FUKUSHIMA
Nuclear Accident
Veryfication:
Were the exposure levels of Childhood actually Low?
By

Masaharu Kawata

Increases in Childhood Thyroid Carcinoma Caused by the Fukushima Nuclear Accident----Verification: Were the exposure levels of Fukushima residents actually low ? ---May 4, 2018

Masaharu Kawata(Nonprofit Organization and Association to Help Chernobyl, Chubu-District, Japan)
Table of Contents(1)

Introduction(2)

Amount of iodine-131 released(3)

I-131 flying leeward and radiation exposure(4)

Iodine-131 concentration in the atmosphere(5)

Examination of radiation exposure in the thyroid gland(5-1) Analysis of I-131 in the thyroid gland by Professor Shoji et al.
(5-2) Analysis of I-131 in the thyroid gland and errors caused by the background radiation(5-3) Issue of I-131 absorption model (chronic and acute absorption)(5-4) Issue of estimating absorbed I-131 by a whole-body counter(6)

Radiation exposure in infants through contaminated breast milk
(6-1) Results of measurements of I-131 in breast milk
(6-2) Findings from examination in breast milk
(6-3) Radiation exposure in the infants of female soldiers who participated in Operation Tomodachi
launched by the US military(6-4) Opinions concerning assessment methods of I-131 radiation exposure dose

(7)

Reactions of the Government and academic societies(8)

Conclusion(1) Introduction
As of March 2018, we are now in the eighth year after the Fukushima Nuclear Accident. According to theInvestigating and Discussion Committee for Prefectural Residents' Health in Fukushima Prefecture, as of December
2017, among 380,000 children who have received a diagnostic test and whose age was 18 or younger at the time of thenuclear accident, 196 were found to have childhood thyroid carcinoma in Fukushima Prefecture. Regarding the reason
for this, the Investigating and Discussion Committee for Prefectural Residents' Health, medical professionals, andacademic societies concluded that there was a low probability of an influence by radioactivity from the nuclear
accident, although they admit to increases in childhood thyroid carcinoma. They also point out that the possible
reasons include (1) detecting latent carcinoma by overdiagnosis and (2) far lower doses of radiation exposure inchildren of Fukushima compared to the victims of the Chernobyl nuclear accident, where the reason for childhood
thyroid carcinoma was determined to be the influence of radioactive contamination. Here, we will investigate whether
the thyroid exposure doses in children in Fukushima were actually low.

(2) Amount of iodine-131 released (herein after referred to as I-131)
Although there are various estimates and assessments regarding the amount of I-131 released, to which thyroid1

carcinoma is attributed (Table 2), we use the data from a report published by the Tokyo Electric Power Company(TEPCO) in May 2012 (Table 1). The whole amount of I-131 released is 473 PBq, while the total amount during thetwo days of March 15 and 16, is 217 PBq, which accounts for 46% of the entire released amount. The amount of I-131
is 14 times greater than that of the total of cesium (Cs). Note: PBq (petabecquerel) = 1015 Bq.
Table 1

Released Amounts of Radioactivity (Published by TEPCO: Calculated Based on May 2012 Data)

Date

I-131

Cs134

Cs137

Date

I-131

Cs134

Cs137

March 12

7.73

0.141

0.106

March 22

0.7

0.025

0.017

March 13

5.012

0.095

0.063

March 23

6.5

0.218

0.213

March 14

48.76

1.031

0.92

March 24

3

0.1

0.1

March 15110.32

2.029

9.783

March 25

10.88

0.656

0.445

March 16106.70

2.156

2.113

March 26

0.2

0.01

0.009

March 1740.033

1.001

0.801

March 27

0.2

0.01

0.009

March 18

22.28

0.777

0.558

March 28

20.779

1.053

0.938

March 19

37.17

2.91

0.734

March 29

9.299

0.828

0.586

March 20

34.8

0.914

0.777

March 30

0.04

0.003

0.002

March 21

8.23

0.319

0.177

March 31

0.04

0.004

0.003

Total

472.673

14.27918.353

Unit： PBq (petabecquerel) = 1015 Bq

Change Over Time of Iodine-131 Released from the Fukushima Daiichi Nuclear Power Station(Prepared Based on Table 1)

Release amount of iodine-131(March 2011)
120.0

110.3

106.7

100.0

80.0

60.0

48.8
40.0

37.2 34.8

40.0
22.3
20.0

20.8
8.2

7.7 5.0

6.5
0.7

10.9
3.0

9.3
0.2 0.2

0.0 0.0

231-Mar30-Mar29-Mar28-Mar27-Mar26-Mar25-Mar24-Mar23-Mar22-Mar21-Mar20-Mar

19-Mar18-Mar17-Mar

16-Mar15-Mar

14-Mar13-Mar0.0

12-MarPetabecquerel/day

Figure 1

Table 2

Released Amount of Radioactivity into the Atmosphere Due to the Fukushima Nuclear Accident andChernobyl Nuclear Accident (unit: PBq)

Chernobyl

Fukushima

I-131

Cs137

Cs134

- 1,760

- 85

- 47

1,800

85

270

37

18.5

160

15

18

Nuclear and Industrial Safety Agency (October 20, 2011)

473

18

14

TEPCO Report (May 2012)100-500

7-20

Reference
UNSCEAR Report (2008)
IAEA Report (2005)

(1)

(2)

Nuclear Safety Commission (May 28, 1987)

(3)
(4)

(5)

UNSCEAR Report (2013 and 2016)(6)

Many arguments adopted data from the United Nations Scientific Committee on the Effects of Atomic Radiation(UNSCEAR) Report to date, which is the basis for the claim that released amounts and contamination levels ofradioactivity by the Fukushima Nuclear Accident are ten times lower than those in Chernobyl. However, we shouldbear in mind that these data are not absolute with a significantly wide margin of error for released amounts ofradioactivity because it is based on various assumptions.

(3) I-131 flying leeward and exposure
In Chernobyl, the total radioactivity released from the nuclear power plant located inland caused radiation exposure.
In the case of the Fukushima Daiichi Nuclear Power Station, the radioactivity released was highly likely to transfer tothe Pacific Ocean because the station is located along the coast, and the accident occurred in early spring on March 12
when the winds often blow from the continent to the Pacific Orcean. Basis on the data from the Japan Mortgage
Association, winds blow from the northwest and north-northwest in the direction of the Pacific Ocean in Fukushima
Prefecture during this season.

Figure2. Map of Fukushima Prefecture.

In that case, what was the actual direction of
the winds at the time of the Fukushima Daiichi
nuclear accident? Although most observation
stations located along the coast were lost
because of the earthquakes, tsunami, and power
failures, some small amount of data from theJapan Mortgage Association about winddirections on March 15 and 16 remained in someareas, including Iitate-mura just 40 km
northwest, Tamura City 45 km west, andOnahama City, located 50 km southwest in thesouthern part of the prefecture, each somedistance from the nuclear power plant.
The wind roses based on these data are shown in
Figure 3.

3

Figure 3 Wind Roses at the Time of Accident
60
N…

N
N…

N… 40
W…
20
W

10
N…
N…

N…
E…

W…

5

E…

E

W

0

E

E…

SW

SE
S…

N…
NE

W…

0

S…

N

E…
W…

SE
S…

S…

S…
S

S

Iitate-mura

Iitate-muraMarch 15, 2011(1a.m.~11. p.m.)

March 16, 2011 (1 a.m.~12 p.m.)

15
NNW
NW 10
WNW
5
W
0

N
NNE
NE
ENE

NNW 6
NW
4

ESE
SE
SSE

NNE
NE

WNW

2

ENE

W

0

E

E

WSW
SW
SSW

N

WSW

ESE

SW
SSW

S

SE
SSE
S

Funehiki-machi, Tamura City

Onahama City

March 15, 2011 (1 a.m. to 11 p.m.)

March 15, 2011 (1 a.m. to 12 a.m.)

From the results of our chronological review of the data of the frequencies of wind direction, we found the following:
the most frequent wind direction was northeast to north-northeast in Onahama from 12 a.m. to 12 p.m. on March 15,
where the radioactive plume moved to Iwaki City (a densely inhabited district with a population of 340,000 people)
located southwest to south-southwest, or to other areas; the most frequent wind direction was almost east to east-southeast
in Iitate-mura (40 km northwest of the nuclear power plant) in Fukushima Prefecture on the afternoon of March 15,
where most of the radioactive plume released during this period of time moved to Iitate-mura and Fukushima City locatedjust past Iitate-mura, (63 km northwest away from the plant). A similar result was obtained for Funahiki-machi in
Tamura City (45 km west of the nuclear power plant) to the west of which Koriyama City (a big city with a populationof 350,000 people) is located. On March 16, northwest to north-northwest winds blowing throughout the day made theradioactive plume float over the Pacific Ocean.
Accordingly, approximately a quarter of the total I-131 released moved to the inland areas of Fukushima, including
a big city, on March 15. Archives of Weather Data Around the Fukushima Daiichi Nuclear Power Plant: March 11
to 25, 2011/Wind Direction and Wind Velocity (Mesoscale Model) consists of wind directions and wind velocity at
the time of the accident visualized by time (http://agora.ex.nii.ac.jp/earthquake/201103-eastjapan/weather/data/wind20110311/). This is a model where wind direction and wind velocity around the nuclear power plant at the time of
the accident are visualized, which support the above-mentioned analysis (Figure 4).
Consequently, the air dose rates significantly increase to as high as 20 to 25 μSv per hour within Fukushima Cityand Iwaki City (7). Graphs obtained by combining the data of the time and amount of released I-131, published by
TEPCO, with the results of measurements of air dose rates at corresponding time points in Fukushima City and Iwaki
City are shown in figures 4 and 5, respectively. As mentioned above, at the time when a high level of radioactivity was4released from the nuclear power plant on March 15, the wind was blowing towards the inland area, so it was inevitablethat many residents would be exposed to radiation. Regarding I-131, most of the amount (25% of the total amountreleased) released on March 15 flowed to inland, which exposed the residents to radiation.
Incidentally, regarding radioactive cesium, 36% of the total amount released, 11.8PBq (a total of 32.7 PBq: Cs134
plus Cs137) flowed inland on March 15, based on calculations from Table 1 (released by TEPCO). The theory, which
has been said, that 10% of the released radioactivity from the Fukushima nuclear accident flowed inland while 90%
moved over the Pacific Ocean is not true. To be precise, at least 24% of the released amount of I-131 and 36% of thetotal of Cs134 and Cs137 are believed to have flowed inland.
An Example of Mesoscale Model for Wind Directions Around the Nuclear Power Plant

Figure5. Release Amount of I-131 and Air Dose Rates Within Fukushima City (March 2011)
30

120

25

100

80

放出I-131

μSv/h

5

31日

30日

29日

28日

27日

26日

25日

24日

23日

22日

21日

0

20日

0

19日

20

18日

5

17日

40

16日

10

15日

60

13日
14日

15

I-131, PBq

20

μSv/h

Figure4

Release Amount of I-131 and Air Dose Rates Within Iwaki City (March 2011)

25

120
100

μＳｖ/h

20

μSｖ/ h

80

15
60
10
40
5

I-131, PBｑ

Figure 6.

20

31日

30日

29日

28日

27日

26日

25日

24日

23日

22日

21日

20日

19日

18日

17日

16日

15日

0

13日
14日

0

The government issued evacuation orders for some residents living within a 20-kilometer radius of the plant,
including Okuma-machi, Futaba-machi, Tomioka-machi, and Namie-machi at 6:25 p.m. on March 12. However, it was
not until April 11 that the outer areas within a 20- to 30-kilometer radius of the plant, including Katsurao-mura,
Namie-machi, Iitate-mura, Kawamata-machi and Minamisouma City (partly), were designated as part of the planned
evacuation zone (area with a possible 20 mSv or more exposure per year) by the officials and evacuation was called
for. Before then, the amount of iodine-131 released accounted for 89% of the total. The evacuation orders were notissued for big cities outside the 30-kilometer circle, including Fukushima City, Koriyama City and Iwaki City.
Accordingly, before March 20, when a large amount of radioactivity flowed inland, most of the residents were exposed
to radioactive iodine and cesium, except for those who voluntarily evacuated in the early stages.

(4) I-131 concentration in the atmosphere
How was I-131 released from the nuclear power plant spread into the air and how were the levels in the atmospherein Fukushima Prefecture? There are no specific values measured in Fukushima Prefecture from March 12 to 18 justafter the accident, when the highest levels of I-131 were released, except for a measurement by TEPCO around thenuclear power plant premises. There are only three measurement results: the actual measurements made by the Japan
Atomic Energy Agency (JAEA) in Tokai-mura, Ibaraki Prefecture, only 110 km south of the Fukushima Daiichi
Nuclear Power Plant at the monitoring posts around the institute starting from just after the accident (8), themeasurements made by the High Energy Accelerator Research Organization (KEK) located in Tsukuba City, Ibaraki
Prefecture, starting from March 15 within the compound of the National Institute for Environmental Studies (9), andthe observation results on or after March 12 made by the CTBT Radionuclide Monitoring Station established in
Takasaki City in Gunma Prefecture (217 km away from the Nuclear Power Plant) by the Center for the Promotion of
Disarmament and Non-Proliferation, belonging to the private organization, the Japan Institute of International Affairs,in order to monitor nuclear testing (10). According to JAEA, the air dose rates in Tokai-mura rose sharply from 5 a.m.
to 8 a.m. on March 15 when northeast to north-northeast winds blew to a maximum of 4 μSv/h from a normal range of
0.03 to 0.04 μSv/h. The concentrations of I-131 in the atmosphere, which were collected at the same time, showed amaximum level of 1,600 Bq/m3 from 6 a.m. to 9 a.m. The I-131 was composed of volatile and particulate elements inan almost half-and-half ratio (8).
6Figure 7.

Change in I-131 Concentrations in the Atmosphereof Momiji-Daira in Fukushima City Around March 15(Hirayama et al.: 11)
In addition, based on an analysis of samples
collected from 14:39 p.m. to 17:34 p.m. on March 15
using a dust sampler performed by KEK, the I-131
concentration was 3.2×10-5 Bq/cm3 (=32 Bq/m3)(9).
In an observation by the CTBT Radionuclide
Monitoring Station, the air collected from March 15
to 16 showed a measurement of 14,680,552 μBq/m3
of I-131 (= 14.68 Bq/m3) (10).
Besides this, in research by Hirayama from KEK
et al., the I-131 concentration in the atmosphere in
Momiji-daira in Fukushima City (61.3 km northwestof the nuclear power plant) was estimated with a model calculation based on a spectral analysis using radiation dose
measurements that Fukushima Prefecture had performed since before the accident at multiple monitoring posts. As aresult, the peak concentration of the I-131 was reached between 5 p.m. and 6 p.m. on March 15 with a maximum
19,100 Bq/m3, and the mean was 3,650 Bq/m3. Concentrations in the atmosphere showing over several thousand
becquerels per cubic meter were maintained until around 4 a.m. on March 16 (11). A graph showing, I-131
concentrations in the atmosphere of Momiji-daira in Fukushima City is cited from the paper written by Hirayama(Figure7).
According to Hirayama et al., the mean concentration × duration (=integral time concentration in the atmosphere)of the atmosphere of Momiji-daira in Fukushima City from March 15 to 16 was 65,700 (Bq h/m3). If this figure iscorrect, in Fukushima City, the I-131 dose inhaled by adults (breathing capacity per day, 20 m3) was 54,750 Bq perday, and the dose inhaled by elementary school students (breathing capacity per day, 10 m3) was 27,375 Bq.
In this paper, the integral time concentration in the atmosphere measured in Hirono-machi, Futaba-gun, (21.4 km
south of the nuclear power plant) during the five days of March 12 to 16 was calculated to be 137,000 Bq h/m3. In
Hirono-machi, I-131 dose inhaled by adults (breathing capacity per day, 20 m3) was 114,000 Bq per day, and thedoes inhaled by elementary school students (breathing capacity per day, 10 m3) was 57,000 Bq.
The officials ordered emergency evacuation preparation zones for Hirono-machi, Tamura City, Kawauchi-mura,
Naraha-machi, and Odakaku of Minamisouma City (20 to 30 km from the nuclear power plant) on April 22, 2011.
Thus, most of the residents were exposed to high levels of radioactive I-131 on or after March 15, except for those
who voluntarily evacuated during the early stages. In particular, Namie-machi in Futaba-gun is spread northwest of
the nuclear power plant. It was found later that this area was included within the severely contaminated areas where
the radioactive plume passed through. However, the residents evacuated to Tushima-district in Namie-machi 29 km
northwest of the nuclear power plant just after the accident. The explosion of reactor unit 3 of the Daiichi nuclear
power plant drove them to make the decision to evacuate to Nihonmatsu City at 10 a.m. on the 15th. Until then, about
8,000 residents stayed in Tushima-district. The explosion of reactor unit 3 drove these residents to begin to evacuatefrom the morning of March 15 to the morning of March 16, during which large amounts of radioactivity werereleased from the nuclear power plant and even the radioactive plumes spread in the northwest direction. The
7

residents in this region should have ingested large amounts of I-131 into the body incomparable with the amounts inFukushima City or Hirono-machi. Actually, the air dose rate measured in Tushima-district in Namie-machi in March
16 was as high as 58.5 μSv/h. A great responsibility was laid upon the Japanese government because they did notmeasure the concentrations in the atmosphere despite knowing of this situation in advance by predictive
investigations with SPEEDI and because they did not inform residents of the predictive investigations results.
It was not until radioactivity measurement started with dust sampling by both the Ministry of Education, Culture,
Sports, Science and Technology (MEXT) (on or after March 18) and Fukushima Prefecture (on or after March 19) that
I-131 or other radioactivity in the atmosphere were continuously measured (12). Based on measurements performed by
MEXT, the following I-131 concentrations were observed: 4,900 Bq/m3 on March 20 in Katsurao-mura of Futaba-gun,
3,700 to 5,600 Bq/m3 on March 21 in Hirono-machi of Futaba-gun, 440 to 290 Bq/m3 on March 25 in Iitate-mura and1,000 Bq/m3 on March 20 in Namie-machi. Such values should have been much higher than those above if measured
from March 15 to 16, when the largest amounts of I-131 were released from the nuclear power plant and the winds
blew inland. Other than those measurements, there are no reliable measurement values because of a large amount oferrors caused by models and assumption used for calculation, although the concentrations of I-131 are estimated basedon the concentrations of I-131, CS134, and CS137 deposited on the ground surface in multiple studies.

(5) Examination of radiation exposure in the thyroid gland
From May to June in 1986, soon after the Chernobyl nuclear accident (April, 26, 1986), the government of the
Republic of Ukraine measured radioactive iodine in the thyroid gland in 150,000 or more residents, including 130,000
children, in three provinces (Kiev, Zhytomyr, and Chernigov) located close to the nuclear power plant followed bymeasurements in children in all provinces (13). A partial extract from this data is shown in Table 3.
Table 3Results of the Thyroid Examination Conducted by the Government of the Republic of Ukraine Just
After the Chernobyl Nuclear Accident (13)Mean thyroid exposure dose by age (mGy: milli gray = mSv)

Province name

<7 Years of Age

7-14 Years of Age

15-18 Years of Age>18 Years of Age

Overall Mean

Vinnitsa

37

13

9.8

9.2

12

Zhytomyr

231

87

67

60

81

Kiev

202

75

58

53

71

Odessite

15

5.2

3.8

3.7

5.1

Chernigov

151

55

43

37

50

Total of Ukraine

55

20

15

14

19

* Only some of 23 provinces are reproduced.

Nothing was more surprising than the fact that the amounts of I-131 in the thyroid gland were measured in as manyas 130,000 children within several weeks after the incident. Given that the measurements were made within one monthafter the accident, the amounts of I-131, of which the half-life is 8 days, could be easily measured. In contrast, how was
the aftermath of the Fukushima nuclear accident handled in Japan?
In Japan, only two sets of actual measurements of I-131 in the thyroid gland are available. In the firstmeasurement conducted by Professor Tokonami, et al. from Hirosaki University, I-131 in the thyroid gland wasmeasured in a total of 62 people consisting of 17 residents in Namie-machi of Fukushima Prefecture and 45 evacuees8from Minamisouma City to Fukushima City from April 11 to 16 one month after the accident (14). In addition,
Professor Tokonami, et al. measured the radioactivity in 2,393 evacuees from Namie-machi from June, at least threemonths after the accident, to August 2011 by using a whole-body counter to estimate the absorbed amounts of I-131
just after the accident based on the ratio of I-131 to Cs134 by which they estimated the thyroid equivalent dose andreported the results (15).
In the other measurement, the Local Nuclear Emergency Response Headquarters performed thyroid examinations
at the request of the Nuclear Safety Commission in a total of 1,080 children aged 0 to 15, consisting of 134 in Iwaki
City of Fukushima Prefecture from March 26 to 27, 631 in Kawamata-machi of Fukushima Prefecture from March 28
to 30, and 315 in Iitate-mura of Fukushima Prefecture from March 29 to 30 (16).

(5-1) Analysis of I-131 in the thyroid gland by Professor Tokonami et al.
Professor Tokonami, et al. investigated the gamma-ray spectrum by applying a 3-inch x 3-inch NaI (Tl) scintillation
spectrometer (JSM-112: Hitachi Aloka) to the neck of subjects. Based on the obtained values, an amount of I-131
expressed in becquerels and the thyroid equivalent dose were calculated. Residents in Namie-machi evacuated underthe evacuation order issued on March 12 from the area located along the coast to Tsushima-district located to thenorthwest of the area. As mentioned above, the radioactive plumes that were released from the nuclear power plant
starting from around 11 a.m. on March 15 should have flowed with the southeast to south-southeast winds toTsushima-district. However, Professor Tokonami performed measurements one month later in 17 Namie-machi
residents, among them only 7 showed measurements not lower than the limit of detection (LOD). Among a total of 45
people evacuated from Minamisouma City to Fukushima City, 39 showed measurements above the LOD, accounting
for 74% of the total of 62 subjects. On the hypotheses that all residents in Namie-machi and Minamisouma City had
acute inhalation from inhalation, 30% of the dose was absorbed into the thyroid gland; the residents were breathing for
4 hours, so the intake dose of I-131 and the thyroid equivalent dose were calculated. The obtained results are shown in
Table 4.

Table 4

Results of the Examination of Radiation Exposure in The Thyroid Gland Caused by the Fukushima Nuclear

Accident by Professor Tokonami, et al. From Hirosaki University (15)Age
Number of People
I-131 Accumulation
Thyroid Equivalent Dose (mSv, on the(KBq)
Hypothesis of All Being by Breathing)
0-9
5
ND-0.017
ND-21
10-19

3

0.09-0.54

3.8-2320-29

9ND-0.59

ND-16

30-39

6

ND-0.17

ND-4.440-49

4ND-1.5

ND-33

50-59

10

ND-1.1

ND-31

60-69

12

ND-0.20

ND-5.370-79

30.090-1.5

2.3-31≥80

2ND-0.70

ND-19

Unknown8

ND-1.4

ND-28

Mean

19 years old or younger (4.2 mSv); adult (3.5 mSv)

Maximum

19 years old or younger (23 mSv); adult (33 mSv)

(Note by Kawata) ND represents the limit of detection (values of ND and background are not presented).
9

The maximum level of I-131 concentration in the thyroid gland of 1,500 Bq was observed in one adult. In this paper,
Professor Tokonami et al. pointed out the possibility, based on the estimation of I-131 concentrations in theatmosphere in Iitate-mura on the afternoon of March 15, that this subject may have inhaled I-131 at a maximum levelof 85,000 Bq and that children 1 to 5 years of age may have been exposed to I-131 at a maximum level of 63 mSv,
which is higher than the actual measurement of 21 mSv.
The breathing time was assumed to be four hours because, although air dose rates suddenly rose after the arrival of
the radioactive plume at Namie-machi around 1 p.m. on March 15, there was no absorption through inhalation because
I-131 was deposited on the ground due to rain starting from around 5 p.m. in the evening, the author explains.
However, this hypothesis is unreasonable. For example, approximately half of the I-131 coming in particulate form
then led to deposition by rain while the remaining half thereof was in gaseous form resulting in limited absorption by
rain. In addition, most of the radioactivity within the plume was unlikely to be deposited on the ground because, basedon data from the Japan Mortgage Association, it was raining lightly with a precipitation rate of 0 to 1.5 mm per hourfrom March 15 to 16 in Iitate-mura adjacent to Tsushima-district. If most of the I-131 had been deposited on the
ground, it would not have arrived at Fukushima City, which is located just past Iitate-mura, which is factuallyinaccurate. Furthermore, the author also explains that many residents were evacuated from Tsushima-district by thetime the plume had arrived after the evacuation order was given on March 15, possibly resulting in prevention ofabsorbing contaminated air. This hypothesis is also factually inaccurate. After the Namie-machi office decided to issue
the evacuation order from Tsushima-district to Nihonmatsu City in the early morning of March 15, residents evacuatedstarting from 10 a.m. and finishing in the evening. Given the air dose rate of 58.5 μSv per hour observed on March 16
in Tsushima-district, the value on the previous day of March 15 should have been much higher. In this connection,even though Fukushima City received rain on March 15 and 16, as mentioned above, a large amount of I-131 in theatmosphere was observed even in the Fukushima City. In this way, given the fact that the measurement of thyroid
exposure dose one month after the accident by Professor Tokonami et al. was based on various hypotheses, theamounts of actual exposure doses could have been greater.

(5-2) Analysis of I-131 in the thyroid gland and background error
A more significant issue is the background radiation (Bkg) at the time of measurement. The government noticed
on March 25, 2011 that the screening level at the time of measurement of radiation exposure in the thyroid gland was
0.2 μSv/h (17). This was based on a model test using a phantom, where if an actual measurement of radiation exposurein the thyroid gland was 0.2 μSv/h, the dose would correspond to I-131 accumulation in the thyroid gland of 4,400 Bq
and to thyroid exposure of an equivalent dose of 108 mSv in a one-year-old infant, leading to the limitation of the Bkg
in measurement environments to not more than this value. Although this hypothesis itself has a large problem, here wewill discuss problems only regarding Bkg. On or after March 15 when I-131 came in, air dose rates as high as 10 to
100 times the 0.2 μSv/h were observed, needless to say within Fukushima Prefecture, even within the peripheral
prefectures. In this environment, it should be very difficult to secure a place in which Bkg was 0.2 μSv/h or lower.
Given a Bkg of 0.2 μSv/h and an actual measurement of 0.22 μSv/h, it was evaluated that the net value was 0.02 μSv/h,an I-131 accumulation in the thyroid gland of a one-year-old infant was 440 Bq, and an equivalent dose of exposure
was 10 mSv. It is highly unlikely that these measurements were performed at high accuracy in this environment where
air dose rates ranged from several micro- to several tens of micro sieverts per hour. The higher the Bkg, the bigger thesubtracted value and the lower the net value. As a result, exposure doses were underestimated. Furthermore, a net valueof measurements becomes inaccurate with large errors. The results of measurements performed by the Local Nuclear
10

Emergency Response Headquarters were actually not clear. These measurement results have been reported on May 12,2011, under the name of the Secretariat of Nuclear Safety Commission (16, 18). A graph representing the results isshown in Figure 8.
Figure 8. Result of Measurement in the Thyroid Gland in a Totalof 1,080 Children from Kawamata-Machi, Iitate-Muraand Iwaki City (18)
In a total of 1,080 children aged 15 years or
younger consisting of 134 children measured at
the health center of Iwaki City, 631 children
measured at the community center of Kawamatamachi and 315 children measured at thecommunity center of Iitate-mura, measurement
results are thought to be as follows: a maximum
dose of 0.1 μSv/h was reported in one child,
0 μSv/h was reported in 598 children (55.4%), andchildren with 0.04 μSv/h or lower accounted for
99% with no children having doses above thescreening level (0.2 μSv/h = 100 mSv as thyroid
Net value of survey meter (μSvh-1)

equivalent dose of a one-year-old infant). This
result was shown in the 2012 Project for

Investigation on Impact of Nuclear Power Plant Disaster—Investigation of Internal Exposure Due to Short Half-life
Such as Iodine at the Early Stage of the Accident—Accomplishment Report (18) and a paper written by E Kim et al.
from the National Institute of Radiological Sciences (19). According to a calculation made by the author or others, themean thyroid equivalent dose was 7.3 mSv in 631 people in Kawamata-machi, 15.9 mSv in 134 people in Iwaki City,
and 14.7 mSv in 315 people in Iitate-mura. Among them, a child 4 years of age was thought to show the maximum
0.1 μSv/h, corresponding to 35 mSv (Figure8).
However, as mentioned above, it is clear that the measurement of background radiation levels (Bkg) has a large
error. Materials showing the actual measurement conditions are attached to the Investigation Progress of Radiation
Exposure in the Thyroid Gland of Children: 20 within the Report by the Secretariat of the Nuclear Safety
Commission issued on September 13, 2012. According to the materials, in the measurements in Yamakiya-district in
Kawamata-machi on March 24, the Bkg was 2.4 to 2.9 μSv per hour, and the measured net value, which was obtainedby subtracted this measurement, was around 0.1 μSv/h with many negative values observed. Needless to say, the datafrom measurements on 66 people on this day, including those performed at the health center of Kawamata-machi,
were not used. In addition, measurements subsequently performed with 1,080 people on or after March 26 also
showed Bkg values ranging from 0.1 to 0.2 μSv/h and net values ranging from 0 to 0.01 μSv/h in most of the data.
These data are far from reliable. For example, when the measured value is 0.21 μSv/h on the assumption that Bkg is
0.2 μSv/h, the following values are obtained by calculation: the net value is 0.01 μSv/h, an I-131 accumulation in a
one-year-old infant is 220 Bq, and the thyroid equivalent dose is 5 mSv. Whereas on the assumption that Bkg is at thesame level as that before the accident (0.04 μSv/h), a dose rate derived from the I-131 deposition amount in the11thyroid gland is calculated to be (0.21-0.04) μSv/h = 0.17 μSv/h and the thyroid equivalent dose is0.17÷0.2×100=85 mSv. As mentioned above, Bkg values can cause a large error in measurements of I-131 deposition
amount in the thyroid gland at the devastated areas just after the accident, from which exposure doses were calculated
and could have been largely underestimated.

(5-3) Issue of I-131 absorption model (chronic and acute absorption)
The third factor that causes errors is the issue related to the timing of the intake of I-131 and the duration (hours) tothyroid examinations. This issue has the largest impact on the assessment of exposure dose. As mentioned above, thescreening level of 0.2 μSv/h defined by the Nuclear Safety Commission was thought to correspond to I-131
accumulation in the thyroid gland of 4,400 Bq and to an equivalent dose of exposure of 108 mSv in the thyroid glandof a one-year-old infant. The basis for this calculation is reported to be as follows: on the hypothesis that a one-yearold infant continued absorbing I-131 (chronic absorption) at a certain level on a daily basis for 12 days starting fromMarch 12 (when the nuclear power plant exploded) to March 24 (when measurements started), the half-life, daily
amounts taken into the body, and accumulated amounts in the thyroid gland were taken into account (Attachment 5-2
of Reference 20). However, as already mentioned above several times, the residents absorbed radioactive iodine into
their bodies mostly on March 15 due to wind directions. Consequently, the exposure dose should be assessed by using
a formula called the single (acute) absorption model, not the chronic absorption model. According to ICRP
(Publication 72), in the single absorption model, the radioactivity accumulates in the thyroid gland and reaches a peak
one day after absorption into the body, followed by a gradual decrease due to the half-life and excretion from the bodyin urine. On the assumption of single absorption (1 Bq) on March 15, for a one-year-old infant, the internal residual
rate on March 26, when the government started measurements, is 0.0308 Bq and the committed effective dose at thistime is 2.338E-06 (Sv/Bq) (=2.338 μSv/Bq). If an actual measured exposure dose is 0.2 μSv/h (4,400 Bq), thecommitted effective dose is calculated to be 2.338E-06×4400=1.0287E-02 Sv (=10.287 mSv) and the thyroid
equivalent dose is calculated to be 257 mSv (the tissue weighting factor for thyroid gland is 0.04). Specifically, thethyroid equivalent dose calculated from values measured 11 days after absorption of I-131 based on a single absorption
model is 2.7-fold greater than that based on a chronic absorption model. Table 5 shows the change in the residual dose
and the thyroid equivalent dose in the thyroid gland in a one-year-old infant based on a single I-131 absorption model
on March 15 on each measurement day from March 26 to 30 for which measurement was performed in 1,080 people
by the government.
As mentioned above, the thyroid equivalent dose significantly varies depending on how I-131 is ingested according
to the day, method, and timing. In this case, considering that the radioactive plume was scattered inland on March 15,
exposure doses should be assessed based on a single absorption model, not on a chronic absorption model, which
would lead to a considerable underestimation. Although I have to admit that accurate measurements and assessments ofthe thyroid gland were difficult in the chaos just after the accident, at a later stage where the truth had come out overtime, the exposure of the thyroid gland should have been properly assessed to correct the exposure doses. These
measurements are likely to lead to such various underestimations or errors. However, once reports or papers about themeasurements are published, the data would be unstoppable without appropriate criticism and be used to publicize thatthyroid exposure in children was very low.

12

Table 5 Change in Time Elapsed from Absorption to Measurement Day in the Thyroid Gland, Residual Rate in the
Thyroid Gland, Effective Dose and Equivalent Dose in a One-Year-Old Infant Absorbing Iodine-131 (1 Bq).
(Calculated by the Author Based on a Single Absorption Model)
Number of lapsed days from absorption

Day 11

Day 12

Day 13

Day 14Day 15Residual Rate (Bq)

3.08E-02

2.73E-02

2.42E-02

2.15E-02

1.90E-02

Effective dose (Sv/Bq)

2.338E-06

2.637E-06

2.975E-06

3.349E-06

3.789E-06

Thyroid equivalent dose (Sv/Bq)

5.845E-05

6.593E-05

7.438E-05

8.373E-05

9.473E-05

257 mSv

290 mSv

327 mSv

368 mSv

417 mSv

1 Bq
Absorptionto measurement day

Thyroid equivalent dose in a one-yearold infant based on a single absorption
model for measured value 0.2 μSv/h(4,400 Bq) (calculated by the author)
Thyroid equivalent dose in a one-year-

108 mSv

old infant based on a chronic absorption
model for measured value 0.2 μSv/h(4,400 Bq) (Reference 20)(5-4) Issue of estimating absorbed I-131 by a whole-body counter
Several reports or papers about thyroid exposure dose are available, most of them estimate I-131 doses in the
thyroid gland just after the accident, based on a ratio of Cs137 or Cs134 to I-131 measured by using whole bodycounters (WB) several months after the accident. In this case, the problem is as follows: Most I-131 taken into thethyroid gland just after the accident was due to absorption of contaminated air on March 15 when the radioactive
plume came inland. However, radioactive cesium was measured by using a whole-body counter after a certain periodof time had elapsed, and most of the cesium exposure was caused by consuming contaminated foods and water. Thus,
the results from estimating accumulated I-131 in the thyroid gland are not replicable because of the complicatedinteraction among differences between iodine and cesium in the circulation pathway in the body, in the routes andtiming of crop contamination, and in the production area of the crops. Assessments of thyroid exposure dose by thesereports and papers are thus thought to be far less reliable.

(6) Infant exposure through contaminated breast milk
As the thyroid gland, a tissue where the growth hormone is produced, contains iodine as a component,
contamination of breast milk by I-131 could be a major factor in exposure in infants with active growth. Nevertheless,it was not until recent years that a lot of specific research was conducted. I-131 taken into the body is accumulated in
the thyroid gland through various pathways. Based on previous studies, approximately 30% of I-131 taken into thebody is transported into the thyroid gland, and the remaining is excreted from the body in urine. The method to directly
analyze secretions excreted from the body, including breast milk and urine, and in order to investigate radioactivity,
such as I-131, Cs134, and Cs137, is called a bioassay. Although some analyses have been performed for Cs137 andCs134 in breast milk and urine since the Chernobyl nuclear accident, there are few analyses of I-131 in breast milk.
In response to the 2007 recommendation of ICRP (Pub. 103), the Radiation Council of Japan issued arecommendation in January 2011 that, regarding exposure management for women who are occupational radiation
workers, countermeasures against radiation exposure for pregnant women, infants, and fetuses should be included in13the domestic systems (21). “It can be regarded that exposure of infants through breast milk is indirectly managed byregulating internal exposure in occupational radiation workers. However, investigations into actual conditions about
the exposure of infants due to radionuclide transfer through breast milk have not been performed in Japan to date.
Investigations into the actual conditions about these issues should, therefore, be performed and considering the results
obtained, it is appropriate to discuss the need for development of a system to implement protective measures reflecting
our country’s situation for infants during lactation,” this recommendation says. Although the Fukushima Nuclear
accident happened just after this recommendation was issued (March 2011), both the Radiation Council and the
Nuclear Safety Commission did not take any concrete measures nor did they perform radioactivity measurements inbreast milk.

(6-1)

Results of measurements of I-131 in breast milk
After the Fukushima nuclear accident, a civic organization called the Network to Examine Breast Milk andSupport Mothers and Children (Mother-and-child Support Net: representative, Kikuko Murakami) collected breast
milk from mothers living in the Tohoku region for examination. This is a rare action in the world. This civicorganization called for the examination of breast milk from the middle of March just after the accident when theyrecalled that at the time of the Chernobyl nuclear accident, a trace amount of radioactivity was detected in breast milkcollected from mothers living in Osaka. A total of nine breast milk samples were collected from March 16 to April 12,
in 4 of which I-131 could be detected. (Table 6 and 22).

Table 6

Results of Examinations by Network to Examine Breast Milk and Support Mothers and Children (22)Name of Lactating

Date of Breast Milk

Date of

Iodine-131 (Bq/Kg)

Place of Residence

Woman

Sample Collection

Examination(Limit of Detection)

A

03/23/11

03/24/11

8.7

B

03/23/11

03/24/11

ND

C

03/23/11

03/24/11

31.8

Moriya City, Ibaraki PrefectureD

03/29/11

04/04/11

6.4

Tsukuba City, Ibaraki PrefectureE

03/29/11

04/04/11

36.3

Kashiwa City, Chiba PrefectureF

03/30/11

03/30/11

ND

Shiroishi City, Miyagi PrefectureG

04/03/11

04/03/11

ND (41.5)

Iwaki City, Fukushima PrefectureH

04/12/11

04/13/11

ND (4.7)

I

04/12/11

04/12/11

ND (6.8)

Tsukuba City, Ibaraki Prefecture
Tsukubamirai City, Ibaraki
Prefecture

Higashishirakawa-gun,
Fukushima Prefecture
Fukushima City

These results were published by the Japan National Press Club of the Ministry of Health, Labour and Welfare (MHLW)on April 20. It was not until from April 24 to May 31 that, in response to this publication, the MHLW performed
examinations of breast milk. Among 119 lactating women, I-131 was detected in breast milk samples collected fromseven on April 24. The obtained results are shown in Table 7 (23). Regarding this evaluation, the MHLW says as follows:“… in this examination, no or very low levels of radioactive materials were detected in breast milk, despite the limited
number of samples and regions,” “If needed, countermeasures, including evacuation orders and restrictions on
consumption of food and drinking, were taken. Even if radioactive materials would transfer to breast milk through air,14

water and food, it is unlikely to have any impact on the health of infants,” and “Given the various advantages of breast
milk from a nutritional viewpoint, there is no need for concern and a person breastfeeding can continue living as usual
free from excessive worry.” Subsequently, the MHLW published the results of an additional examination of breast milk(108 people) performed from May 18 to June 3 (24), where no radioactive materials were detected in 101 people, a trace
amount of radioactive cesium (2.0 to 6.7 Bq/Kg) was detected in 7 people and I-131 was not detected in any people.

Table 7 Results of Examinations in Breast Milk by the MHLW (Only People with Samples Radioactive
Materials Detected) (23)Date of Breast Milk

I-131

Sample Collection(Bq/Kg)A

April 25

3.5

Iwaki City, Fukushima Prefecture

B

April 25

3.0

Hitachiomiya City, Ibaraki PrefectureC

April 25

8.0

Mito City, Ibaraki PrefectureD

April 25

2.2

Shimotsuma City, Ibaraki PrefectureE

April 25

2.3

Kasama City, Ibaraki Prefecture

F

April 25

2.3

Kasama City, Ibaraki PrefectureG

April 25

2.3

Chiba City

Name of Subject

Place of Residence

Table 8 Results of Examinations in Breast Milk by the Joso Consumer Cooperative(Only People with Samples Radioactive Materials Detected) (25)Name of Subject

Date of Breast Milk
Sample Collection

I-131 (Bq/L)

Place of Residence

1

March 2248.8

Moriya City, Ibaraki Prefecture

2

March 24

11.3

Tsukuba City, Ibaraki Prefecture

3

March 30

55.9

Kashiwa City, Chiba Prefecture

4

March 31

12.0

Moriya City, Ibaraki Prefecture

5

March 31

9.8

Tsukuba City, Ibaraki Prefecture

6

April 6

16.1

Kashiwa City, Chiba Prefecture

The other organization that performed an examination of I-131 in breast milk is the Joso Consumer Cooperative in
Ibaraki Prefecture. This consumer cooperative detected I-131 in breast milk collected from six lactating women (25).
Since then the Mother-and-Child Support Net has continued examinations, where a total of 421 samples have been
analyzed. I-131 has not been detected since the detection in breast milk samples on May 5 (5.5 Bq/Kg: Iwaki City,
Fukushima Prefecture). Radioactive cesium was detected in 24 people. Regarding the Fukushima nuclear accident, thisis all the examination of breast milk that has been carried out. We compared the examination results by the MHLW
with those by the Mother-and-Child Support Net, showing that the analyses by the Mother-and-Child Support Net havea high level of detection limit (2 to 10B Bq/Kg) due to the relationship between the amount of samples and measuringtime, while the analyses by MHLW with a low level of detection limit (1 to 2 Bq/Kg) have higher detection rates.
Accordingly, if the limit of detection was lowered in examinations performed by the Mother-and-child Support Net,
radioactive materials were highly likely to be detected in much more breast milk.

15

(6-2) Findings from examination of breast milk
When a mother is breastfeeding her child and takes I-131 into her body through inhalation and food, what will
happen? Regarding this question, ICRP or other organizations are proposing models related to the transition to eachtissue in the body (internal pharmacokinetic model). For example, immediately after I-131 is taken into the body,
approximately 50% is excreted in urine and 30% is absorbed into the thyroid gland. Considering the half-life of I-131(8.04 days), 30% of the residual dose in the body is thought to be transferred to the breast milk. Kotaro Tani et al. fromthe National Institute of Radiological Sciences in Chiba City established a model to estimate the amounts of I-131
taken into the bodies of lactating women from the concentration in breast milk based on the above-mentioned internal
pharmacokinetic model and published a paper (26). Tani et al. also published a paper in which exposure doses in a
lactating woman were estimated by using this model from I-131 concentrations in breast milk measured by the MHLW
(27).
Figure 9 is a graph cited from the paper, showing to what extent transition to the breast milk changes dependingon the number of lapsed days after lactating women absorb 1 Bq of I-131 through inhalation and ingestion. Using thiscoefficient, the I-131 dose first inhaled or ingested by a lactating woman can be estimated from the I-131 concentrationin breast milk on the examination day.
Figure9Graph of Transfer Coefficient of I-131 (1 Bq) Taken into Maternal Body to Breast Milk (Reference 27)

In this paper, the authors insist that this model closely matched the transfer coefficient of I-131 to breast milk
proposed by the ICRP-Pub 95.

Using this model, the absorbed I-131 doses in lactating women (March 15 single absorption model) andthe exposure doses in the infants who took the breast milk were calculated based on the I-131
concentrations in breast milk examined by the MHLW (Table 8), and the results are shown in Table 9.
Mothers living in Mito City, Tsukubai City, Moriya City, and Hitachiomiya City in Ibaraki Prefecture, 100 to
200 km from the nuclear power plant, ingested several hundred thousand to one million becquerels of I-131 throughinhalation, water, and vegetables. It is surprising that, consequently, not only did the thyroid equivalent dose in thesemothers reach 100 to 400 mSv but also the thyroid equivalent dose in the infants who fed on the breast milk ranged
from 300 to 1,200 mSv. However, these calculation results were not provided in any paper and did not become
available to the public, except when reported at the Expert Conference of the Ministry of the Environment, held on
May 20, 2014 (28). In the paper (27), Tani et al. did not use or discuss the estimated values for the doses of I-131 bylactating women through breast milk obtained by this pharmacokinetic model because in the author’s opinion the16values were too high to be realistic. Instead, they estimated the inhalation doses from I-131 concentration in theatmosphere at the time of the accident measured by Mito City and Tsukuba City and estimated the I-131 doses ingested
by lactating women from the contamination levels of tap water and vegetables at the time. Based on both estimations,they assessed the I-131 exposure doses by lactating woman. The obtained results are cited in Table 10. The maximum
thyroid equivalent dose is 3 mSv or lower in lactating women, as well as 11 mSv or lower in infants. The differencesfrom Table 10 are just surprising. The authors are not saying that the pharmacokinetic model is wrong. However,which is correct?

Table 9

Doses of I-131 Taken by Lactating Woman and Thyroid Exposure Doses in Their Infants Obtained by
Calculation from the Concentrations in Breast Milk (28)
Equivalent Dose

Measurement

Estimated Intake

Value of Iodine-

Dose in

131 in Breast

Lactating

Milk

Women

(Bq/Kg)

(Bq)

A

3.5

439,000

10

189

524

B

3

376,000

8.3

162

449

C

8

1,000,000

22

432

1199

D

2.2

276,000

6.1

119

330

E

2.3

289,000

6.4

124

345

F

2.3

289,000

6.4

124

345

G

2.3

289,000

6.4

124

345

Name of Subject

for the Thyroid
Effective Dose

Gland in(mSv)

Lactating
Women (mSv)(mSv)

Equivalent Dosefor the Thyroid
Gland in Infants(Sv/Bq)(mSv)

According to the ICRP-Pub95, CD3 concerning thyroid equivalent doses in infants caused by contamination ofbreast milk, when a mother breathes in 1 Bq of gaseous I-131 in the atmosphere, 28.3% of this is provided to the infant
through breast milk, resulting in a thyroid equivalent dose of 1 μSv in the infant at 15 weeks of age. That is, when amother inhales 1,000 Bq or 100,000 Bq, 1 mSv or 100 mSv, respectively, is passed on to the infant. These values areclose to the estimated values by Tani et al. in Table 10. As already mentioned, the radioactive plume that moved inlandon March 15, just after the accident, included high levels of I-131. Residents in Fukushima Prefecture were highly
likely to have inhaled I-131 in amounts as high as several tens of thousands to one hundred thousand becquerels or
higher on March 15, 2011, as stated in the paper by Hirayama et al (11). It cannot be ruled out that their thyroid
equivalent doses ranged from several tens to several hundreds of mSv or higher. Professor Nobuya Unno et al. from
Kitasato University also wrote a paper about an analysis of results from examinations of breast milk conducted by the
MHLW and Mother-and-Child Support Net (29). In this paper, Unno et al., based on the idea from the example ofChernobyl that the I-131 contamination in breast milk was caused by water or food (milk in the case of Chernobyl) notby inhalation, estimated that the cause was contamination of vegetables and water for which contaminations werecovered by the media at the time.

17

Table 10

Doses of I-131 Intake and Thyroid Equivalent Doses in Lactating Women and Infants (from Paper 27)
Lactating Woman

Place ofResidence

Inhalation
I-131 in

I-131 ingaseous form

particulate form

2.8 mSv

0.84 mSv(7.2 KBq)(5.6 KBq)

TsukubaMoriyaInhalation
Ingestion

Ingestion

I-131 in

I-131 ingaseous form

particulate form

<0.38 mSv

Mito

KasamaInfant0.23 mSv

0.14 mSv(600 Bq)(920 Bq)(breast milk)

10-11 mSv

<0.86 KBq

3.3 mSv

1.1 mSv<0.36 mSv

(1.0 KBq)(0.78 KBq)

(2.8-3.1 KBq)

<0.84 KBq
<0.22 mSv

1.1-1.7 mSv<500 Bq(290-450 Bq)<0.26 mSv
<600 Bq

0.28 mSv

0.18 mSv(80 Bq)(130 Bq)

1.1-1.8 mSv(290-480 Bq)(6-3) Radiation exposure in the infants of woman soldiers who participated in Operation Tomodachi, launchedby the US military
After the Fukushima nuclear accident, the United States Forces, Japan (USFJ), provided humanitarian assistance in theform of Operation Tomodachi, including delivering relief supplies to victims. Among a total of 53,000 soldiers who
participated in this operation and their family members, 588 were pregnant women, 560 of whom gave birth after theoperation. For 1,082 women who had infants less than 1 year of age, the United States Department of Defense assessed
the exposure doses in the fetuses and infants exposed to the radiation during the two-month operation in order topublish a 110-page report (30). For this purpose, each USFJ base measured the concentrations of radioactive materials
in the atmosphere since March 13, 2011. Although there is no evidence of direct analyses of breast milk, absorbed
amounts of I-131 into the body were calculated from I-131 concentrations in the atmosphere and amounts inhaled by
pregnant or lactating women (28 m3/day), and then exposure doses in fetuses and infants were calculated according to
the ICRP acute absorption model. For infants, the exposure dose was obtained by adding I-131 ingested through breast
milk to that inhaled directly into the body through inhalation. One example of the results is shown in Table 11.
The iodine-131 concentrations in the atmosphere used for this calculation, for example in Yokota base from March
14 to 15, were up to 19 Bq/m3. Other than that, there is a report about exposure doses of 53,000 people, including
soldiers who participated in Operation Tomodachi (31). In any case, given that the exposure of the thyroid gland of
infants of the U.S. Army women who worked at Yokota base 240 km away from the Fukushima nuclear power plant,
which caused the accident, ranged as much as 8.9 to 21 mSv, it cannot be overestimated how much radiation exposure
there was of the thyroid gland in infants in Fukushima and Ibaraki prefectures, where the concentrations in theatmosphere were much greater.

18

Table 11

Exposure Doses in Infants Who Were Exposed Due to the U.S. Operation Tomodachi(Total of I-131 exposure doses through breast milk and breathing) (30)Name of the US Army Base

Effective Exposure Dose (mSv)

Thyroid Equivalent Dose (mSv)

Misawa base0.03-0.07

0.04-0.16

Yokota base0.58-1.3

8.9-21

Akasaka Press Center

0.54-1.2

8.9-21

Atsugi base0.48-1.1

7.7-18

Yokosuka base0.45-1.0

7.7-18Camp Fuji

0.15-0.37

2.5-6.1

Iwakuni base0.02-0.05

0.36-0.89

Sasebo base0.03-0.07

0.46-1.1

Note: Among these, there are no data on women conducting operations at J-village located near
the nuclear power plant(6-4) Opinions concerning assessment methods of I-131 radiation exposure dose
As mentioned above, radiation exposure in the thyroid gland by I-131 cannot be accurately assessed because various
errors, including Bkg, tend to occur. In particular, in the measurement method where a dosimeter is directly applied tothe thyroid gland, the measurements are easily affected by contamination of the environment. Also, accurate
assessment becomes impossible as time passes due to the half-life of I-131 (8 days). On the contrary, it is a bioassay
using breast milk and urine that allows for biologically accurate measurements. With this method, measurements are
not easily affected by Bkg, and prolonged measurement times can lower the limit of detection, resulting in higher
detection rates. In the case of using breast milk as samples, however, this method has the disadvantage that the numberof samples is limited because collection of a large volume of samples is often difficult due to differences between eachindividual lactating woman.
On the other hand, the bioassay using urine, which has been rarely performed to date, has many advantages asfollows: (1) A large volume of sample can be collected because anyone without regard to the age and gender excretes
urine every day (1 to 3 liters) and (2) continuous measurements for an individual are possible. (3) Based on previous
studies, 50% of I-131 taken into the body is excreted in urine and 30% is accumulated in the thyroid gland, which
results in high concentrations leading to reliable detection accuracy. Considering these conditions, the most reliable
method to assess I-131 exposure doses may be a urine examination conducted immediately after the accident.

(7) Reactions of the Government and academic societies
As mentioned above, the MHLW issued a notification on April 30, 2011 saying, “Considering the trace amounts ofradioactivity detected and the restriction on the consumption of air, water, and foods (standards for I-131 at the time
were 300 Bq/Kg for milk and drinking water and 2,000 Bq/Kg for vegetables and other foods), even if radioactivity
were to be transferred to breast milk, there should be no significant impact; therefore, a mother may provide her baby
with breast milk free from anxiety.” Was this issued for the purpose of soothing mothers who were worried about
radioactivity detected in breast milk, I wonder (32)? On May 2, a similar opinion was published from the Japan Society
19

of Obstetrics and Gynecology (33). However, the MHLW conducted the examination of breast milk more than one
month after the nuclear accident when I-131 became difficult to detect due to its short half-life (8.04 days) and after
many mothers already provided their infants with contaminated breast milk. It is clearly risky that the government
issues reports based on ambiguous grounds and that specialists write papers even though scientifically soundassessment is impossible.
In contrast to the responses of the Japanese government and the Japan Society of Obstetrics and Gynecology, theAmerican College of Obstetricians and Gynecologists placed a policy proposal titled Radioactive Accidents andChildren in the academic journal (35) Pediatrics (2003), saying “In a case where radioactivity is released into theatmosphere due to a nuclear test, nuclear accident, accident during transportation, or terrorism, children may besignificantly affected. Particularly, given that iodine-131 is likely to significantly affect the thyroid gland of infants,
policymakers should encourage mothers to stop providing breast milk.” In response to this proposal, researchers fromthe National Cancer Institute and Memorial Sloan Kettering Cancer Center in New York commented, “In the case of aradioactive accident when the distribution of stable iodine is difficult, breastfeeding should be stopped to prevent
exposure of infants.” (36)The Japan Science Council, which is the center of learning, published a report on September 1, 2017, titled Effectsof Radiation Exposure on Children and Issues in the Future――To Utilize the Available Scientific Findings inFukushima (34). In this Japan Science Council report, the equivalent doses of thyroid gland exposure are estimated to
be 16 to 35 mSv for adults, 27 to 58 mSv for children 10 years of age and 47 to 83 mSv for children 1 year of age.
However, the contents are almost an exact copy of the Annex A of United Nations Scientific Committee on the Effectsof Atomic Radiation (UNSCEAR) 2013 Report. There is no verification conducted by the council itself about any
scientific rationale. The UNSCEAR 2013 Report was in turn based on the following two papers: the above-mentioned
paper written by Shoji et al. from Hirosaki University (14) and the paper written by Eunjoo Kim et al. from the
National Institute of Radiological Sciences based on the results from thyroid examinations in 1,080 people, which wementioned above in the report from the Nuclear Safety Commission (19). Other than that, no direct investigations andanalytical data on exposure of the thyroid gland are available. Nevertheless, the media and many critics, including
scientists, currently give the UNSCEAR report absolute priority and are insisting that “exposure to radiation in the
thyroid gland in Fukushima was low.”（8）Conclusion
Seven years have elapsed since the Fukushima nuclear accident. The government and Fukushima Prefecture are trying
to greatly reduce the scale of the various examinations regarding radioactivity, which they have conducted to date. As
one of these reductions, the scale of the thyroid examinations in children whose age was under 18 years at the time of
the accident in Fukushima Prefecture has been reduced. They are insisting that the reason for this reduction is that
detection of thyroid carcinoma because of overdiagnosis may cause children and parents unnecessary worry andanxiety, leading to reputational damage. Also, they plan to conduct examinations not in all children, which have been
covered to date, but only in children who want to, because increases in thyroid carcinoma are considered not
attributable to radiation exposure based on markedly low levels of exposure doses in Fukushima unlike Chernobyl.
This is a completely irrational and unscientific opinion. Whereas they admit the increases in thyroid carcinoma, if they
will not investigate the cause at all and only reduce the scale of the examinations, the cause will not be understandable.
In the case of Chernobyl, the increases in childhood thyroid carcinoma actually peaked ten years after the accident. The
number is still increasing in Fukushima. The argument that the exposure doses are low is unreliable because only
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investigations, which are based on a detection method using very little data and causing probable errors andunderestimation as mentioned above, have been conducted.
One of the major causes of this is that no immediate investigations and analyses were conducted after theaccident. Particularly, I-131, which is the cause of thyroid carcinoma, has a half-life of 8 days, leading to difficulty indetection and a large error when more than one month has elapsed after the accident. The reason is that the government
and electric power companies who have continued promoting nuclear power plants in Japan, as well as scientists in the
Nuclear Power Village, all assumed that a severe accident involving a nuclear power plant would never occur in Japan
and, therefore, did not prepare for the worst-case scenario. In the case of Chernobyl, a large-scale investigation could
be conducted at the time of the emergency. The reason is said to be that ironically, at the time of the accident in 1986,
the government of the Soviet Union had a system to measure radioactivity in the case of nuclear war caused by theCold War between the Soviet Union and the United States in.
A reduction in the scale of the examinations is not only for thyroid carcinoma. Currently, approximately 3,000
monitoring posts located at various places in the prefecture are measuring and displaying air dose rates. Among them,
the Nuclear Regulatory Agency of the Japanese government currently plans to remove 2,400 monitoring posts locatedwhere the air dose rate has declined to not more than 0.23 μSv/h. As for the reason, the Nuclear Regulatory Agency
says that “… the existence of monitoring posts causes reputational damage, as if the place has a high level of
exposure.” Just the opposite is true. Residents in Fukushima have experienced various specific damages and losses
caused by radioactivity to date; therefore, they know well that a low measured value of radioactivity is the very thingthat gives a sense of security. If the monitoring posts are removed, in the case of any accident in the ongoing
decommissioning of the nuclear power plant, they would not be able to know facthe level and so become anxious
instead, and reputational damage would be reignited in people outside the area who do not know the facts.
Furthermore, Fukushima Prefecture plans to reduce the scale of inspections of every bag of rice produced in
Fukushima, which have been conducted to date. Certainly, seven years have elapsed since the accident andconcentrations of radioactive cesium in rice produced in Fukushima have significantly reduced. Among 9,800,000 bags
investigated in the 2017 fiscal year, radioactivity above the LOD (25 Bq/Kg) was detected in only 35 bags (0.0004%).
However, the reputational damage for rice produced in Fukushima is continuing, and rice farmers’ trouble is not yet
over. One of the causes is the current standard value in food (100 Bq/Kg). No matter how many times you tell urban
consumers that the value is under the standard, they are still not convinced. Because they think about the possible valueof a 90 Bq/Kg. If the scale of the inspection of every bag is reduced, the possibility cannot be ruled out that the
reputational damage could be further widespread.
Recently, there is an argument that talking about the increase in thyroid carcinoma and contamination problem inFukushima would lead to discrimination against residents in Fukushima. It is true that some persons exposed toradiation in Hiroshima and Nagasaki lived all their lives while hiding the fact that they had been exposed to radiationeven from their spouses or children for fear of being discriminated against. However, it is also true that, as a result, thismasked the fact and consequences of radiation exposure, resulting in an uncertain locus of responsibility and thereby
leading to being unable to receive compensation. Regarding discrimination due to the fact that a person has been
exposed to radiation, the person who discriminates is the problem while the person exposed to radiation bears no
responsibility. Trivializing radiation exposure is a huge problem originating from Hiroshima and Nagasaki. Too muchfear of being discriminated against resulted in masking the fact of radiation exposure, thereby leading to trivializing thedamage caused by radioactivity. Ironically, Professor Shunichi Yamashita from Nagasaki University, acclaimed as anexpert in radioactivity and who was installed as a vice-president of Fukushima Medical University after the Fukushima21

nuclear accident, and Professor Kenji Kamiya from the Research Institute for Radiation Biology and Medicine,
Hiroshima University, both insisted everywhere that radioactivity in Fukushima is not frightening.”
This is nothing but reflecting this history. Efforts should be made to understand again that the fact of radiation
exposure is different from the problem of discrimination and to make people consider the idea that discrimination is
not allowed as common sense whatever the facts are. It is clear that these various problems all relate to themeasurement of radioactivity, which is a basic system. Although, unfortunately, the nuclear accident happened, aiming
to keep its impact to a minimum through immediate and accurate measurements and analyses is essential. Conducting
a widespread publicity campaign that sounds as if the fact of radiation exposure does not exist based on uncertain
information can never guarantee the safety and security of the victims of the nuclear accident.
（9）Reference
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SOURCES AND EFFECTS OF IONIZING RADIATION: UNSCEAR 2008, Report to the General Assembly with
Scientific Annexes. Vol.II, Scientific Annexes C, D and E.

2.

CHERNOBYL: Looking Back to Go Forward: Proceedings of an international conference Vienna IAEA (2005)

3.

Report of the Soviet Union and Report of INSAG (Nuclear Safety Commission on May 28, 1987)

4.

Nuclear and Industrial Safety Agency (October 20, 2011)

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Estimation of the released amount of radioactive materials into the atmosphere in the Fukushima Daiichi Nuclear
Power Plant accident (Tokyo Electric Power Company in May 2012)

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SOURCES, EFFECT AND RISKS OF IONIZING RADIATION: UNSCEAR (2013 Report Scientific Annex A) and
DEVELOPMENT SINCE THE 2013 UNSCEAR REPORT ON THE LEVELS AND EFFECTS OF RADIATIONEXPOSURE DUE TO THE NUCLEAR ACCIDENT FOLLOWING THE GREAT EAST-JAPAN EARTHQUAKEAND TSUNAMI (UNSCEAR 2016 white paper)

7.

Fukushima Prefecture: Measurement results of environmental radioactivity level in seven regions within Fukushima
Prefecture (provisional value: monitoring 1)

8.

Furuta et al.: Monitoring results of special environmental radiation involved in the Fukushima Daiichi Nuclear Power
Plant accident―interim report (JAEA Review 2011-035 (2011).

9.

High Energy Accelerator Research Organization (KEK): Measurement results of types and concentrations ofradioactive materials in the air performed in Tsukuba City (April 25, 2011).

10. The radionuclide monitoring status in the CTBT radionuclide monitoring station established in Takasaki (the Centerfor the Promotion of Disarmament and Non-Proliferation of The Japan Institute of International Affairs)
11. Hideo Hirayama, Hiroshi Matsumura, Yoshihito Namito, Toshiya Sanami Estimation of I-131 concentrations in theatmosphere over time using NaI (Tl) detector pulse height distribution measured at monitoring stations in Fukushima
Prefecture. Journal of Atomic Energy Society of Japan 2015, Advance Publication by J-stage,
doi:10.3327/taesj.J14.027
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www.nature.com/scientificreports. DOI:101038/srep12426.
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the Accident in Fukushima (6th Expert conference about health control of the residents related to the nuclear accident
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