Monday, 23 September 2013

13 Million Bananas per day

0.01mrem is equal to 10-7Sv  
(Picture from
Last week, at an “Echange Linguistique” with two of our friends, the subject of nuclear power came up very briefly. As far as these two French ladies were concerned 
There were no intermediate steps in the conversation and for them these two things were equivalent and inevitable.

It was very revealing, and I was appalled by their ignorance, but I couldn't immediately enter into an argument which would rapidly have become very heated and found me at the limits of my command of French.

The fundamental problem is that the public lacks any understanding concerning radiation and also lacks any ability to appreciate that the numbers are important when it comes to all environmental challenges to living organisms, including radiation.  Since we are all surrounded by radiation from natural sources it's a very good thing that the body has repair mechanisms and it's only when these can no longer cope, or when the exposure to radiation is too intense over too long a period, that cancers result.

Even radiation units are difficult to understand. Firstly, there are many different ways to measure the intensity of radiation emissions  and then there are the concepts of an absorbed dose of radiation (measured in Grays) and the biological effects of a committed dose of radiation on a human body (measured in Sieverts ). This is dependent on the type of radiation and the tissues which are irradiated.

The Banana Equivalent Dose
Since bananas contain potassium, which has a small percentage of radioactive Potassium-40 they emit radiation. 

One somewhat whimsical attempt to make all of this more relevant to ordinary people is the Banana Equivalent Dose BED, which is usually rounded up to 0.1 µSieverts. 

So I decided to calculate how many bananas were equivalent to the average radiation dose of 2.7mSv per year received by a typical UK citizen, which works out to 74 bananas/day. 

The exposure limit for a worker in a nuclear power station is 0.18mSv/year or 5 bananas /day.

Back in the late eighties I had radiation treatment for cancer and received 5,400 rads across my abdomen over a six week period.  This is equivalent to 54Sv or 12,857,143 bananas/day and I'm still here!

So, if they ever find this post, as well as equating nuclear power with cancer, I expect that these two French ladies will also stop eating bananas! 


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