Sunday, July 15, 2012

New Study on Children's Exposure to Fukushima Radiation Raises More Questions Than It Answers

One of the most distressing aspects of the Fukushima crisis from my perspective is the effort to trivialize the significance of the event by scientists and regulators.

I've posted previously about the NRC's assertion that such an event is very unlikely to occur in the US despite the fact that both San Onofre and Diablo nuclear power plants sit on or in close proximity to faults next to the ocean

We've also seen how science has sought to manipulate public and regulatory opinion about the scope and severity of the disaster by equating all forms of radioactive fallout with gamma exposure and by failing to develop experimental designs that allow for investigation of delayed effects caused by exposure to ionizing radiation 

The most obvious kind of impression management strategy has been to trivialize the scope of the disaster by failing to acknowledge the myth of cold shutdown. The Fukushima plant has been releasing radioactive emissions for almost a year and a half now. 

Cold shutdown is a myth and the radiation releases into the air and sea have been ongoing.

Consequently, any and all estimates of releases based on data from March through May of 2011 are PARTIAL.

The most recent effort to trivialize the effect of radiation from Fukushim can be found here:

Thyroid doses for evacuees from the Fukushima nuclear accident. Nature.

[excerpted] A primary health concern among residents and evacuees in affected areas immediately after a nuclear accident is the internal exposure of the thyroid to radioiodine, particularly I-131, and subsequent thyroid cancer risk. In Japan, the natural disasters of the earthquake and tsunami in March 2011 destroyed an important function of the Fukushima Daiichi Nuclear Power Plant (F1-NPP) and a large amount of radioactive material was released to the environment. Here we report for the first time extensive measurements of the exposure to I-131 revealing I-131 activity in the thyroid of 46 out of the 62 residents and evacuees measured. The median thyroid equivalent dose was estimated to be 4.2 mSv and 3.5 mSv for children and adults, respectively, much smaller than the mean thyroid dose in the Chernobyl accident (490 mSv in evacuees). Maximum thyroid doses for children and adults were 23 mSv and 33 mSv, respectively.

MAJIA HERE: First, it is noteworthy how small the sample size is in this study: "In total, 62 people aged from 0 to 83 years old (of which accurate information on age was unavailable for eight people) underwent the measurement with informed consent."

MAJIA HERE: Second, the following passage is odd. It acknowledges that some children were in extensively contaminated areas but the study extrapolated their exposure from adults, and fails to tell us whether or not those adults were from the extensively contaminated areas: 

"Some children were known to have stayed in heavily contaminated areas from March 11th to 18th. As the most conservative scenario, we estimated the thyroid dose to children, using the atmospheric I-131 concentration assessed from the thyroid measurements of adults."

Majia here: notice all the estimations in the article about how calculations for kids were extrapolated. Notice also that exposure is limited to March 15 in this passage:

 [Excerpted] "As mentioned earlier, we considered that the rainfall on March 15th resulted in deposition of ambient radioactive materials on the ground and subsequent less possibilities to inhale them. The maximum I-131 activity detected in the thyroid of an adult was 1.5 kBq. Assuming the inhalation exposure took place for 4 hours on the afternoon of March 15th (see above), we estimated that this person could inhale as much as 85 kBq of I-131. Using the thyroid activity and breathing rate16, the maximum atmospheric I-131 concentration was estimated to be 23 kBq m−3. In our data analysis, we did not consider I-132 exposure due to lack of information. "

Majia here: It is interesting that even with this set of limitations the article here finds that the children might have been subject to doses on excess of 50 millisieverts:

[Excerpted] "Using the maximum atmospheric concentration, the thyroid dose for different age groups from inhalation of I-131 was calculated for children as shown in Table 2. In this estimation the dose for 1-, 5- and 10-year-old children could exceed 50 mSv. If children in this age range remained in Tsushima District after the radioactive plume arrived in the afternoon of March 15th, they might have experienced further exposure to I-131

Majia here: Yet, the study results indicate an exposure of only 4 millisieverts for kids? How is that? Well, look at this passage from the methodology section. The study is using a lot of estimations in its calculations and one of those estimations is based on the premise that iodine-131 was inhaled only on March 15th

[Excerpted] "Where DT,0 is the thyroid equivalent dose (mSv) assuming that they inhaled I-131 on March 15th, t is the elapsed time between March 15th and the measured date, Teff is the effective half-life of I-13117, f is the equivalent thyroid dose coefficient16, 17, and i is the thyroid uptake factor equal to 0.3. The effective half-lives of 3 months (from 0 to 1 year of age), 5 years (more than 2 to 7 years of age), 15 years (more than 12 to 17 years of age), and adult (more than 17 years of age) were calculated using each biological half-life given by ICRP Publication 6717, and they were estimated to be 4.67, 5.94, 7.15, and 7.27 days, respectively."

MAJIA HERE: This research study's conclusions based on 61 subjects, using a methodology that entailed a scintillation spectrometer held to the neck during the period of April 12 to 16th 2011 presuming .3 uptake RAISES MORE QUESTIONS THAN IT ANSWERS.

[Excerpted] We measured activity in the thyroid during the period from April 12th to 16th, 2011, using a 3-inch × 3-inch NaI(Tl) scintillation spectrometer (JSM-112, Hitachi Aloka Medical, Ltd., Tokyo). We wrapped the detection head with plastic foil and cleaned the neck with alcohol wipes so as to avoid radioactive contamination. We then placed the detection head on the cleaned part of the neck and started the measurement.

MAJIA HERE: I cannot comment on whether a scintillation spectrometer held to the neck is a reliable indicator of iodine-131 uptake. 

But I can suggest that the sample size was not adequate and the assumptions about the time and amount of uptake raise many more questions than they answer.

I've asked for feedback on my analysis at Enenews and here it is:

BOBBY 1: Majia, in addition to the procedural defects noted by FRCSR, the study did not account for I-132, I-133, I-135, and I-129, and used the flawed ICRP measurement model which has been criticized and replaced by Chris Busby and the ECRR.

It is likely that there was much more I-132 and I-135 than I-131 exposure in the early days.

CHRISK9: Good post and analysis of the study on your blog. your question about the type of scintillation detector is one of the best questions to ask because that was the first thing that stood out to me.

The small one inch detector would never be used in the real world for accurate detection. And even the 4 inch version, even though it is better is not how accurate iodine measurements would ever be taken in any operating plant in the United States. They could be used to indicate the presence of iodine, but should not be a tool of quantitative measurement. 

And the study was conducted a month after exposure started and peaked for an isotope I131 that has a half life of 7 days. One sixteenth of the dose received the during the first few days would be all that is left.

There are other issues with this study, but it is not worth commenting further if the basics are wrong to start with.

The correct way to measure iodine is with a whole body counter in a shielded room. The counting would take about 5 minutes per person, and these counters are located in every nuclear facility in Japan or elsewhere. It would take a day or two to move one and set it up, but it is fairly simple to do.

MAJIA HERE: I appreciate the feedback.

Here are some other data points that contribute to concerns about the conclusions drawn from this study about children in Fukushima's exposure to Iodine 131:

Just 0.8% of children in 2001 Japanese control group had thyroid cysts or nodules — 36% in Fukushima study
Taken from thyroid examination section of the sixth report of Fukushima Prefecture Health Management Survey (Section 7 here) translated by Fukushima Voice:

Majia Here: I am not saying that this data set is the truth as contrasted with the comparatively low level of exposure extrapolated from the study published at Nature.

What I am saying is that there were quite a few accounts published in the Japanese news media that children in Fukushima have thyroid nodules and this development is very worrying.

Given efforts to trivialize the disaster, I hope to raise questions about the adequacy of the Nature study in predicting Fukushima children's exposure to iodine-131.

The release of iodine 131 was not restricted to March 15 2011.

Iodine 131 has been detected many times in radioactive sewage sludge in many areas in Japan

Furthermore, evidence exists that efforts have been made to censor data on children's thyroid exposure. Please see the following narrative and citations:

On July 6 2011 the Japanese press Kyodo reported that in a March survey of 1,080 children aged 0 to 15 in Iwaki, Kawamata, and Iitate, 45% of kids in Fukushima survey had thyroid exposure to radiation[i] 

In August, NHK reported that Japan’s nuclear commission had erased children’s exposure data derived from a test of 1,000 children aged 15 or younger who had been screened for radiation affecting their thyroid.[ii] The report stated that one four year old child had a thyroid exposure of 35 millisieverts, but that the amount was “not considered a health threat.” 

This exposure level accounts only for Iodine-131 and does not incorporate the child’s total exposure to other radionuclides. In April 2012, the Peace Philosophy Centre posted the results of the Fukushima government’s March 2012 survey of 38,001 children under 18 located in thirteen Fukushima prefecture cities. Thyroid nodules (5.0mm) or cyst (20.0mm) were detected in 13,460 individuals, or 35.3% of the sample. These results were an increase of 5.6% from a January pre-test.[iii]

[i]              “45% of Kids in Fukushima Survey Had Thyroid Exposure to Radiation,” Mainichi (2011, July 5):
[ii]           Nuclear Commission Erases Children's Exposure Data,” NHK (2011, August 11):
[iii]          Sources: Actual research document available here: The Peace Philosophy department posted the results:; Translation provided by Blogger Fukushima Diary:


  1. Your comment on how children's exposure was estimated based on adults is a good catch. They mention that the children were in highly contaminated areas, but not the adults. This raises questions on how the sample was collected, that they may have made the amount of exposure look smaller than it actually was.

    Second, they did not consider I-132, but that could be extrapolated from the CTBTO measurements from Takasaki.

    There was 14.6 million uBq/m3 of I-131 on 3/15-3/16. But notice there was 11.1 million uBq/m3 of I-132. Also the 27 million of Te-132 decays into I-132. So there was quite a bit more I-132 than I-131.

    Also the CTBTO report of March 27 listed 370 million uBq/m3 of I-135 on this date.

    This amount was subsequently removed from the CTBTO report, allegedly from equipment failure. Putting it all together, there was 26 times as much iodine total as there was iodine-131, mostly short half-life, but still damaging isotopes.

    Then there is the ICRP measurement technique, which is produces a far lower iodine measurement than the ECRR one, a factor of 600 or so.

    Plus as you said, iodine emissions did not stop in March 2011. Keeping the Petkau effect in mind, small exposures over a long period of time are worse than large one-time exposures.

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