My granite countertops and radiation test results

9 years ago

I tend to like gadgets so when I was on Amazon buying something else and a Geiger counter for $200 was suggested I read the reviews to see if it worked on granite counters. People said it did so I ordered it.

Turns out my kitchen (beige and black splotches) at .17- .22 uSv/h are normal like background.

My granite topped buffets (black with grey speckles) are normal at .17-.18.

But my bathroom counters at .30-.32 are a little higher. They are a sandy beige with medium pattern.

A single brown granite tile on the top of a portable humidifier is .22-.26.

When set on an open drawer about a foot away from the bathroom counters the reading is .18-.21.

The chair seat in front of the bathroom counter is .19-.25.

The tub which has tile is at .18.

My table in front of the computer where I'm typing this is .16-.22.

On top of my dog crate is .18.

Near the head of my bed on the side table is .16.

The guide that came with it says:

.10 is as low as it gets

.21 is pretty normal for background and depends on local geology

.42 happens occasionally and to keep an eye on it.

.83 is an alert and to stay out of the rain and unnecessary trips

1.25 risk of cancer if exposed for a year

4.17 risk of cancer if exposed for 90 days

20,000 annual limit for nuclear workers

100,000 annual limit for Fukushima workers

If anyone has done some testing and wants to share I'd be interested in the range. My husband went shopping with his brother for granite so I gave them the Geiger counter and they did report two hotter slabs at .44 and .46 but most were about .28. I'll have to go myself at some point to check it out.

I'm very pleased with both my kitchen and the buffet tops. I am considering a remodel for the bathroom as I had only refreshed it when I put the granite in and now I want a new tub. I will probably change out the granite tile on the humidifier for a porcelain tile that doesn't radiate at all.

Featured Answer

karin_mt

9 years ago

Not really. In 2008 there was a big dustup about it. But real data is always interesting and relevant, no matter what year it is. :)

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Comments (14)

karin_mt
9 years ago
That's excellent! We've talked about this topic several times but none of us has ever actually measured anything. It's always more useful and fun to have actual numbers. Maybe you could open up a little service to help out those who are worried about this? (I'm kidding, but it's actually not the worst idea ever.)

Thanks for sharing your results!
mmmm12COzone5
Original Author
9 years ago
Actually my dad suggested I do just that to recover the cost of the meter. I felt it might complicate my taxes or something but I would measure my neighbors counters for free or a lunch out. :-)
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PRO
Joseph Corlett, LLC
9 years ago
This is so 2008...
mama goose_gw zn6OH
9 years ago
mmmm12, do you have kids? I see great science fair project potential. ;)
mmmm12COzone5
Original Author
9 years ago
Interesting idea. I bet it would make a good project.
Nothing Left to Say
9 years ago
Science fair project that requires a trip to a stone yard. That's genius!
LE
9 years ago
Do they say what they expect the variability around the measurements to be. A lot of those look like essentially the same number. Also, as you probably know, most "granites" are not granite at all. But I always like real data as well, although I figure the cosmic radiation from a single airline trip is much more of a contributor to my rad dose than my counters unless they come from a uranium deposit...
mmmm12COzone5
Original Author
9 years ago
The Geiger counter is counting the particle hits. A solid square flashes when it gets a hit. You get your first reading in 10 seconds. Then the reading updates every ten seconds. The device draws a little square and when the square is complete (40 seconds) then that is considered an accurate reading. Depending on what is emitted at a particular time your reading can go up or down a little bit. I think the market isn't counter top purchasers but rather those affected by Fukushima and the like.

I imagine if I let it sit for a long time in one location it would drift into a single time averaged number. I posted the range to show the variability in the measurements and where they overlapped. It beeps sometimes when it gets alot of hits in rapid fire. There is an alarm mode that you can set to a threshold. My guess is that when you get a lot in rapid succession it thinks it is going over the alarm threshold and starts giving audible hits. It is default set to .3. My husband said when he put it up near hot granite he got the beeping and I get it in the bathroom granite.
LE
9 years ago
Yes, I think you are right that the length of time for each measurement is another variable. A longer term average would be a better measurement. You'd also likely see small variations from taking measurements in slightly different locations, depending on how large a field the instrument is measuring and how variable the composition of your "granite." If the Geiger counter is for measuring Fukushima-level radiation, it could be considered of "screening level" accuracy-- what you need is a go- no go decision, so getting that quickly would be more important than precision or accuracy either one.

I don't understand the point in the guide that says "stay out of the rain" though! Because it is assuming you are concerned with fallout?
mmmm12COzone5
Original Author
9 years ago
last modified: 9 years ago
Good point! I should have mentioned that when I took the measurements I did them in different places on the counters, at the ends, near the backsplash, in the middle etc. The range I put up reflects the different locations. When I took them I set the Geiger counter down and walked off. I then came back and took a picture with my camera so I could remember where the measurement was. The time that elapsed before I came back was variable but longer than 40 seconds. Could have been minutes or hours (as in the case when I left it out on the deck to get an outdoor measurement .17). Or when I left it in my built in Japan car which also was .17.

Yes I think the .83 guideline pertains to putting it outdoors to check conditions. If you see it that high they suggest you stay indoors for optional trips and not go out in the rain no matter what.

Given that my husband did see one slab at .6 I would probably change that out if I had it. My kitchen and buffet tops are fine but I must admit I look at my bathroom granite a little differently given that it sets off the alarm and comes it at .3 ish. It is probably fine for it to be that high but I don't mind using it as an excuse to remodel. The decorative granite tile that was on my humidifier has already been relocated to the garage. I don't need even that little extra bit of radiation next to anyone sleeping.
fouramblues
9 years ago
I'd be interested to see a bunch of measurements from the same exact spot, to see what the expected variability of the measurement is. Interesting thread!
mmmm12COzone5
Original Author
9 years ago
last modified: 9 years ago
Some pics to show you what my granite looks like and readings.

Kitchen granite (above)
Black and grey granite on buffet furniture(above and below)
Kitchen granite (above) another location

Brown granite tile on humidifier (above - lower reading. below - higher reading)

Bathroom granite (above and below).

Surface of my chair in front of bathroom granite.

In going back through my photos I misrepresented the bathroom granite. I have a .25-.28 reading on the narrow strip in front of the sink. A .28 on a narrow strip at the end just beyond a sink but next to a 4" side splash. And a .29 on a larger section to the right of a sink. So should have said .25-.32 is the range for the bathroom counter. I did more measurements for the bathroom than any other area because of the .30 and .32 readings but if I take out the narrow strips it is probably a .29-.32 for reading similar to what I did with the others.
cawaps
9 years ago
I visited the Hanford Reach Museum in Richland, Washington, last fall. If Hanford (the Hanford Project, Hanford Reservation) doesn't ring a bell, think Manhattan Project. Anyway, they had an activity where you got to use a Geiger counter to measure the radioactivity of a number of things, including vintage Fiestaware (orange). The Geiger counter was clicking like crazy for the Fiestaware (sorry, I don't remember exact numbers for comparison). Apparently uranium oxide was a common ingredient in ceramics glazes until WWII, used to create vivid colors. Fiestaware resumed its use after the war, and kept using it through 1972 (modern Fiestaware is not radioactive).

Anyway, if you have any vintage ceramics, you might test them as well.