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 (Wikipedia, Photographer:
Fir0002).

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.