● このスライドは、非営利かつ個人的な目的に限り閲覧することができます。
The following presentation slides are shared with symposium participants exclusively for personal, non-commercial,educational purposes.

● このスライドの著作権は、講演の発表者本人に帰属します（図表等の引用箇所は除く）。如何なる国・地域においても、また紙媒体やインターネット・電子データなど形態に関わらず、スライドの全部または一部を無断で複製、転載、配布、送信、放送、貸与、翻訳、販売、変造、二次的著作物を作成すること等は、固く禁止します。
Copyright of these slides belongs to the presenter and/or the Radiation Medical Science Center for the Fukushima
Health Management Survey, Fukushima Medical University (except figures, tables, etc., cited from other sources).
It is strictly prohibited to reproduce, reprint, distribute, transmit, broadcast, loan, translate, sell, modify, and/or
create derivatives of any slides, in any physical or electronic medium anywhere in the world.

2024年 福島県立医科大学『県民健康調査』国際シンポジウム
公立大学法人福島県立医科大学放射線医学県民健康管理センター
国際シンポジウム事務局（広報・国際連携室）✉ kenkani@fmu.ac.jp Tel: 024-581-5454(平日9～17時)
2024 Fukushima Medical University International Symposium on the Fukushima Health Management Survey
Secretariat of International Symposium
Office of Public Communications and International Cooperation, Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima Medical University✉ kenkani@fmu.ac.jp, TEL: +81-24-581-5454 (Weekday, 9a.m. - 5 p.m. JST)Session 1 【Insights - what we have learned from the people of Fukushima】

Basic Survey－Experience in dose estimation involving around
two million people
Tetsuo Ishikawa
Radiation Medical Science Centerfor the Fukushima Health Management Survey
Fukushima Medical University
1

Circumstances in the early post-accident period
Environmental radiation level(ambient dose rate) jumpedup

It was difficult for residents to get information on their radiation
exposure dose levels, because radiation measurement devices such asmonitoring posts or personal dosimeters were not widely available

https://www.pref.fukushima.lg.jp/sec/16025d/h22-24-7houbu.html

Maximum value was observed on
March 15 （around 24 µSv/h）Monitoring post
（The device indicating
ambient dose at thatplace）
These devices
were not widely
available just after
the accident

Mar 31
3月31日

Mar 26
3月26日

Mar 21
3月21日

Mar 16
3月16日

Level before the accident （around 0.05 µSv/h）

Mar 11
3月11日

dose rate
Ambient空間線量率（µSv/h）Changes in ambient dose rate in Fukushima City

Personal dosimeter（The device which records integrated
exposure dose for a person who wears it）
https://www.city.fukushima.fukushima.jp/hokenhk/bosai/bosaikiki/shinsai/hoshano/hosha/hkenkou-kanri190205.html

Purpose and eligible people for the Basic Survey⚫ Residents were asked to record and send back information on their
behavior in the early post-accident period (self-administeredquestionnaire). Individual external doses (exposure doses fromradiation in environment) were estimated based on their behaviors andnotified to respondents by post.

⚫ The purpose was to ascertain the level of exposure of the entire
population of the prefecture due to the accident and to link such data
to the improvement and maintenance of their health into the future.
⚫ Eligible people were registered residents in Fukushima Prefecture
between March 11 and July 1, 2011 (around 2.06 million people).
Questionnaires were distributed from June 30, 2011.

••

Those who lived in the prefecture between March 11 and July1, 2011, but whose resident registration was outside theprefecture.
Those who lived outside the prefecture and commuted towork or school in the prefecture.

For those who fall into the above two categories, questionnaires
are sent upon their request.
3

Sample of ｂehavior record sheet to the questionnaire (major part)
Behavior record sheet form for the period from March 11, 2011（the day of earthquake） to March 25

The items to be filled in for the period fromMarch 26 to July 11, are:
⚫ Area(s) of residence⚫ Average time spent outdoors per day⚫ Place of regular outing (place of employment oreducation）, etc.

Period for dose estimation： four months
from March 11, 2011 to July 11, 2011

Infants and children are also included in
the eligible people
For minors： Guardian’s signature isrequired for submission of thequestionnaire4Outline of dose calculation method
Information on
whereabouts including
staying indoor or outdoors
Dose reduction effects
by staying indoors is
also considered

Questionnaire
surveySource: National Institutes for Quantum Science and Technology“System overview”, The external exposure doses estimation evaluation system
https://www.qst.go.jp/uploaded/attachment/2123.pdf

Results of ambient dose
measurements
Digitized behaviorrecords

Daily ambient dose ratemaps

Whereabouts areconverted to thelongitude and thelatitude data

National Institute of Radiological Sciences (current name:National Institutes for Quantum Science and Technology)
developed a computer program for this calculation

Individual doses
were estimated bysuperimposing
digitized behavior
records and ambient
dose rate maps
5

Flow of the Basic Survey
Dose estimation for individual respondents

Distribute questionnaire form

Collect questionnaire responses

Digitize behavior records

Questionnaire writing
supportExample: “I was at my relative’shouse” (such information
cannot be converted tolongitude and latitude, anddose estimation is not possible)

Ask the respondents and supplement records,
if an address or building name is ambiguous(more than 60,000 people)

Number of responses peaked at around 8,000 per dayAnalysis to identify the general trend

Estimate doses using calculation program

Aggregate the dose estimate data

Send results to respondents

Report to the Oversight Committee
Publish in academic journals

Providing scientific information toindividuals about radiation exposure in
the early post-accident period, when
there was no sufficient information
was made available for residents.

Scientific data and insight on thesituation of radiation exposure inFukushima are disseminated nationallyand internationallyActivities to support completing the questionnaire (writingsupport) and study on representativenessWriting support was mainly offered at the following places•

Temporary housing facilities•

Thyroid Ultrasound Examination venues(public facilities）•

Health check venues in municipalities•

City halls and other government buildings, etc.

Overall response rates for the entire prefecture: 27.7％（as of March 31, 2023 for all 59 municipalities）
The response rates more than 50% : 8 municipalities
The response rates 40% - 50%: ２ municipalities（Areas marked in red in the right figure）

Writing support boothResponse rates bymunicipality>50%
40 - 50%
Other areas：less than 40%

The results of the study on representativeness indicate that the dose
distributions obtained thus far are considered also to be unbiased dose
distributions for the entire prefecture.

Ishikawa T et al.: Radiat Environ
Med 8(2) 118-126 (2019)7

Notification to individuals of exposure doses
The results of dose estimation are sent to each individual

Major part of the result report

Notification of exposure doses
The result of external exposure doseｓ estimation based on yourresponses to the questionnaire of the Basic Survey is asfollows:
Estimated external exposure doses received during“estimation period” is printed here
were estimated at:

Estimated exposure doses （mSv）
The results of dose estimation has been sent to around 555,000 respondents including
those with behavior records of less than 4 months

Estimated external doses over the four months following the accident
Sources: materials for 48 OversightCommittee Meeting（as of March 31, 2023）
thMean doses for each region
Mean:0.2 mSv

Mean:
1.4 mSv< 1 mSv: 77.3%< 2 mSv: 94.9%< 3 mSv: 97.2%
Mean: 0.7 mSv

Kenpoku

Aizu

SosoKenchu●Mean:
1.0 mSv

KennanMinamiaizu

Mean:
0.1 mSv

Mean:
0.6 mSv

Fukushima
Daiichi Nuclear
Power Plant

The distribution of 467,256
respondents, excluding former
radiation workers< 1 mSv: 62.2%< 2 mSv: 93.8%< 3 mSv: 99.3%
Mean: 0.8 mSv
Maximum： 25 mSv

Evaluation by Oversight Committee

Iwaki

Mean:
0.3 mSv

Radiation doses estimated so far areunlikely to cause adverse effects on
health, although this conclusion is basedon external exposure doses estimatedonly for the first four months following
the accidentImportance of behavior records in dose estimation
On April 22, 2011, “Planned evacuation zone”(area marked in yellow in the right figure) wasestablished, because the cumulative dose
received by residents was likely to reach 20
mSv within one year after the accident

Iitate Village

30km

20km
The residents were instructed toevacuate within around one month.
Actual timing of evacuation wasconsidered to be different among theresidents

The national government
issued the evacuation orderfor the 20 km radius on
March 12, 2011 (the next dayof the earthquake)

NamieTown

Fukushima
Daiichi Nuclear
Power plant

https://www.pref.fukushima.lg.jp/site/portal/cat01-more.html

Importance of behavior records in dose estimation（Namie Town and Iitate village）
WHO： World Health Organization
UNSCEAR： United Nations Scientific Committee
on the Effects of Atomic Radiation

WHO 2012 report
10～50 mSv
（Adults in Namie Town and IitateVillage）
Almost lessthan 10%Major assumptions used forestimating the first-year dose after
the accident
Residents stayed in the planned
evacuation zone for four months andthen evacuated out of it
They spent 8 hours outdoors per day

UNSCEAR 2013 report
Two typical evacuation scenarios were
5.0, 7.0 mSv （Adults in Namie Town） assumed for Namie Town and Iitate
7.8, 8.0 mSv （Adults in Iitate Village） Village, each

UNSCEAR 2020/2021 report
0.25～3.1 mSv （Adults in NamieTown）
0.36～5.5 mSv （Adults in IitateVillage）

Actual evacuation patterns estimatedfrom behavior records obtained in
the Basic Survey (5 typical patterns
for Namie Town and 4 typical patterns
for Iitate Village)

石川徹夫：福島原発事故・県民健康調査① 被災者の被ばく線量推計. 公衆衛生 87巻, 1094-1102 (2023)より引用（一部改変）

Assessment of internal thyroid exposure doses using behavior records
Behavior
records
after theaccident＋

Estimation of external
exposure doses(Basic Survey)

Ambient dose
rate maps

Conversion toexternal thyroid
doses

Results from projects otherthan the Basic Survey

Behavior
records afterthe accident

Behavior
records afterthe accident

Behavior recordsobtained in the BasicSurvey＋＋

Airborne radioiodine
concentrations in the earlypost-accident period(estimation by computersimulation)
Waterborne radioiodine
concentrations in the earlypost-accident period(estimation by combination ofsimulation and measurements）＋
Estimation of internal
thyroid doses (viainhalation)＋
Estimation of internal
thyroid doses (viaingestion)

Total thyroid doses are used
for case-control studies on
thyroid cancer

Summary -significance of the Basic Survey for estimating
doses in the early post-accident period⚫

Basic Survey estimates individual external doses, when measuring instruments were notwidely available. Notification of exposure doses was sent to around 555,000 respondents.

⚫

The mean dose for the whole prefecture was 0.8 mSv and the maximum dose was 25 mSv.

⚫

Although the activities to improve the response rate has been continued, it has not changed
substantially, thus, we implemented “Study on representativeness.” As a result of the study
and its analysis, it indicated that the dose distributions obtained thus far are considered to
be an unbiased depiction of dose distribution for the entire prefecture.

⚫

According to the Oversight Committee evaluation, radiation doses estimated so far are
unlikely to cause adverse effects on health, although this conclusion is based on external
exposure doses estimated only for the first four months following the accident.

⚫

In contrast to the overestimation of doses initially reported by international organizations
based on the assumption of safety first perspective, the more close and realistic estimations
are reported with the special significance of assessments based on the behavior records
obtained through the Basic Survey.

⚫

Behavior records obtained from the Basic Survey were also used to evaluate internal thyroid
exposure doses.

● このスライドは、非営利かつ個人的な目的に限り閲覧することができます。
The following presentation slides are shared with symposium participants exclusively for personal, non-commercial,educational purposes.

● このスライドの著作権は、講演の発表者本人に帰属します（図表等の引用箇所は除く）。如何なる国・地域においても、また紙媒体やインターネット・電子データなど形態に関わらず、スライドの全部または一部を無断で複製、転載、配布、送信、放送、貸与、翻訳、販売、変造、二次的著作物を作成すること等は、固く禁止します。
Copyright of these slides belongs to the presenter and/or the Radiation Medical Science Center for the Fukushima
Health Management Survey, Fukushima Medical University (except figures, tables, etc., cited from other sources).
It is strictly prohibited to reproduce, reprint, distribute, transmit, broadcast, loan, translate, sell, modify, and/or
create derivatives of any slides, in any physical or electronic medium anywhere in the world.

2024年 福島県立医科大学『県民健康調査』国際シンポジウム
公立大学法人福島県立医科大学放射線医学県民健康管理センター
国際シンポジウム事務局（広報・国際連携室）✉ kenkani@fmu.ac.jp Tel: 024-581-5454(平日9～17時)
2024 Fukushima Medical University International Symposium on the Fukushima Health Management Survey
Secretariat of International Symposium
Office of Public Communications and International Cooperation, Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima Medical University✉ kenkani@fmu.ac.jp, TEL: +81-24-581-5454 (Weekday, 9a.m. - 5 p.m. JST)