Radioactive bananas

Posted on 5th Sep 2017

Banana

Disclaimer: The post below describes bananas as radioactive. Even though this is true, you should not worry. Basically everything in everyday live is radioactive, the amount however is almost negligible. In this bananas are no different from potatoes, nuts, beer…shall I go on?

I sometimes like to use bananas put a perspective on the dose received from scatter radiation. This novel approach often triggers interest in people and emphasizes the negligibility of the dose we are talking about.

In a minor group it does however fuel their already existing radiophobia. I remember a single case when a banana was purposely left in my classroom. Ever since I started to emphasize that basically everything is radioactive, one should not worry about it.

To calculate the amount of radioactivity I focus on the isotope which causes the highest contribution to the dose. In this case it is potassium of which a certain amount (0,0118 %) is the naturally existing isotope potassium 40 with a half-life of roughly 1,25 billion years.

The Chiquita bananas contain 450 milligram of potassium which results in ± 0,053 milligram potassium 40. Using among other things Avogrado’s number you can calculate amount of radioactivity.

Calculation

So a  Chiquita banana contains about 13 Bequerel of radioactivity, this results in a 85 micro Sievert dose. Should you worry? Absolutely not, when comparing to a single chest X-ray this results in eating about two bananas, each day, for a year. Not something everyone does but most certainly not something people are ever worried about.

I am certainly not the first person to do this, people have been using bananas in this context for some time now. This has become known as the banana equivalent dose.

You should not stop eating bananas because they are radioactive, if you do you should give up on all food. Keep in mind, everything is radioactive it is nothing to worry about.

Image source: https://upload.wikimedia.org/wikipedia