A microwave dose of bananas

What is the analogy of the 'banana equivalent dose' for a mobile phone? Picture from http://www.cellfoam.com/

What is the analogy of the 'banana equivalent dose' for a mobile phone? Picture from http://www.cellfoam.com/

The BBC this week highlighted the relevance of the Banana Equivalent Dose – the dose of ionising radiation received as a result of eating a  banana. I commented on this just over a year ago (Would you eat a radioactive banana? ) where I pointed out that although the use of bananas to measure radioactive dose seems like a comic stunt, it is actually a serious metrological issue.

Measurement is the quantitative comparison of an unknown quantity with a standard unit. Ideally the standard unit should be familair to the people who will use the measurement. And ideally the the standard unit should be of a similar magnitude to the unknown quantity – this makes it easy for human beings to register the significance of the measurement. The banana equivalent dose is a useful unit because it is typical of the doses received by people outside the Fukushima fallout zone – they might be receiving the equivalent dose of 24 bananas per day (2.4 microsieverts per day compared with a standard expectedUK dose of 7 microsiverts per day). This is a lot of bananas from a dietary perspective, but quite appropriately, few people would fear radiological consequences.

This week I read more stories of anxiety caused by the erection of mobile phone masts. It made me wish there was an equivalent measure to the banana equivalent dose for non-ionising radiation. People’s anxiety is made clear in one quote from the Richmond and Twickenham Times:

Mrs Morgan said: “I did a study of radiation [before] and as far as I know nothing has been proved that this radiation coming from these things are not harmless to human beings. Until they prove they are harmless I think they shouldn’t be erected.”

Sadly, the proof of safety that Mrs Morgan desires is impossible. There is currently no evidence of harm, but it may be that in 20 years, some evidence of harm from prolonged use may become apparent. However, if it does become apparent those who oppose the construction of mobile phone masts maybe responsible for an increase in the population dose.

The dose of non-ionising radiation from the phone masts is tiny compared with the dose from actually using a mobile phone. By opposing the construction of nearby mobile phone masts, when people use their phones they emit more microwave radiation than they would for a nearby mobile phone mast. If we had an equivalent of the banana equivalent dose, for non-ionising radiation we would be able to quantity this.

Perhaps it should be in terms of a one minute mobile phone calls to a mast 500 metres away. Then we could say:

  • If the mast is built near your home your extra dose will be the equivalent of X minutes of mobile phone calls to a mast 500 metres away, but the dose from every mobile phone call you make from home will be reduced by the equivalent of  Y minutes of mobile phone calls to a mast 500 metres away
  • If the mast is not built near your home, you will receive no extra dose of radiation  from the mast, but the dose from every mobile phone call you make from home will be increase  by the equivalent of  Y minutes of mobile phone calls to a mast 500 metres away

If you have any ideas about how to express this non-ionising equivalent dose I would love to hear about them.

P.S. I asked my son whether he would eat a radioactive banana.No! ‘ he said, ‘I don’t like bananas!’. I then asked  ‘Would you eat radioactive chocolate?‘ to which he replied without a moment’s hesitation: ‘Of course I would!‘.

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