Monday, March 21, 2011

The Banana Equivalent Dose, or Your Food is (always has been) Radioactive

I keep forgetting that people have no idea regarding radiation.

Once upon a time, a long time ago, in a land not too far away, I worked for the Department of Energy in a building where several of the rooms were so radioactive you couldn't enter, and my job involved handling radioactive isotopes for use in various experiments. Mostly they where stored in lead boxes, but I had to take them out of the boxes, put them in the experimental apparatus, run the experiments and put them away. I was exposed to detectable but not dangerous levels of radiation. Radiation wasn't the biggest danger in that building, as it contained a tower of pressurized carbon tetrafluoride, (a cousin of carbon tetrachloride that used to be a cleaning solution - only nastier). We didn't hold radiation drills - though there were alarms. We did hold drills on what to do if the carbon tetrafluoride containment failed.

But I digress. Suffice it to say that I know a little bit about radiation and radiation hazards.

Radiation is usually measured in Roentgen Equivalent Man units or rems. There are other measurements, and you can invent your own, so someone came up with the Banana Equivalent Dose.

Here is fact number one. You are exposed to radiation every single day. There is always radiation around you, and there always has been. Get over being afraid of radiation. Too much radiation will kill you, but even if you go live in a fallout shelter, you can't get away from all of it.

Fact 2. Your food is radioactive. Almost all of it. Always has been.

We can detect the (ridiculously small amount of) excess radiation in bananas. (They can set off the radiation detectors at the ports where they are imported.) They are slightly more radioactive than the average bit of food, because they are high in potassium - which is good for you and why we eat bananas. But it means they contain some radioactive potassium. (Very little - but in measurable amounts.)

One thousand banana-equivalent-does of radiation (or the radiation you would ingest if you ate 1000 bananas in a VERY short time, like a few hours) has the same effect on your health as smoking something less than 2 cigarettes. Or in more mathematical terms 1 BED = 0.01 mrem or 0.00001 rem. Doses of radiation of more than 50 rem but less than 200 rem (or much more than your average banana) will make you sick but rarely kill unless there are other issues. Doses in excess of 1000 rem are fatal. (Between 200 and 1000 you will be very sick, and the higher the dose, the worse off you will be.)

Other foods with "excess" radiation include nuts (and peanut butter), sunflower seeds, etc. Brazil nuts are particularly radioactive.

But now that you know this DON'T stop eating the bananas. Or the nuts. They are good for you. Just don't follow the fear mongers when they try to start the next crazy parade.

(Note: OK the banana equivalent dose isn't a really good method for talking about radiation and its hazards. But neither is the insanity you see on the 24-hour news coverage. NPR "news" was actually discussing the Godzilla movies yesterday. I nearly crashed my car. Godzilla? Really? There isn't anything more informative to be talking about like the new war - or is it a police action - in Libya, the state of the economy or the efforts of folks like the Red Cross to do something besides spread fear.)


Zendo Deb said...

Too be completely accurate, I didn't work for the DoE. I was a summer intern in the Nuclear Structures Group at Oak Ridge National Lab.

It was a horrible experience, mostly because pure research in high-energy physics is just completely a mess. But it convinced me I didn't want to major in physics. So I went home at the end of summer and changed my major to mathematics. MUCH more organized and beautiful even.

NotClauswitz said...

Yay! First truly useful explanation I've read, bananas included.

Jake (formerly Riposte3) said...

The banana equivalent dose may not be a really good method for talking about radiation and its hazards, but it is a good way to give people a little perspective and to show that the MSM is exaggerating the dangers. It's not a quantitative measurement, but it's a good beginning teaching tool.

Also, welcome back! I hope everything has settled down for you in the best way it can.

BobG said...

Glad to see you back; I missed your blog.