Yellow Alert!

Today I learned about a unit of radiation exposure called the BED. This is a unit of measurement based on the radiation exposure from…

See, bananas contain a lot of potassium, which contains 0.01% potassium-40, which is radioactive. The upshot is that the radiation exposure from eating a banana is 1 BED (banana equivalent dose), or roughly equivalent to 0.01 millirem (mrem). Of course, you’d never be able to eat enough bananas to be dangerous since your body would just excrete the excess potassium.

This is also roughly the exposure from having a single smoke detector.


Yes, you read that right. Living near a coal plant exposes you to three times the radiation of a nuclear plant. This is due to the presence of thorium and uranium in coal. But these levels are still ridiculously low.


A typical human body contains some potassium-40.

2 mrem is also roughly your exposure from a NY to LA flight, due to your increased altitude (less atmosphere shielding you from the effects of galactic cosmic rays).


Again, this is due to your increased altitude. Mt Everest is more like 800 mrem (80,000 bananas) per year.


The granite in the walls is mildly radioactive. By comparison, the Vatican is about 800 mrem (80,000 bananas) per year.

…assuming no radiation shielding. But, yeah, that’s a lot of bananas.

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Steve D

Steve D

Steve consists of approximately 60% water and 40% organic molecules, arranged in a configuration that is, among over things, capable of describing itself in this manner.


  1. March 19, 2011 at 8:17 pm

    “Banana equivalent dose.” Ha!

  2. March 19, 2011 at 8:20 pm

    I found it on Wikipedia, so it must be true!

  3. March 19, 2011 at 8:22 pm

    I wonder what Ray Comfort’s banana count is? #requiredMention

  4. March 19, 2011 at 9:31 pm

    Where do computer monitors fit into this? I’m curious because I sleep with one on my chest every night.

  5. March 19, 2011 at 10:19 pm

    XKCD scooped me again! Munroooooooe! (shakes fist)

  6. March 20, 2011 at 2:13 am

    So if we wait long enough…all of vatican city will die off from cancer?

    I don’t think I can wait that long.

  7. March 20, 2011 at 11:03 am

    @Steve D: Did you just enact Munroe’s Law on your own article? Bravo! You win! (or lose. I don’t know)

  8. March 20, 2011 at 11:29 am

    But what if the person you’re sleeping next to is Felicia Day?

  9. March 20, 2011 at 2:08 pm

    Splendid visual comparison!

  10. March 20, 2011 at 9:34 pm

    Just watch: now people won’t eat bananas.

  11. April 11, 2011 at 10:19 am

    I’m pretty sure Denver is radioactive because it’s built on granite (which contains Uranium, a radioactive element), not because it is at a high altitude. This is why homes in Denver must pass a radon test before being sold. Since the radioactivity comes from the ground, if your home is on a large granite deposit and closed up, over a couple years it can fill with radon, raising radioactivity levels in the house to unsafe doses.

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