Sunday, February 19, 2012

(Updated) Max 23 Millisieverts External Radiation Exposure for Fukushima Residents in the First 4 Months of the Nuke Accident

From Jiji Tsushin (2/20/2012):


The Fukushima prefectural government and Fukushima Medical University announced on February 20 that the maximum external radiation exposure in the first 4 months after the March 11, 2011 accident was 23.0 millisieverts among the residents who are not radiation workers. Total 10,000 residents of Fukushima have been surveyed.

The survey, with Dr. Shunichi "Damashita" Yamashita in charge, consists of detailed questions for the residents in order to estimate the radiation exposure. The residents have to fill out the pages with information on their whereabouts, on what day, for how long, what they were doing, etc. Dr. Yamashita's group considers the information with the SPEEDI simulation done specifically for Fukushima Prefecture to figure out the radiation doses in Fukushima in the early days of the nuclear accident.

The press conference is on-going in Fukushima right now, and the information has not been uploaded on the Fukushima government website yet.

(UPDATE) Jiji has filled in more details:

  • 10,468 residents in Namie-machi, Iitate-mura, Kawamata-machi Yamakiya District

  • Highest (23 millisieverts) from a woman who lived in the planned evacuation zone [no mention of which town]
  • 2 people exceeded 20 millisieverts

  • 58.0% of people tested: less than 1 millisievert

  • 99.1% of people tested: less than 10 millisieverts

  • 71 people exceeded 10 millisieverts

  • Max for radiation workers: 47.2 millisieverts

  • "It is difficult to imagine there would be an effect on health", says the Fukushima prefectural government.

If you recall, over 30% of 3,765 children from the same towns tested for thyroid abnormalities were found with lumps/nodules and/or cysts.


Chibaguy said...

Ionizing radiation damages health. That is why workers have limits. Who in the world would subject a nation of people to fallout over months? It is not even over as levels spike. It just want to frame this for a few deniers on this blog. These limits cannot be compared with an airplane ride nor a banana. There are radionuclides from multiple explosions. The data stated above does not seem to consider internal radiation as well which if far worse. This is not an x-ray or CT scan but cesium, strontium and even plutonium falling on you. This is a disgrace.

Anonymous said...

"It is difficult to imagine there would be an effect on health", says the Fukushima prefectural government.

Excellent doublespeak. A+++ How many locals believe it at face value?

arevamirpal::laprimavera said...

How many? Probably the majority. There is a medical doctor in Fukushima who's been telling people radiation is good for you (no, not Dr. Yamashita). I featured him on this blog. Apparently he's still doing it.

Chibaguy said...

@Ex Skf - why do not fellow doctors stand up and put these people in their place? A radiologist would be able to do this. I can see a conflict if a doctor spoke freely to a patient due to health insurance coverage but do not know why they take the argument out in the open. What happen in Chernobyl will happen here - no mistake.

arevamirpal::laprimavera said...

@Chibaguy, I've read that most doctors in Fukushima are under the sway of Dr. Yamashita and the official position that there is no effect of radiation on heath. So are many doctors outside Fukushima, thanks to the tight control of the medical associations. I hear that even the pathologists are under pressure.

When a concerned mother brings her child to a doctor and mentions "radiation", the doctor will scornfully and openly laugh at her, as many report on twitter. Anecdotes.

Atomfritz said...

Be aware that this official information is derived from statistic assumptions, and statistics can be well used to bagatellize and deceive.

In doubt, the actual values are probably way higher than in the official statistical model.

Anonymous said...

They're estimating the radiation by asking people where they've been and what they've been doing? How does that work? Do those people track their own radiation exposure accurately?

It's terribly naive if they're estimating the radiation exposure based on known sources of radiation. Obviously, they wouldn't be able to estimate how much they're getting from unknown sources.

If they really wanted to know, they'd have to test each individual accurately, but they're not going to bother doing that because it costs MONEYYYYYYYYYYYY.

And of course it's hard to imagine the health effects when they can't see it and try to ignore it. Ask any regular person if they can imagine being afflicted by cancer or various other diseases and illnesses. I doubt they'd say yes.

Chibaguy said...

Thanks Ex Skf - whatever oath the doctors and politicians have to take seems meaningless. I think one problem is that the men in this country are detached from reality. However, I have seen cases were the mother is not concerned but the father is. Radiation is not something that is abstract and this is where I get frustrated.

farfromhome said...

Chibaguy said...
"Ionizing radiation damages health. That is why workers have limits."

Right!! I have been saying this for the longest time! If this radiation and/or contamination was not harmful, then why would the workers have to be protected and measured so heavily? These are not controlled and monitored substances, they are 'contaminants'! And you add to this mix the internal contamination from food and water....the cumulative effect.

I am horrified for the people living in these areas, especially parents of young children.

doitujin said...

those murderers...

Yosaku said...


As with farfromhome, I second your base position that "Ionizing radiation damages health. That is why workers have limits."

However, I wanted to ask you why you believe various forms of ionizing radiation cannot be compared. Is it that you don't agree with the Sievert as a derived unit of measure, the values of the dose coefficients for various isotopes or weighting factors for different types of decay, or something else?

I'm just curious as I see that sentiment echoed frequently.

I'll be the first to admit that internal dosimetry isn't perfect. Scientists are constantly making proposals that this dose coefficient or that weighting factor should be raised or lowered. But still, I think it remains the best (only?) method at our disposal for making these comparisons.

I'm keen to hear your thoughts.

Atomfritz said...

Yosaku, the whole weighting of the radiation forms and their dangerousness into one unit "Sievert" itself is completely arbitrary when you consider the particular properties and behaviors of contaminants.

Just to take an example, the permissible tritium releases are usually far higher than the permissible cesium releases. Why? Tritium mostly is released in the cooling water, so it doesn't concentrate much locally, don't fall out like Cesium or even like Plutonium.
So, it is convenient to "value" the tritium's beta activity arbitrarily as 1/20th of the plutoniums' alpha.

This is actually in no way scientifically proofed, it's still the same what the 1940s' Hanfords' politically influenced publications propagate, which were never questioned seriously, because it is so difficult, next to impossible, to prove/disprove such things. Aside from the fact that it's always very dangerous for scientists' careers to touch particular politically dangerous dogmas.

Radiation isn't that simple. This complexity cannot really be modeled into one simple number like a Sievert "count".
So the seemingly low (micro-) Sievert-numbers are also being used to deceive people and suggest them, that there is low danger.
And there are even other ways to keep radiation measurements "low", like metering in 1 meter height and not on the bottom where your feet are or you sleep.

Anonymous said...


Here is an example of one of the studies done that provide information on radiation exposure.

Bruno said...

By contrast to external radiation, internal radioactive contaminants accumulate in the body if the biological half-life is large (1.5 years for cesium, see ).

Thus even a low daily intake of contaminants can lead to a very high internal Sievert dose by internal alpha, beta or gamma radiation. Only the latter can be measured easily.

Tritium in the form HTO (partially tritiated water) has a very short biological half-life of only 7-14 days, because the water throughput in the body is large.


netudiant said...

Hi Bruno,
No question that internal exposure is way more dangerous than external, just think about the poor man poisoned in the UK with Polonium, the doctors were helpless.
That said, the biological half life of cesium in the human body is thankfully a lot shorter than the 18 months your sources give. According to the CDC, it is about three months, less for children and infants.

arevamirpal::laprimavera said...

@netudiant, if they continuously ingest radioactive cesium, like they've been doing in Japan for 11 months now, it doesn't quite matter what the biological half-life is. The level is maintained.

Anonymous said...

Would you check these numbers, maybe not all info hear or I have not understood all of it, thanks.

10468 Total people
99.1% people tested less than 10 millisieverts, that is 10373.788 people.
00.9% would be over 10 millisieverts or 94.212 people (not 70.97304 [71] people or 00.678%),
This is a 30% or 23.23896 people higher figure of over 10 millisieverts exposure [the 00.9% is correct just number wrong I believe].

Maybe an excel formula was used to arrive at this. Maybe the formula was set to count numbers below 10 and one to count above 10. This would then not count a 10 figure. Just a suggestion to look at, it is easy to over look.

arevamirpal::laprimavera said...

@anon at 3:07PM, I'm checking the original data. Hold on.

Yosaku said...


Thanks, as always, for your comments. In your second paragraph, I think you're mixing two concepts: (Sieverts) and limits.

As for limits, these are generally set by assuming a maximum yearly allowance and then working backwards. As far as I can tell, it has nothing to do with cooling water, etc. The Canadian Nuclear Safety Commission has, to my mind anyway, the best description of limit setting (for Tritium, see

Also, I believe (and you should check me on this) that Tritium beta decay releases 18.6 keV while Plutonium-239 alpha decay releases 5.157 MeV, which is the largest single reason why the valuations are so different, although biological half-life, as pointed out by Bruno, is also significant.

Again, though, I'm happy to hear your thoughts.

Yosaku said...

arevamirpal::laprimavera at 2:26 PM,

That is exactly right. However, I think it should be noted that biological half-life is still extremely important as the equilibrium level is a function of both daily intake and biological half-life.

I really think the UNSCEAR chronic ingestion chart that you posted many months ago is one of the most useful links you have provided (and you have provided a _lot_ of useful links).

Yosaku said...

Anonymous at 3:07 pm,

I think the issue is that the 10,468 number included radiation workers (放射線業務従事経験者を含む), whereas the number of individuals who exceeded 10 mSv was in reference to regular citizens only (一般住民).

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