who preliminary dose estimation from the nuclear accident after the 2011 great east japan earthquake...

7/29/2019 WHO Preliminary dose estimation from the nuclear accident after the 2011 Great East Japan Earthquake and Tsun

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Preliminary

dose estimationrom the nuclear accident

ater the 2011 Great East Japan

Earthquake and Tsunami


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WHO Library Cataloguing-in-Publication Data

Preliminary dose estimation rom the nuclear accident ater the 2011 Great East Japan

earthquake and tsunami.

1.Radiation injuries. 2.Accidents, Radiation. 3.Radiation dosage. 4.Radiation monitor-

ing. 5.Risk assessment. 6.Nuclear power plants. 7.Earthquakes. 8.Tsunamis. 9.Japan

I.World Health Organization.

ISBN 978 92 4 150366 2 (NLM classication: WN 665)

This report contains the collective views o an international group o experts, and does not

necessarily represent the decisions or the stated policy o the World Health Organization.

World Health Organization 2012

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nization, 20 Avenue Appia, 1211 Geneva 27, Switzerland (tel.: +41 22 791 3264; ax:

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The designations employed and the presentation o the material in this publication do not

imply the expression o any opinion whatsoever on the part o the World Health Organiza-

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concerning the delimitation o its rontiers or boundaries. Dotted lines on maps represent

approximate border lines or which there may not yet be ull agreement.

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preliminary dose estimation from the nuclear accident after the 2011 Great east Japan earthquake and tsunami / 1

ACKNOWLEDGEMENTS

AcknowledgementsThis report on the initial evaluation o radiation exposure rom the nuclear accident

ater the 2011 Great East Japan Earthquake and Tsunami is the result o the work o an

International Expert Panel convened by the World Health Organization (WHO). The work

relied on the contribution o more than 30 scientists, some o whom participated in

expert panel meetings to develop this document and some o whom contributed within

their institutions.

WHO is particularly grateul to Ms Jane Simmonds (Health Protection Agency, HPA,United Kingdom) or her ecient and instrumental contribution as Chair o the expert

panel. A scientic editorial group was part o the production and reviewing process

or the preparation o this report, and their assistance is grateully acknowledged:

Dr Stephanie Haywood (Health Protection Agency, United Kingdom), Dr Philippe Verger

(WHO), Dr Maria del Rosario Prez (WHO) and Dr Emilie van Deventer (WHO).

Thanks are expressed to all the participants and contributors, with special gratitude or

their major contributions to the ollowing panel members:

Lynn Anspaugh

Mikhail Balonov

Carl Blackburn

Florian Gering

Stephanie Haywood (Rapporteur)

Gerhard Proehl

Shin Saigusa

Jane Simmonds (Chair)

Ichiro Yamaguchi

WHO also acknowledges the contribution o other experts rom the Food and Agriculture

Organization o the United Nations, the International Atomic Energy Agency, and the

International Agency or Research on Cancer as members o the panel; and the partici-pation o representatives o the United Nations Scientic Committee on the Eects o

Atomic Radiation and representatives o the Government o Japan, as observers.

The WHO Cluster o Health Security and Environment nancially supported the develop-

ment o this report.


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2/preliminary dose estimation from the nuclear accident after the 2011 Great east Japan earthquake and tsunami

ContributorsDr Lynn Anspaugh3

University o Utah, USA

Dr Mikhail Balonov1,2,3

Institute o Radiation Hygiene, Russia

Mr Peter Bedwell

Health Protection Agency, United

Kingdom

Mr Antony Bexon


Kingdom

Dr Carl Blackburn2

Food and Agriculture Organization o the

United Nations, Austria

Dr Volodymyr Berkovskyy1

International Atomic Energy Agency,

Austria

Mr David Byron1



Dr Tom Charnock


Kingdom

Dr Michael Dinovi

Food and Drug Administration, USA

Dr Sergey Fesenko

Food and Agriculture Organization o theUnited Nations, Austria

Ms Brigitte Gerich3

Federal Oce o Radiation Protection,

Germany

Dr Florian Gering1,2,3

Federal Oce o Radiation Protection,

Germany

Dr Vladislav Golikov


Dr Stephanie Haywood1,2,3


Kingdom

Dr Jean-Ren Jourdain1,2

Institut de Radioprotection et de Sret

Nuclaire, France

Dr Catherine Leclercq,

Istituto Nazionale di Ricerca per gli

Alimenti e la Nutrizione, Italy

Dr Lionel Mabit3



Dr Gerhard Proehl1,2

International Atomic Energy Agency,Austria

Mr Jonathan Sherwood

Health Protection Agency, UnitedKingdom

Dr Shin Saigusa1,2,3

National Institute o Radiological

Sciences, Japan

Dr Kazuo Sakai1

National Institute o Radiological

Sciences, Japan

Ms Jane Simmonds2,3


Kingdom

Dr Diego Telleria1,3

International Atomic Energy Agency,

Austria

Mr Joseph Wellings


Kingdom

Dr Ichiro Yamaguchi2

National Institute o Public Health,

Japan

Dr Irina Zvonova


ObserversMr Malcolm Crick3

United Nations Scientic Committee

on the Eects o Atomic Radiation

Secretariat

Mr Takashi Kiyoura1

Permanent Mission o Japan in Vienna,

Austria

Mr Ichiro Ogasawara1

Permanent Mission o Japan in Vienna,

Austria

Mr Yuji Otake2,3

Permanent Mission o Japan to the

International Organizations in Geneva,

Switzerland

Dr Ferid Shannoun1,2

United Nations Scientic Committee

on the Eects o Atomic Radiation

Secretariat

Dr Wolgang Weiss1

United Nations Scientic Committee on

the Eects o Atomic Radiation

World Health OrganizationDr Emilie van Deventer2,3

WHO headquarters

Dr Kazuko Fukushima2,3

WHO headquarters

Dr Dominique Maison2

WHO headquarters

Ms. Asiya Odugleh-Kolev

WHO headquarters

Dr Maria del Rosario Perez1,2,3

WHO headquarters

Dr Isabelle Thierry-Che3

International Agency or Research on

Cancer. France

Dr Angelika Tritscher2,3

WHO headquarters

Dr Philippe Verger1,2,3

WHO headquarters

1 Participant in the International Expert Pa-

nel meeting in Vienna, June 2011


nel meeting in Geneva, September 2011


nel meeting in Geneva, October 2011


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CONTENTS

Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Observers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

World Health Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Executive summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Preace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

1.2 Purpose and audience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.3 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

1.4 Overview o the methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

1.5 Endpoints and scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

1.5.1 Dosimetric endpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

1.5.2 Age groups considered . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

1.5.3 Geographical coverage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

1.5.4 Time rame. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

1.5.5 Protective actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

1.6 Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

2. Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.1 Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.2 Input data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.2.1 Radionuclide composition and deposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.2.2 Environmental monitoring data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

2.2.3 Food monitoring and consumption data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

2.3 External radiation doses rom radionuclides deposited on the ground (groundshine) . . . . . 27

2.3.1 Inside Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

2.3.2 Outside Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

2.4 External radiation doses rom the radioactive cloud (cloudshine). . . . . . . . . . . . . . . . . . . 28

2.4.1 Inside Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

2.4.2 Outside Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

2.5 Internal radiation doses rom inhalation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

2.5.1 Inside Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

2.5.2 Outside Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

2.6 Internal radiation doses rom ingestion o ood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

2.6.1 Ingestion doses inside Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

2.6.2 Monitoring o Japanese ood outside Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

2.6.3 Ingestion doses outside Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

2.7 Internal doses rom ingestion o tap water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372.8 Doses due to the releases o radionuclides to the sea . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

2.9 Summary o key assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Contents


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3. Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

3.1 Presentation o results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

3.2 Age dependence o dose estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403.3 Geographical distribution o doses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

3.3.1 Estimated eective doses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

3.3.2 Estimated thyroid doses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

3.3.3 Doses to the southern hemisphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

3.4 Results or ood ingestion doses in Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

3.5 Results or tap water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

4. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

4.1 Temporal distribution o the dose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

4.2 Infuence o protective actions on the dose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

4.3 Contribution o the dierent exposure pathways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 514.4 Comparison to doses rom other radiation sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

4.5 Comparison o dierent methodologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

4.6 Comparison with in vivo human measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

4.6.1 Monitoring in Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

4.6.2 Monitoring outside Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

4.7 Main sources o uncertainty and limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

4.7.1 Estimating time-integrated air concentrations based on deposition measurements 60

4.7.2 Assumed radionuclide composition in Japanese locations . . . . . . . . . . . . . . . . . . 61

4.7.3 Location actor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

4.7.4 Use o ICRP dose coecients or Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

4.7.5 Source term . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

4.7.6 Dispersion modelling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

4.7.7 Ingestion doses in Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

5. Summary and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Reerences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

Annex 1. Declaration o interests statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

Annex 2. Examples o doses rom dierent sources o exposure . . . . . . . . . . . . . . . . . . . . . . . . 79

Annex 3. Input parameters or the dose assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

1. Inhalation dose coecients. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

2. Ingestion dose coecients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

3. Inhalation rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

4. External dose per unit deposit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

5. Dose reduction actor: external dose rom radioactive material in air . . . . . . . . . . . . . . . . . 86

Annex 4. Source term or use in dispersion-based calculations . . . . . . . . . . . . . . . . . . . . . . . . . 87

Annex 5. Example o input monitoring data rom Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90


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CONTENTS

Annex 6. Models or external and inhalation doses in Japan (Approach A and Approach B) . . . . . 95

1. Model or external dose rom nuclides deposited on soil . . . . . . . . . . . . . . . . . . . . . . . . . 95

1.1 Eective dose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 951.2 Thyroid dose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

2. Model or external dose rom radioactive cloud . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

2.1 Eective dose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

2.2 Thyroid dose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

3. Model or internal dose rom inhalation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

3.1 Eective dose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

4. Input data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

4.1 Surace activity density o 137Cs (ACs137

) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

4.2 Surace activity density o other nuclides (Am) . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Reerences to Annex 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Annex 7. Models or external and inhalation doses outside Japan (Approach C). . . . . . . . . . . . . 101

1. Model or external dose estimation or radionuclides deposited on the ground . . . . . . . . . 101

2. Model or external dose estimation or radionuclides in the radioactive cloud . . . . . . . . . . 101

3. Model or internal dose rom inhalation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

Reerences to Annex 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

Annex 8. Model or ingestion doses in Japan (Approach D) . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

1. Model or dose calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

2. Input data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

3. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

Annex 9. Model or ingestion doses outside Japan (Approach E) . . . . . . . . . . . . . . . . . . . . . . . 117

1. Model or dose estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

2. Input data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

3. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

Reerences to Annex 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120


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EXECUTIVE SUMMARY

Executive summaryThe earthquake and tsunami in Japan on 11 March 2011 led to releases o radioactive

material into the environment rom the Tokyo Electric Power Companys Fukushima Dai-

ichi nuclear power station. This report describes an initial estimate o radiation doses re-

sulting rom this accident to characteristic members o the public in populations around

the world.

In line with its dened role in radiation emergency response among international or-

ganizations, the World Health Organization (WHO) is responsible or public health risk

assessment and response. Thereore soon ater the accident, WHO initiated a health risk

assessment to support the identication o needs and priorities or public health action

and to inorm Member States and the public.

The aim o the health risk assessment is to estimate at global level the potential health

consequences o human exposure to radiation during the rst year ater the Fukushima

Daiichi nuclear power plant accident. The assessment covers inants, children and adults

living in the Fukushima preecture, nearby preectures, the rest o Japan, neighbouring

countries, and the rest o the world.

Because the health risk assessment requires an estimation o radiation doses delivered

to the population, WHO established an International Expert Panel to make an initial

evaluation o radiation exposure o people both inside Japan and beyond, as a result o

the accident. The panel members were required to sign a declaration o interests, and no

conficts o interest were identied or any o them. The dose assessment was conducted

by more than 30 experts who served in their individual capacities, either participating

in the Expert Panel meetings or providing technical contributions rom their respective

institutions. All participating experts were selected on the basis o their scientic com-

petence and experience.

Additionally, the panel included representatives o the International Atomic Energy

Agency, the Food and Agriculture Organization o the United Nations and WHO in view

o the relevance o their areas o expertise. The United Nations Scientic Committee on

the Eects o Atomic Radiation, which has initiated a two-year assessment o the expo-

sure levels and eects that will be submitted to the United Nations General Assembly

in 2013, participated as an observer in the WHO assessments to ensure compatible

approaches and data sources or the two United Nations activities. The Government o

Japan also designated representatives to attend the meetings o the panel as observers.

Three panel meetings were convened in June, September and October 2011.

This report provides data on eective doses and equivalent doses to the thyroid in mem-bers o the public resulting rom exposure over the rst year ater the accident or dier-

ent regions o the world, with greater spatial detail or the estimated doses inside Japan

and, in particular, in the Fukushima preecture.


10/124


The assessment was designed to provide preliminary dose estimates and was based on

inormation publicly available rom relevant Japanese government institutions, collected

up to mid-September 2011. To validate the results o the dose estimates, the panel useda variety o dosimetric approaches and made comparisons with existing data on human

in-vivo monitoring measurements (e.g. whole body counting and thyroid measurement).

As ar as possible, the input data were measurements o levels o radioactive material

in the environment (e.g. levels o dierent radionuclides on the ground) and levels o

activity concentration in oodstus. When direct monitoring data were not available, es-

timates based on simulations were used as input or the dose models.

The methodology used to calculate the doses relies on the most recent dosimetric and

biokinetic models or dierent population subgroups (i.e. inants, children and adults).

It considers all major routes o exposure i.e. external exposure (rom cloudshine andgroundshine) and internal exposure (rom ingestion o oodstus and inhalation).

The estimated doses are presented in order-o-magnitude dose bands o characteristic

individual doses or each region considered. These are not the ull ranges on the doses

that may be received by all individuals within each region. The main sources o uncer-

tainty in the dose estimates are discussed in the report.

This assessment is intended to be realistic. However, given the limited inormation avail-

able to the panel during the time rame o its work, the assessment contains a number

o assumptions (e.g. radioactive cloud composition and dispersion, time spent indoors/

outdoors, and consumption levels). In particular, some assumptions regarding the imple-mentation o protective measures are conservative (e.g. the assumption that people in

the most aected areas outside the 20-kilometre radius continued to live there or our

months ater the accident) and some possible dose overestimation may have occurred.

All eorts were made to avoid any underestimation o doses.

In this context, using conservative assumptions, the assessment shows that the total

eective dose received by characteristic individuals in two locations o relatively high

exposure in Fukushima preecture as a result o their exposure during the rst year ater

the accident is within a dose band o 10 to 50 mSv. In these most aected locations,

external exposure is the major contributor to the eective dose. In the rest o Fukushima

preecture the eective dose was estimated to be within a dose band o 1 to 10 mSv.Eective doses in most o Japan were estimated to be within a dose band o 0.1 to 1

mSv and in the rest o the world all the doses are below 0.01 mSv and usually ar below

this level.

The characteristic thyroid doses in the most exposed locations o Fukushima preecture

were estimated to be within a dose band o 10 to 100 mSv. In one particular location the

assessment indicated that the characteristic thyroid dose to one-year-old inants would

be within a dose band between 100 and 200 mSv, with the inhalation pathway being

the main contributor to the dose. Thyroid doses in the rest o Japan were within a dose

band o 1 to 10 mSv and in the rest o the world doses are estimated to be below 0.01

mSv and usually ar below this level.

Outside the most aected areas o Fukushima preecture, the exposure rom ood is the

dominant pathway. Due to the assumptions applied the dose rom ingestion may be over-


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EXECUTIVE SUMMARY

estimated, especially in locations outside Fukushima and its neighbouring preectures,

and the reasons are discussed in the report.

This report represents the rst international eort to assess global radiation doses rom

the Fukushima Daiichi nuclear power plant accident considering all major exposure

pathways. It provides timely and authoritative inormation on the anticipated scale o

doses in members o the public or the rst year ater the accident, based on input data

available to the International Expert Panel within the time rame. Nevertheless, this dose

assessment should be considered as preliminary. The availability o urther monitoring

data and more detailed inormation about implementation o protective measures will

allow or more rened assessments in the uture.


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PreaceThe World Health Organization (WHO) conducts a programme on radiation and health

which aims to promote sae and appropriate use o radiation to protect patients, work-

ers and members o the public in planned, existing and emergency exposure situations.

WHO's involvement in radiation and health began within a decade o its ounding, and

the International Commission on Radiological Protection has been in ocial relations

with WHO since 1956. In 1972 the World Health Assembly requested the Director-General to cooperate with the International Atomic Energy Agency, the United Nations

Scientic Committee on the Eects o Atomic Radiation, and other international orga-

nizations in evaluating the world situation regarding the medical use o ionizing radia-

tion and the eects o radiation on populations.1

Global public health security is one o the key priorities o WHOs agenda. The World

Health Assembly requested the Director-General in 2005 to enhance WHOs capacity to

implement health-related emergency preparedness plans, and to prepare or disasters

and crises through timely and reliable assessments.2 The nature o WHOs work on emer-

gencies whether resulting rom natural, intentional or accidental events requires a

high level o coordination with a variety o partners within the United Nations system, as

well as with other external partners. One o the lessons rom the 1986 Chernobyl nuclear

accident was the need to strengthen international cooperation in radiation emergencies.

The Joint Radiation Emergency Management Plan o the International Organizations,

last published in 2010, establishes the mechanisms or implementing a coordinated

response and denes the roles o each party. Within this joint plan, WHO is responsible

or the coordination o public health risk assessment and response.

The decentralized structure o WHO with its headquarters in Geneva, Switzerland,

six regional oces and 149 country oces provides optimal conditions or interact-

ing with the Organizations 194 Member States. Ater the 11 March 2011 Great East

Japan Earthquake and Tsunami, TEPCO's Fukushima Daiichi nuclear power station was

severely damaged and a signicant amount o radioactive material was released into the

environment. The potential risks o human exposure to radiation resulting rom this ac-

cident received priority attention around the world. As the United Nations directing and

coordinating authority on international public health issues, WHO was directly engaged

in assessing and communicating public health risks. Since the onset o the accident,

WHO's response has been articulated through the Organizations Western Pacic Re-

gional Oce, based in Manila, Philippines, assisted by WHO headquarters and the WHO

Centre or Health Development in Kobe, Japan.

1. See World Health Assembly resolution WHA25.57.

2. See World Health Assembly resolution WHA58.1.


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PREFACE

Assessment o the health risks arising rom this accident requires knowledge o the

radiation doses delivered to populations within Japan and beyond. To that end, WHO

established an International Expert Panel to undertake an initial assessment o radia-

tion doses received by populations inside and outside Japan as a consequence o the

Fukushima Daiichi accident. The panel consisted o independent scientic experts and

representatives o WHO, the International Atomic Energy Agency and the Food and Agri-culture Organization o the United Nations. The United Nations Scientic Committee on

the Eects o Atomic Radiation and the Government o Japan participated as observers.

This report summarizes the results o the dose assessment conducted by the panel. It

represents the rst international eort to estimate radiation doses rom this accident at

the global level, taking into account all the signicant exposure pathways. This report

is primarily intended or use by the WHO Health Risk Assessment Group to inorm an

initial assessment o health risks incurred as a consequence o the Fukushima Daiichi

accident. It provides inormation to Member States and the public on the anticipated

scale o doses or the rst year ater the accident.


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The earthquake and tsunami in Japan on 11 March 2011 led to releases o radioactive

material into the environment rom the Tokyo Electric Power Companys Fukushima Dai-

ichi nuclear power station. This report describes an estimate o radiation doses to the

public resulting rom this accident. These doses, characteristic o the average doses, and

presented in this report as "characteristic doses", are assessed or dierent age groups in

locations around the world, using a set o assumptions described in the text.

The dose assessment described in this report was undertaken by an International Expert

Panel convened by WHO in June 2011 with the aim o completing its work within a short

timescale and is thereore preliminary in nature.

This dose evaluation orms one part o the overall health risk assessment o the global

impact o the accident at the Fukushima Daiichi nuclear power plant, which is being

carried out by WHO. This health risk assessment is the subject o a separate WHO report

that is intended to inorm public health actions.

The present assessment will orm one input into a two-year scientic study to assess the

radiological consequences o the Fukushima Daiichi nuclear power accident that is to be

published by the United Nations Scientic Committee on the Eects o Atomic Radia-

tion (UNSCEAR) in 2013. More rened assessments will no doubt be conducted and

reported in the uture as additional data become available.

The panel agreed to concentrate on the most important contributors to dose rather than

attempting to analyse all aspects comprehensively. As this assessment is intended to

be realistic, the panel made conservative assumptions only when data were insucient

(e.g. with regard to the timeline o implemented protective actions). The dose estimates

were based primarily on the best input data available up to mid-September 2011. The

results are presented in a level o detail commensurate with the availability o data andthe preliminary nature o the assessment. The report is the rst study to present an esti-

mate o the doses around the world, incorporating all exposure pathways that contribute

signicantly to radiation dose.

1.1 Background

On 11 March 2011 Japan suered a magnitude 9 earthquake, the largest ever re-

corded in the country. The epicentre was just over 180 km rom the site o the Fu-

kushima Daiichi nuclear power plant that had six nuclear reactors, each with its own

uel storage pond. At the time o the accident, three o the sites nuclear reactor units

(reactors 13) were operating at power. Reactor 4 was reuelling, and reactors 5 and

6 were shut down or maintenance. Reactors 13 were automatically shut down when

the earthquake occurred. However, less than one hour ater the earthquake a massive

1. Introduction


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1. INTRODUCTION

tsunami generated by the earthquake inundated the nuclear site at Fukushima Daiichi

with seawater.

The damage caused by the fooding o the site resulted in loss o cooling to the three

reactor units. This led to eventual overheating, hydrogen explosions and a probable

partial melting o the core o the three reactors. As a consequence, major releases o

radioactive material to the environment occurred. These releases were initially to the

air, but subsequently there were also radioactive releases to the sea through discharge

o water used to cool the reactors and the spent uel ponds (1). The nuclear accident

was eventually classied at Level 7, the highest on the International Nuclear and Ra-

diological Event Scale (INES) (2).

Measures were taken by national authorities to protect their populations rom the con-

sequences o the nuclear accident. In Japan, initially a three-kilometre evacuation zonewas put in place around the site, which was soon increased to a 20-kilometre evacuation

zone with a 30-kilometre sheltering zone. As the availability o environmental monitoring

data increased, other protective actions were implemented to reduce doses in the longer

term, including the relocation o people in some areas (designated by the Japanese au-

thorities as deliberate evacuation areas) (Figure 1). Stable iodine or thyroid blocking

was pre-distributed. Provisional regulatory limits or the radioactive content o ood were

established quickly ater the accident, and monitoring was conducted by local govern-

ments based on testing guidelines prepared by the Government o Japan. Foods were

to be tested beore going to the market in early harvest season and the oods ound to

contain higher concentration o radioactive nuclides than the provisional regulatory lim-

its were subject to appropriate measures. Furthermore, in the case that the contamina-

tion was spread over an area, distribution restrictions were implemented or the oods

in that area. Similarly, monitoring o tap water was conducted, both by central and local

government and by the water supply utilities, with especial emphasis in Fukushima and

neighbouring preectures.

Around the world, governments considered steps to protect their citizens. The primary

concern was or those residing in or visiting the most aected regions o Japan in the days

and weeks ater the earthquake, but there was also consideration o whether any steps

were needed within their own countries (such as restrictions on ood imports rom Japan).

By mid-2011 detailed inormation was provided in authoritative reports relating to the

nuclear accident issued by the Japanese government (3,4,5) and the IAEA (6).

1.2 Purpose and audience

The purpose o this study is to estimate radiation exposure or populations around the

world in the rst year ollowing the Fukushima Daiichi nuclear power plant accident. The

study ocuses on radiation exposure o members o the public.

This report is primarily intended or use by the WHO Health Risk Assessment Group to

inorm an initial assessment o health risks incurred as a consequence o the FukushimaDaiichi accident. It also provides inormation to Member States and the public on the

anticipated scale o radiation doses. Ultimately, the report is expected to serve as sup-

port or policy-makers and decision-makers.


16/124


Hirono TownHirono Town

Iwaki City

Kawbuchi Village

Ono Town

Koriyama City

20 km

30 km

Katsurao Village

Minami Soma City

Motomiya City

Nihonmatsu City

Fukushima City

Date City

Hobaramachi-Tomizawa

Tsukudatemachi-Tsukidate

Ryozenmachi-Shimooguni

Ryozenmachi-Kamioguni

Ryozenmachi-Ishida

Jisbara, Kashima Ward

Ohara, Haramachi Ward

Ogai, Haramachi Ward

Takanokura, Haramachi Ward

Oshigama, Haramachi Ward

Baba, Haramachi Ward

Katakura, Haramachi Ward

Itate Village

Soma City

KawamataTown

Miharu

Town

Hirata Village

Naraha Town

Tomioka Town

Okuma Town

Futaba Town

Fukushima

Dai-ichi NPS

Fukushima

Dai-ni NPS

Namie Town

Restricted area

Deliberate evacuation areaEvacuation-prepared area in case of emergency

Regions including specific spots recommended for evacuation

Restrictedarea

Deliberateevacuation

area

2010 Zenringo.,LTD.

Tamura City

Evacuation-prepared

areain case of

emergency

Shimokawauchi

Figure 1. Restricted area, deliberate evacuation area and regions including specic spots recommended

or evacuation (as o November 25, 2011)

Source: Adapted rom http://www.meti.go.jp/english/earthquake/nuclear/roadmap/pd/evacuation_map_111125.pd (reproduced with permission).


17/124


1. INTRODUCTION

1.3 Scope

This report provides a preliminary estimate o radiation doses to the public resulting romthe accident at the Fukushima Daiichi nuclear power plant. The doses are characteristic

o the average doses, and are assessed or dierent age groups in locations around the

world.

This report does not include:

doses within 20 km o the Fukushima site, since most people in the area were rapidly

evacuated. While some dose may have been received prior to evacuation, such assess-

ment would have required more precise data than were available to the panel.

doses to workers, because the evaluation o occupational radiation exposure requires

a dosimetric approach dierent rom the one used or members o the public. Theassessment conducted by the WHO Health Risk Assessment (HRA) Expert Working

Group will incorporate inormation on workers exposure provided by the Government

o Japan.

health risks and possible public health actions, since the doses calculated here will

serve as input to a subsequent analysis by the HRA Expert Working Group which will

evaluate the health risks due to the radiation exposure resulting rom the accident.

1.4 Overview o the methodology

An assessment o the doses received ollowing a release o radioactive material tothe environment requires data on a number o aspects, such as measured levels o

radionuclides in the environment, in tap water and in oodstus, estimated amounts

o radioactive material released, atmospheric dispersion and deposition patterns, the

nature o subsequent transer in the environment, and the location and habits o the

population or whom doses are being assessed.

Following the Fukushima accident, humans were exposed to radioactive material by sev-

eral pathways (Figure 2). The major exposure pathways were:

external exposure rom radionuclides deposited on the ground (groundshine);

external exposure rom radionuclides in the radioactive cloud (cloudshine); internal exposure rom inhalation o radionuclides in the radioactive cloud (inhala-

tion);

internal exposure rom ingestion o radionuclides in ood and water (ingestion).

All o these exposure pathways were considered in the assessment. The expert panel also

considered the relative importance o additional pathways, such as external radiation rom

material deposited on skin and clothing. The panel agreed that these additional pathways

would be o much lower importance and thereore not included in this preliminary study.

As ar as possible, the assessment described in this report has been based directly on mea-

surements o levels o radioactive material in the environment, such as levels o dierent

radionuclides deposited on the ground or in soil, or ound in oodstus. This has been the

approach to the estimates o dose in Japan, where ocial measurement data published


18/124


by the Government o Japan have been the primary source. However, such data were not

generally available or the rest o the world. Consequently, environmental modelling pre-

dictions based on an estimated source term in combination with atmospheric dispersion

modelling and environmental measurements were used to estimate doses outside Japan.

1.5 Endpoints and scenarios

The Panel took into account a number o actors, assumptions and scenarios to estimate

the radiation doses required. These are discussed below.

1.5.1 Dosimetric endpoints

The dosimetric endpoints o this study are eective doses and equivalent doses to the

thyroid, resulting rom exposure over the rst year. Box 1 denes the dosimetric terms

used.

The eective dose is calculated as the sum o the external dose received during the as-

sessed period, which in this assessment is the rst year ollowing the start o the release,

and the committed eective doses (to age 70 years1) rom intakes o radionuclides by

1. The integration period is 50 years or adults and up to age 70 years or children.

Figure 2. Exposure pathways to humans rom environmental releases o radioactive material

Source: IAEA report on Environmental consequences o the Chernobyl accident and their remediation: twenty years o experience (2006) p. 100

(reproduced with permission).


19/124


1. INTRODUCTION

ingestion and inhalation over the same period (Box 2). The eective dose in this report

includes the contribution rom dose to the thyroid.

In considering the radiological consequences o the Fukushima accident, the panel

agreed that the use o eective dose would be an appropriate quantity or this dose as-

sessment. The concept o eective dose enables external and internal exposures rom

dierent types o radiation to be combined (7). It is particularly appropriate to use e-

ective dose or external gamma radiation that irradiates the whole body more or less

uniormly. Radioactive isotopes o caesium are likely to be signicant in terms o health

consequences and environmental impact ater a major nuclear accident. For internal

exposures, an important contribution to the committed dose is likely to be due to the

ingestion and inhalation o isotopes o caesium (8). Since the bio-distribution o caesium

in the body is quite homogeneous, all organs are irradiated, and hence the eective dose

is a good indicator o the impact o such intakes.

In addition to eective dose, the Panel agreed to assess thyroid doses because the intake

o iodine-131 (131I) is also likely to be an important contributor to overall exposure. In

this case the distribution in the body is ar rom uniorm, with the thyroid being the most

exposed organ. Ater the Chernobyl accident in 1986, elevated incidence o thyroid can-

cer was ound in people who were children at the time o the accident (see, or instance,

WHOs 2006 report on health eects o the Chernobyl accident (9).

The thyroid doses were assessed in terms o equivalent dose, which is the dose delivered

to an organ allowing or the biological eectiveness o dierent types o radiation. The

Dosimetric quantities are needed to assess human

radiation exposures in a quantitative way. The

International Commission on Radiological Protection

(ICRP) provides a system o protection against the

risks rom exposure to ionizing radiation, includingrecommended dosimetric quantities.

The undamental measure o radiation dose to an

organ or tissue is the absorbed dose, which is the

amount o energy absorbed by that organ or tissue

divided by its weight. The international unit o

absorbed dose is the gray (Gy), which is equal to one

joule per kilogram.

The response o tissues and organs varies or

dierent types o radiation. Also, tissues and

organs have dierent radiosensitivity to radiation.

The equivalent dose in a tissue or organ is the

absorbed dose averaged over that tissue or organ,

urther applying a radiation weightingactor that

varies by radiation type and is related to the density

o ionization created. The international unit o

equivalent dose is the sievert (Sv).

An additional and requently used concept is the

eective dose, which is the sum o the products

o absorbed dose to each organ multiplied by the

radiation weighting actormentioned above and a

tissue weighting actorthat takes into account the

radiosensitivity o tissues and organs. The international

unit o eective dose is also the sievert (Sv).

The radioactivity o a substance (also called "activity")

is the rate at which the radioactive decay processes

take place. It is measured in becquerels (Bq),

dened as one disintegration per second. The ICRP

has developed a set o dose coecients or use in

assessing the exposures resulting rom inhalation oringestion o radionuclides. These dose coecients,

expressed as Sv/Bq, have been specied or a range o

body organs.

Source: Adapted rom Re. 10

Box 1. Dosimetric quantities


20/124


thyroid dose is the sum o external dose to the thyroid in the rst year and the committed

equivalent doses to the thyroid (to age 70 years2) rom intakes by ingestion and inhala-

tion over the rst year ollowing the start o the release.

It should be noted that, although the units are the same, thyroid doses and eective

doses are two dierent quantities that cannot be compared. Thyroid doses are organ-

specic equivalent doses, while the eective doses represent the sum o the products o

the absorbed doses to each organ multiplied by the respective tissue weighting actors

(see Box 1). Eective doses were estimated using ICRP dose coecients which incorpo-

rate tissue weighting actors as specied in ICRP publication 60 (7). Based on this, the

tissue weighting actor used or thyroid is 0.05.

1.5.2 Age groups considered

For the purposes o this assessment, three age groups were considered: adults, children

aged 10 years, and inants aged one year. These age groups are judged to be sucient

to ensure consideration o younger, more sensitive members o the population (11).

Doses to the etus and breasted inant were also considered (see section 3.2) but were

not evaluated separately. Doses to six-month-old inants have been considered or the

consumption o ormula milk made up with tap water.

2. The integration period is 50 years or adults and rom time o intake up to age 70 years or children.

The physical hal-lie is the period o time or one-

hal o the atoms o a radionuclide to disintegrate.

Physical hal-lives can range rom a ew microseconds

to billions o years. The biological hal-lie is theperiod o time required to eliminate one-hal o the

radioactivity rom the body. The actual rate o halving

the radioactivity in a living organism is determined by

a combination o both the physical and biological hal-

lives o the radionuclide, called the eective hal-lie.

While or certain radionuclides the biological processes

are dominant, or others physical decay is the

dominant infuence. For instance, the physical hal-lie

o 134Cs and 137Cs is 2 years and 30 years respectively,

but their biological hal-lie is much shorter (several

months). In adults, 10% is excreted in the rst ew

days ater the intake and the rest leaves the body with

a biological hal-lie o about a hundred days. The

biological hal-lie o cesium increases as a unction

o body mass and age, which means that it leaves the

body quicker in children and adolescents compared to

adults (e.g. data rom urinary assays and whole-body

counting suggested that the biological hal-lie o 137Cs

in children is around 50 days).

In assessing radiological exposures arising rom

inhalation and ingestion, there is a distinction between

the time period over which the intake occurs and the

time over which the exposure (the radiation dose) to

the body ensues. For example, intake rom inhalation

on a single day may give rise to the body being

internally exposed to radiation over a period o days

and months, and possibly over a much longer period,

depending on the eective hal-lie.

The committed dose (eective or equivalent) is thedose that an individual will receive once a radionuclide

intake has taken place. When it is not specied, the

integration period considered or the assessment is 50

years or adults and the period o time needed to reach

the age o 70 years or children.

Box 2. Temporal distribution o the exposure ater intakeo radionuclides


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1. INTRODUCTION

1.5.3 Geographical coverage

Estimates have been made o doses in dierent regions o the world, with greater spatial

detail in the estimated doses presented or Japan, and in particular or the Fukushima

preecture.

Doses in the ollowing ve areas have been considered:

the Fukushima preecture, where doses are likely to be among the highest o those

received by members o the public (see Figure 3);

the preectures in Japan nearest to the Fukushima region (see Figure 4);

all other preectures in Japan (see Figure 4);

countries neighbouring Japan; other areas o the world.

!

1 Date

2 Fukushima City3 Soma City4 Iitate5Minami Soma6 Kawamata

7 Nihonmatsu City

8 Namie9 Katsuraobl Tamura Citybm Koriyama Citybn Kawauchibo Narahabp Hironobq Iwaki City@

#

$%

^

& *

(

BLBM

BN

BOBP

BQ

Fukushima prefecture zone 1(western least contamined)

Fukushima prefecture zone 2(eastern least contamined)

a c-137 (B/2)

(cv v ag 28)

Figure 3. Locations in Fukushima preecture considered in the assessment

Source: http://radioactivity.mext.go.jp/en/contents/4000/3168/24/1270_0912_2.pd (reproduced with permission).

Readngs o the Airborne monitoring survey by MEXT in the Western part o Fukushima preecture.


22/124


1.5.4 Time rame

The estimated doses rely on measurements available until mid-September 2011. The

doses estimated are those resulting rom intakes and external exposures during the rst

year ater the accident. Extrapolation beyond this time rame on the basis o the input

data used or this preliminary assessment would be uncertain and thereore was not per-

ormed. While intakes are considered over the rst year, some o the exposures resulting

rom the intake will continue beyond that period (see Box 2).

For the radionuclides released in the Fukushima accident, the great majority o the

committed doses rom inhalation and ingestion are expected in the rst year. This is

particularly the case or the isotopes o iodine due to their short physical hal-lie. For

caesium isotopes, although the physical hal-lie is longer, the biological hal-lie is not

long, particularly in children (see Box 2) (8).

1.5.5 Protective actions

During the Fukushima Daiichi nuclear power plant emergency, public health protective

actions were implemented at dierent times. In the early phase, urgent protective ac-

tions aimed at preventing the short-term radiation exposure included evacuation, shelter-

ing, pre-distribution o stable iodine, and ood and water restrictions. As the availability

o environmental monitoring data increased, other protective actions were implemented,

Hokkaido

Aomori

Akira

Yamagata

Niigata

Nagano

Toyama

Gifu

Aichi

MieNara

ShigaKyoto

OitaSaga

Hyogo

Totori

OkayamaShimane

Hiroshima

Yamaguchi

Fukuoka

NaoasakiKumamoto

MiyazakiKagoshima

Kagawa

Ehime Kochi WakayamaTokushima

Shizuka

Ishikawa

Fukui

Fukushima

Ibaraki

Tokyo Chiba

TochigiGunma

Saitama

YamanashiKanagawa

Miyagi

Iwate

Figure 4. Neighbouring preectures considered in the assessment

2

1 Yamagata

2 Miyagi 1 northern

3 Miyagi 2 southern

4 Fukushima 1 western

5 Fukushima 3

6 Fukushima 2 southern

7 Tochigi 1 northern

8 Tochigi 2 southern

9 Gunma 1 northern

bl Gunma 2 southern

bm Ibaraki 1 northern

bn Ibaraki 2 central

bo Ibaraki 3 southern

bp Saitamabq Tokyo

br Chiba 1 western

bs Chiba 2 central

1

3

45

6

7

89

bl

bm

bn

bobp

bqbr

bs


23/124


1. INTRODUCTION

including relocation o people to reduce doses in the long term. Protective actions are

discussed below together with the modelling approach adopted to account or each.

Movement o people

Evacuation Most people within 20 kilometres o the nuclear power plant were rapidly

evacuated. Thereore, the panel chose not to estimate doses in this area. Some dose may

have been received prior to evacuation but the assessment o this required more precise

data than were available to the panel at the time o the assessment, including detailed

inormation about the implementation o protective actions (see Box 3).

Sheltering Sheltering was implemented in the short term or residents within a zone be-

tween 20 and 30 kilometres radius rom the plant (see Box 3). It is possible that in some

locations sheltering was prolonged (i.e. beyond the rst ew days) and in such cases it

could not be observed as stringently as a very short-term measure. People would, or

example, have to leave the house or at least short periods to obtain ood supplies i the

measure was in place or periods in excess o a ew days. The panel had no access to de-

tailed inormation on the stringency with which this countermeasure was implemented,

nor the timing o the introduction o the countermeasure and its duration. Thereore, the

eect o sheltering in reducing dose during the early phase o the emergency has not

been considered or the present dose assessment.

However, the rst year doses account or the shielding provided by buildings, resulting

in reduced external radiation dose during the period o time people are assumed to be

Movement o people in the early phase o the response

In the early phase o a nuclear emergency (within

the rst ew hours/days), urgent protective actions

regarding movement o people may be implemented

to prevent radiation exposure, taking into account

projected doses that people may received in the short-

term (e.g. eective dose within 2-7 days, thyroid dosewithin one week). Decisions are based on nuclear

power plant conditions, amount o radioactivity

actually or potentially released into the atmosphere,

prevailing meteorological conditions (e.g. wind speed

and direction, precipitation), and other actors.

Evacuation is the urgent removal o populations

within a radius around the event site, which is most

eective when used as a precautionary action beore

an airborne release takes place. Sheltering is an urgent

protective action implemented primarily to provide

shielding against external exposure and by using a

structure or protection rom an airborne plume and/

or deposited radionuclides (e.g. people being advised

to remain permanently indoors with the doors and

windows sealed). In contrast to sheltering, which is

an urgent action in the early phase o the emergency,

people spend a proportion o time indoors as part

o their normal liestyle. The shielding provided by

the building while people are indoors would reduce

external exposure compared to outdoor doses, but

the protection against inhalation exposure would be

much less due to air exchange between the indoor and

outdoor environments.

Movement o people in a later phase o the response

As environmental and human monitoring data

increases, other protective actions may be

implemented, taking into account the doses

that a population may receive over the long-term

(e.g. eective dose during one year). Temporary

relocation is a non-urgent movement o people rom

a contaminated area to a temporary housing to avoid

chronic radiation exposure. It may be a continuationo the urgent protective action o evacuation (as a

longer-term action). I return ater relocation is not

oreseeable within one or two years, relocation is

considered as permanent and is oten called

re-settlement.

Box 3. Movement o people


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indoors as part o a normal liestyle. No protection rom inhalation doses or such normal

indoor residency has been assumed since, in the longer term, radioactivity concentra-

tions in indoor air are expected to become similar to those outdoors and the protectionprovided against inhalation doses would be small.

Relocation Outside the 20 kilometre radius, inhabitants o the most aected area,

coined the deliberate evacuation area (Figure 1), were subject to relocation at dierent

times ater the accident. For the assessment o doses in this area, only doses in the rst

our months o the rst year have been estimated, with the assumption that relocation

took place at our months, and thereore that no doses were received beyond the rst our

months. Inormation provided by the Government o Japan indicates that in parts o this

zone the relocation occurred beore our months.

Stable iodine uptake

Stable iodine was pre-distributed but it is thought that only a small number o persons

in specic locations in Japan actually consumed stable iodine as actual consumption (as

opposed to distribution) o stable iodine was not ocially recommended in most places.

Thereore, the Panel assumed that stable iodine tablets were not taken by members o

the public, either in Japan or elsewhere.

Food and water restrictions

The assessment o ingestion doses was based on the results o all monitoring tests, in-

cluding ood on the market, ood beore shipment and ood produced in the distribution-

restricted areas. The assessment does not explicitly model the eect o the imposition

o ood restrictions.

It is known that restrictions on tap water were applied in several villages. The assessment

o doses rom ingestion o water in this study is cautious and is based on ocial data on

levels o radioactivity measured in tap water not assuming any water restrictions.

1.6 Procedures

An International Expert Panel was established to make an initial assessment o the pos-

sible range o radiation doses produced as a consequence o the accident in populationsinside and outside Japan. The panel consisted o independent experts, selected on the

basis o their scientic competence and experience, and representatives rom WHO, the

International Atomic Energy Agency (IAEA) and the Food and Agriculture Organization

o the United Nations (FAO). The participation o technical sta rom these three United

Nations agencies was essential, given the relevance o the assessment to the agencies

respective roles, mandates and expertise.

The experts were selected on the basis o their scientic competence and experience in

the assessment o human exposures arising rom radioactive material in the environment.

The panel included experts on internal and external dosimetry, ood and water saety,

public health, and radioecological modelling. The experts were required to disclose anyinterests. No conficts o interest were identied or any o the participants.


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1. INTRODUCTION

UNSCEAR has initiated a two-year assessment o the exposure levels and eects o the

Fukushima accident, and its main scientic report will be submitted to the United Nations

General Assembly in 2013. UNSCEAR participated in the panel as observer to ensure thatapproaches and data sources or the two United Nations assessments were compatible.

Close cooperation was maintained while the two assessments were in progress.

Collaboration with the Government o Japan and relevant Japanese institutions was

deemed to be crucial or the successul completion o the work as they provided much

o the ocial data or the dose assessment.

The panel met on three occasions during 2011 (on 30 June in Vienna, 56 September in

Geneva, and 1314 October in Geneva) and chiefy worked electronically. The detailed

dose calculations, not included in this report, have been shared with the participating

organizations in order to inorm their respective activities.

The technical work was distributed between the experts. There were three components

to the dose assessment, namely:

Doses in Japan rom external irradiation and rom inhalation were assessed on the

basis o measurements by both the Institute o Radiation Hygiene in Russia and the

Federal Oce o Radiation Protection in Germany. The two institutes used similar but

not identical assumptions. These are presented in chapter 2, sections 2.3.1, 2.4.1

and 2.5.1, and are urther explained in Annex 6.

On the basis on ood monitoring data, WHO assessed estimates o dose to the Japa-

nese people rom ingestion o ood produced in certain regions o Japan. This as-sessment also included consideration o the doses outside Japan rom consumption

o ood produced in Japan and exported. This assessment is presented in chapter 2,

section 2.6, and is urther explained in Annex 8.

Doses in the rest o the world were assessed by the United Kingdoms Health Protec-

tion Agency on the basis o assumed source terms combined with dispersion model-

ling and environmental measurement data rom around the world.3 Where appropriate,

this assessment assumed a methodology and input data consistent with those used

in the measurement-based assessments. This assessment is presented in chapter 2,

sections 2.3.2, 2.4.2 and 2.5.2, and is urther explained in Annex 7 and Annex 9.

3. For the ingestion pathway outside Japan, consumption o locally-produced ood was considered.


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This chapter summarizes the approaches and input data used in the estimation o doses

to population groups living in particular locations. The dierent exposure pathway mod-

els and related assumptions are presented (see Figure 5).

2.1 Approaches

As described in section 1.4. the dose contribution rom the ollowing our pathways was

taken into account in dierent geographical locations within and outside Japan:

external exposure rom radionuclides deposited on the ground (groundshine);

external exposure rom radionuclides in the radioactive cloud (cloudshine);

internal exposure rom inhalation o radionuclides in the radioactive cloud (inhala-

tion);

internal exposure rom ingestion o radionuclides in ood and tap water (ingestion).

Several approaches were used to calculate the doses to corroborate the results. For the

external radiation and inhalation pathways inside Japan, two approaches were developed

using dierent assumptions (Approach A and Approach B), providing a range o results

and a validation mechanism or the chosen methods. Outside Japan, an approach based

on an atmospheric dispersion model was used (Approach C). For the ingestion pathway

within Japan, a model (Approach D) based on ood measurements (mainly around the

Fukushima preecture) was developed, while outside Japan an environmental model es-

timating radionuclide concentrations in locally-produced ood rom an assumed source

term (Approach E) provided the relevant data

2.2 Input dataAll the available radiological measurement data used in this assessment are publicly

available on the web sites o Japans Ministry o Education, Culture, Sports, Science and

Technology (12) and Ministry o Health, Labour and Welare (13). The Government o

Japan has provided this inormation to the Incident and Emergency Centre o the IAEA

in Vienna on a regular and requent basis since the Fukushima accident. The inorma-

tion has been collated by IAEA into a database. Relevant inormation available within the

timescale o the assessment has been shared with the panel or the purpose o this study.

2.2.1 Radionuclide composition and deposition

Assessment o the impact o the accident requires consideration o the spectrum o all

signicant radionuclides released. In this assessment, this has been done through as-

sumed radionuclide compositions and assumed source terms.

2. Methodology


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2. METHODOLOGY

External and

inhalation

inside Japan

(Approach A, B)

External and

inhalation

outside Japan

(Approach C)

Ingestion

inside Japan

(Approach D)

Ingestion

outside Japan

(Approach E)

Dose model

(Annex 9)

Dose (Sv)

Effective and thyroid

(all ages together)

Measured food

radionuclide

concentration

(Bq/kg)

Dose model

(Annex 8)

Dose (Sv)


Source

term

Atmospheric

dispersion

model

Calculated surface

activity density (Bq/m2)

and air activity density

(Bq/m3)

Dose model

(Annex 7)

Dose (Sv)


Measured surface

activity density

(Bq/m

2

)

Dose model

(Annex 6)

Dose (Sv)


Calculated food

radionuclide

concentration

(Bq/kg)

Calculated surface

activity density

(Bq/m2)

Atmospheric

dispersion

model

Source

term

Figure 5. Approaches used in the assessment

Environmental

model


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Measurements o radionuclides in the environment, which orm the basis o the dose as-

sessment or Japan, are available or only a subset o radionuclides released in the acci-

dent. Fortunately, the radionuclides that contribute most signicantly to dose are repre-

sented in those measurements. In this study, dierent radionuclides were accounted or

in the various exposure pathways. The assessment o doses rom inhalation and external

radiation in Japan assumed a radionuclide composition or the releases which covered

nine key radionuclides (see Annex 6). For the rest o the world, up to 16 radionuclides

were specied in the estimated released source terms used in the study (see table A4.1

and more detailed inormation in Annex 4). The assessment o doses rom ingestion

o ood in Japan was based on the measured levels o iodine-131 ( 131I), caesium-134

(134Cs) and caesium-137 (137Cs) in ood samples reported by the Government o Japan.

At present, source term estimation or the Fukushima accident is associated with con-

siderable uncertainty. The source terms used in this assessment are applied only to esti-

mation o doses outside Japan. Two source terms were used as input to an atmospheric

dispersion model, which are similar in terms o the overall magnitude o the main radio-

nuclides released but dier in the time dependence o the releases (see Annex 4).

2.2.2 Environmental monitoring data

Environmental monitoring data or Japan include measurements o radionuclides in air,

soil, oodstus, drinking-water and resh water. More data are available or the areas with

higher levels o radioactive material than or the less aected areas.

The environmental measurement data used as primary input to the assessment are sur-

ace activity densities. Measured levels o deposited radionuclides are available or all 47

Japanese preectures, and levels in Fukushima preecture show signicant variation with

location. These measurements include a very small component rom the global allout

rom nuclear weapons-testing.

Gamma dose rates are available rom a wide range o monitoring locations in Fukushima

preecture and show considerable variation with location. Gamma dose rates are also

available or the other 46 Japanese preectures and, by September 2011, they indicated

levels which were within the background range or Japan (the natural background rangereported to the panel was 30100 nSv/h, which is consistent with the data reported by

the Fukushima preecture authorities) (14).

The data on radioactivity concentrations in air are very limited. This is partly due to the

ailure o equipment in many locations close to the nuclear power plant as a result o the

earthquake and tsunami. Where data do exist there is insucient coverage or the early

days o the release to enable the data to be used in this assessment. For this reason, ra-

dioactivity concentrations in air in Japan have been derived rom modelling on the basis

o the measured levels o radioactivity deposition on the ground.

2.2.3 Food monitoring and consumption data

To assess exposure rom radionuclides in ood the International Expert Panel decided

to use measurements rather than modelling wherever possible. The monitoring o ood


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2. METHODOLOGY

produced in Japan was published on the Japan's Ministry o Health Labour and Welare

web site (13). The monitoring data included the results o oods that were not distributed

on the market such as marine products rom Fukushima preecture and other oods romdistribution-restricted areas.

The results o ood radionuclide concentration monitoring around the world have been

received by the International Food Saety Authorities Network (INFOSAN)1 and compiled

in a comprehensive database. Data rom monitoring o ood exported rom Japan is gen-

erally available on the web sites o the corresponding authorities.

Regarding ood consumption in Japan, the Japanese National Institute or Health and

Nutrition (NIHN) provided data based on the 2009 National Health and Nutrition Survey

Outside Japan, ood consumption data were taken rom the WHO GEMS/Food consump-

tion cluster diet G (15).

2.3 External radiation doses rom radionuclides deposited

on the ground (groundshine)

External radiation doses rom radionuclides deposited on the ground (groundshine) rep-

resent a signicant long-term exposure pathway. For the purposes o this assessment, the

external gamma dose integrated over the rst year ollowing the accident was calculated

or locations both in Japan and in the rest o the world.

2.3.1 Inside Japan

In the study, two slightly dierent approaches (A and B) were applied to estimate the

external eective and thyroid doses rom radionuclides on the ground. The ull details o

the model are given in Annex 6 and the input parameters are provided in Annex 3.

The doses in Japan have been estimated on the basis o the measured ground deposition

levels (surace activity densities). In Approach A the dose calculations were perormed

using dose rate coecients, representing the values o gamma dose rate in the air (at

one metre above the ground) normalized to a unit deposit o each radionuclide in com-

bination with dose conversion actors to convert these to eective and thyroid doses.

Approach B directly used both eective and thyroid dose coecients per unit deposito each radionuclide. Unlike Approach B, Approach A accounted or the shielding eect

rom radionuclide penetration in soil, leading to a small (approximately 5%) reduction

in the estimated external doses in the rst year. Finally, small dierences were assumed

in the composition o the deposited radionuclides, based on alternative sources or the

soil contamination measurements used (see Annex 6 or reerences on this issue). Both

approaches took into account the radioactive decay over the period or which the dose

was calculated.

External doses can be signicantly lower indoors than outdoors due to the shielding e-

ects o the building. This was taken into account by using a location actor o 0.4 or

building type and an assumed occupancy actor o 66% (i.e. two thirds o the time perday spent indoors). Details o the method are presented in Annex 3 (Table A3.9).

1. The International Food Saety Authorities Network (INFOSAN) is a joint initiative o FAO and WHO.


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2.3.2 Outside Japan

For the rest o the world, very ew data were available on the levels o ground deposition

as a result o the accident. Thereore, instead o a measurement-based approach, a mod-

elling approach (Approach C) was adopted to estimate the global ground depositions re-

quired to assess external doses. The calculations were undertaken with estimated source

terms (Annex 4) and using atmospheric dispersion modelling to predict depositions and

hence external doses using the dose coecients (see Tables A3.6 and A3.7 in Annex 3)

as in the measurement-based approach.

The doses outside Japan were based on an atmospheric dispersion model utilizing global

weather data or the period o dispersion and recirculation. The United Kingdom Met O-

ces NAME III (Numerical Atmospheric dispersion Modelling Environment, version 5.2)

dispersion model (16) was used. NAME III is a complex model used to estimate disper-sion and deposition o gases and particulates. It incorporates both radioactive decay pro-

cesses and estimates o the external dose rom the radioactive cloud. Input data or this

model include time-varying three-dimensional meteorological data and estimations rom

radar-measured rainall data and the Met Oces numerical weather prediction unied

model (17). The output represents time-averaged and time-integrated activity concentra-

tions in air, and in wet, dry and total ground depositions o radionuclides.

The panel was aware that international experience using complex dispersion models such

as NAME III to predict the global dispersion arising rom Fukushima indicates that, at ar

distances, model predictions are in general substantially lower than measurements. To

ensure that doses in the rest o the world are not consistently underestimated, the pre-

dictions o the NAME III model or two dierent source terms (see Annex 4) were used

in conjunction with measured concentrations o radionuclides rom around the world,2

to obtain global distributions o activity concentrations in air and ground depositions or

input into the dose calculations. As a result o this combined approach, the estimations

o the NAME III model showed good agreement with the radiological measurements and

were considered to orm a sound basis or the subsequent dose estimation.

2.4 External radiation doses rom the radioactive cloud

(cloudshine)2.4.1 Inside Japan

In the context o this accident, external exposure rom cloudshine is o secondary impor-

tance to external exposures arising rom groundshine. However, it is the only pathway o

relevance or noble gases, which do not deposit on the ground and or which any inhala-

tion doses are negligible. Most releases o noble gases rom the Fukushima site would

have occurred early in the release and are not expected to provide a signicant contribu-

2. These data include locations in Austria, Denmark, France, Germany, Sweden, Philippines, North America,

and Alaska, but at November 2011 they were still largely unpublished. Published examples are in: (Prepara-

tory Commission or the Comprehensive Nuclear-Test-Ban Organization, or CTBTO) air monitoring station data

published on the web site o the Philippines Nuclear Research Institute. The United States Environmental

Protection Agencys RadNet data can be seen at: http://www.epa.gov/japan2011/.


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2. METHODOLOGY

tion to radiation exposure inside Japan and thus, this exposure to noble ga

who preliminary dose estimation from the nuclear accident after the 2011 great east japan earthquake...

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