Fukushima and the Banana Equivalent Dose

After seeing sensationalist headlines in the newspapers about “Australians Exposed to Radiation!” and constant talk about radiation leaks and a recent radiation spike etc with relation to the Fukushima Nuclear Power plant, I started wondering why none of these news sources seemed to ever mention how MUCH radiation was leaked, or what amount of radiation is was spiked to… or how much exposure the Australians were exposed to.

I don’t want to just go on a rant about how frustratingly terrible the news sources are for ommiting this incredibly simple and IMPORTANT element of these stories, although that is an obvious temptation….but seriously, I want to know. And I think that in order for people like me (non-nuclear physicists), I think they should present the information in the form of the Banana Equivalent Dose.

The Banana Equivalent Dose (BED)

You see, because of the high Potassium levels in Bananas, they are significantly more radioactive than most foods. As such, for simplicity of explaining radioactive exposure, the “Banana Equivalent Dose” system was devised, and is used as simply as it sounds:  “They were exposed to 50 Bananas worth of Radiation” for example.

Finding the Information

So I set out to try to find out exactly how much radiation has been released from the power plant. I found a few articles (1, 2) which repeated the same piece of information:

Japanese radiation readings:

Monitoring of radiation levels on the spot is ongoing. At point MP4, where a reading of 1,015μSv was detected yesterday, a radiation level of 44.6μSv was recorded at 00:30 this morning, and a level of 36.7μSv at 6:00am. After the start of venting around 9:20, a reading of 76.9μSv was recorded at 9:20 and of 70.3μSv at 9:30.

The radiation spiked up to 30 bananas a day (2 days ago) and then fell back down to 1 to 2 bananas per day.

UPDATE: Unit 2 has had serious damage and radiation levels on the edge of the plant compound briefly spiked at 8217 microsieverts per hour but later fell to about a third that. Normal annual doses for a year will occur in one day.

Meanwhile, two BBC (1, 2) articles provided the following radiation levels:

The Kyodo news agency reports that a radiation level of 1,557 microsieverts per hour was registered on Sunday… Later measurements included 750 microsieverts per hour at 0200 on Monday, and 20 microsieverts per hour at 1145….after Tuesday’s explosion, readings at the site rose again beyond safe limits – 400 millisieverts per hour


After the explosions and fire, radiation dosages of up to 400 millisieverts per hour were recorded between reactors three and four at the Fukushima Daiichi site, about 250km north-east of Tokyo.

A single dose of 1,000 millisieverts causes temporary radiation sickness such as nausea and vomiting.

Later, a reading of 0.6 millisieverts (mSv) per hour was made at the plant’s main gate, the International Atomic Energy Agency said.

And finally, of course, Wikipedia provides a great summary of the facts:

Dose-equivalent rates reported from the stations rose as high as 400 millisievert per hour

Fukushima Radiation Levels

So, working with that information, we have a worst radiation level of 400millisieverts per hour, measured from between the 3rd and 4th reactors. So at its worst levels, the plant has been measured releasing 4,000,000 BED. (1 banana = 0.0001mSv. Wiki) The rest of the time, the radiation has been sitting around 200 – 10,000 BED. So the general radiation levels of the power plant is perhaps akin to working in a Banana plantation, plus a bit, while the large spike is definitely a significant amount of radiation.

That 4 million BED of radiation was measured in the compound, and based on the comment by the BBC article, that “A single dose of 1,000 millisieverts causes temporary radiation sickness such as nausea and vomiting” means that someone standing, unprotected, in the the middle of the facility would feel those effects of radiation sickness after about 2.5 hours.

I guess more importantly than ‘feeling sick’ is the risk of death caused by that sort of exposure. The wiki article gives some goo dexamples of Dose levels, and observes that 100mSv per year is clearly carcinogenic – so 400mSv would obviously have a very strong risk of causing, probbaly multiple, cancers.

All that being said though – I don’t think anyone is standing unprotected anywhere near the nuclear reactor. There is a 20km exclusion zone, and my understanding of this radiation, is that it rapidly decays – it isn’t uranium leaking out or anything like that – nothing permanent or with a giant half life. One article stated that these radiactive particles which produce these readings last seconds… That seems to conflict with the fears of radiation heading over towards Tokyo, but then, I have only heard standard media talking about those sorts of fears, and I am not very convinced that they actually know what they are talking about.

Nonetheless, the whole situation is being handled with absolute care, and no risks seem to be being taken…

Human Exposure

Through all of my searching, I could not find one mention of exactly how much radiation was detected on the people exposed to radiation, or anything to help identify what had happened. The headlines typically sounded terrible, but once in to the story, it was clearly stated that the radiation was measured at “very low levels”, and that there was no risk of negative health affects. But no story that I have seen has provided numbers. I expect the BED of the exposure, based on the fact that the standard BED INSIDE the reactor is typically around 200-10000, they have probably experienced less than 1 year of smoking would expose them to.

But without any actual reporting, I can’t say.

The Hype and Fear Mongering

While trying to find this information, I found a lot more fear mongering and hype than anything else. For example, this article: http://www.businessinsider.com/cesium-and-iodine-radiation-fukushima-ines-scale-2011-3 is by far my favourite. It dedicates itself entirely to exploring the nuclear situation, and talked about nothing other than the reactors, and the radiation, the history of nuclear disasters, the rating given to this nuclear event etc. It quoted experts about the nuclear situation… and then, out of the blue, in the second last paragraph it slips in the death toll from the Earthquake and Tsunami, right before the last paragraph which quote the death toll from Chernobyl.

Ahhh, tell me you aren’t trying to create an incredible sense of fear about nuclear accidents???

Basically this article reads like this:

<Ten paragraphs of all of the possible problems of nuclear fall out, radiation, and tragedy>

People have been asked to evacuate from a 20km radius around the plant.

The death toll is said to be expected to reach 1700. Over 680 have been found dead and number of people found dead is rising hourly as more people are found.

Approximately 4,000 people were killed in Chernobyl.

There is no attempt to explain that the death toll is from the Tsunami, and the following paragraph about the ‘death toll of Chernobyl’ is surely doing its best to make it sound like the death toll is somehow a result of the Nuclear Power Plant accident?!??!?!?

This example is pretty special though.

The normal type of fear mongering that I found looks more like this one: http://cryptogon.com/?p=21138 which basically comes down to big bold headlines about radiation leaks, people being exposed, and warnings from official bodies. Again, no details, no facts, no perspective about the actual threat. Just generic statements that make everything sound really bad.


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Fukushima and the Banana Equivalent Dose, 8.8 out of 10 based on 12 ratings

3 Replies to “Fukushima and the Banana Equivalent Dose”

  1. Il est l’heure de la banane !

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    Rating: 3.0/5 (2 votes cast)
  2. I’m sorry Shane but you are incorrect.
    Banana equivalent dose does not make sense at all.
    First, Potassium has been in our environment, and our bodies have a way of dealing with it. The Cesium, Strontium, Plutonium and other isotopes that now are released into the environment on a massive scale are new to our environment, and our bodies mistake these for Calcium, Potassium and Iron elements. Our bodies don’t see the difference.
    Why is this bad at all? Those particles are lodged in the bone (near bone-marrow) in the testicles (Plutonium), cross the placental barrier and are then are used as “building material” – they irradiate (alpha radiation in the case of Plutonium and Uranium) the surrounding cells, constantly, and will cause these cells to die, or form cancers in 100% of the cases. So there’s no question of “maybe”. Lucky for us, our body has a way to dispose of cancer cells, and you can eat certain food to help it do that.
    There’s also the question that the nuclear industry has used the idea of “dillution is solution” which I sadly find in your article again. This idea has been proven wrong, for the simple fact that radioactive particles bio-accumulate in the foodchain (just like DDT or Mercury for instance). Seaweed soak up radiation as an example, so it’s a good thing to have the food tested (which is not happening).

    Your article therefore needs revision, if you’ve got additional questions, or need proof of what I wrote, don’t hesitate to contact me.

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    Rating: 2.6/5 (5 votes cast)

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