If I may present a female perspective on use of a kitchen... I have heard many men say "no one actually touches the granite". Not a single woman has expressed that opinion. Anyone who spends much time in a kitchen knows that cooks are indeed in regular contact with their counter tops.
This morning I was in the kitchen of a woman that was concerned about her granite. The hottest spot was near the edge of a granite table top where she anticipated spending several hours a day. She indicated she would be seated very near the granite, abdomen possibly touching the edge, often leaning over the top of the granite. Her breasts and internal organs would be exposed to gamma radiation for several hours each day. Most women would not consider that situation acceptable.
I surveyed another home where a 15-year old boy spent several hours a day sitting on the granite island. One of the hotter spots in that home was where the young man spent much of his time. Daily exposure to gamma radiation does not seem a good thing for his future progeny.
In yet another home I saw elementary age children seated at a granite bar for extended periods of time, doing their homework and playing games. Fortunately, the granite in that home was not particularly radioactive. The mom decided to have her children do their homework at a wooden table, just to minimize any small risk.
This forum has been consistently hostile toward persons taking field measurements. There has been little assistance to those of us trying to develop a standard protocol and collect data according to that protocol. Before the "esteemed gentlemen" of the forum tell me yet again that I am not bright enough to determine whether 500 is greater than 10, please consider whether you would wish your wives or grandchildren to be the guinea pigs in this experiment.
Linda Kincaid
On Wed, Dec 3, 2008 at 7:41 PM, al gerhart wrote:
Mr Johnson,I don't know of anyone using a pancake probe for measuring granite and claiming major hazards. We are using scintillators, and on the occasions we do use a pancake, we offer shielded measurements along with the raw readings. The Gamma spectrum readings can't be tarred with that brush either. And a strong enough Beta source has it's own set of potential problems.
The PM 1703 is completely capable of being used as a trip wire for granite fabricators and consumers. We are running Arrow Tech dosimeter readings on the slab we are using for the full scale Radon test and if anything, the results are mostly conservative. Here is the latest readings, in urem/hr.
http://forum.solidsurfacealliance.org/download/file.php?id=237&mode=viewor for the entire thread, here http://forum.solidsurfacealliance.org/viewtopic.php?f=7&t=56&p=338#p338
I appreciate the expert advice, but sometimes what is needed is a close answer NOW rather than an accurate quantitative measure that might be 30% lower. No one is ripping out thousands of dollars of granite on the say so of a quick test, but having the Radon guys doing a quick scan that homeowners can afford is better than knowing nothing, if only for the reduction in stress.
And yes, calibration is important along with the over response of the PM 1703, but factoring in the small amount of the total radiation that the PM 1703 is capable of reading and the readings are still very conservative. A ten minute gamma spectrometry run will hit a half million counts, sometimes over a million counts in ten minutes, or 50 to 100 thousand counts per minute. compared to eight thousand counts off a pancake probe. Slice it anyway you want, the meter over responds to what it measures by some percentage, but it isn't coming close to counting more than 8 to 16% of the total radiation that a small crystal gamma spec can pick up. Dr. Llope says we could be reading far less, from 2 to 3% of the total radiation.
As to the geometry of the measurements, countertops are in close contact to the genital regions when used, or right over your lap if sitting. I would think that the protocols for radiation work will need rethinking before applying to this topic. Or are the nuclear plants making workbenches and desk tops out of their extra waste? As for distance and dose, our pancake can read radiation out to six feet and more, from a 200 uR/hr granite hot spot. And the scintilator is sensitive enough to hit 30 uR/hr walking around some slab yards. If there is any Bordeaux within twenty feet, forget about measuring other stones nearby unless you isolate.
Here are some distance readings. Niagra Gold, around 200 uR/hr on contact4 inches 2280 cpm12inches 840 cpm24 inches 600 cpm36inches 480 cpm60 inches 180 cpm72 inches 120 cpm
Background during tests was 60 cpm.And if I hear the phrase "lay on a granite countertop" again, I'm gonna start screaming. It is one thing to ridicule something when you have all the data, it is another to measure a handful of stones, even a handful of slab yards, and base one's opinion on such limited data.
And there are guidelines for building materials including granite countertops. China has them, so does most of the EU. One can argue that the US doesn't have any guidlines, but for the clean up requirements for industry or the nuclear power industry to have any integrity, they should be applied to granite countertops as well. Do that or raise the clean up levels. Just don't continue the hypocrisy. If the granite industry is advocating 30 mrem yearly maximum, as they did in the latest MIA study, a granite countertop at 50 uR/hr will get you there in 150 days. ALARA and plain old common sense says that selling radioactive consumer products is not a good thing.
Fiesta ware and lanterna mantles are poor arguements as well unless you have several tons of the darned things in your home. I've done four slab countertop jobs before (4,000 pounds), but I've seen floors, showers, vanities, window sills, even entire rooms covered with stone. I suggest that despite good intentions, the risks are being minimized by those without knowing the extent of the problem. At AARST, Air Chek had a small core sample, maybe 2" in diameter, putting out 1 mrem. What else is out there?
Radiation safety measurements should be regulated by the state, but meters aren't. If someone is willing to do a survey, then call an expert if something concerning is found, how is the public harmed in anyway? Should we then take the alarm meters from our first responders? They might start a panic with them after all. Good lord, if you can read a digital clock, you can understand what the meter is telling you.
All I am saying is measuring one granite yard doesn't qualify you as an expert. No one is agains nuclear power, everyone advocates measuring whole house Radon when checking granite countertops, so why not use this controversy to educate people about ALARA and show that you just might get more exposure from your granite countertop than you will get from living next door to a power plant.
Respectfull, unless I hear "lay on a granite countertop" again.AL
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-- ________________________Linda Kincaid, MPH, CIH Industrial Hygiene Services20255 Glasgow DriveSaratoga, CA 95070(408) 998-4642
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