Small head size and delayed body weight growth in wild Japanese monkey fetuses after the Fukushima Daiichi nuclear disaster




To evaluate the biological effect of the Fukushima Daiichi nuclear disaster, relative differences in the growth of wild Japanese monkeys (Macaca fuscata) were measured before and after the disaster of 2011 in Fukushima City, which is approximately 70 km from the nuclear power plant, by performing external measurements on fetuses collected from 2008 to 2016. Comparing the relative growth of 31 fetuses conceived prior to the disaster and 31 fetuses conceived after the disaster in terms of body weight and head size (product of the occipital frontal diameter and biparietal diameter) to crown-rump length ratio revealed that body weight growth rate and proportional head size were significantly lower in fetuses conceived after the disaster. No significant difference was observed in nutritional indicators for the fetuses’ mothers. Accordingly, radiation exposure could be one factor contributed to the observed growth delay in this study.


The Fukushima Daiichi nuclear power plant (NPP) disaster that occurred in March 2011 exposed a large number of humans and wild animals to radioactive substances. Several studies of wild animals in Fukushima investigated health effects of the disaster, such as morphological abnormalities in gall-forming aphids (Tetraneura sorini, T. nigriabdominalis)1 and pale grass blue butterfly (Zizeeria maha)2, hematological abnormalities in carp (Cyprinus carpio)3, and chromosomal aberrations in wild mice (Apodemus argenteus, Mus musculus)4. However, there is no research investigating long-term exposure to radiation on mammals that typically have long life-span to date. This study is the first report to observe long-term biological effects of the pre- and post-NPP disaster on non-human primates in Fukushima.

We previously studied radioactive exposure and its effect on health of Japanese monkeys (Macaca fuscata) inhabiting Fukushima City, which is located approximately 70 km from the Fukushima Daiichi NPP5, 6. After the NPP disaster, the range of radiocesium soil concentrations in Fukushima City was 10,000–300,000 Bq/m2. Hayama et al.5 investigated chronological changes in muscle radiocesium concentrations in monkeys inhabiting Fukushima City from April 2011 to June 2012. The cesium concentration in monkeys’ muscle captured at locations with 100,000–300,000 Bq/m2 was 6000–25,000 Bq/kg in April 2011 and decreased over 3 months to approximately 1000 Bq/kg. However, the concentration increased again to 2000–3000 Bq/kg in some animals during and after December 2011, before returning to 1000 Bq/kg in April 2012, after which it remained constant.

Fukushima monkeys had significantly lower white and red blood cell counts, hemoglobin, and hematocrit, and the white blood cell count in immature monkeys showed a significant negative correlation with muscle cesium concentration6. These results suggested that the short-term exposure to some form of radioactive material resulted in hematological changes in Fukushima monkey

The effects associated with long-term low-dose radiation exposure on fetuses are among the many health concerns. Children born to atomic bomb survivors from Hiroshima and Nagasaki showed low birth weight, high rates of microcephaly7, and reduced intelligence due to abnormal brain development8. Experiments with pregnant mice or rats and radiation exposure had been reported to cause low birth weight9, 10, microcephaly11,12,13, or both14, 15. We identified one similar study on wild animals16, which reported that the brains of birds captured in the vicinity of the Chernobyl NPP weighted lower compared to those of birds captured elsewhere.

The population of Japanese monkeys in Fukushima City had been systematically managed since 2008 according to a management plan based on law and regulated by Fukushima Prefecture to reduce damage to agricultural crops. Our research group studied the reproductive and nutritional status of the Japanese monkey population by performing autopsies on individuals captured and euthanized by Fukushima City17. These Japanese monkeys were the first wild primate population exposed to radiation as result of nuclear disaster. However, there was no other study either in Chernobyl or Fukushima that followed fetal development over time or compared fetal development before and after long-term radiation exposure in the same wild animal populations.

The objectives of this study were to compare changes in the fetal development of Japanese monkeys in Fukushima City before and after the NPP disaster to determine evidence of developmental delay in Japanese monkey fetuses.


Radiocesium was detected in mothers’ muscle that had conceived after the NPP disaster (Table 1). Mean muscle radiocesium concentration was 1059 Bq/kg for mothers that mated in 2011 and gave birth in 2012 (n = 14), although the concentration decreased gradually in subsequent years up to 22 Bq/kg for mothers that gave birth in 2016 (n = 3). Because muscle tissue was not available prior to the NPP disaster, muscle radiocesium concentrations for individuals captured pre-disaster could not be measured. However, muscle radiocesium concentrations in wild Japanese monkeys captured in 2012 in Aomori Prefecture, which is also located in the Tōhoku region 400 km north from the NPP, were below the detection limit2, therefore, we assumed that the muscle radiocesium concentrations in the Japanese monkeys in Fukushima City prior to the disaster were also below the detection limit.

Similarly, although the air dose in the area of Fukushima City inhabited by the Japanese monkeys was 1.1 to 1.2 µSv/h in April, 2011, it has decreased, reaching 0.10 to 0.13 µSv/h in May, 2016 (Table 2). Based on these measurements, it is estimated that monkeys in this area received accumulated air doses of at least 12 mSv over the five years since the NPP disaster.

The descriptive statistics for Japanese monkey fetuses in Fukushima were shown in Table 3. The median body weight (g) and median body weight growth rate (g/mm) were significantly different between pre- and post-disaster groups (p = 0.032 and 0.0083, respectively). The mean biparietal diameter (mm), occipital frontal diameter (mm), head size (mm2), and proportional head size (mm) were significantly different between pre- and post-disaster groups (p = 0.046, 0.018, 0.014, and 0.0002, respectively). CRL was not significantly different between the two groups. Regression lines describing association of body weight and CRL in pre- and post-disaster groups were described in Fig. 1. Post-disaster regression line was significantly lower than pre-disaster regression line (p < 0.0001) (Table 4). Regression lines describing association of head size and CRL in pre- and post-disaster groups were described in Fig. 2. Post-disaster regression line was significantly lower than pre-disaster regression line (p < 0.0001) (Table 5).

The body fat index for the mothers of these fetuses was not significantly different before and after the NPP disaster (Z = 1.213; P = 0.219).


Body weight and head size relative to the CRL were lower in fetuses conceived after the NPP disaster compared with fetuses conceived prior to the NPP disaster. Japanese monkeys in Fukushima City first conceive in fall when they were five years old and gave birth in spring when they were six years old17. Thus, we assumed that all the mothers we examined that conceived babies after the NPP disaster were continuously exposed to radiation from at the time of the disaster in 2011.

Growth retardation of the fetuses could be caused by the deterioration of the mothers’ nutritional status. However, we did not observe any difference in the body fat index of mothers pre- and post-NPP disaster. Therefore, the growth retardation of the fetuses was unlikely to be associated with to the mothers’ nutritional status. Other factors such as climate changes or food nutrient components might have affected the growth of fetuses. The limitations of this study were that we were not able to obtain samples to look at histological change that might have contributed to the cause of delayed fatal growth and the sample size were relatively small because of the nature of the sampling collection. It might have been ideal to compare monkeys from the evacuation order area to monkeys from the non-contaminated area of Fukushima; however, there was no other area such besides the one in this study that performed systematic large-scale capturing aimed at seizing hundreds of monkeys. In addition, there had been access limitations beyond the evacuation order area. For these reasons, it is impossible to replicate an equivalent study elsewhere at this time.

In experiments using mice and rats, radiation exposure has been reported to cause reduced fetal weight, microcephaly, and reduced brain mass9,10,11,12,13,14,15. However, most of these experiments involved exposing the mother to a single radiation dose at a fetal age of 10 days or later when the brain undergoes development. Such exposure may be qualitatively different from the low-dose, long-term exposure following an NPP disaster. The radiation doses in these experiments varied substantially. Hande et al.9 exposed mice to 9 mGy of 70 kilo-Volt peak X-rays at fetal ages of 3.5, 6.5, and 11.5 days, and found that birth weight was reduced relative to the control mice in all cases. Uma Devi et al.15 exposed mice to 0.25 Gy at a fetal age of 11.5 days and observed reduced head size at birth. In addition, they observed negative correlation between radiation dose and head size in fetuses exposed to 0.05 to 0.15 Gy.

The number of low birthweight children born to residents of some highly contaminated areas of Belarus increased between 1982 and 1990, after the Chernobyl NPP disaster18. Hujuel et al.19 conducted a longitudinal survey of women exposed to radiation through dental treatment who subsequently gave birth. They reported that women exposed to 0.4 mGy or more had increased risk (odds ratio 2.27) of giving birth to a child weighing 2500 g or less. Goldberg et al.20 elucidated the relationship between the level of radiation exposure as a result of medical exams prior to conception and birthweight, and found that birthweight decreased by 37.6 g for every cGy of exposure. Such medical exposure is believed to affect the mother’s gonads and endocrine glands rather than the fetus itself. There is still uncertainly to determine whether the retarded growth we observed was a direct effect of the radiation exposure.

Otake and Schull8 conducted a temporal variation study of mothers exposed to radiation by the atomic bombs in Hiroshima and Nagasaki. They did not observe any effect in newborns that had been exposed between fetal ages of 0 to 8 weeks, and the highest rates of microcephaly and other brain damage occurred in newborns exposed between fetal ages of 8 to 15 weeks. Given that the latter period was when the human brain undergoes rapid development, damage due to radiation exposure during this period might cause severe effect on fetuses.

The previous research suggested that the low birthweight and small head sizes observed in fetuses conceived after the NPP disaster were result of radiation exposure. However, we were not able to quantify the external and internal radiation dose in individual wild animals. Although radiocesium was detected in the muscles of all individuals captured after the NPP disaster, the cumulative exposure was unclear since the biological half-life of radiocesium in monkeys was approximately 3 weeks5. Furthermore, because of the small sample size, it was difficult to determine the causal relationship of exposure dosage and the effect on fetuses.

Although we showed that fetal proportional head size reduced after the NPP disaster, it was not possible to identify anatomically which part of the brain was developmentally retarded. Hossain et al.12 studied the brains of 6- to 12-month-old mice that were exposed to cobalt 60 at a fetal age of 14 days. Brain weight decreased at exposure rates of 0.5 to 1.5 Gy and the number of neurons in the hypothalamus in the CA3 region decreased significantly. We started to perform histological examination brain of fetuses and juvenile monkeys conceived after the NPP disaster to identify the regions of the brain that were developmentally retarded and the effect of retarded growth on post-natal development for further study.


1, Akimoto, S. I. Morphological abnormalities in gall-forming aphids in a radiation-contaminated area near Fukushima Daiichi: selective impact of fallout? Ecology and Evolution. 4, 355–369 (2014).

2, Hiyama, A. et al. The biological impacts of the Fukushima nuclear accident on the pale grass blue butterfly. Scientific Reports. 2, 570, doi:10.1038/srep00570 (2012).

3, Suzuki, Y. Influences of radiation on carp from farm ponds in Fukushima. Journal of Radiation Research. 56, i19–23, doi:10.1093/jrr/rrv076 (2015).

4, Kubota, Y. et al. Chromosomal aberrations in wild mice captured in areas differentially contaminated by the Fukushima Dai-Ichi nuclear power plant accident. Environ. Sci. Technol. 49, 10074–10083 (2015).

5, Hayama, S. et al. Concentration of radiocesium in the wild Japanese monkey (Macaca fuscata) 15 months after the Fukushima Daiichi nuclear disaster. PLoS ONE. 8, e68530 (2013).

6, Ochiai, K. et al. Low blood cell counts in wild Japanese monkeys after the Fukushima Daiichi nuclear disaster. Scientific Reports. 4, 5793, doi:10.1038/srep05793 (2014).

7, Miller, R. W. & Blot, W. J. Small head size after in-utero exposure to atomic radiation. Lancet. 2, 784–787 (1972).

8, Otake, M. & Schull, W. J. In utero exposure to A-bomb radiation and mental retardation; a reassessment. Bri. J. Rdiol. 57, 409–414 (1984).

9, Hande, M. P., Uma Devi, P. & Jageta, G. C. Effect of “in utero” exposure to low dose energy X-rays on the postnatal development of mouse. J. Radiat. Res. 31, 354–360 (1990).

11, Uma Devi, P., Hossain, M. & Bisht, K. S. Effect of gamma radiation on fetal haemopoietic system in the mouse. Int. J. Radiat. Bio. 74, 639–646 (1998).

12, Bang, D.-w. et al. Dose-induce relationships on the prenatal effects of gamme-radiation in mice. J. Vet. Sci. 3, 7–11 (2002).

13, Hossain, M., Chetane, M. & Uma Devi, P. Late effect of prenatal irradiation on the hippocampal histology and brain weight in adult mice. Int. J. Devl. Neuroscience. 23, 307–313 (2005).

14, Uma Devi, P. & Hossain, M. Effect of early fetal irradiation on the postnatal development of mouse. Teratology. 64, 45–50 (2001).

15, Kim, S. H. et al. Dependance of malformation upon gestational age and exposed dose of gamma radiation. J. Radiat. 42, 255–264 (2001).

16, Uma Devi, P., Baskar, R. & Hande, M. P. Effect of exposure to low dose gamma radiation during late organogenesis in the mouse fetus. Radiat. Res. 138, 133–138 (1994).

17, Møller, A. P., Bonissoil-Alquati, A., Rudolfsen, G. & Mousseau, T. A. Chernobyl birds have smaller brains. PLoS ONE. 6, e16862 (2011).

18, Hayama, S., Nakiri, S. & Konno, F. Pregnancy rate and conception date in a wild population of Japanese monkeys. J. Vet. Med. Sci. 73, 809–812 (2011).

19, Peterova, A. et al. Morbidity in large cohort study of children born to mothers exposed to radiation from Chelnobyl. Stem Cells. 15(suppl 2), 141–150 (1997).

20, Hujoel, P. P., Bollen, A. M., Noonan, C. J. & del Aguila, M. A. Antepartum dental radiography and infant low birth weight. JAMA. 291, 1987–1993 (2004).

21, Goldberg, M. S., Mayo, N. E., Levy, A. R., Scott, S. C. & Poitras, B. Adverse reproductive outcomes among women exposed to low levels of ionizing radiation from diagnostic radiography for adolescent idiopathic scoliosis. Epidemiology. 9, 271–278 (1998).

22, Primate Research Institute, Kyoto University Guideline for fieled reserch for nonhuman primates. Accessed 28 January, 2017.

23, Japanese Ministry of Environment. 2012 Japanese Red List. Accessed 28 January, 2017.

24, Newell-Morris, L. L. Age determination in Macaque fetuses and neonates. Nursery care of nonhuman primates (ed. Ruppenthal, G. C.) 93–115 (Plenum Press, 1979).

25, Hayama, S., Mizutani, N., Morimitsu, Y., Shirai, K. & Nigi, H. Indices of body fat deposition in wild Japanese monkeys. Primate Res 14, 1–6 (1998).

26, Fukushima Prefecture website. Available: Results of air dose rate monitoring survey by Fukushima Prefecture. Accessed 20 January, 2017.

Read more :

Radiation levels exceeding state-set limit found on grounds of five Chiba schools

n-kashiwa-a-20170614-870x580Radiation levels exceeding the state safety limit have been detected on the grounds of five schools in Kashiwa, Chiba Prefecture.


Radiation levels exceeding the government-set safety limit of 0.23 microsieverts per hour have been detected on the grounds of five schools in the city of Kashiwa, Chiba Prefecture, the prefectural board of education said Monday.

Between late April and mid-May, the board officials detected radiation levels of up to 0.72 microsieverts per hour in certain areas of the schools, including Kashiwa High School and Kashiwa Chuo High School. The areas — including soil near a school swimming pool and drainage gutters — are not frequented by students, but the board closed them off and will work to quickly decontaminate them, the officials said.

Kashiwa has been one of the areas with high radiation readings since the 2011 nuclear disaster at Tokyo Electric Power Company Holdings Inc.’s Fukushima No. 1 power plant.

According to NHK, the board of education had been checking the soil on the school premises in Kashiwa after radiation levels beyond the state limit were detected in shrubbery near the city’s public gymnasium. The board will announce the results of radiation tests at other schools in the prefecture around the end of July, NHK reported.

0.24 to 0.72 microsievert per hour at five schools in Kashiwa city, 47km from Tokyo

Capture du 2017-06-12 17-21-21.png


In January 2017, the Chiba Prefectural Board of Education was notified that radiation above the national standard level was measured at the Kashiwa city central gymnasium.

Following that report the Chiba Prefectural Board of Education conducted an investigation in Kashiwa city from late April to the middle of May 2017.

A radiation level exceeding the national standard of 0.23 microsievert per hour was detected on the premises of five schools in Kashiwa City, The radiation measured at 1 meter above ground level ranged from 0.24 to 0.72 microsievert.

At Kashiwa High School, Higashi Tsukuba High School and Middle School, Kashiwa Chuo High School, Kashiwanami High School and Kusanami Takayanagi High School, at places where usually no one enters: near a pool, at the back of a bicycle parking lot, etc..

The prefectural Board of Education decided to cordon those hot spots, to prohibit the entry and to decontaminate those places by soil removal.

They are also planning to conduct a radiation levels survey to the schools outside of Kashiwa city.

Capture du 2017-06-12 20-07-17.png

Kashiwa city, 47.1km from Tokyo


Fukushima Radiation, What Prospects for Humanity : a Conversation with Helen Caldicott


Do not go to Japan. Do not under any circumstances take your children to Japan, because you don’t know what you’re eating and where the food is sourced…

And the Japanese are trying now to export their radioactive food to London and elsewhere. Taiwan has refused to receive it. But, it’s dangerous and it’s going to continue to be dangerous for the rest of time. It’s sad.Dr. Helen Caldicott (from this week’s interview.)



Length (59:09)

Click to download audio (MP3 format)

Arnie Gundersen, a nuclear educator and former nuclear industry senior vice president, has referred to it as “the biggest industrial catastrophe in the history of mankind.” [1]

Six years ago this week, a tsunami, triggered by a category 9.0 earthquake, slammed into the site of the Fukushima Daiichi nuclear facility on the north east coast of the Japanese island of Honshu. The natural disaster resulted in the failure of systems keeping the reactor cores and spent fuel rods cool, leading to core meltdowns in three of the plant’s reactors, as well as damage from consequent hydrogen explosions. [2]

Enormous quantities of radioactive particles were released into the atmosphere and the water table leading to the Pacific Ocean. Approximately 170,000 people in the vicinity of the plant were immediately evacuated.

The World Health Organization downplayed the health risks from the catastrophe, concluding in their 2013 Health Risk Assessment from the nuclear accident that the risks of contracting certain cancers in certain sex and age groups were only “somewhat elevated.” The report also concluded “no discernable increase in health risks from the Fukushima event is expected outside Japan.” [3]

Nevertheless, a health management survey examining 38,000 children in Fukushima found three children diagnosed with thyroid cancer. The natural incidence is one in one million. [4]

Further, a December 2011 peer-reviewed report in the International Journal of Health Sciences found that in the 14 weeks immediately following the event, there were 14,000 excess deaths in the United States connected with radio-active fall-out from the Fukushima meltdowns. [5]

 The Japanese government has been so successful in its efforts to assuage the concerns of the wider public that Prime Minister Abe was able to secure Tokyo as the site for the 2020 Olympic Summer Games! As of this month, the Abe government ends its housing subsidies to people evacuated from the area proximate to the nuclear facility, forcing those fearful of the lingering radiation to fend for themselves abroad. [6][7]

The nuclear accident may have profound consequences for all humanity, and possibly all life on Earth, yet the severity of the situation doesn’t seem to merit major headlines.

On this, the sixth anniversary of the start of the Fukushima crisis, we spend the hour with world renowned nuclear watchdog, Dr. Helen Caldicott.

 In this interview, conducted and recorded on International Women’s Day, Dr. Caldicott talks about the high radiation reading recently recorded at Unit 2, efforts to contain the radioactive water spilling out of the facility, projected health risks from the cesium, tritium, strontium and other isotopes spewing from the site and much, much more. Caldicott also extends the discussion to talk about Canada’s role in nuclear proliferation and the threats posed by the new Trump Administration and Cold War atmosphere in which it is situated.

 Dr. Helen Caldicott is a physician and co-founder of Physicians for Social Responsibility. She is a nominee for the Nobel Peace Prize, the recipient of the 2003 Lannan Prize for Cultural Freedom, and author or editor of several books including Nuclear Madness: What You Can Do (1979), If You Love This Planet: A Plan to Heal The Earth (1992)The New Nuclear Danger: George W. Bush’s Military-Industrial Complex(2001), and Crisis Without End -The Medical and Ecological Consequences of the Fukushima Nuclear Catastrophe (2014). She is currently the president of the Helen Caldicott Foundation ( Her latest book, Sleepwalking to Armaggedon: The Threat of Nuclear Annihilation will be available in bookstores in July, 2017.

15,550 Bq / kg radioactive cesium school rooftop sludge in Chiba prefecture


Noda city (Noda-shi on the map) is located in Chiba prefecture, at the northern doorstep of Tokyo.

Noda City announced on January 24 that more than 15,550 Becquerels of radioactive cesium exceeded the criteria of designated waste (more than 8,000 bq per 1 kilogram) from the rooftop sludge of Municipal Nittsuka Elementary School. It is the first time that sludge exceeded the standard value in the city. The city already removed the sludge, in accordance with procedures as specified waste based on the Special Measures Law.

In response to the high radiation dose measurements found in Kashiwa city public property site this month, the city started inspection of sludge etc. and dose measurement at 300 public facilities. The country’s decontamination standard is 0.23 microsieverts per hour with a measurement height of 1 meter (50 centimeters for children-related facilities), but the city has independently set the measurement height to be a more severe 5 cm. There are no places that have exceeded city standards so far.

Meanwhile, on the 14th and 15th, they measured sludge on the roof of 12 elementary and junior high schools that were the subjects of solar panel roofing projects. As a result, they found doses exceeding city standards at five schools, up to 0.85 micro-Sievert was measured. City removed the sludge and checked radioactive cesium concentration. Only the sludge of Yotsuka-sho, had concentration of cesium exceeding the standard value of designated waste.

The removed sludge is temporarily stored at a temporary storage place surrounded by containers on the city hall premises. Approximately 5 cubic meters of targeted waste is treated, and four schools sludge which cesium concentration was found within the standard value were treated as general waste.

Translated from Japanese by Hervé Courtois


February 2017: 184 Thyroid Cancer Suspected/Confirmed (1 Additional Case)


  • One more case of suspected thyroid cancer was diagnosed by cytology since the last report.
  • No additional surgeries since the last report: the number of confirmed cancer cases remains at 145 (101 in the first round and 44 in the second round)
  • Total number of confirmed/suspected thyroid cancer diagnosed (excluding a single case of benign tumor) is 184 (115 in the first round and 69 in the second round)
  • The second round screening data is still not final (confirmatory examination still ongoing).
  • Thyroid Examination Evaluation Subcommittee will be convened in May or June 2017 to evaluate the results of the second round screening.

On February 20, 2017, less than two months since the last report, the 26th Oversight Committee for Fukushima Health Management Survey convened in Fukushima City, Fukushima Prefecture. Among other information, the Oversight Committee released the latest results (as of December 31, 2016) of the second and third rounds of the Thyroid Ultrasound Examination (TUE). Official English translation of the results will be posted here. The narrative below presents basic facts of TUE and its current results in perspective, including information covered during the committee meeting and the subsequent press conference.

As of December 31, 2016, there is only 1 more case with cancer or suspicion of cancer from the second round, making a grand total of 184 (185 including the single case of post-surgically confirmed benign nodule) for the first and second round screening results combined. The number of surgically confirmed cancer cases, excluding the aforementioned case of benign nodule, did not change from the previous report (101 from the first round and 44 from the second round), and the remaining 38 (14 from the first round and 24 from the second round) continue to be under observation.

The second round screening (the first Full-Scale screening) was originally scheduled to be conducted from April 2014 through March 2016, and the primary examination (with the participation rate of 70.9% and the progress rate of 100.0%), is essentially complete. But the confirmatory examination (with the participation rate of 79.5% and the progress rate of 95.0%) is still ongoing.

The third round screening (the second Full-Scale Screening) began on May 1, 2016 and is scheduled to run through March 2018–the end of Fiscal Year 2018. As of December 31, 2016, 87,217 out of the survey population of 336,623 residents have participated in the ongoing primary examination at the participation rate of 25.9%. The confirmatory examination began on October 1, 2016, with the participation rate of 29.6% so far.

Full-Scale Screening (first and second)
To be conducted every 2 years until age 20 and every 5 years after age 20, the Full-Scale screening began with the second round screening (the first Full-Scale Screening) in April 2014, including those who were born in the first year after the accident. There are 381,282 eligible individuals born between April 2, 1992 and April 1, 2012. As of December 31, 2016, 270,489 actually participated in the primary examination.

The participation rate remained the same as 3 months earlier at 70.9% but lower than 81.7% from the first round screening. Results of the primary examination have been finalized in 270,468 participants, and 2,226 (increased by 4 since the last Oversight Committee meeting) turned out to require the confirmatory examination.

The confirmatory examination is still ongoing for the second round. Of 2,226 requiring the confirmatory examination, 1,770 have participated at the participation rate of 79.5% (increased from the previous 75.8% but still lower than 92.8% from the first round screening). So far 1,681 have received final results including 95 that underwent fine needle aspiration cytology (FNAC) which revealed 69 cases suspicious for cancer.

Confirmation of thyroid cancer requires pathological examination of the resected thyroid tissue obtained during surgery. There has been no additional surgical case since the last reporting. As of December 31, 2016, 44 underwent surgery and 43 were confirmed to have papillary thyroid cancer. One remaining case was confirmed to have “other thyroid cancer” according to the classification in the seventh revision of Japan’s unique thyroid cancer diagnostic guidelines. A specific diagnosis was not revealed, but it has been reported as a differentiated thyroid cancer that is not known to be related to radiation exposure and it is allegedly neither poorly differentiated thyroid cancer nor medullary cancer.

The third round screening or the second Full-Scale Screening has covered 87,217 or 25.9% of the survey population of 336,623. The primary examination results have been finalized in 71,083 or 81.5% of the participants, revealing 483 to require the confirmatory examination. Results of the confirmatory examination have been finalized in 64 of 143 (29.6%) that have been examined. FNAC was conducted in one person with a negative result: No cancer case has been diagnosed from the third round as of now.

Confusing issues
Conducted every 2 years up to age 20, the TUE transitions at age 25 to milestone screenings to be conducted every 5 years. Some residents are beginning to participate in the age 25 milestone screening, and if they have never participated in the TUE, their milestone screening results will be added to the second round screening results. Thus the number of the second round screening participants is expected to increase even though the screening period technically ended in March 2016.

However, the third round screening survey population excludes the age 25 milestone screening participants: their results will be tallied up separately.

Also in some cases, confirmatory examinations from the second and third rounds might be simultaneously ongoing, or there could be significant delays in conducting confirmatory examinations due to logistical issues such as the lack of manpower. A two-year screening period originally designed for subsequent rounds of the Full-Scale Screening is essentially spread over a longer time period, overlapping with the next round of screening. A precise interpretation of results from each round of screening might be nearly impossible.

A newly diagnosed case in the second round
In the second round, only 1 case was newly diagnosed by FNAC with suspicion of cancer. It is a female from Koriyama-City who was 17 years old at the time of the March 2011 disaster. Her first round screening result was A1.

Prior diagnostic status of the cases newly diagnosed with cancer in the second round
Of 69 total cases suspected or confirmed with cancer in the second round, 32 were A1, 31 were A2, and 5 were B in the first round. One remaining case never underwent the first round screening (no information such as age, sex or place or residence, is available regarding this case).

Thirty-two cases that were A1 in the first round, by definition, had no ultrasound findings of cysts or nodules, whereas 7 of 31 cases that were previously diagnosed as A2 had nodules with the remaining 24 being cysts. All 5 cases that were previously diagnosed as B were nodules, and at least 2 of them had undergone the confirmatory examination in the first round.

This means 56 (32 “A1” and 24 “A2 cysts”)of 69 cases had no nodules detected by ultrasound in the first round which could have developed into cancer. This is 81% of the second round cases suspected or confirmed with cancer. It has been speculated by some that these 56 cases were new onset since the first round, suggesting the cancer began to form in 2 to 3 years after the first round screening, conflicting with the common notion that thyroid cancer in general is slow growing.

Akira Ohtsuru, the head of the TUE, explained that even though some of the small nodules are very easy to detect by ultrasound, exceptions arise when 1) the border of the lesion is ambiguous, 2) the density of the lesion is so low that it blends into the normal tissue, or 3) the lesion resembles the normal tissue. Thus, it is not because the nodules newly formed since the first round screening, but because the nodules were simply not detected even though they were there, that cases which previously had no nodules are now being diagnosed with cancer. Ohtsuru said that when such previously undetected nodules become relatively large enough to become detectable by ultrasound, they might look as if they suddenly appeared. Ohtsuru added that nodules that have already been detected by ultrasound do not to appear to grow very rapidly in general.

This is a better, more legitimate explanation than the previous ones he offered that stated the nodules were present in the first round albeit invisible. However, 56 out of 69 cases seem like a lot to be explained by this.

An issue of the female to male ratio
The female to male ratio of cancer cases warrants a special attention. For thyroid cancer, the female to male ratio is nearly 1:1 in the very young, but it is known to increase with age and decrease with radiation exposure. (See below Slide 2 in this post for more information). In the second round, the female to male ratio has been ranging from 1.19:1 to 1.44:1 overall, but the FY2015 municipalities have consistently shown a higher number of males than females with the most recent female to male ratio of 0.7:1.

What Ohtsuru said about the the female to male ratio boils down to the following:

The female to male ratio for thyroid cancer is influenced by the reason for diagnosis and the age. When the confirmatory examination of the second round screening is completed, the data will be analyzed by adjusting for age and participation rates by sex. The female to male ratio in Japan’s cancer registry data, including all ages, is around 3:1, but it used to be bigger at 4:1 or 6:1 in the 1980’s and earlier. In Fukushima, the TUE was conducted in asymptomatic youth around puberty–a different condition than the cancer registry. Yet even in the cancer registry, the female to male ratio tends to be close to 1:1 up to the puberty. Autopsy data of occult thyroid cancer in individuals who died of causes other than thyroid cancer show the female to male ratio of 1:1 or smaller (more males) in adults. This fact indicates that thyroid cancer screening would yield the female to male ratio close to 1:1 even in adults. Thus, it is scientifically expected that thyroid cancer screening in general leads to a smaller female to male ratio.

He is claiming that thyroid cancer diagnosed by cancer screening before becoming symptomatic–as opposed to symptomatic thyroid cancer diagnosed clinically–is expected to show the female to male ratio near 1:1 or smaller, i.e., as many males are diagnosed as females, or more males are diagnosed than females.

To say the least, calling extrapolation from autopsy data to screening “scientific” seems a bit of a stretch. Furthermore, Ohtsuru’s claim does not add up scientifically. South Korea, where active screening increased the incidence of thyroid cancer, did not observe a smaller female to male ratio as shown in the table of thyroid cancer incidence by sex and age group compiled from Ahn et al. (2016). It is obvious the female incidence is much higher than the male incidence without actually calculating the ratio.

Thyroid cancer incidence by sex and age group per 100,000 
in the 16 administrative regions in Korea
 Compiled from Supplementary Tables 2 & 3 in Ahn et al. (2016) Thyroid Cancer Screening in South Korea Increases Detection of Papillary Cancers with No Impact on Other Subtypes or Thyroid Cancer Mortality (link)

Furthermore, Ohtsuru’s claim that the female to male ratio tends to be close to 1:1 up to the puberty in the cancer registry is not corroborated by the actual data. The table below was compiled from the National estimates of cancer incidence based on cancer registries. The number of thyroid cancer cases for each sex was listed side-by-side for each year and age group. Then a total from 2000 to 2012 was tallied for each sex and age group to obtain the female to male ratio, because the number of cases varies from year to year. Even without knowing exactly which age range Ohtsuru meant by “up to the puberty,” it is clear that the female to male ratio is not at all close to 1:1.

The number of thyroid cancer cases by sex and age group from 2000 to 2012
Compiled from the National estimates of cancer incidence based on cancer registries in Japan (link)

According to this study, the female to male ratio peaks at puberty and declines with age, as excerpted below:

The increased F:M ratio in thyroid cancer incidence does not remain static with age. Female predominance peaks at puberty. […] This pattern occurs as the thyroid cancer incidence begins to increase at an earlier age in females than in males, leading to a rise in the F:M ratio. The ratio starts to decline as the male incidence rate begins to increase and, concurrently, the rate of increase in female incidence rate slows down. The steady decrease in F:M ratio with age continues, and the peak male rate does not occur until between 65 and 69 years of age, compared with the earlier peak female rate between 45 and 49 years of age, just before the mean age of menopause at 50 years.

An issue of the participation rate
The primary examination participation rate of 70.9% in the second round screening is lower than 81.7% in the first round. Most notable is the participation rate of the oldest age group: 52.7% for ages 16-18 (age at exposure) in the first round plummeted to 25.7% for ages 18-22 (age at examination) in the second round. It is 6.6% for ages 18-24 (age at examination) for the ongoing third round so far.

Younger age groups in school have maintained pretty high participation rates thanks to the school-based screening. The older age group often leave the prefecture for college or jobs, and it becomes increasingly difficult to get them to participate, especially with their interests fading in their busy lives.

The status of the new third-party committee
The “international, third-party, neutral, scientific, up-to-date and evidence-based” expert committee proposed by Chairman Hokuto Hoshi at the last committee meeting is being discussed at the prefectural level in consultation with the central government. The prefectural official admitted that the plan was to establish an independent entity that will offer, from a neutral standpoint, latest knowledge of thyroid cancer needed by the Oversight Committee.

A committee member Tamami Umeda from the Ministry of Health, Labour and Welfare elaborated on her vision of the third-party committee as an entity to review and organize the latest clinical and epidemiological knowledge and studies. It would be separate from the Thyroid Examination Evaluation Subcommittee that is intended to evaluate and analyze the status of the TUE, including the evaluation of radiation effects. (Note: In reality, the Thyroid Examination Evaluation Subcommittee has been far from being effective in analyzing the TUE data due to lack of information released by Fukushima Medical University on the premise of protecting personal clinical data).

Explaining that international organizations frequently separate a scientific review process from discussions relating to policy making in order to maintain neutrality, Umeda said she thought a similar process might be useful for the Fukushima Health Management Survey. This comment drew questions from committee members as well as the press about the status of the Oversight Committee itself: Is it a policy-making body? Is it not scientific enough?

It would make more sense to invite experts to join the Thyroid Examination Evaluation Subcommittee to incorporate knowledge gained from the latest research on thyroid cancer. Why it has to be an “international” committee is unclear other than to say that it was recommended by the Organizing Committee of 5th International Expert Symposium in Fukushima on Radiation and Health, including Shunichi Yamashita. A former chair to the Oversight Committee, Yamashita resigned from the position in March 2013 amid controversies surrounding “secret meetings.” Although no longer involved with the Oversight Committee, he has maintained ties with the Survey as Founding Senior Director of the Radiation Medical Science Center for the Fukushima Health Management Survey, the Office of International Cooperation for the Survey.

China warns nationals visiting Japan over high radiation levels in Fukushima



The Chinese Embassy in Japan on Sunday issued an alert to its nationals who have plans to travel in Japan, reminding them of the high-level radiation inside a damaged reactor of the Fukushima Daiichi nuclear plant.

Tokyo Electric Power Company (TEPCO), the facility’s operator, announced last week that the radiation levels detected inside the plant’s No. 2 reactor had reached 650 Sieverts per hour, even higher than the previous record of 530 Sieverts per hour in January.

Even with a 30 percent margin of error, the reading is described by many experts as “unimaginable.” It is much higher than the 73 Sieverts an hour, which was detected in 2012, one year after the nuclear plant’s collapse. Under such exposure, a person would only be able to survive a few minutes at most.

The TEPCO on Thursday sent a remotely controlled robot into the reactor, equipped with a camera that is designed to withstand up to 1,000 Sieverts of cumulative exposure. The robot was pulled out after it broke down only two hours into the probe.

The company is planning to send better robots to conduct more detailed probes. However, it insists that radiation has not leaked outside the reactor.

Last week, Chinese Foreign Ministry spokesman Lu Kang said China has issued safety alerts to its nationals over the high-level radiation. He added that China hopes that the Japanese government could clarify how they are going to thoroughly eliminate the impact caused by the nuclear accident.

Six years have now passed after three reactors at Fukushima’s nuclear power plant were damaged by a devastating 9.0-magnitude earthquake and a subsequent tsunami on March 11, 2011. After the accident, the local government ordered residents living within 30-kilometer radius around the Fukushima nuclear plant to evacuate.