Environmental Geology at The University of Akron, Akron, Ohio. Dr. Chyi studied 13 of the most popular granites used throughout the United States as determined by an industry-wide survey. Due to their popularity these 13 granites, are believed to represent up to 85% of the granite countertop market in recent years. The granite types are as follows:
1. New Venetian Gold, Brazil; medium grained, yellow-beige gneiss with many dark red garnets
2. Uba Tuba, Brazil; A medium- to coarse grained, olive-green granite
3. Santa Cecilia, Brazil; A coarse-grained, yellow-grey gneiss with up to pie-sized, red garnets
4. Tropic Brown, Saudi Arabia; medium-grained, brown granite
5. Absolute Black, India; black basalt
6. Tan Brown, India; A black-brown igneous rock with big, shapeless, brown-red feldspar crystals
7. Giallo Ornamental, Brazil; coarse-grained, brown-yellow granulite with some brown-red garnets
8. Crema Bordeaux, Brazil; Juparana Crema Bordeaux (Brunello). A coarse- to very coarse-grained, pink to red granite with areas of quartz, alkali feldspar and quite a lot of ore
9. Baltic Brown, Finland; brown-black granite
10. Giallo Veneziano, Brazil; medium- to coarse-grained, ochre-yellow to golden-brown, also light pink, gneiss
11. Dakota Mahogany, USA; medium- to coarse-grained, brown-red granite
12. China Black, China, a fine-grained plutonic rock
13. Yellow Star, China, a medium-grained yellow to pink granite
The testing methodology was designed to measure the amount of radon which each granite type would add to the interior of a 2,000 square foot, normally ventilated home with 8 ft ceilings. The results show that Crema Bordeaux (the most active in terms of radon emissions) would contribute a concentration component of less than 0.28 pCi/L, or less than 7% of the EPA's recommended actionable level of 4.0 pCi/L. This radon amount is well below a level which might cause health concerns. Tropic Brown and Baltic Brown, second and third in radon emanation based upon Dr. Chyi’s testing, amounted to only 1% of this action level. The other granites tested added almost immeasurable amounts of radon to the house. Radon atoms in pore spaces and fractures are of minimal concern in the case of granite countertops
Dr. Chyi’s test results show that the granites that are currently found in the United States’ market place are insignificant contributors to radon levels in the home. “Based on the testing results and EPA standards, we can conclude that the most popular granites used as countertop surfaces pose no health threat to homeowners. If proper resealing is applied once a year or at other frequencies determined by the industry, the radon emanation can be further reduced”.
Daniel J. Steck, Ph.D. also ran a test on interior radon and granite, and this is what he had to say.
“The average radionuclide contents of your building material samples are similar to other average granite samples and other common earth-derived building materials such as brick and soil. Thus, the amount of gamma radiation emitted from similar masses of these building materials will be approximately the same;
There is little sample-to-sample variation in the radon family radionuclide concentrations; the radon flux is somewhat larger for the counter-top squares than for the smaller samples. This indicates that the effective diffusion length is only on the order of the thickness of the counter-top samples, i.e. several centimeters. Thus, material thicker than 5 cm (2") most likely will not emit more than the counter-top samples.
While we feel that health safety is a great concern especially in our homes, for an industry to attempt to gain financially by “scare tactics” or under the auspices of “Eco friendly” is reprehensible. We urge the consumer to not be taken in by these alarmist tactics.