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Radioactive Bananas??

December 8, 2010

Or, “Geeking Out with Family.”

Holidays are a time for family get togethers, complete with teasing, pranks, in-jokes and, if your family is like mine, geeky conversations like this one I had with my sister on Facebook:

Sister of TinyScientist: Ok so I Stumbled Upon a webpage talking about nuclear power plants measuring small leaks in Banana Equivalent doses claiming that all bananas (and apparently brazil nuts) are slightly radioactive due to the fact that they contain Potassium-40. While the idea makes sense to me they used wikipedia as a source. (yeah) So I’d like to know if this is something new I can use to avoid eating bananas when offered one by people who don’t know any better.  I realize that any radiation is probably less than that emitted by most “granite” countertops. But nevertheless…

TinyScientist: Where do you come up with this stuff?


Yes, we have some bananas

Yes, apparently there is a semi-organized proposal to measure exposure to radiation not in picocuries but in Banana Equivalent doses, although I would check that Wikipedia entry and make sure it doesn’t have a creation date of April 1.

As for using radioactivity of bananas as an excuse for not eating them, I would say not such a good excuse. 1) K-40 is about 0.01% of all potassium in the world. In the soil, in a banana, in you yourself (yes, humans, slightly radioactive). The amount of banana you would have to eat to get a lethal dose of radiation is so big that you would be more likely to overdose on just straight potassium than to die from radiation sickness. 2) Your body regulates potassium very very tightly, so any net gain in potassium you would get from eating food, including K-40, would automatically get peed right back out.   Same reason it’s hard to overdose on vitamin C or any other water-soluble vitamin, you just get rid of the extra in your urine.  Note: KCl (potassium chloride) is lethal, but only if injected in large doses. and 3) K-40 is also found in potatoes, cocoa powder and all sorts of other foods. So unless you also want to give up brownies and hash browns, I would not get crazy-go-nuts about radioactive potassium.

PS granite countertops have uranium and thorium, as does lots of porcelain (RADIOACTIVE TOILETS!!!).  Don’t lick the toilet and you should be good 😉

PPS can I make this into a blog post? I think its hilarious.

Sister of TinyScientist: Fun with Radiation!  Yay for units of measure no one understands! Hurrah for Picocuries!

You’re more than welcome to turn it into a blog post. I always enjoy being the source of other people’s paranoia. 🙂

Where I come up with this stuff: Stumble Upon (google it) it’s like Digg and that other weird “I like this webpage/story/cute picture of a cat hugging a chicken” stuff.

Here is the original Banana Equivalent Dose article on Wikipedia that I found. It originated on April 6th and has been modified as recently as October 23.

I knew about the countertops, not the toilets though it doesn’t surprise me. The radiation there comes mostly from true granite and other igneous materials that contain uraninite, minor radiation can also be found in zircon (most countertops aren’t really “granite” but are granitoids, syenite, diorites, monzonites. Though I’ve found that the ones that really make people squeal with joy aren’t even igneous rocks, they’re metamorphic. Realtors always get defensive when I say the counters aren’t really granite until mom tells them that I am a geologist and that I’m speaking about mineral compositions rather than the marketing names for any and all phaneritic natural-or not- stone counters).

While uraninite (in my understanding) isn’t likely to be found in large quantities outside igneous rocks, detrital zircons can be found in sedimentary and metamorphic rocks (they have a really high melting point so they usually survive the metamorphic processes). Though they are typically very small and wouldn’t produce much radiation more than the typical background radiation.


Yeah, so that’s what holidays are like in our house.

My younger sister and I share a love of hiking, photography, bad puns and science.  I’m a biologist, she’s a geologist with a serious interest in astrophysics.  Even though she refers to biology as “squishy science” and I barely passed first year Calculus, she and I still have more in common with each other than we do with our parents — two people who are sick to death of science museums and glad we can finally geek out over science by ourselves.  It could be worse.

Have a happy, geeky, holiday season everybody!

  1. Mary Bankhead permalink

    This makes me want to eat bananas! You’ve fulfilled my “learn something new today” requirement, so I can move on to doing laundry. Not sure if I should be happy about that or not, but holidays at your house sound fun!

    • Hi Mary,

      I’m glad I could supply your something to learn and a break from laundry 🙂 Holidays at our house are strange, but fun. Hope your holidays are happy!

    • April permalink

      Good to see some of my non-family facebook friends drawn into the family crazy 🙂
      Go Ducks!

  2. April permalink

    You know Dad was secretly geeking out too…
    and Mom has her own nerdyness

    I think they were just happy that we didn’t try to drag them to rock concerts or get arrested.

  3. Dad WAS secretly geeking out too. When he wasn’t yelling at the TV that it had gotten something wrong during NOVA or whatever. We are SUCH a bunch of weirdos. . .

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