Once a granite has been tested, can all slabs of that type be considered safe?
June 5th, 2008
Think of the earths crust as a big mixer, or like a bunch of big mixers side by side. Some mixers will run longer, so the mixture might be pretty uniform. Other mixers might get bumped on once or twice, leaving little uniformity in the mix. Some mixers might have new ingredients added right before the end, resulting in veins or pockets of materials.
Granite can be uniform, but usually it isn’t. Some of the more uniform types are Absolute Black or Uba Tuba. These tend to test in a narrow range. But even within a single quarry, Uba Tuba will vary widely in color and quality, from quarry to quarry, the difference is even more pronounced.
Some granites are conglomerations, lots of movement and colors happening. These types of granite are the most unpredictable. I have seen slabs that test 15uR/hr on one spot, test 150 uR/hr on wide portions of the slab, then test 800 uR/hr on hot spots.
Currently, only a four or five hundred samples or so have been tested and reported worldwide. Some of the more comprehensive tests tested 80 stones or more, others tested a dozen or less. To my knowledge, no one but the SSA has ever tested multiple samples of the same type granite to find a range the stone usually tests in. So this science is in its infancy, too soon to say that any particular stone will always test safe.
To complicate things, the granite industry tends to be very fragmented. Sometimes a farmer opens a quarry, sells blocks to a processor that slices and polishes the slabs, then an importer buys the slabs and imports them, reselling to a slab yard or fabricator. In china, a licensed trader has to export the slabs, adding a another layer to the supply chain.
The importers, slab yards, and even the fabricators don’t want people shopping around on price, so they tend to use different names for the same stone. Called the name game, this can be a problem to consumers. You find a nice stone, but can find it in only one slab yard. Sometimes you can’t find any info at all on the Internet on your choice of stone. This becomes important for testing, who knows the real name of the stone so it can be tracked back to the quarry?
Plus, is there a chance that once a stone is know to test high radiation, nothing keeps the sellers from just changing the name so the stone can be sold. Our granite suppliers tell us that the stone industry is one of the most corrupt industry’s around. The going rate for bribing an inspector/agent is 4% of the value of the slab, so a $10 bribe will get a substandard slab left on the shipment instead of being rejected.
So, to be certain, we recommend that all slabs be tested prior to purchase. Our shop insists on this. It just makes sense given the expense of the projects.
7 Responses to 'Once a granite has been tested, can all slabs of that type be considered safe?'
Leave a Reply
You must be logged in to post a comment.
on June 7th, 2008 at 8:55 am
EDIT NOTE: The following posts were reinserted after the site had to be removed and reset due to a conflict with our main website. The original poster was MustangLippy.
June 5th, 2008 at 1:02 pm
Hello! Interesting information. As a homeowner about to embark on a kitchen remodel I have a few questions if you’d be kind enough to help me out please:
1) Is there a comprehensive list somewhere on the web (I have not found it) ranking the granites according to their mR/hr?
2) We are contemplating installing Verde Butterfly. What are is the mR/hr on it?
3) I understand Uba Tuba and Absolute Black are usually low risk. Can they still have hot spots?
4) A local radon remidiator told me that testing the granite in the fabricators yard wouldn’t tell us much. He said we’d need a test protocol where the environment that the slab is in would have to be tested with the slab removed and then with the slab in place. The area would have to have closed house conditions during both tests. Can we really determine the radon levels that will be emitted by testing the slab in the stone yard?
5) Which would be the more feasible route? Install the granite and buy a radon meter to continuously monitor radon levels in our home or go to the granite yard with a geiger counter?
6) Would you install Uba Tuba or Absolute Black in your home?
7) Would you install Verde Butterfly?
Do you know of any fabricators in the Raleigh/Durham NC area that test their granite?
Thanks much!
Angela
(Edit note: This comment was inserted by the administrator after the site had to be reset. Original poster was MustangLippy).
on June 7th, 2008 at 8:56 am
MustangLippy Says:
June 5th, 2008 at 1:06 pm
Sorry, one more question.
All granite emits radon. If you have good ventilation in your home is this enough to disperse the radon so that it is not harmful?
on June 7th, 2008 at 8:57 am
Al Says:
June 6th, 2008 at 1:00 am
Hi Angela,
1) There is no comprehensive list of tested granites on the internet, or anywhere else for that matter. The SSA has tested around 100 stones so far, some of which are duplicates. Duplicate testing is important, to build an expected range for a particular granite.
In the coming days, I will start to post what data we have. Some of the data was from our Callibrated Geiger counter, and reads in mR/hr, some data came from our PM 1703 scintillators and is in uR/hr. I’ll post on the differences.
Check back in around the tenth of June or so.
2) Verde Butterfly has been tested twice, once with a scintillator, which measures only the Gamma content, not the Beta or Alpha. That test showed 20 uRhr over background. The other test was using the Geiger counter, 360 cpm, or .6 mR/hr for Alpha, Beta, Gamma.
3) Uba Tuba has been tested several times, .2 , .25 , .4 , and .6 mR/hr for Alpha, Beta, Gamma. Gamma only tests resultied in 8 and 11 uR/hr, pretty quiet on Gamma.
Absolute black has been tested at .14 mR/hr Alpha, Beta Gamma.
Both Uba Tuba and Absolute Black tend to be very uniform through out the slab, so while some slabs are hotter than others, there haven’t been many hot spots turn up so far.
4) If all you have is a hammer, every problem looks like a nail. The Radon guys are professional at what they do, measuring Radon in homes, but they sometimes don’t know alot about measuring radiation itself.
The Radon mitigator was correct that testing before and after would be useful, but don’t you really want to know about a problem before you spend thousands of dollars on the top? The closed house is needed, since air currents and even humidity from humans can affect the readings.
Some testing has been done for Radon emission only, but the results vary widely depending on samples. Some studies say that Radon is emitted in the same percentages as the Uranium content. Other studies claimed 80 or 90% Radon emitted compared to the Uranium content. Other studies said less emission. Again granite is a natural product, no way to know which sample or slab will have more Uranium, thus more Radon emission than the other.
All that said, one fact remains, that the Uranium content will vary widely in granite from slab to slab. Measuring the radioactivity will tell you how much is present, but it won’t tell you where the radiation is coming from. It might be Uranium, where Radon comes from. It might be Thorium, where Thoron comes from (another radioactive gas, less deadly though), or it might be from Potassium 40.
Ah, heck, still no answer, huh? The variation from slab to slab means that YOUR slab has to be tested for Radon if that is the highest concern. This can be done with an electric Radon meter. Put the sample in an air tight container (one test used plastic buckets with tight lids, paint buckets) with the meter, and watch it for a few days through a plastic tape covered window cut in the side.
5) If you can afford to replace the countertop, installing first would be a very accurate way to find out the Radon emission. But, were I you, I would use a Geiger counter to find the lowest level granite in the color you want. Cheaper…
Here is a link to your states Radon map, from the EPA site.
http://www.epa.gov/iaq/radon/zonemap/northcarolina.htm
If you live in one of the red or orange zones, you might want a Radon meter anyway. Home Safety Systems sells a good one, it isn’t EPA certified, but it is the same meter that others sell that have had the EPA certify their products. Not sure how that works, the certification, but the meters look identical, probably are. In any case, it will be accurate enough for our purposes.
6) Absolute Black would be my choice for my home if I was just concerned about radiation or Radon, but do your homework. Lots of doctored slabs out there, it UV fades (we keep one in the showroom that has done it), and it can etch if it has any calcite in it. Do the lemon juice test before buying it, in several places on the slab. If they try to stop you from doing it, leave the yard and shop elsewhere. Some acetone on a rag will tell you if the slab has been dyed or doctored, same deal, if they put up a fuss, what does that tell you.
But if the question was about which stone made a better top, I would have to say Uba Tuba because of the etching and UV problems that AB can have. I’ve yet to find one that didn’t UV damage, the etching isn’t as common.
7) No, I would chose Uba Tuba or Absolute Black over the Verde Butterfly, unless I could find a low level Verde Butterfly. Still with only two tests done on Verde Butterfly, that might change.
I don’t know of any fabricators in your area, will see if anyone I know in the trade knows of a trustworthy shop. Might pay $25 for your local Angieslist.com membership to see what the local consumers say about who ever you decide to go with.
On your last question, I think it is too soon to say that ALL granite emits Radon. The testing just hasn’t been done. But it is a safe bet that most granites do emit some Radon. Ventilation in the home helps prevent Radon from building up to equilibrium levels, but it doesn’t prevent the exposure when standing near the granite top.
Here is a very crude way of putting it, but it usually makes sense. If the family dog has gas, the further away Fido is the better, but it eventually dissapates through out the room. Radon is a gas as well, concentrated dose near the point of emission, spreads out through out the home eventually. Will you breath more in if you are standing over the top for thirty minutes or if you breath the diluted dose while sleeping at night? No one really knows.
We are working on acquiring the Radon testing equipment,but at this time,we have few answers but the studies written on the subject.
For now, testing the radiation content is the only way to sort the possibly good from the possibly bad.
I will look back through the scientific studies this weekend and see if Uba Tuba, Absolute Black, or Verde Butterfly has been tested. Check back by mid week.
Thanks for the excellent questions,
Al
on June 7th, 2008 at 8:58 am
MustangLippy Says:
June 6th, 2008 at 11:48 pm
Hi Al,
Thanks for the thoughtful response. I particularly liked the dog analogy. I’ll have to remember that when explaining all this to my husband.
I’ll look forward to an explanation behind the meaning of mR/hr and uR/hr. If you could please couch it in terms that a liberal arts major can understand that’d be terrific (can I get you fries with that?).
I just wanted to share with you my experiences at two different fabricators today.
The first I found on Angie’s List. They sell granite, Zodiaq and other solid surface countertops. When asked if I was interested in granite I explained that I was hesitant because of the question of radon. The lady helping me looked puzzled but her colleague, who happened to be in the room, chipped in with “oh, I read that report. It was commissioned by competitors to granite. There’s nothing to it.” When I said that actually there was more than one report she just pooh-pooh’ed me and the notion and left the room.
Great customer service huh? Especially ironic as they could just have said “really, Radon worries huh? In that case let me guide you over to our excellent selection of quartz countertops.”
The second fabricator was recommended by a work colleague. I’d already been talking to him about Verde Butterfly, and he had it out in his shop ready for me to view. It was stunning. I could have hung it on my wall as art just as it was. I sadly explained to him my concerns about Radon expecting to be dismissed as a fruit-loop again. Especially as the only medium he deals in is granite so if I don’t want granite he’s lost a sale.
Nothing of the sort. He knew nothing of the issue but was interested. Asked me to pull some information together for him. If I wanted to run around his yard with a geiger meter I don’t think he would have stopped me. I think he’s just relieved he’s not married to me.
Upshot is I have decided to go with Uba Tuba. Not as pretty but I’ll sleep better at night. Especially with the radon meter I am installing.
on June 7th, 2008 at 8:58 am
Al Says:
June 7th, 2008 at 7:32 am
Angela,
I asked one of our scientist friends if he had any data yet on Uba Tuba or Verde Butterfly. Most of the data can’t be released, but I might get a yea or ney on these two colors for you.
No promises though…
on June 7th, 2008 at 8:59 am
MustangLippy Says:
June 7th, 2008 at 7:59 am
Tell him I’ll send homemade chocolate brownies….or a picture of my darling children who don’t want Mommy to irradiate them so her kitchen can look pretty.
Seriously, when will all the data he is collecting be published? Is there a timeframe? And what about the non=profit that is also doing the study in the Houston area. Any timeframe on that?
Angela
(Edit note: This is the last of the insertions needed after the site was reset)
on June 26th, 2008 at 3:46 am
Angela,
An update on the Houston testing effort. They have tested over 100 homes so far, found a few countertops of concern. More homes are waiting, but the lack of certified Radon technicans is slowing the work.
Not sure on Dr. Llope’s work.