Comparing radiation doses

fukushima-july-2011 This post is more an appeal for info than anything useful in itself. But I'll probably update it if I get anything. Fukushima refers. My question, in the context of the area around Fukushima that is contaminated by radioactivity, is

how much is actually contaminated, in the sense of now having radioactivity levels higher than naturally occurs in granite-based areas like Cornwall? How much has been officially declared "contaminated" isn't a very interesting number

In response, M points me to map around FukushimaNPP/; here for example is July 2011 (take care to do what I didn't, and scroll down to the integrated dose map. But unfortunately I don't know how that compares to radiation levels in Cornwall. I made brief pathetic efforts on google to find out, but then gave up and wrote this. Over to you.

[Ah, hold on, I've just realised something. Thinking forwards, we don't care about the integrated dose from the start, if we're worrying about what will be uninhabitable in the future. What we care about is the area that will settle, in say 6 months time, to a value that will be bad, then -W]


* More stupidity about Fukushima
* More dangerous than nuclear meltdowns...
* Kan Canned
* Nuclear meltdown in Hokkaido [that's enough JEB - ed]

More like this

Apparently background radiation in Cornwall is about 7.5 mSv/yr (0.8uSv/hr), lower than in most of the yellow area of the figure. On the other hand, according to this, background levels in Ramsar, Iran, are up to 260 mSv/yr, higher than anywhere outside a few sq km around the Fukushima accident site.

The least contour on the radiation map is 1 micro-Sievert per hour, or 8.766 milli-Sieverts per annum. The background radiation in London is 2 milli-Sieverts per annum, and in Cornwall that rises to 7 milli-Sieverts per annum. A full body CT scan exposes you to 8 milli-Sieverts.

The highest highest contour on the radiation map is 35 micro-Sieverts per a hour, or 306.81 milli-Sieverts per annum.

That, however, understates the level of release. Underneath the July 11 Dose monitoring map, there is am Integrated Dose Map, which shows doses of 100 milli-sieverts over a large area, and more than 400 milli-Sieverts in the immediate vicinity of the reactor.

[Ah, thanks for pointing out the integrated map, I'd missed that in my haste. A quick comparison against the definitive reference - xkcd - would indicate, then, that the orange bits and above are unsafe but yellow and green should be safe enough -W]

Only a slightly different tact, the dose rate in UK latitudes at 37,000 is about 5 micro Sv/h (high energy radiation). It is true that this is short term exposure, but at least helps to out the magnitudes of the dose rates into context.

Another way to put those figures into perspective is to compare them to the radiation doses over 20 years from Chernobyl of:

Liquidators >100 mSv
Evacuees >33mSv
Residents in High Contamination areas >50 mSv

Based on that, the population inside the yellow area on the map will experience radiation doses equivalent to those exposed to Chernobyl, and would expect the consequent estimated 4% increase in mortalities due to cancer compared to the general population (approx 0.6% increased deaths overall)

In Germany the threshold for longterm resettlement is 100mSv/a of external radiation from longlived radionuclides. Any place with 12µSv/h or more is "hotter" than that. The rationale behind that number is as follows; in Germany people will pick up 170mSv during a 70 lifetime on average, with a large span of 100mSv to 400mSv per lifetime. On the one hand resettlement is a grave intrusion into people's lifes and should only be considered, if this helps to avoid a dose of the order of a lifetime dose. This consideration goes especially for children. On the other hand you will adopt easily taken measures (like staying indoors to avoid doses beyond 10mSv) in order to avoid much lower doses. The Commission tasked by the government came up with the 100mSv/year threshold.

Cornwall is not really comparable, because there the radiation risk is coming from radon, which as an internal radiation source affects the lung tissue, hence the acceptable dose is lower than for external radiation.

Here's a site claiming 7.4mSv/a (0.9µSv/hour) for Cornwall:

The unit for values on this particular map is uSv/h (micro sievert per hour).
[Another map on the same document shows time-integrated values in mSv (milli sievert).

By Kooiti Masuda (not verified) on 26 Aug 2011 #permalink

A couple of comments and questions:

As far as I understand it, you can't just multiply the micro sievert per hour dose rate by the number of hours in a year to project dose as that would assume that people are outside 24 hours a day. The actual dose should be less, perhaps by quite a bit.

Is the integrated dose calculated on the basis of being outside 24 hours a day?

The integrated dose includes contributions from short lived radio isotopes of iodine, nitrogen and noble gases that have dispersed and/or decayed to insignificant levels. So the current hourly dose rate cannot be directly compared to the integrated dose.

I think the best measure is to look at the radioactive isotopes of biologically active elements like iodine and strontium.

It seems like most of the more exotic elements like plutonium and uranium are not terribly dangerous. They don't absorb well when ingested and don't concentrated themselves in the body.

Additionally, the coal industry shoots many tons of uranium into the US atmosphere every year with apparently little effect. Also, since they decay so slowly (a few billion years for uranium and millions of years for plutonium) I wouldn't think they'd cause much cellular damage from very low dosages.

Looking at:…

It seems like strontium is the only "long"-lived isotope to worry about and perhaps that can be cleaned up relatively easily.

By TheGoodLocust (not verified) on 26 Aug 2011 #permalink

Cornwall is not really comparable, because there the radiation risk is coming from radon, which as an internal radiation source affects the lung tissue, hence the acceptable dose is lower than for external radiation.

Yep, it's the same for Finland with its granite bedrock. The radon trickles into the homes and decays inside people's lungs. This is one case in which the effect of background natural radio-activity on health is actually epidemiologically detectable (barely).

The Finnish building code takes this very seriously.

By Martin Vermeer (not verified) on 26 Aug 2011 #permalink

The hormesis blogging brigade will be along promptly.

Anticipatory debunking: Ramsar has a few high radiation areas, associated with hot springs that emit radon gas, and much of the Ramsar area isnât particularly radioactive.

Look at Table III â it lists four cities in the Ramsar region and compares the mean radon levels to the US and Swedish regulatory recommendation levels.

For Sweden, for existing construction, the recommended level is 400 Bq/m3. One of four Ramsar cities shown there has mean levels is 615. The other three citiesâ mean measures are below 400 Bq/m3.

Measuring the radon right at the hot springs would get the much larger numbers â but what counts is actual human exposure over time. Radon is inhaled -- and exhaled. It's a noble gas, it doesn't accumulate in the body.

Cesium is different; it bioaccumulates.

In the current situation, most of the air dose comes from the soil. I have learned from a session of public lectures by the Japanese Society of Soil Science and Plant Nutrition whose informational web pages are here (in Japanese).

The most relevant nuclides are cesium 134 (half life 2 years) and cesium 137 (30 years). Iodine 131 (8 days) has already decayed. (It must have been included in the time-integrated dose.) Strontium 89 (50 days) and strontium 90 (29 years) are also detected. The situation of strontium is less known than cesium due to difficulty in measurements, but it is considered that the dispersion of strontium via the atmosphere is much less than that of cesium.

So, unless new explosion occurs, the time-integrated dose in the near future is approximately the instantaneous dose multiplied by the number of hours for the person to be outdoors. The instantaneous dose will decrease to approximately 3/4 of the present value in 2 years since roughly the half comes from cesium 134.

By Kooiti Masuda (not verified) on 26 Aug 2011 #permalink

Totally OT: Your blog feed has been broken at this end (Firefox, Sage, RSS) for about a week.

By Vinny Burgoo (not verified) on 26 Aug 2011 #permalink


Perhaps I didn't make myself clear; I meant to say I was under the impression that cesium doesn't bioaccumulate in humans.

By TheGoodLocust (not verified) on 26 Aug 2011 #permalink

Perhaps the map does not tell the entire story. I've recently seen a feature in the German political TV magazine Frontal 21 (public TV) on the aftermath of Fukushima. They reported that some Japanese outside the officially affected zones had their selfgrown food tested. They found 7 kBq/kg in Shitake mushrooms from Date and 35kBq/kg from Cs137 in Rice from Motoyima, where 0.5kBq/kg is allowed for human consumption. Both are outside the affected area according to the MEXT map. The farmer allegedly found radiation levels of 90µSv/hour near his house.

Usually Frontal 21 is ok when it comes to facts, but I can't vouch for the accuracy of the numbers; especially the 90µSv/hour seem excessively high given other measurements by CRMS in the area.

manuscript (German),6753,7022891,00.pdf
video (German)…
CRMS website and map

Clearly the true reason behind fan death is dehydration.

Maybe I shouldn't post that on SK websites....

On the other hand, if it gets them to drink more water it might actually prevent deaths.

By TheGoodLocust (not verified) on 26 Aug 2011 #permalink

> under the impression that cesium doesn't
> bioaccumulate in humans.

You still haven't read to the end of the sentence at the Wikipedia link you gave as your source for your wrong idea.

[Subsequent comments don't seem to have gone in your favour -W]


Post the sentence fragment then since my eyes appear to be glazing over it. My reading of it is that it does not bioaccumulate in humans.

By TheGoodLocust (not verified) on 26 Aug 2011 #permalink

The bottom line for most people is of course not radiation maps, sieverts or becquerels but how much risk they face from radiation.

The linked paper compares radiation risk to some other risks and finds that the mortality risk from air pollution in central London to be an order of magnitude higher than from radiation dose to those evacuated from the Chernobyl "strict control zones". Even in the case of those living illegally in those zones, the risk of mortality is still less than from London air pollution.

Chernobyl was an accident. Air pollution is business as usual.

Are passive smoking, air pollution and obesity a greater mortality risk than major radiation incidents?

TEPCO deserves some significant blame for the mess that happened.


failed to ask for help soon enough
mismanaged the whole disaster
did not prepare an adequate site to cope with a tsunami
were running obsolete reactors when more modern, safer designs are available.

[I think there is no doubt that TEPCO, and possibly other reactor operators worldwide, and not nearly as competent as they could be. They are helped in this by the secrecy that surrounds the reactors; a more open and competetive environment would help -W]

@ 24's link gives us the result that a one pack a day smoker who moved into Fukushima but gave up the pack a day would become significantly healthier (umm, OK, have a lower risk of dying younger).

At that sort of level of relative risk I'm afraid I can't get all that worked up about the radiation spewed around the place.

Cesium does bioaccumulate, but it does not do so strongly. It is because Cs usually go together with K which animals actively exchange with the environment. According to studies prior to the accident, sea fish contain radioactive cesium 10 to 100 times denser than in seawater, but not 1000 to 10000 times denser as in the case of mercury.

By Kooiti Masuda (not verified) on 28 Aug 2011 #permalink

> cesium
Yep. That's what it says on Wikipedia, past the line break:

"Radiocaesium does not accumulate in the body
as effectively as many other fission products" explains it well:
once "the source of exposure is removed, much of the cesium will readily clear the body along the normal pathways for potassium ...."

This is well studied, there is a "sizable database on the time-dependent distribution and retention of radiocesium in the human body."

> can't get all that worked up
Nobody need be who's getting the average dose; the statisticians have already complained that it won't be possible to detect the health effect on the exposed population.

> spewed

There's the problem--the locally high concentrations, not the overall average (click the PDF file links at the bottom for the numbers)

Ah, you kids nowadays, you missed all the fun of the 1960s. Note the references to deep ocean circulation/Broecker -- a lot was being learned from tracing these new isotopes:,%2021th%20session%20(Suppl.%20…

@Kooiti Yes, I am aware that it bioaccumulates in other organisms (mostly plants) and in creatures that have a diet mainly based on those organisms, but does it do so with humans under "normal" dietary conditions?

It seems, and I could be wrong, that the cesium will quickly cycle out of the body.

If you live near Fukushima you should lay off the lichen (and other contemporarily odd foods) for a while and you should be fine.

By TheGoodLocust (not verified) on 28 Aug 2011 #permalink…

"... cesium and potassium are not utilized interchangeably in normal biological systems. Although the two elements are related, the body has a greater binding capacity for Cs than for K. Further evidence of the relative binding capacity for Cs and K .... in our study, Cases 1 and 2 had biological half-lives for cesium of 90 and 155 days, respectively, while potassium half-lives were 42 and 41 days, respectively. These values are compatible with reported values as summarized in Table V." (p. 1269)

The above is consistent with other references. There's no support anywhere for wossname's odd notion that humans are unique in the biological world in how they handle cesium.


1) I never said humans handle cesium in a "unique" way (that would be a strawman on your part). I said bioaccumulation of cesium, for mammals anyway, is based on diet. That was a short way of saying that in order to bioaccumulate cesium you need to ingest more than you excrete.

2) I asked you to show me the sentence in wikipedia that supports your assertion. You mocked me over it multiple times. So was it or was it not there?

3) You've posted links, such as google, which support bioaccumulation in non-humans.

4) Your latest link, a 50 year old study with a sample size of 4, doesn't cut it either. Purposely ingesting cesium in a single dose is not a natural diet and does not prove or imply bioaccumulation.

5) For your benefit:

6) How does the body react to sustained cesium intake? Do cells start discriminating against cesium over time?

7) Further reading:

By TheGoodLocust (not verified) on 28 Aug 2011 #permalink

snide | August 27, 2011 11:49 PM --- Easy to be wise after the event. Do read Henry Petroski's "To EngineERR is Human".

By David B. Benson (not verified) on 28 Aug 2011 #permalink


Your latest link adds nothing new. I'm already aware that cesium will stay in the body for a short period of time.

The question is one of bioaccumulation.

Please address my previous numbered points - esp. number two since I don't like making grievous errors.

Additionally, your latest link brings with it problems of its own since the Japanese diet has significantly changed since the 1960's both due to cultural changes and the expansion of global trade.

By TheGoodLocust (not verified) on 28 Aug 2011 #permalink

An extensive system of radiation monitors is going in at schools in Fukushima -- I'd guess these are meant to 'instill confidence' (see that page for many more links).

Washing surfaces and cleaning out gutters and ditches around schoolyards ought to remove the little hot spots reported earlier.

There's a climate-change aspect to this. There's an unexpected amount of Chinese nuclear test fallout detectable in the background radiation measurements worldwide, because of a decadal change in dust storms -- search (done this way to get past the spam-eater): dust+storm+chinese+nuclear+test will find "Association for Asia Research- Dust storms have increased ten-fold" among other reports.

Somewhere on a news source from Japan was a brief article stating that the Japanese govenment is setting a 1 mSv/yr standard for school children. Generously assuming this is for being outside 8 hours/day, it seems they won't be allowed to do a year abroad in Cornwall?

By David B. Benson (not verified) on 28 Aug 2011 #permalink

According to this report testing of urine from a number of children in Fukushima yielded maximum readings of 1.13 becquerels of cesium-134 per 1 litre of urine from an 8-year-old girl, and 1.30 becquerels of cesium-137.

Typically the human body contains about 5000 becquerels of potassium-40. At these levels it wouldn't really matter if the biological half life of cesium in humans was a decade.

quokka | August 28, 2011 7:26 PM --- I assume that level of potassium is for adults. What about children? Just use the mass ratio?

By David B. Benson (not verified) on 28 Aug 2011 #permalink


Don't know for certain, but it would seem a reasonable assumption.

Further on cesium contamination, it would seem that TEPCO has pretty much stopped discharge of contaminated water into the sea.

> somewhere in a news source

One such report is at the Asahi link above at 7:02.

It sounds like an aspiration, a desirable outcome, rather than a mandated limit.

"The education ministry on Aug. 26 also informed the Fukushima prefectural government that it had decided on a policy of seeking to limit the annual level of radiation children in the prefecture are exposed to at school to under 1 millisievert."

Conversion tool:

Background levels at
(obfuscated to get past the spam filter)
doubleyou doubleyou doubleyou

The low results from children quokka links above (dated June 30) supports the cautious approach taken. There should be more screening results available since then, and presumably ongoing study.

Cesium -- because there's no natural source for the radioactive isotopes -- has offered few opportunities for study and assumptions have been made that will be checked.

"The International Commission on Radiological Protection (ICRP) assumes that cesium and potassium are homogenously distributed throughout the whole body of an organism. However, the presented results show that there is a non-uniform distribution of 137Cs and 40K in different skeletal bones and their adherent tissues .... ... minimum values of 137Cs and 40K in the ribs were 29.9 and 21 Bq kgâ1 fresh mass ... and the maximum values 332 and 132 Bq kgâ1 fresh mass ...."

Yes, that's only one cow:

Yes, that's not a huge amount of radioactivity.

Note that the assumption of even distribution throughout versus the observation of local concentration in different tissues.

Much is still guesswork here. That's why precautions are taken before facts are certain.

"snide | August 27, 2011 11:49 PM --- Easy to be wise after the event. Do read Henry Petroski's "To EngineERR is Human"."

TEPCO was corrupt and inept before the event, that much was already well known. Nothing was done to fix that. A leaderless organisation is one that is already headed for failure.

The moment the tsunami shut down the cooling systems, there was a desperate need for outside help. But, for exmaple, that was not asked for till it was all over. Then they finally asked for fresh water, which the Americans were able to supply, from a military base right there in Japan. That took two weeks to organize.

[I'm not sure what your point is. I could take the motto that TEPCO was incompetent, but that tells you nothing about the intrinsic safety of nooks. Or I could take the motto that TEPCO was corrupt, and so inevitably are all nuke owners, so all nooks are unsafe. Which did you mean? -W]


The IAEA has described the on the ground response by management and staff at the Fukushima Daiichi plant as "exemplary" in it's preliminary report. It's not at all clear that a significantly better outcome could have been achieved no matter what else was done. It is very possible that the fate of the reactors was sealed once the diesel generators were lost. It's also possible that the outcome could have been significantly worse, were some other decisions taken.

You can interpret this how you will, as being the work of TEPCO corporation or the local plant management. I'm inclined to go for the latter.

For all the blather spoken about risk to plant workers, in view of the multiple problems faced, the loss of most instrumentation and questionable reliability of that which remained functional and what must at times been very trying working conditions, the health of the plant workers has been quite well protected. No case of acute radiation sickness and relatively modest radiation dose to perhaps a hundred or so workers. Job well done on that measure.

The maps linked by quokka #43 (August 30, 2011 5:13 AM) show radioactive Cesium (in Bq/kg) in soil. The depth of the layer to be surveyed was 15 cm in rice paddies and 30 cm in other crop fields.

By Kooiti Masuda (not verified) on 31 Aug 2011 #permalink