Hot countertops?

March 28, 2009 7:21 PM

How can we test granite countertops to ensure there are no unusually high levels of radiation? Looking for someone near Berkeley, CA who can do this for us ASAP. Who should we call?

We're in escrow to buy a new house, still in the inspection period until Wednesday. The house has granite countertops. A NYT article last year suggested that some granite may emit dangerously high levels of radiation. While others have said there's little cause for concern, and while we know the risk is actually quite low, we'd really love to know BEFORE removing inspection contingencies that there are no such problems in this house.

Does anyone know where we can find a test for this (radon machine? geiger counter?) sometime between now and Tuesday, in or around Berkeley?

posted by quinoa to home & garden (16 comments total)

I study radiation biology, and I don't think you have anything to worry about.

Between now and tuesday, you are probably out of luck. You could buy and have overnighted to you a geiger counter, there are some on Amazon. This won't tell you anything specific about what's in your granite, just give you a measure of the ionization in air. You could also show up at UC Berkley and ask a friendly grad student to run a couple simple tests for you.

If you end up buying the house without getting it tested but are curious or worried send a sample to me, I'll test it and get you some numbers on uranium and radon content and your expected dose. Just mefi mail me.
posted by pseudonick at 7:49 PM on March 28

Amazon also has radon detectors for about a hundred dollars, you could get one of those overnighted. I guess the worry is about inhaling radon, which is a uranium series decay product.

One reason to be reassured, when radon builds up in basements and things, it has all the soil beneath the house in which to build up. The volume of the marble, no matter how enriched in uranium it is, is miniscule in comparison.
posted by pseudonick at 8:03 PM on March 28

This sounds like junk science. Homes that have radon problems sit on top of thousands of feet of granite. Two inches of granite in your kitchen is not going to cause any problem.
posted by JackFlash at 9:05 PM on March 28

Lawrence Berkeley National Lab has radiological control technicians. I doubt they'd want to come survey your counter tops if you asked officially, but if you somehow got to talk to one of these techs on the phone, they might be willing to swing by on the way home on Monday as a personal favor, unofficial (no documentation). I would, for a six-pack of beer. I live in WA state, though.
posted by ctmf at 9:32 PM on March 28

JackFlash, the problem is that there are different types of granite, with different trace elements in them. In the past few years, imports of exotic granites from foreign countries have increased, and some of those granites can be pretty radioactive. Common granite from your local quarry, maybe not so much.
posted by exphysicist345 at 9:46 PM on March 28

Thanks for the tips, everyone. I'm dreaming that someone will mefi mail me and say "I'm one of those LBL techs mentioned in ctmf's answer."
posted by quinoa at 10:14 PM on March 28

Followup question: can anyone explain whether any of the items on eBay listed as a geiger counter (some are under $30) is a thing that would help me test this out myself? Or could you help interpret the results?
posted by quinoa at 10:22 PM on March 28

Try placing some unexposed film on the counter overnight then develop the film, any radiation should leave a trace as it passes through.This is how fallout was detected, bomb blasts in Utah exposed packaged film in Rochester N.Y.
posted by hortense at 10:36 PM on March 28 [1 favorite has favorites]

An article from the New York Times hardly constitutes science. This the the type of crap popular journalism that pollutes science.

You might be interested in this study.

All building materials contribute to radioactivity and radon in a home. The largest contributors are ceramic tile and the gypsum in the drywall. The contribution of a granite counter top is minuscule compared to these other sources which are much greater by volume. You would have 10 times more exposure by moving from New York at sea level to Denver at over 5000 feet than from a counter top.

Other articles by Kate Murphy, the author of the article cited by the OP include:

"Does this Song Match My Sofa"
"Love at the Door"
"A Texas Taj Mahal, made by a surgeon's hands"
"Ike leaves massive litter — of squirrels"
"Boom Times for Job Site Thieves"
"Not Just Another Jelly Bean, and Proud of It"
"Knife Skills: Creating Feasts for the Eyes"
"I Love You, but You Love Meat"
"Birder Admits Killing Cat, but Was It Animal Cruelty?"
"Demand and prices down sharply for antique furniture"
"Slabs Are Joining Scoops in Ice Cream Retailing"
"People Who Share a Bed, and the Things They Say About It"
"For the busy couple, a bathroom break"
posted by JackFlash at 11:47 PM on March 28 [4 favorites has favorites]

I reiterate, I believe any risk to you from a marble table is very very small. That said:

Geiger counters measure ionization events in air. It is basically a box full of gas with an electrical field across it, when radiation passes and ionizes the gas, positive and negative ions go in opposite directions, creating a signal that measures the ionization. If you hold them up to uranium bearing ores, or old orange fiestware plates made with uranium, or thorium lantern mantles they click like crazy. GM's are useful for detecting external radiation (radiation born in the granite that might hit you).

Buying one might reassure you the granite isn't crazily radioactive.

The current issue is not an external issue but an internal one, what people seem to be worried about here is the Uranium in the marble undergoing radioactive decay into Radium, and then into Radon gas which seaps out of the marble. The short lived radon gas might escape from the table and get inhaled. If the radon gas decays while it is in your lungs, it changes into a heavy radioactive solid that will continue to undergo a series of radioactive decays and potentially cause cancer. That sounds scary, but the relative risk is very small. You take the same risks from radioactive potassium every time you eat a bananna. And we may even have the science wrong, some people think small amounts of radiation are good for you. A recent study showed small levels of radon reduced the incidence of lung cancer.

Amazon has plug in radon sensors for ~140$ but they need 48 hours to collect data before they will give a reading. They will read in either picoCuries per m^3 of air or in Bq/m^3 of air. (Curies and Bq are the feet and meters of radiation) You can compare the number you get in the room with the EPA guideline of 4picoCuries/m^3. If you wanted to you could calculate exactly the theoretical chance you will get cancer based on whatever concentration of radon you measured in air. But that's another question.
posted by pseudonick at 12:14 AM on March 29

This is the reference to which the link should point.

Thompson, R.E.; Nelson, D.F.; Popkin, J.H.; Popkin, Z. (2008). "Case-control study of lung cancer risk from residential radon exposure in Worcester County, Massachusetts.". The Radiation Safety Journal (Health Physics) 94 (3): 228–241

The thing to understand is these risks are so ubiquitous and there are so many confounding factors, it's difficult to estimate the effects of low doses of radiation. To be conservative all regulatory bodies assume the linear no threshhold model is true. The LNT model says small doses of radiation are proportionally just as hazardous as large doses of radiation, where we better understand the deleterious effects. This may be true, it may not be. There is interesting work being done on the effects of low doses of radiation.
posted by pseudonick at 12:23 AM on March 29

No, you don't want the ebay geiger counters. Who knows if those things are even remotely calibrated to known sources? (For $30, they're not). Also, most of those are very high-range devices for use after nuclear attacks, not for detecting very low level stuff.

If you do want to do something like that, the limit is 5 mrem/hour at a distance of 30 cm from the surface to be considered a Radiation Area. Your dose limit as a member of the general public would be 100 mrem per calendar year. [cf. 10 CFR 835] To be considered radioactive material, the granite would have to contain greater than a certain activity per gram of material, which would require sampling by chipping some of it up and taking to a large, very sensitive, VERY expensive multichannel analyzer to check out - so the ebay machine won't help you there.

It's so unlikely that your granite is significantly radioactive (more than normal background levels) that I really, really wouldn't worry about it unless you had some specific reason to suspect that.
posted by ctmf at 12:40 AM on March 29

ctmf, I like most of your post, except for this comment:
No, you don't want the ebay geiger counters. Who knows if those things are even remotely calibrated to known sources? (For $30, they're not).

Those are the words of a lab rat. Calibration is about ensuring the label-claimed significant digits are still significant. This question is one of ballpark numbers.

Worked for a decade in Quality industry. Nothing wrong with lab rats - but an out-of-spec micrometer can still measure "cut into inch-sized cubes" well enough for any kitchen.
posted by IAmBroom at 7:28 AM on March 29

I'm not any sort of scientist but I wonder if it would be instructive to evaluate how much danger there would be if through some accident he happened to have gotten hold of a one-inch or two-inch slab of uranium ore, which I assume would be the upper limit of risk? Because I don't think that workers mining uranium wear lead suits or anything even though they're exposed to way more material than that every day, do they?
posted by XMLicious at 8:14 AM on March 29

Yeah, probably not a big deal. If you really want to make some kind of test, do the Polaroid film trick. This page has a number of experiments.

If it was me, I'd get a hunk of uranium ore, a piece of lead and two unexposed Polaroid "negatives". Place the hunk of lead on the suspect countertop, then place one of the pieces of film on top of it. On a nearby surface (the stove? a table?), place the hunk of uranium onto the other piece of film. After some amount of time, compare results.

The film with the uranium should show a white blob on a dark background. The countertop exposure will probably show nothing. If there is any radiation, you might get a gray background with a black glob the shape of the hunk of lead. Comparing the intensity of the uranium blob with the gray background of the countertop exposure will give you the relative radioactivity of the countertop. If you get nothing from the countertop, I'd imagine you are good. If you get anything approaching the level from the uranium, conduct further testing.

I would imagine that the easiest way to mitigate any radiation that's coming from it would be to simply make sure there is a little negative pressure ventilation in the kitchen. I believe that the type of radiation that could possibly be emitted by the countertop is alpha radiation. As you can see, it's quite dangerous, but also easily mitigated. Even is the thing was lousy with radiation, just using a cutting board or a plate would keep the stuff out of your food.

(Or get your hands on some radioactivity exposure tags that people wear in areas with radiation exposure potential. I think they are calibrated to "react" in an intensity over time sort of way. So a "flash" of high radiation will react the same way as say 8 hours of low exposure. Find out how the tags are supposed to behave at certain levels, and place one on the counter, another one on the basement floor, and another one somewhere else as a control. I would expect that none of them react at all. If they react, conduct further tests.)
posted by gjc at 9:01 AM on March 29

IAmBroom: guilty, and you're mostly right.

I'm assuming the question isn't about his counter tops being the Juarez scrap metal accident, but more about a very low, slightly-above-background over a long time issue. For that, calibration accuracy plays a part in your counting statistics and you have to adjust background and sample collection times to compensate. It's easy to get misleading results from a random process like radioactive decay.

I could make a radiac that could detect the scrap metal fiasco. I don't know if those ebay machines are legit or not. The only one I recognized was parts, not a functioning unit.
posted by ctmf at 12:17 PM on March 29