Radioactive Banana Math

Quote of the Day

I never did a day's work in my life. It was all fun.

— Thomas Edison


I have been reading about the hazards of space travel to Mars. During this reading, I occasionally see references to space radiation hazards in terms of Banana Equivalent Dose. I find this a strange unit. Then today I read a blog post by Anne Marie Helmenstine that discussed how bananas are slightly radioactive. I liked her discussion and I thought I would go through the math here.


Why are Bananas Radioactive?

Bananas are radioactive because they contain potassium and potassium has an isotope (40K) that is radioactive. This same isotope is present in humans, which means that humans are also slightly radioactive.

Banana Data

Figure 2 shows the data that Google puts out when you type in "Amount of Potassium in a Banana".

Figure 2: Banana Characteristics from Google Search.

Figure 2: Banana Characteristics from Google Search.

While there is a lot of data here, I will only use the amount of potassium (422 mg) in a typical banana (118 gm) to estimate the rate of radioactive decay.

Measuring Banana Radiation

Here is a Youtube video of a person measuring the radiation from a banana. You can hear the sound of the Geiger counter. Ignore his comments about bananas being dangerous because of radiation levels. We are always exposed to low-level radiation.


Figure 3 shows my quick analysis of Anne's results.

Figure 3: My Analysis of the Radiation Emission from a Banana.

Figure 3: My Analysis of the Radiation Emission from a Banana.

Definition of Mole Information on Potassium


Numbers all confirmed. I also read that Brazil nuts are relatively radioactive.

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2 Responses to Radioactive Banana Math

  1. Pingback: Cat Litter and Radioactivity | Math Encounters Blog

  2. Pingback: Banana Equivalent Dose | Math Encounters Blog

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