Al Gerhart
New Member
What a great thread on this subject!
Hello,
I am pretty deep into this subject, and can answer a lot of questions on the subject if anyone has any. Keep in mind that I am helping many of the researchers looking into this, so I have some stuff available that isn't published yet.
There are studies out there on the Radon emanation from granite, ranges from nothing to thousands of pCi per square foot per hour. The record was Stan Liebert's find in the Sugarman home in up state NY, the case used for the NY Times story. As to research papers, well, even the Marble Institute's study done by Dr. Chyi found a .27 pCi/L increase in a homes level if a small amount (13 linear feet) of Crema Bordeaux is used in a 2,000 square foot home. Now, there were many problems with that study, as it was paid for by the MIA, it was expected to support their position, but it shattered their previous claims of no Radon from granite, or immeasurable amounts.
At the AARST conference (American Association of Radon Scientists and Technologists), there were two studies specifically on granite countertop radtiation and Radon, and two discussion sessions on what to do about the problem.
One study, by Bill Brodhead, showed over 500 pCi/sf/hr of Radon coming from one of the samples I provided. Bill calculated that in the right circumstances, a small tight home, a small countertop, the Radon levels could hit 4 pCi/L. Now most granites aren't his bad, they range from very little, say 8 pCi/sf/hr and up. But no one is concerned about the safer granites, it is the hot ones that need taken off the market.
Another study was by Dr. Mike Kitto, who showed several startling discoveries. Mike had accepted a grant from Sensa, a natural stone company (also owned by Silestone, or C & C North America to be precise), and studied thirty or forty stone samples and some of the quartz products as well. The study was set for peer review after the conference, but then something happened.
Back in May, I had shipped a sample of Niagara gold granite, from a remnant purchased from one of my competitors. At 220 uR/hr, it was pretty hot but I had no way to test for granite. So I sent a large section to Brodhead for testing, who cut it in half, sending half to Dr. Kitto at the NY state Health Dept. Broken in shipment, half was tested, the other half appreared in the NY Times story and on the CBS Morning show a bit later.
That Niagara Gold sample hit over 500 pCi/SF/hr, which convineced the researchers to keep looking. Later I sent more samples to both Brodhead and Kitto, as well as other scientists leading the effort. So Kitto stopped the peer review, reopened the study to include samples other than what he was provided with initially by the stone company.
Another amazing result from Kitto's study was that one could put a high Radon producing granite slab under a low Radon producing slab and the Radon from the lower would penetrate the upper slab easily. What we think as "solid rock" is anything but. As a fabricator, I can tell you that water soaks right through, so I guess it shouldn't have been a surprise.
On the radiation issue, well the hottest found to date was around 17 mR/hr, with one hot spot cored out (2.5" diameter core) that hit 1.080 mR/hr. One hundred hours of contact, or less than 30 minutes a day for a year, would put you over the 100 mR per year additional radiation dose recommended by the experts.
The average granite out there is under 20 uR/hr gamma, or around .2 or .3 mR/hr if you count all radiation. If you look at it in terms of background radiation, the "safe" granite will double, triple or quadruple your radiation that you get from natural sources all around you. As a granite fabricator, we have a limit of 25 uR/hr gamma, mainly out of concern for our workers.
Sensa has used this as a marketing tool, 300 cpm or around 53 uR/hr gamma is their limits for fabrication and sale.
Sorry for the long post, but I felt the info needed to be out there. Let me know if I missed anything. I'll end my saying that many of the granites out there are perfectly safe, but the problem is that we don't know which ones are dangerous.
For more info, solidsurfacealliance.org solidsurfacealliance.org/blog
Thanks,
Al
Hello,
I am pretty deep into this subject, and can answer a lot of questions on the subject if anyone has any. Keep in mind that I am helping many of the researchers looking into this, so I have some stuff available that isn't published yet.
There are studies out there on the Radon emanation from granite, ranges from nothing to thousands of pCi per square foot per hour. The record was Stan Liebert's find in the Sugarman home in up state NY, the case used for the NY Times story. As to research papers, well, even the Marble Institute's study done by Dr. Chyi found a .27 pCi/L increase in a homes level if a small amount (13 linear feet) of Crema Bordeaux is used in a 2,000 square foot home. Now, there were many problems with that study, as it was paid for by the MIA, it was expected to support their position, but it shattered their previous claims of no Radon from granite, or immeasurable amounts.
At the AARST conference (American Association of Radon Scientists and Technologists), there were two studies specifically on granite countertop radtiation and Radon, and two discussion sessions on what to do about the problem.
One study, by Bill Brodhead, showed over 500 pCi/sf/hr of Radon coming from one of the samples I provided. Bill calculated that in the right circumstances, a small tight home, a small countertop, the Radon levels could hit 4 pCi/L. Now most granites aren't his bad, they range from very little, say 8 pCi/sf/hr and up. But no one is concerned about the safer granites, it is the hot ones that need taken off the market.
Another study was by Dr. Mike Kitto, who showed several startling discoveries. Mike had accepted a grant from Sensa, a natural stone company (also owned by Silestone, or C & C North America to be precise), and studied thirty or forty stone samples and some of the quartz products as well. The study was set for peer review after the conference, but then something happened.
Back in May, I had shipped a sample of Niagara gold granite, from a remnant purchased from one of my competitors. At 220 uR/hr, it was pretty hot but I had no way to test for granite. So I sent a large section to Brodhead for testing, who cut it in half, sending half to Dr. Kitto at the NY state Health Dept. Broken in shipment, half was tested, the other half appreared in the NY Times story and on the CBS Morning show a bit later.
That Niagara Gold sample hit over 500 pCi/SF/hr, which convineced the researchers to keep looking. Later I sent more samples to both Brodhead and Kitto, as well as other scientists leading the effort. So Kitto stopped the peer review, reopened the study to include samples other than what he was provided with initially by the stone company.
Another amazing result from Kitto's study was that one could put a high Radon producing granite slab under a low Radon producing slab and the Radon from the lower would penetrate the upper slab easily. What we think as "solid rock" is anything but. As a fabricator, I can tell you that water soaks right through, so I guess it shouldn't have been a surprise.
On the radiation issue, well the hottest found to date was around 17 mR/hr, with one hot spot cored out (2.5" diameter core) that hit 1.080 mR/hr. One hundred hours of contact, or less than 30 minutes a day for a year, would put you over the 100 mR per year additional radiation dose recommended by the experts.
The average granite out there is under 20 uR/hr gamma, or around .2 or .3 mR/hr if you count all radiation. If you look at it in terms of background radiation, the "safe" granite will double, triple or quadruple your radiation that you get from natural sources all around you. As a granite fabricator, we have a limit of 25 uR/hr gamma, mainly out of concern for our workers.
Sensa has used this as a marketing tool, 300 cpm or around 53 uR/hr gamma is their limits for fabrication and sale.
Sorry for the long post, but I felt the info needed to be out there. Let me know if I missed anything. I'll end my saying that many of the granites out there are perfectly safe, but the problem is that we don't know which ones are dangerous.
For more info, solidsurfacealliance.org solidsurfacealliance.org/blog
Thanks,
Al
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