Banana Equivalent Dose

Let us have no more of these miserable statistics, which only paralyze the brain and freeze the blood.

— From the book Blackett's War. A plea by a British politician to not be distracted by facts.

Figure 1: Cavendish bananas, the most common desert variety.

Figure 1: Cavendish bananas, the most common
desert variety (Wikipedia, Photographer:

I recently have been reading quite a bit about the hazards of traveling to Mars – one of the major hazards is radiation. This Mars reading has driven me to write a number of posts that look at the effects of radiation exposure in our daily lives here on Earth.

I wrote a post a while back on how bananas are slightly radioactive because of their potassium content. The calculations that I performed in that post confirmed the level of banana radioactivity reported in a number of places (example). However, I was not able to calculate the biological impact of this radiation because that requires knowledge of things like

  • type of radiation
  • energy radiation
  • sensitivity of the tissue to the radiation

I had no idea where to find this information, so I just computed the activity level (i.e. decay rate). I recently found an old EPA/Oak Ridge document (10 MByte) that provides some of this biological information and I thought I would use it to expand calculations to include the biological impact (called Equivalent Dose) of the banana's radiation level. This information has allowed me to confirm a number I have seen for the  Banana Equivalent Dose of 78 nanoSieverts (nSv).

Figure 2 shows the calculations. The links in the image are alive. I am not done researching this topic – I still want to know how the data in the Oak Ridge paper were derived.

Figure 2: Calculation for Banana Equivalent Dose.

Figure 2: Calculation for Banana Equivalent Dose.

Elementary Charge General Discussion Potassium in a Banana 40K in a Banana 40K in a Banana Oak Ridge Document
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2 Responses to Banana Equivalent Dose

  1. Ronan Mandra says:

    I looked up Sieverts (Sv) at:
    According to that wiki page, 5 to 10 μSv is a typical radiation dose for one set of dental radiographs. Maximum allowed radiation exposure for NASA astronauts over their career is 1 Sv. So, 78 nSv is very low.

    • mathscinotes says:

      I completely agree with you. I wanted to learn to compute the dose level with a simple example and the banana equivalent dose was the easiest one to compute (single source of radiation from 40K). Eventually, I want to understand how dose calculations are done from wide spectrum radiation. This was my baby step in that direction.


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