MARBLEX's Natural Stone News - September Edition

It is likely that no one in the remodeling and kitchen & bath industry has gone the last month without hearing something about the "radon and granite" issue. The media has picked up on this juicy tidbit and run with it, without doing their proper due diligence or putting their results within a scientific context. So, this month, Stonetech will attempt to provide some basic facts to help you and your customers clear up some misconceptions. Note: This issue regards granite only - marble, travertine, limestone, etc. are not relevant.

First, let me say that the best overview of the truth is represented in this document presented by the Marble Institute of America: The Truth About Granite and Radon/Radiation.

The issue at hand is two-fold: Radon and radiation:

RADON:

�         Radon (Rn) is a radioactive gas which is emitted from the ground and granite through the decaying process of Radium (Ra). There is an ambient level (0.4 (picocuries per litre) pCi/L) found outside and 1.3 pCi/L found indoors. The EPA has determined that 2.0 pCi/L is the maximum acceptable indoor level before remediation should take place;

�         Different granites emit different levels of radon, ranging from very low emissions (Absolute Black, Ubatuba, Santa Cecelia) to very high emissions (Crema Bordeaux). Note: This information is based on a test of 13 materials. The bulk of the materials on the market are untested. Crema Bordeaux was tested at 292 pCi/L BUT this measurement was conducted in an airtight sealed box. This does not represent the average home, where the HVAC unit exchanges the air about 6 times an hour, doors and windows are opened, and the house itself is not airtight. What is important to note is that when the measurement is adjusted to compensate for the volume of an average home the results are quite different: A 2000 SF home with 8 ft ceilings calculates as follows (I will spare you the dilution factor and volume calculations) - 292 pCi/L X 22 � 24,000 cubic feet = 0.27 pCi/L. So, the most emissive granite thus far, Crema Bordeaux, adjusts to a radon factor level about half of the ambient outdoor radon level;

�         In one of the most current studies, the researcher found that 92 of 95 stones tested emitted negligible to no radon (http://wjllope.rice.edu/saxumsubluceo/LLOPE_StoneRadRn.pdf)

�         THERE IS NO WAY TO TEST AN INDIVIDUAL SLAB OR A LOT OF STONE FOR RADON WITHOUT A LABORATORY;

�         A radon test kit will not work for a slab. It only tests for ambient levels within the home after 27 days of exposure;

�         Any concerns over radon exposure in the home would be mitigated by a monthly opening of the windows and doors and/or a radon mitigation system;

� Summary: The amount of radon produced by even the most "productive" of granites is equivalent to half the radon exposure you would be subjected to standing outside.

RADIOACTIVITY:

�         Some granites contain trace amounts of Uranium (U), generally found within biotite (a mineral related to mica), which are the dark formations often found in certain granites. Radioactivity is the energy given off by the decaying of uranium. It is measured in terms of millirem (mRem) per hour. All humans on this planet are exposed to radiation from a variety of sources: medical, radio waves (cellular phones), cosmic energy, smoke detectors, and medical testing (xrays, etc). In fact, 11% of your annual radiation exposure comes from radionuclides found within the body. The average annual exposure for an American is 300-360 mRem/year, which equates to an exposure rate of 0.04 mRem/hr. It is unavoidable unless you live in a lead box;

�         Radiation exposure is a cumulative effect. Exposure to different sources over time "adds up." The concern is that granite provides an unnecessary additive effect to annual radiation exposure;

�         Like radon, there is a "background level" of radiation found in the average home. Almost all granite tested falls well below this background level and most studies agree that the additional effect poses no increased risk;

�         It is possible that certain spots on certain slabs maybe "hotter" than other areas of the slab. These areas tend to be very small. The cumulative effect however is very negligible. The rate of occurance is very, very rare.

�         The bottom line is that radiation is everywhere and there are no meaningful concerns within the scientific community. As a comparison - 2 mRem/yr comes from sleeping next to someone for 8 hours a night, about as much as a radioactive hot spot! So unless your customer plans on sleeping over the hot spot for 8 hours a night, there is not much cause for concern.

In closing, there is much research left to be conducted. The solid surface and quartz industries have a vested interest in reduced demand for natural stone products. There will be an ongoing debate within the trade and scientific communities for some time to come.