UNSCEAR

United Nations Scientific Committee
on the Effects of Atomic Radiation

DEVELOPMENTS SINCE THE 2013 UNSCEARREPORT ON THE LEVELS AND EFFECTS OF
RADIATION EXPOSURE DUE TO THE NUCLEAR
ACCIDENT FOLLOWING THE GREAT EAST-JAPAN
EARTHQUAKE AND TSUNAMI
A 2015 white paper to guide the Scientific Committee’s
future programme of work

EVALUATING RADIATION SCIENCE FOR INFORMED DECISION-MAKING

DEVELOPMENTS SINCE THE
2013 UNSCEAR REPORT ON THE LEVELSAND EFFECTS OF RADIATION EXPOSURE
DUE TO THE NUCLEAR ACCIDENTFOLLOWING THE GREAT EAST-JAPAN
EARTHQUAKE AND TSUNAMI

A 2015 white paper
to guide the Scientific Committee’s
future programme of work

UNITED NATIONSNew York, 2015

This document is available on the UNSCEAR website at www.unscear.org.
Any inquiries regarding this document should be sent to the UNSCEAR secretariat(unscear@unscear.org).
The views expressed herein are those of the authors and editors and do not necessarily reflect
the views of the United Nations.
© 2015. United Nations for the English edition.
© 2015. United Nations for the Japanese edition prepared by BLC Corporation, Osaka, Japan.
All worldwide rights reserved.
This publication has not been formally edited.

CONTENTS
EXECUTIVE SUMMARY .......................................................................................................... v
I.

INTRODUCTION ....................................................................................................... 1

II.

EVALUATION OF NEW INFORMATION .............................................................. 2III.

UPDATES ON RADIONUCLIDE RELEASES TO ATMOSPHERE,DISPERSION AND DEPOSITION ............................................................................ 4IV.

UPDATES ON RADIONUCLIDE RELEASES TO WATER,DISPERSION AND DEPOSITION ............................................................................ 6V.

UPDATES ON EVALUATION OF DOSES FOR THE PUBLIC ............................. 8VI.

UPDATES ON EVALUATION OF DOSES FOR WORKERS .............................. 15VII.

UPDATES ON HEALTH IMPLICATIONS FOR WORKERS AND
PUBLIC ...........................................................................................................................17VIII.

UPDATES ON EVALUATION OF DOSES AND EFFECTS FOR
NON-HUMAN BIOTA ............................................................................................. 20

IX.

CONCLUSIONS ....................................................................................................... 22

ACKNOWLEDGEMENTS ....................................................................................................... 26
APPENDIX A. COMMENTARY ON COMMON THEMES IN CRITIQUES OF
THE 2013 FUKUSHIMA REPORT .......................................................................... 27
REFERENCES ........................................................................................................................... 37

The attachments cited in this white paper are electronically available for download fromhttp://www.unscear.org/unscear/en/publications/Fukushima_WP2015.html

iii

EXECUTIVE SUMMARY
This summary is extracted from the report of the United Nations Scientific Committee on the
Effects of Atomic Radiation to the seventieth session of the United Nations General Assembly. 1[…]
5.
Following its assessment of the levels and effects of radiation
exposure due to the nuclear accident after the 2011 great east-Japan
earthquake and tsunami, as presented in its 2013 report to the General
Assembly (A/68/46) and the supporting detailed scientific annex, 2 theCommittee had put in place arrangements for follow-up activities to enable
it to remain abreast of additional information as it was published in thescientific literature. A considerable amount of additional relevant
information had already been published or become available before thepublication of the scientific annex. New material is still being publishedand will continue to be in the foreseeable future, including underinternational and national initiatives. 3
6.
The Committee identified a large number of new publications that had
become available between the time it conducted its assessment and the endof 2014, and systematically appraised about 80 of those in the lead-up to its
sixty-second session. More than half of those 80 publications corroborated
one or another of the major assumptions made by the Committee in its
2013 report. None of them challenged the report’s major assumptions oraffected its main findings, while some needed further analysis or more
conclusive evidence from additional research. The Committee, as part of its
continued efforts to identify and systematically evaluate new information
as it came to light, would appraise other publications already identified andevaluate and periodically report how those publications affected theconclusions reached in its 2013 report. Depending on the outcome, theCommittee expected to consider, at an appropriate time, the need to updatethat report.
7.
The Committee expressed its gratitude to organizations andindividuals that had engaged in the debate on the Committee’s findings,
and in some cases had publicized critiques of the 2013 report. It discussed
and endorsed a commentary on the main themes appearing in thosecritiques to provide greater clarity where its judgement and/or impartiality
had been questioned. The Committee considered the debate on its findings
an important element of transparency and had therefore engaged inscientific forums, public dialogues and other outreach activities (see also
section 6, entitled “Outreach activities”).
8.
The Committee requested the secretariat to make the findings of its
review of new scientific literature and its commentary on the critiques
available as a non-sales publication in both English and Japanese.

1

Official Records of the General Assembly, Seventieth session, Supplement No. 46 (A/70/46).
United Nations publication, Sales No. E.14.IX.1.
3
At the time of the sixty-second session, the International Atomic Energy Agency report on the accident,
entitled “The Fukushima Daiichi accident: report by the Director General”, had not been made public,
and had thus not been evaluated by the Committee for the purposes of the present report.
2

v

I.

INTRODUCTION

1.
The Committee had assessed radiation exposures of the public, workers and nonhuman biota that resulted from the 11 March 2011 accident at the Fukushima Daiichi
nuclear power station (FDNPS), discussed the health implications, and presented its findings
in its annual report to the United Nations General Assembly in August 2013. 4 The United
Nations subsequently published the Committee’s findings and the detailed scientificannexes underpinning them on 2 April 2014 [U6]. The publication (referred to hereafter as
the “2013 Fukushima report”) was well received by the General Assembly, governments,
the scientific community and the media/public in Japan.
2.
The Committee’s assessment had, in general, been based on information disclosed or
published before the end of October 2012. Subsequently, much additional relevant
information has been published or become available and this activity is likely to continue
for the foreseeable future. The Committee intends to remain abreast of such developments
because they may have implications for the results of its assessment (for example incorroborating, challenging or refining its findings and/or contributing to addressing
identified research needs); doing so will enable the Committee to take informed and timely
decisions on the need to refine or update its findings. The Committee expects that providing
sound scientific appraisal of new material will also help (a) those affected by the accident tobetter understand the situation and (b) inform decision-making.
3.
Accordingly, at its sixty-first session (21–25 July 2014), the Committee hadrequested the secretariat to “submit for consideration at its sixty-second session(1-5 June 2015) preliminary plans […] for follow-up activities to update and consolidate
some of the findings and conclusions of the Committee’s assessment of the radiologicalconsequences of the Fukushima Daiichi nuclear accident”. It also asked the secretariat to“promptly develop a standing mechanism to stay aware of new scientific developments inthe follow-up to the accident. That mechanism should be based on the special arrangementsthat had been developed for conducting its recent assessment of the accident. The
Committee also asked the secretariat to report annually on the implications for theCommittee’s programme of work”.
4.
In response, the secretariat developed a project plan of follow-up activities, which
has since been endorsed by the Committee and is being implemented. The project comprises
two phases: Phase I, a systematic and ongoing review of new information; and Phase II, an
update of the 2013 Fukushima report at an appropriate time. The overall aim of Phase I (upto at least 2016 and beyond) is to “keep the Committee regularly apprised of theimplications of new publications and research activities related to the accident with a view
to initiating a formal update of the 2013 Fukushima report (i.e. Phase II) at an appropriatetime”. The more specific objectives of Phase I include:(a) To systematically keep the overall radiological situation on the FDNPS accident
under review by collecting and appraising published information;(b) To collect and evaluate progress made in, and plans for, major research projects andprogrammes related to pending questions;4

Official Records of the General Assembly, Sixty-eighth Session, Supplement No. 46 and corrigendum(A/68/46 and Corr.1).

1

2

2015 WHITE PAPER(c) To promptly identify inconsistencies between information issued after October 2012
and the 2013 Fukushima report;(d) To conduct ad hoc analyses to help clarify the situation and which could be usedsubsequently in any update of the 2013 Fukushima report;(e) To respond to questions and critiques of the 2013 Fukushima report;(f) To report annually to the Committee at its regular sessions on the outcomes of the above.
5.
This white paper describes progress with the initial implementation of the projectplan and presents a summary of the main outcomes of the initial follow-up activities that
underpins the findings reported by the Committee to the General Assembly. The initialfollow-up activities were largely confined to addressing objectives (a) and (e) above, that is
the systematic collection and appraisal of new information, and responding to questions andcritiques on the 2013 Fukushima report. The new information screened and appraised in thisinitial stage has, with a few exceptions, been limited to peer-reviewed publications inEnglish-language journals; the scope will be extended in future years to other sources of
new information relevant to the FDNPS accident and, in particular, those that could have
implications for the findings of the 2013 Fukushima report. These will include datacompilations, evaluations and reports prepared or carried out by national and intergovernmental bodies, including organizations in the United Nations system. 5
6.
The white paper comprises a digest of new information and its implications for the2013 Fukushima report, set out in chapters II to VIII, together with an appendix that
contains a commentary on broad themes included in the few critiques that had been made of
the 2013 Fukushima report. In addition, two electronic attachments have been developed toprovide technical information that supplement the 2013 Fukushima report and address key
technical issues for which there had been requests: the first provides information on power
calculations for epidemiological studies that underpin the analyses carried out and reported
in appendix E (Health implications) of [U6]; and the second summarizes the underlying
methodology and data used in developing isodose maps of annual external exposure in
Japan and their variation with time.

II.

EVALUATION OF NEW INFORMATION

7.
The scope of new information analysed by the Committee in this first digest wasnecessarily more restricted than expected for future years. This was, firstly, because theinitial period to be covered (27 months, from October 2012 to December 2014) significantly
exceeded that foreseen for subsequent annual digests (i.e. 12 months); secondly, theappraisals covered by this report had to be completed within a relatively short time period(3 months compared with about 9 months expected for subsequent years). In this first digest,
the Committee has, with three exceptions, limited its analysis to publications in English inpeer-reviewed journals. One exception was an article on the distributions of bird species,
which was published in a book; this was included because of its relevance to an issue ofsome scientific debate. The other two exceptions comprised a report by the Japanese
5Inter alia, data and reports issued by the Fukushima Medical University (e.g. the Fukushima HealthManagement Survey), and the International Atomic Energy Agency’s report on the accident (“The Fukushima
Daiichi Accident: Report by the Director General”), which had not yet been published at the time of theCommittee’s sixty-second session.

DEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 3

Ministry of Health, Labour and Welfare (MHLW) on re-assessment of doses to workers,
and a peer-reviewed publication in a Japanese-language journal on dietary intakes following
the accident. These two publications were identified, from systematic searches of peerreviewed publications in Japanese-language journals and of reports issued by Japanese
Ministries or governmental organizations, as new information that might have a significant
impact on the assumptions and/or findings of the 2013 Fukushima report.
8.
The Committee developed and implemented a systematic approach to identify,
screen and appraise new information for the purposes of this white paper. The Committee
identified several hundred new publications. In selecting publications for screening review
and for more detailed appraisal, particular consideration was given to whether:− The publication significantly challenged the assumptions in the 2013 Fukushimareport;− It materially affected the conclusions of the 2013 Fukushima report;− It had the potential to address research needs identified in the 2013 Fukushimareport.
As a result, this digest focuses almost exclusively on new information that has significant
implications for the 2013 Fukushima report; it is not intended, and should not be interpreted,as providing a new overview of all relevant information relating to the FDNPS accident.
The lack of reference to any particular publication in this digest is not a reflection on its
worth or quality; it merely indicates that it was not considered to have significant
implications for the 2013 Fukushima report.
9.
The numbers of publications in each topical area that were selected for screening
and/or more detailed appraisal are indicated in table 1. For some topical areas (particularly,
releases to atmosphere, dispersion and deposition, and doses and effects for non-humanbiota), the Committee was unable to screen and/or appraise all potentially relevantpublications because of time and resource constraints; those not included in this digest areplanned to be included in the next review.
10.
The following chapters describe the main outcomes of the screening and appraisal of
new sources of information for each topical area in turn. In each case, a brief recapitulation
is provided of some of the main assumptions, findings and research needs set out in the2013 Fukushima report to highlight those of particular relevance to the sources of new
information reviewed. This is followed by a summary of the outcomes of the appraisals, andconclusions about the implications both for the 2013 Fukushima report and any follow-up
activities. Finally, chapter IX sets out overall conclusions from this first digest and includes
some tabular summaries which focus on those sources of new information which challenge(or could potentially challenge, subject to further analysis) the assumptions/findings of the2013 Fukushima report, or where the contribution to addressing identified research needs
has been judged to be significant.

42015 WHITE PAPER

Table 1. Numbers of new sources of information screened and appraised by topical area
Topical area
Releases to atmosphere, dispersion and depositionc

Screened
126aAppraised
12b

Releases to water, dispersion and deposition

43

18

Doses to members of the public

17

12

Doses to workers

26

7

Health effects for workers and the public

24

10

d

20e

Doses and effects for non-human biota

61aThe outcomes of screening of a further 16 sources of information are planned to be reported in the second digest.
These new sources of information were selected for appraisal based on their potential impact on the assumptions and findings of the2013 Fukushima report; the outcome of appraising the remainder screened for appraisal is planned to be reported in the second digest.
cConsideration was limited to information on releases to and subsequent dispersion in the marine environment. The transfer of radionuclides
to, and their dispersion in, freshwater systems (e.g. from run off from catchments) was excluded from consideration in this review, otherthan the contribution such sources or pathways make to the continuing release of radionuclides to the marine environment.
d
The outcomes of screening of a further 29 sources of information are planned to be reported in the second digest.
e
These new sources of information were selected for appraisal based on their potential impact on the assumptions and findings of the2013 Fukushima report; the outcome of appraising the remainder screened for appraisal is planned to be reported in the second digest.
bIII. UPDATES ON RADIONUCLIDE RELEASES TO ATMOSPHERE,DISPERSION AND DEPOSITIONA.

Recapitulation of 2013 Fukushima report

11.
The Committee had reviewed estimates of total releases to the atmosphere of 131I andCs (the two most significant radionuclides from the perspective of exposures of people
and the environment); these estimates ranged generally from 100 to 500 petabecquerels(PBq) for 131I and from 6 to 20 PBq for 137Cs. The averages of the published estimates wereabout 10% and 20%, respectively, of the corresponding releases to the atmosphere estimatedfor the Chernobyl accident. On a number of occasions, the meteorological conditions weresuch that radionuclides released to the atmosphere were dispersed over mainland Japan, andthen were deposited on the ground by means of (a) dry deposition, and (b) wet deposition
with rain and snow. The main deposition occurred to the north-west of the FDNPS site, but
significant deposition also occurred to the north, south and west of the FDNPS site.
137

12.
In general, the Committee had relied on measurements of the deposition densities ofradionuclides as the basis for its estimates of doses to the public from external exposure andfrom inhalation. However, in order to estimate doses where measurement data were
unavailable for the periods when exposures occurred (e.g. for evacuees) and could no longer
be obtained, the Committee had needed to use an estimate of the source term (including the
temporal patterns of release rates) together with appropriate atmospheric transport,
dispersion and deposition modelling (ATDM) to estimate levels in the environment andresulting doses to people. The Committee had chosen a published source term for thispurpose [T4]. The releases of the radiologically dominant radionuclides 131I and 137Cs in thissource term were 120 and 8.8 PBq, respectively. While at the lower end of the range of
published estimates, and possibly an underestimate of the total release, the Committee had
considered this source term as the most appropriate for estimating doses incurred as a resultof dispersion over the land mass of Japan (see paragraphs B15–B16 in [U6]).

DEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 5

B.
13.

Findings of review of new publications

Based on its appraisals, the Committee noted the following in particular:(a) None of the 12 publications appraised materially affected the main findings orchallenged the major assumptions of the 2013 Fukushima report, and five provided
confirmation of the assumptions in whole or part;(b) Several publications [A1, C1, K4, W3] demonstrated that inverse or reverse
modelling can reasonably be applied to reconstruct the source term confirming theassumption made in [U6];(c) New estimates [A1, C1, K4, W3, Z1] of the total amounts of 137Cs, 131I and 133Xe
released were broadly consistent with the ranges quoted in [U6], although tending to
be at the lower end of the ranges;(d) More detailed information about the temporal pattern of the release has beenreported [K4, W3]. This new information was the result of considering new datasets(e.g. dose rate measurements, and new data on 137Cs concentrations in air with hightemporal resolution [T12]) and using inverse or reverse modelling;(e) Several new studies have been published which investigated levels of radionuclides
other than isotopes of tellurium, iodine and caesium in the environment and confirm
the assumption in [U6] that those other radionuclides do not significantly contributeto the exposure of the population [H8, S3, T5, Z1];
(f) The absence of significant quantities of fuel materials and radionuclides of low
volatility in the release and accordingly in environmental media has been confirmed[S3, T5, Z1];(g) The findings of the 2013 Fukushima report [U6] relating to a narrow region along
the coast to the south of FDNPS in which the ratio of 131I relative to 137Cs was
significantly elevated have been confirmed [H8], and it has been noted that the135
Cs/137Cs ratio was also different in this area [Z1];(h) One study [Z1] identified the release from the Unit 2 reactor as the major
contribution to the total release based on the ratios of various isotopes of caesium
and plutonium.

14.
In its 2013 Fukushima report [U6], the Committee had used the Terada et al. [T4]source term to estimate levels of radionuclides in the environment where measurements
were not available or could no longer be made. This source term was the last but one (thenavailable) in a series of estimates made by a group of researchers at the Japan Atomic
Energy Agency (JAEA), in which each estimate was a refinement of the one before. Katata
et al. [K4] is the latest estimate in this series and has been derived using improved
atmospheric and oceanic transport, dispersion and deposition models, as well as new
information on measured levels of radiation dose or radionuclides in the environment. The
total releases of 131I and 137Cs estimated by Katata et al. were 151 and 14.5 PBq,
respectively, compared with the previous estimates of Terada et al. of 120 and 8.8 PBq.
While these differences in total releases are relatively small in the context of the ranges of
releases quoted in [U6] (100–500 PBq for 131I and 6-20 PBq for 137Cs), they disguise more
substantive differences (of an order of magnitude or more) over particular periods of time.

62015 WHITE PAPER

C.

Potential implication of new publications

15.
The Committee has taken note of the refinements made to the source term estimate
used in [U6]. In any further or updated assessment, the Committee would, therefore,
recommend the use of the latest estimate in preference (together with consistent ATDM).
The Committee does not, however, expect that use of this latest source term estimate would
alter significantly the doses it estimated in [U6], with the possible exception of estimateddoses to evacuees (see paragraph B16 of [U6]). The impact on the estimated doses toevacuees would be influenced by detailed differences between the Terada et al. [T4] andKatata et al. [K4] source term estimates over the periods before and during evacuation whenpeople may have been exposed (see chapter V).
16.
The Committee has identified that research in the following specific areas would have thegreatest potential to contribute to addressing the needs identified in the 2013 Fukushima report:(a) Further in-depth studies of the wet deposition schemes used in ATDM and of theeffects of grid sizes;(b) Inverse and reverse modelling to estimate the source term making use of allavailable measurement data (in particular, the more recently available hourly 137Csconcentrations in air derived from filter tapes in instruments monitoring suspended
particulate matter [T12]).

IV. UPDATES ON RADIONUCLIDE RELEASES TO WATER,DISPERSION AND DEPOSITIONA.

Recapitulation of 2013 Fukushima report

17.
The Committee had concluded that the direct discharge and releases from FDNPS tothe ocean mainly occurred during the first month following the accident, and that thecontinuing releases were unlikely to affect the Committee’s assessment of doses to the
public significantly. The Committee had concluded that these direct releases were about
10-20 PBq for 131I and 3–6 PBq for 137Cs, mainly on the basis of estimates derived using
three-dimensional modelling. In addition, the Committee had found that the release to theocean from deposition from the atmosphere was about 60–100 PBq for 131I and 5−8 PBq for
137
Cs, with only a small percentage of this occurring within a radius of 80 km from FDNPS.
The Committee had concluded that measured levels of 137Cs in seawater near the FDNPS
site declined rapidly from a peak of 68,000 Bq/L on 7 April 2011 and were generally below
200 Bq/L by the end of April, after which the rate of decrease was much smaller.
Concentrations decreased rapidly with distance from the coast: at 15 km and 30 km offshore
from the FDNPS site, they were about 100 times and 1,000 times lower, respectively, thannear the FDNPS site. The measured levels of 137Cs in sediment generally lay between
10 and 1,000 Bq/kg of dry sediment, except in the port of FDNPS, where measured levels
were much higher.
18.
At the time the 2013 Fukushima report [U6] was finalized, radioactive water had
still been leaking on the site, and groundwater had been transporting radionuclides into theaquatic environment. The Committee had also noted the appearance of significant amountsof fission and activation products in stagnant water in the basements of the reactor andturbine buildings. The Committee had identified that key priorities for scientific researchDEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 7

were to improve the characterization of the leaks and releases to the aquatic environment,
and forecasting and quantifying the long-term transport and mixing of these releases.
B.

Findings of review of new publications

19.
Of the 18 publications appraised, 6 none materially affected the main findings orchallenged the major assumptions of the 2013 Fukushima report. Several publications
addressed the identified research needs and their contributions are summarized in thefollowing paragraphs.
20.
The estimates of direct discharges and releases to the marine environment and ofindirect input from deposition from the atmosphere have not been significantly challenged
by recent publications. Kanda [K3] estimated continuing releases of 137Cs between
June 2011 and September 2012 totalling 20 TBq, less than 1% of the total release before
June 2011. Tsumune et al. [T11] suggested that deposition to the ocean surface from theatmosphere could have been underestimated, because no measurements were available toconstrain this term in atmospheric dispersion models. Bu et al. [B7] considered the releaseof plutonium isotopes to the marine environment to be negligible, because no concentrations
attributable to FDNPS were detected in marine sediments.
21.
None of the papers dealing with the dispersion of radionuclides in seawater challenge
the general finding that concentration of radionuclides were very low other than relatively
close to FDNPS. They do, however, enable improved specification of the spatial and temporalscales of the dispersion. This is particularly true for coastal waters, where Oikawa et al. [O2]made a major effort to reanalyse the Ministry of Education, Culture, Sports, Science andTechnology of Japan (MEXT) dataset, which had initially reported high detection limits: thelevels in most samples outside a radius of 30 km from FDNPS were initially reported as notdetectable (less than about 6–9 Bq/L), whereas the new more sensitive analysis has identified
the variations of 137Cs concentration at the surface, intermediate and bottom depths, with
detectable levels between 0.1 and 1 mBq/L. This has demonstrated a downward transport of137
Cs from spring to winter (2011), likely due to physical oceanic processes. More generally,
as initially reported, observations and models have indicated that 137Cs concentrations inseawater decreased rapidly with time: one year after the accident, levels associated with directdischarges and releases remained significantly higher than the pre-accident levels only in the
coastal zone around FDNPS [T11]. At a larger scale, numerical models have indicated that thelevels of 137Cs in seawater had decreased to the pre-accident levels 2.5 years after the accident[K7]. While initial measurements, which were mostly restricted to the ocean surface, pointed
to a major eastward dispersion of released radionuclides with the Kuroshio Current,
observations at depths of 100−500 m have identified a southward transport of a significant
amount of caesium [K1, K10].
6

Consideration was limited in this first review to publications addressing releases and deposition to, anddispersion in, the ocean. The transfer to and dispersion in freshwater bodies of radionuclides (e.g. run off fromcatchments) is being addressed in an increasing number of publications and is an important element of the
F-TRACE programme (Long Term Assessment of the Transport of Radioactive Contamination in theEnvironment of Fukushima) [I1]. The Committee will continue to monitor developments in this area but does
not expect its main conclusions in the 2013 Fukushima report to be challenged by any new findings in thisfield – albeit, without negating the importance of ongoing research in this area and its possible relevance tofuture mitigation activities.

82015 WHITE PAPER

22.
Analysis of a large set of sediment cores has led to estimates of the inventory of
137
Cs in ocean sediments of between 38 and 200 TBq for the coastal region around FDNPS[B4, K12, O3], corresponding to about 1% of the total release. The penetration of 137Cs into
the sediment was found to be deeper than 0.14 m (14 cm) for water depths less than 150 m.
The spatial repartition of 137Cs in the sediment seemed to be driven by several factors. First,
the distance from FDNPS dominated within the 3 km zone; beyond this zone, the 137Cs
inventory [B4] and concentration at the surface [A2] seemed to be related to the sedimentgrain size (with larger values associated with finer grained sediments). This picture, drawn
from low resolution sampling, must be tempered by the results of high resolution
measurements that revealed strong heterogeneities of 137Cs concentrations in the sediment at
the small scale (1 m to 100 m), with isolated peak values larger than 5,000 Bq/kg [T6].
23.
Extreme weather events such as typhoons could lead to the transfer of significant
quantities of radionuclides associated with sediment drained from river basins to the coastal
zone. Observations [Y2] indicate that the largest river system affected by deposition fromFDNPS (the Abukuma river basin) discharged about 5 TBq of 137Cs from August 2011 to
May 2012 (about 1% of the total deposition over the basin catchment). Yamashiki et al. [Y2]estimated that 61% of this 10-month transfer occurred during an 8-day period, corresponding
to the passage of Typhoon Roke. These sediments were responsible for an increase in theconcentrations of 137Cs in the marine sediment mostly confined near the river mouth.
C.

Potential implication of new publications

24.
The Committee has concluded that its findings in this area of the 2013 Fukushimareport remain valid and are largely unaffected by new information that has since been
published. The observed southward transport of caesium at deeper ocean levels has indicatedthat the barrier afforded by the Kuroshio Current is not as significant as initially thought. The
Committee has noted several publications that will contribute to an improved understandingof the release and subsequent dispersion of radionuclides in the marine environment.

V. UPDATES ON EVALUATION OF DOSES FOR THE PUBLIC
A.

Recapitulation of 2013 Fukushima report

25.
The Committee’s aim had been to make realistic estimates of doses to definedgroups of individuals considered representative of the different subsets of the Japanese
population. For the assessment of doses to the public from external exposure, the Committee
had used models with parameter values mostly derived from European studies after the
Chernobyl accident, and validated with numerous individual thermoluminescent dosimetermeasurements conducted in the affected Bryansk region of Russia. The Committee had used
these models in its 2013 Fukushima report in combination with population-averaged
deposition densities of radionuclides for Japanese districts or prefectures, derived by
combining measurements of radionuclide deposition densities with data on the age
compositions and typical occupancy factors of different groups of the Japanese population
based on the 2010 Japanese census.
26.
For the assessment of doses to the public from internal exposure, the Committee had
considered two exposure pathways, inhalation and ingestion. Exposure from inhalation had
been assessed only from radionuclides in the passing radioactive plume, with subsequentDEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 9

inhalation of resuspended radionuclides considered insignificant. Exposure from inhalationof radionuclides in the passing plume had been estimated from deposition density
measurements using ratios of the concentrations of radionuclides in air to deposition density
levels derived using the assumed source term and atmospheric transport, dispersion anddeposition modelling.
27.
Intakes of radionuclides in food and drinking water in the first year following theaccident had been assessed using the database of food and drinking water measurements
carried out in Fukushima Prefecture and other prefectures of Japan. This database included
many measurements made for food inspection purposes and therefore had some bias
associated with the sampling: samples with potentially elevated activity concentrations weremore likely to have been selected. However, at the time of preparation of the 2013 Fukushimareport, no other food measurements had been available.
28.
For subsequent years, a modified form of the recognized European model,
FARMLAND [B6], had been applied for estimating the transfer of radionuclides throughterrestrial food chains, with some transfer coefficients adjusted for the conditions andagricultural practices of contemporary Japan. The model had been used in combination with
input data on population-averaged deposition densities of radionuclides for Japanesedistricts or prefectures.
29.
For residents of evacuated communities, where it had not been possible to use
measurements of radionuclide concentrations in the environment, the Committee had
estimated time-varying concentrations of radionuclides in the environment using theassumed source term for releases to atmosphere and ATDM. Doses from external exposureand from inhalation had then been estimated for the periods before, during and after
evacuation using scenarios representing the movements of residents derived from the resultsof a survey using questionnaires.
30.
Measurements of radionuclides in people, such as whole-body-counter (WBC) andthyroid measurements, provide a direct source of information on internal exposure.
However, at the time of preparation of the 2013 Fukushima report, the number of thyroid
measurements had been limited (about 1,100 persons) and these data had been able to be
used only to corroborate doses to the thyroid in a few settlements estimated using numericalmodels. In addition, data from WBC measurements had become available to the Committee
only at a late stage of report preparation, and comprehensive data analysis had not beenpossible. Nevertheless, some assessment of doses from internal exposure based on humanmeasurements had been carried out by the Committee and were presented in the 2013 Fukushimareport (see paragraphs 116–118 of [U6]).
B.

Findings of review of new publications

31.
Of the 12 publications appraised, none materially affected the main findings of the 2013
Fukushima report, while 10 provided confirmation of the main assumptions in whole or part.
1.

External exposure

32.
External exposure of the public has been considered to different extents by Harada etal. [H1], Ishii et al. [I6], Koike et al. [K8], Nagataki et al. [N1] and Takahara et al. [T2].

102015 WHITE PAPER

33.
Harada et al. [H1] demonstrated a correlation between outdoor dose rate (ambient dose
equivalent rate from deposited radionuclides) and personal dose rate (personal dose equivalent
rate due to external exposure) that might be used to reconstruct doses for groups andindividuals and therefore validate estimates of doses from external exposure (see figure I).
34.
Another large series of individual measurements by Optically Stimulated Luminescent
Dosimeter (OSLD) of dose to more than 1,000 students from external exposure over a twoyear period, as well as forecasts of doses for the next 10 years, was presented by Koike et al.
[K8]. The Committee has some reservations about calibration and the statistical processing of
the data. However, the measurements are in good agreement with the estimates of doses fromexternal exposure for Miharu town set out in the 2013 Fukushima report.
35.
A review of estimated doses to individuals from external exposure, based either on
personal measurements or interviews conducted by Japanese experts between 2011 and early
2013, was reported by Nagataki et al. [N1]. There is reasonable agreement between the datareported in the paper and that used in the 2013 Fukushima report, supporting the assumptionsin the latter. Data of this type are potentially useful for reconstruction of doses to individuals
and for epidemiological studies, and to improve national models for assessing doses.
36.
Takahara et al. [T2] reported on the development of a probabilistic model for dose
assessment based on measurements conducted in early 2012. They studied doses to residentsof Fukushima Prefecture from external exposure by measuring ambient dose equivalent
rates and monthly doses to 500 individuals, as well as behaviour patterns of various
population groups, including indoor and outdoor workers, and pensioners. The paper
contributes to both independent assessment of model parameters for estimating doses fromexternal exposure, and validation of the results. It also partially confirms the model
parameters used in the 2013 Fukushima report.
37.
The Committee has noted significant progress in a number of areas that willcontribute to enhancing the quality and reliability of estimated doses from external
exposure. These include: the further clarification of patterns of external exposure; thevalidation of dose estimates with individual measurements; and the development of anational probabilistic model for estimating doses from external exposure. It has also notedthat there was little new information (at least not reported in peer-reviewed publications)available in other areas, including: the migration of caesium radioisotopes in various
environments; the determination of shielding parameters for Japanese buildings; theassessment of the effectiveness of urban decontamination; and long-term dose ratemeasurements in inhabited areas.

DEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 11

Figure I. Correlation between outdoor ambient dose equivalent rate and personal dose
equivalent rate from deposited radionuclides
The fitted line corresponds to a relationship where y = 0.0403 + 0.4534x; r = 0.6274, p < 0.0001

2.

Internal exposure

38.
Internal exposure of the public has been considered to different extents by Harada etal. [H1], Hayano et al. [H3], Ishii et al. [I6], Matsuda et al. [M1], Nagataki et al. [N1],Sato et al. [S2] and Torii et al. [T7]. Some relevant information has also been presented by
Hirakawa et al. [H5] and Tsubokura et al. [T9].
39.
Two papers [H3, M1] focused on early WBC measurements that provided the mostreliable retrospective assessment of dose from internal exposure due to early inhalation
and/or ingestion of caesium radionuclides (see figure II). Some uncertainty associated withthe results presented by Hayano et al. [H3] should be noted because of the methodology
used and assumptions made. The Committee converted the WBC measurement data tocommitted effective dose assuming early acute intake, regardless of whether this was byingestion or inhalation. The resulting doses from internal exposure to caesium radionuclides
were about three times lower than those estimated in the 2013 Fukushima report using thedatabase on measurements in foodstuffs and inhalation modelling.
40.
The review paper of Nagataki et al. [N1] also contains data on WBC measurementsthat imply low effective doses from internal exposure to the residents of Fukushima
Prefecture in later periods of time, mostly in 2012.

122015 WHITE PAPER

Figure II. The estimated committed effective dose to adult residents of Minamisoma City
based on WBC measurements conducted 110–140 days after the FDNPS accident assuming
early intake of caesium radionuclides [H3]41.
Harada et al. [H1] estimated doses from internal exposure to residents in three areas
within 20–50 km of FDNPS resulting from intakes of caesium radionuclides during thesummer of 2012 by ingestion (based on analysis of meal duplicates) and by inhalation(based on analysis of air dust). The results demonstrated that, in the summer of 2012, thedoses from internal exposure were two orders of magnitude lower than the doses fromexternal exposure as measured by personal OSLD (see figure III). The estimated doses frominternal exposure due to inhalation of resuspended materials were two orders of magnitude
lower than those due to ingestion.
42.
A low ingestion rate of caesium radionuclides by residents of Fukushima Prefecturein the winter of 2011–2012 and the summer of 2012 was corroborated by analysis of meal
duplicates collected from 200 families by Sato et al. [S2], although details of sampling andmeasurement procedures used were lacking. Among 200 meals analysed, only 12 were
found to have average concentrations of more than 1 Bq/kg. For the highest measured
caesium radionuclide levels in food, the assessed annual effective dose from ingestion did
not exceed 0.1 mSv.
43.
Hirakawa et al. [H5] summarized information from interviews with municipal staff anda collection of government documents relevant to bans on food and drinking water inFukushima Prefecture during the first weeks after the nuclear accident. They confirmed thatearly evacuees from the 20-km zone were fed before and during the evacuation with stored
foods or supplies from unaffected areas, and that consumption of fresh food was unlikely,
clarifying conditions during the first weeks after the accident. It should be noted, however, thattap water and river water was consumed during the period before drinking water measurements
were started. Furthermore, they confirmed that the fraction of local foods on markets inFukushima Prefecture was about 15–30%, in agreement with the 25% figure assumed in the2013 Fukushima report for estimating doses due to ingestion after the first year.

DEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 13

44.
The Committee has noted significant progress in a number of areas that will contributeto enhancing the quality and reliability of estimates of doses from internal exposure; theseinclude: the further clarification of internal exposure patterns; validation of dosimetric models
with individual WBC measurements; and confirmation that doses from internal exposure due
to ingestion and inhalation of resuspended radionuclides are much smaller than doses fromexternal exposure. It has also noted that there was little new information (at least not reported
in peer-reviewed publications) in other areas that have the potential to further enhance thequality and reliability of estimates of doses from internal exposure including: the dynamics ofthe variation over time of the concentration of caesium radionuclides in various foods(agricultural and wild) and in a staple food basket; and the development of deterministic andprobabilistic models for the assessment of doses from internal exposure.
Figure III. Cumulative probability plot of annual effective doses in 2012 to adult residents of
the Tamano area of Soma City from external exposure, and from internal exposure due toingestion and due to inhalation of resuspended materials [H1]3.

Countermeasures (early and intermediate)45.
The Committee has so far found no peer-reviewed publications in English on theeffect of countermeasures or remediation of contaminated areas on doses. Several
potentially relevant publications were identified in Japanese, but time and resource
constraints did not allow for these to be translated and appraised for this digest; it is envisaged
to include them in the next digest. Dose estimates presented in the 2013 Fukushima report did
not take account of longer-term remedial measures to reduce doses from external exposure
to deposited radionuclides and doses from internal exposure due to ingestion of foodstuffs;
they may, therefore, have been overestimates of the actual doses that have been or will bereceived in practice. Measurements of dose rates have been made before and after
decontamination of settlements in the evacuated Special Decontamination Area, but themeasurements have not yet been reported in peer-reviewed literature. Access to these dataor their publication in the peer-reviewed literature would enable improvements to be madein the quality and reliability of the dose estimates in the 2013 Fukushima report. Similarly,
information on the extent of remedial measures in the agricultural environment and their

142015 WHITE PAPER

impact on the transfer of radionuclides to foodstuffs would allow further improvement in theestimation of doses due to ingestion.
C.

Potential implication of new publications

46.
The Committee has concluded that its findings in this area of the 2013 Fukushimareport remain valid and are largely unaffected by new information that has since been
published. Further whole body measurements have given added weight to the statement in
the 2013 Fukushima report (based on the more limited measurements then available) that
effective doses from ingestion of radionuclides in foodstuffs may, in practice, have been much
lower than those estimated theoretically (and reported generally in the 2013 Fukushimareport) using the database on food measurements; analyses based on studies of duplicate
meals further support this statement. By far the majority of the new publications broadly
support or confirm the main assumptions made in, and the findings of, the 2013 Fukushimareport, in particular:(a) That doses to the general public in Japan decreased substantially after 2011 asforeseen in the 2013 Fukushima report;(b) That the contribution to the total effective dose from internal exposure due tocontinuing intakes of radionuclides in foodstuffs is small, and the contribution of
exposure from inhalation of resuspended caesium radionuclides is negligible;(c) That doses from external exposure as measured by personal dosimeters or estimatedfrom dose rate measurements and personal interviews are in broad agreement with theinformation reported in the 2013 Fukushima report.
47.
The Committee has identified research in the following specific areas as having thegreatest potential to contribute to addressing the research needs identified in the 2013
Fukushima report:(a) Continuation of studies of migration of caesium radionuclides in urban, agriculturaland forest environments and their transfer to various foods (agricultural and wild);(b) Determination of parameter values necessary for regional and national models of
doses (e.g. shielding parameters of buildings; time spent outdoors and indoors in various
building types, in different seasons, and as a function of age and social group; andparameters related to the system of food distribution and consumption habits ofcultivated and wild foods).
48.
In chapter III, the Committee highlighted the new estimate of the source term forreleases to atmosphere and its potential implications for the assessment of doses to evacuees
presented in the 2013 Fukushima report. It would be beneficial if the Japanese authorities
were to carry out a detailed evaluation of the doses received by those evacuated using thisnew source term, with consistent meteorological data and ATDM, and a detailed analysis of
the movements and behaviours of those residents of evacuated communities.

DEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 15

VI. UPDATES ON EVALUATION OF DOSES FOR WORKERS
A.

Recapitulation of 2013 Fukushima report

49.
The main aim of the Committee’s work had been to judge the extent to which theindividual doses reported in Japan provided a true and reliable measure of the doses actually
incurred by workers, and therefore the extent to which the reported doses could support a
reliable commentary on the implications for health. By the end of October 2012, the Tokyo
Electric Power Company (TEPCO) had reported statistics on doses to about 25,000 workers
at the FDNPS site, most of whom were employed by contractors. According to TEPCO’s
reports, the average effective dose to FDNPS workers over the first 19 months after theaccident had been about 10 mSv. About 34% of the workforce had received effective doses
over this period above 10 mSv, while 0.7% of the workforce (corresponding to
173 individuals) had received effective doses more than 100 mSv. The highest reported
effective dose was 679 mSv for the TEPCO worker who also had received the highest
reported committed effective dose due to internal exposure (590 mSv). Dose statistics had
been reported separately for a few hundred emergency services workers.
50.
The Committee’s independent assessments of the doses due to internal exposure fortwelve workers (out of a total of thirteen) who had committed effective doses due to internal
exposure higher than 100 mSv had confirmed that they had received absorbed doses to thethyroid due to inhalation of 131I in the range of 2 to 12 Gy.
51.
The reliability of the internal exposure assessments for the much larger number ofworkers with lower assessed internal exposures had been evaluated by performing
independent assessments for randomly selected samples of workers.
52.
The Committee had confirmed the reliability of assessments reported by TEPCO for
those of its workers where a positive measurement of 131I in the body had been made.
However, for most of the workers, in vivo monitoring of 131I in the thyroid had not started
until mid- to late-May 2011, and in many cases this delay had meant that 131I could no longer
be detected. For the same reason, the contribution to internal exposure from intakes of shorterlived radionuclides such as 132Te and 133I had not been able to be reliably assessed. The
Committee had not been able to confirm the reliability of assessments reported by TEPCO for
those of its workers for whom 131I had not been detected in the body, nor the reliability of theinternal exposure assessments reported by contractors for their workers.
53.
The Committee had judged that the major factor potentially affecting the reliabilityof external exposure assessments had been the sharing of electronic personal dosimeters
during March 2011, with only one worker in a team wearing a dosimeter for many missions.
54.
The Committee had had insufficient information on beta irradiation to make an
informed assessment of doses to the eye lens of workers (paragraph 143 in [U6]).
B.

Findings of review of new publications

55.
Of the seven publications appraised, two had the potential (albeit unlikely) tomaterially affect the main findings of the 2013 Fukushima report, while all seven provided
some confirmation of one or other of the report’s major assumptions.

16

2015 WHITE PAPER

56.
Kurihara et al. [K11] reported results of measurements of 131I in the thyroid of
560 FDNPS workers which provide committed effective dose estimates that are consistent
with those presented in the 2013 Fukushima report.
57.
Suto et al. [S5] presented results of dicentric chromosome assay for 12 workers. This
work was known of at the time of preparation of the 2013 Fukushima report, although thework was unpublished at that time. The aim was to perform medical triage and planning forthe selected workers. The results presented show that estimated whole body absorbed doses
were less than 300 mGy for all 12 workers, and that no acute radiation syndrome effects
were expected for the workers examined.
58.
Naoi et al. [N3] reported doses from external exposure, and from internal exposure toradiocaesium, for Self-Defense Force (SDF) personnel. The reported doses from external andinternal exposure were broadly consistent with those reported in the 2013 Fukushima report.
59.
Tsubokura et al. [T10] presented the first results of in vivo measurements of 134Cs and137
Cs for workers who were not emergency workers, but who were performing decontamination
tasks (during 2012) in villages near FDNPS. Measured levels of 134Cs and 137Cs in the wholebody were below the detection limit of 300 Bq in all cases, and the authors concluded that,while the results may not be completely representative of all decontamination workers,
resuspension of radioactive materials led to minimal intakes of radionuclides.
60.
Yasui [Y4] reported on a re-evaluation of worker doses, carried out in July 2013.
The Committee had been aware of this re-evaluation at the time of its 2013 Fukushimareport, but had not been able to take full account of it at that time. The need for the reevaluation arose because of significant discrepancies between doses from internal exposure
assessed by TEPCO and those assessed by contractors of TEPCO, resulting from differencesin the methods adopted for dose assessment. These discrepancies prompted new guidancefrom the Japanese Ministry of Health, Labour and Welfare (MHLW) on the standard
methods to be used, which resulted in a revision of committed effective doses for a few
hundred workers. Yasui [Y4] reported that, as a result of this re-evaluation, the numbers ofworkers found to have received committed effective doses (from internal and external
exposure) 7 in the dose ranges 50−100 mSv and over 100 mSv increased by a few per cent.
Yasui [Y4] also reported that the standard methods it had prescribed were considered by
MHLW to be sufficient to account adequately for the contribution of the short-lived
radionuclides 132I and 132Te. MHLW estimated the contribution from 132Te to the committed
effective dose, given the uncertainties, to be approximately 10% of the contribution from131
I; in the 2013 Fukushima report, the Committee had estimated the contribution fromshort-lived radionuclides in total (including, for example, 133I) to be in the order of 20%
relative to that from 131I.
61.
The re-evaluation reported by Yasui [Y4] only concerned workers where significant
differences were found between doses assessed by TEPCO and those assessed bycontractors, and where there were doubts over the validity of the assessment. MHLW [M3]reported that, following the identification by TEPCO in January 2014 that the committed
effective doses of nine workers had been assessed by methods other than the standard
methods defined by MHLW, it had carried out a re-examination of the data for all workers,other than those re-assessed in the first re-evaluation. It concluded that the committed
7

In both Yasui [Y4] and MHLW [M3] the time period used to present the results of the re-evaluations of doses
was 11 March to 31 December 2011.

DEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 17

effective doses for 1,536 workers may have been assessed by a method other than thestandard methods. The MHLW therefore instructed TEPCO and primary contractors tocarry out a further re-evaluation of the committed effective doses.
62.
MHLW [M3] reported that, as a result of this second re-evaluation, estimates ofcommitted effective dose have been increased for 142 workers. Increases in the estimates ofcommitted effective dose range from 1 mSv to 90 mSv. As a result there have been further
small increases (that is by one or two) in the numbers of workers with committed effective
doses above 100 mSv, and with doses between 50 and 100 mSv. Most of the increases
occurred in workers with committed effective doses less than 50 mSv.
C.

Potential implication of new publications

63.
While significant changes have been made to doses estimated for some workers in
the first and second re-evaluations reported by Yasui [Y4] and MHLW [M3], the Committee
does not expect that these will materially affect its main findings in the 2013 Fukushimareport [U6]. This would, however, need to be confirmed by a fuller analysis of the data andmethodologies adopted in the re-evaluations of doses requested by MHLW.
64.
The Committee did not find any new information that would enable it to reach informed
judgments on the exposure of the lens of the eye or on improving the quality of its dose
estimates in the various areas identified in the 2013 Fukushima report (e.g. exposures toradionuclides not detected by in vivo measurements, and reliability of using shared dosimeters).

VII. UPDATES ON HEALTH IMPLICATIONS FOR WORKERS AND
PUBLICA.

Recapitulation of 2013 Fukushima report

65.
The Committee had found that health risks resulting from the Fukushima accident
were expected to be far lower than those for the Chernobyl accident, owing to thesubstantially lower doses received by the public and workers. No deterministic effects fromradiation exposure had been observed among the public and none had been expected. No
increase in spontaneous abortions, miscarriages, perinatal mortality, birth defects or
cognitive impairment had been expected from exposures during pregnancy. Nor had a“discernible increase in heritable disease among the descendants of those exposed from theaccident” (paragraph 224 of [U6]) been expected. No discernible radiation-related increases
in rates of leukaemia or breast cancer (two of the most radiogenic cancer types), nor in othertypes of solid cancer besides possibly thyroid cancer, had been expected. A large excess of
thyroid cancer due to radiation exposure, such as occurred after the Chernobyl accident, hadbeen able to be discounted, because the estimated thyroid doses due to the FDNPS accident
were substantially lower than those sustained around Chernobyl. However, the sensitive
ultrasound-based thyroid screening of those under 18 years old at the time of the accident had
been expected to detect a large number of thyroid cysts and solid nodules, including a numberof thyroid cancers “that would not normally have been detected without such intensive
screening” (paragraph 225 of [U6]). However, similar or even slightly higher rates of cysts
and nodules were found in the prefectures of Aomori, Yamanashi and Nagasaki that had notreceived significant radionuclide deposition from the accident. The substantial numbers that182015 WHITE PAPER

had already been observed in the Fukushima Health Management Survey (FHMS) 8 had been
considered likely due to the sensitivity of the screening and not to radiation effects.
66.
Among FDNPS emergency workers, deterministic effects had been considered
unlikely, but the Committee had not been able to preclude the possibility of hypothyroidism,
nor assess the risk of cataracts due to insufficient information on doses to the lens of the eyefrom beta irradiation. Although 2−3 excess cancers could be inferred over the lifetime
among workers with doses greater than 100 mSv (mainly from external exposure), theCommittee had considered it unlikely that such increased incidence of cancer due toirradiation would be discernible. The Committee had judged the magnitude of any inferredrisk of thyroid cancer among workers to be such that any increase in incidence due toradiation exposure would likely not be discernible.
67.
The Committee had noted that the most important health effects that had been
observed among the general public and among workers were considered to be on mental
health and social well-being [W2], but that estimation of the occurrence and severity of such
health effects was outside of the Committee’s remit.
B.

Findings of review of new publications

68.
None of the 10 publications appraised challenge the assumptions or findings of the2013 Fukushima report; instead they served to strengthen or complement those findings.
69.
Nagataki and Takamura [N2] reported that (as of March 2014) 51 out of the 287,056
individuals (177 per million) in the FHMS screening programme had a diagnosis of thyroid
cancer. The study of thyroid screening results in areas where people were not exposed toradiation resulting from the accident that is most comparable to the FHMS programme isthat of young people in Aomori, Nagasaki and Yamanashi prefectures [H4]. This study,
using instrumentation and methodology similar to the FHMS study, found rates of thyroid
nodules and cysts that were nominally somewhat higher than the FHMS study. One thyroid
cancer was found among the 4,365 children (prevalence of 230 per million) screened at ages
3–18 years. A relatively small study (1,214 screened individuals) by Iwaku et al. [I7] ofchildren in the Kanto region found rates of thyroid nodules or cysts nominally higher thanthose in the FHMS study, and also found no differences in rates for those screened before orafter the Fukushima accident. Nagataki and Takamura [N2] summarized thyroid cancer
results from three other thyroid screening studies of non-exposed young people. In two
university screening programmes the results were: 3 among 9,988 (300 per million) Japanese
students at Chiba University and 3 among 2,307 (1,300 per million) at Okayama University
were diagnosed with thyroid cancer. At Keio High School, 1 among 2,868 (350 per million)
female students was diagnosed with thyroid cancer. As a supplement to the thyroid
nodule/cancer data, Watanobe et al. [W1] reported no indication of excess hypothyroidism,
immune thyroiditis or other thyroid dysfunction among children of the Fukushima Prefecture.
70.
Taking all of the screening studies in non-exposed areas or times together indicates aprevalence of thyroid cancer of 380 per million compared to 177 per million in the FHMS.
The Committee recognizes that the prevalence rates are not fully comparable, because the8

The Fukushima Health Management Survey is a large programme of health questionnaires and healthscreening conducted by Fukushima Medical University with Japanese government funding. The screening has
two primary components: thyroid disease screening among those exposed at ages 0–18 years, and screening of
women who were pregnant or breast-feeding at the time of the FDNPS accident and their offspring.

DEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 19

age distribution of those screened in the FHMS was younger than those of most of thecomparison studies, and the degree of comparability of the screening methods is unknown
except for the Hayashida et al. study [H4]. However, the studies are supportive of thesuggestion that the apparent increased thyroid cancer rate among young people in
Fukushima Prefecture was probably due to screening, at least at the time of the reported
FHMS results in March 2014. Furthermore, the typical delay or latent period between
exposure and appearance of thyroid cancer is an additional indicator of the apparent increase
being due to screening.
71.
Significant excess rates of non-cancer health end points because of radiation
exposure are not expected in the Fukushima Prefecture population because of the relatively
low exposures and limited population sizes, but actual data to support or refute thoseassumptions are needed. Three other publications are therefore worthy of mention here as
they provide information on heart disease, reproductive outcomes and other non-cancer
health assessments.
72.
Some of the first information regarding pregnancy and birth outcomes was reported
by Fujimori et al. [F1]. Compared to all Japan, the rates of untoward pregnancy outcomes intheir survey of 8,600 women in Fukushima Prefecture pregnant at the time of the FDNPS
accident were slightly lower for stillbirths, preterm births, and low birthweight, and slightly
higher for birth defects. They concluded that there was no clear evidence of excess adverse
birth outcomes in Fukushima Prefecture.
73.
Yamaki et al. [Y1] obtained information from hospital registries in Fukushima
Prefecture on the numbers of admissions for acute myocardial infarction (AMI) during thetwo years before and two years after the triple disaster of earthquake, tsunami and nuclear
accident. Overall, there was no greater frequency of AMI admissions after the disaster,although they reported a suggestive post-disaster excess frequency in one of the six districtsof Fukushima Prefecture. They attributed the possible excess frequency to the distressassociated with the aftermath of the earthquake and tsunami. A radiation aetiology for AMI
would be most unlikely within two years after exposure.
74.
Yamashita [Y3] reported that rates of obesity, glucose metabolic dysfunction,
hyperlipidaemia, and liver dysfunction after the triple disaster were high compared withthose before, but he attributed the increase to changes in lifestyle, diet and exercise after
the evacuation.
C.

Potential implication of new publications

75.
The Committee has concluded that its findings in this area of the 2013 Fukushimareport remain valid and are largely unaffected by new information that has been publishedso far. Rather, the new information has given added weight to its statement that the highdetection rate of nodules, cysts and cancer in thyroid surveys was a consequence of theintensive screening and highly sensitive nature of the equipment being used, and not of
additional radiation exposure resulting from the accident.
76.
The Committee has noted, and will remain abreast of, ongoing research andinvestigations into the health implications of the accident and, in particular, the healthsurvey being carried out in the Fukushima Prefecture. It has identified the following specificareas where further data or information would have the greatest potential to contribute toaddressing the research needs identified in [U6]:202015 WHITE PAPER(a) Ideally, further thyroid screening data from non-exposed Japanese young people forcomparison with the FHMS thyroid nodule and cancer rates would be valuable, if such a
study were deemed ethically appropriate;(b) In the absence of further screening data, publication of the FHMS numbers ofscreened individuals, thyroid nodules and thyroid cancers by age and sex, because thiswould permit more accurate comparisons with the existing data from those unexposed,
and with observations made after the Chernobyl accident;(c) Where practicable, making available further data on the FHMS screening study, forexample, on estimates of doses, which would permit a comparison of dose groups, and on
the incidence of other health effects (such as childhood leukaemia, other solid cancers,
birth defects among those conceived after the accident), which would, in time, provide
indications of whether the frequency of health conditions varied by radiation dose;(d) Making available data pertaining to the health of the FDNPS emergency workers,
especially among those who received higher doses.

VIII. UPDATES ON EVALUATION OF DOSES AND EFFECTS FOR
NON-HUMAN BIOTA
A.

Recapitulation of 2013 Fukushima report

77.
The Committee had estimated radiation doses due to the accident to non-humanbiota through the application of suitable models. The corresponding estimates of effects dueto the radiation exposure had then been inferred through synthesis of the Committee’s
generic evaluations of dose–effects relationships. Exposures of both marine and terrestrial
non-human biota following the accident had been, in general, too low for acute effects to beobserved, although some exceptions had been considered possible because of local
variability. The Committee had concluded that, in general, population-relevant effects on
non-human biota in the marine environment would have been confined to areas close towhere highly radioactive water was discharged and released into the ocean. Although theCommittee had not been able to exclude a risk of effects to individuals of certain terrestrial
species, in particular mammals, it had considered observable effects at the population level
to be unlikely. It had concluded that any radiation effects would have been constrained to alimited area where the deposition density of radioactive material was greatest, and that,beyond this area, the potential for effects on biota was insignificant.
78.
The Committee had made reference to studies in which effects in various terrestrial
biotas had been observed in areas contaminated by the FDNPS accident [H6, M4, M5]. It
had noted that the substantial impacts reported for populations of wild organisms from thesestudies were inconsistent with the main findings of the Committee’s theoretical assessment.
The Committee had expressed reservations about these observations, noting that
uncertainties with regard to dosimetry and possible confounding factors made it difficult to
substantiate firm conclusions from the cited field studies.

DEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 21

B.

Findings of review of new publications

79.
Of the 20 publications appraised, the Committee identified eight that wereinconsistent with the main findings of the 2013 Fukushima report; nine provided
confirmation of the major assumptions in whole or part.
80.
Several new publications provided information on radionuclide activity levels in
non-human biota (e.g. [H2, K2, T3, T8]) and on processes influencing transfer (e.g. [K5,K6, O1]). The results from these studies appeared to have no major repercussions for thefindings of the 2013 Fukushima report, although synthesis of the newly published data
could help refine the transfer models originally applied. Exposures derived for non-humanbiota in recent studies [F2, K9] generally corresponded closely to the estimates made in the2013 Fukushima report, providing support for the robustness of the Committee’s assessment
approach and the validity of the associated exposure calculations. An exception possibly
existed for the marine environment where elevated concentrations of caesium radionuclides
in benthic marine fish were found to persist [S4].
81.
The Committee’s reservations about the field studies reporting observed effects onterrestrial biota [H6, M4, M5] have been reflected in comments on these studies in theintervening period from other scientists (e.g. [B2, B3]). Notwithstanding these reservations,
the work cited, and more recent and related publications by the same groups, remained (as ofend 2014) the only analyses of data pertaining to population-relevant environmental effects.
82.
Several publications by Mousseau and Møller [M2, M6, M7, M8, M9] provided
additional information on their original studies [M4, M5] by, inter alia, presenting moredetails on the statistical models applied and dismissing the influence of certain confounding
factors, such as the effect of the tsunami itself. There was no change to the authors’ original
conclusions that abundances of butterflies, cicadas and birds decreased with increasingradiation levels, although the authors agreed that the original dose measurements may nothave provided an accurate measure of the actual doses received by mobile animals [M7]. In
contrast, a recent study [I5], found distributions of two bird species which were uncorrelatedwith radiation levels for areas affected by the FDNPS accident. Ishida [I5] noted that theseresults were inconsistent with the conclusions of Møller et al. [M4] about birds in the
FDNPS area and that the design of the bird count survey by Møller et al. was inappropriate
for discriminating the effects of radiation exposure from other environmental factors.
83.
Several papers [H7, N4, T1] provided a comprehensive defence of an earlier
publication cited in the 2013 Fukushima report concerning the impacts of radionuclide
releases on the Pale Grass Blue Butterfly (Pseudozizeeria maha) [H6]. The authors provided
an in-depth description of the methods applied and more detailed data analyses.
Furthermore, one particular study [N4] augmented the general findings by studying theimpact of ingestion of leaves on the larvae of the aforementioned butterfly species. The
authors of this suite of publications maintained that exposures due to releases from the
FDNPS accident would have led to mortality and abnormalities in the studied butterfly
species, that mutations would have been passed on to the progeny and that populations
would have decreased considerably in areas close to FDNPS. They further rejected thepossibility of confounding factors such as the impact of the tsunami itself. Whilst notingsome technical errors, where doses were wrongly specified in units of becquerels andreference was made to dose–response models that were inappropriate for the end points
being studied in some of these publications (e.g. Nohara et al. [N4]), the observations
indicating increases in particular effects that were correlated with indicators of radiationdose under field-relevant conditions merit further investigation. The publications cannot be222015 WHITE PAPER

easily dismissed nor, accepting the integrity of the datasets, can the results be convincingly
explained using existing understanding of radiation effects on environmental systems.
84.
The Committee had assessed exposures of non-human biota and associated effects ingeneral in its scientific annexes to the 1996 and 2008 reports [U3, U5]. The benchmarks set
out and used in those annexes, and in the 2013 Fukushima report itself, were based on a large
synthesis of information derived primarily from radiobiological literature spanning many
decades of experimental work and (to a limited extent) including analyses of fieldobservations from earlier accidents. They thus constituted the most profound insight that
could be achieved into the doses at which biological effects were likely. However, thisinformation, in large part, pertained to exposures of small groups of individuals, maintained inisolation and under controlled laboratory conditions. There will clearly be some limitations to
the applicability of this information when extrapolating to infer effects for ecosystems
exposed to ionizing radiation. Disturbances induced by stressors cannot be entirely grasped
from knowledge of the stressor’s effects on individual organisms, considering that such
effects may act as triggers of perturbation, which propagate through higher levels of biologicalorganization within ecosystems [B5]. This view appears to be supported by recent metaanalysis of effects data, suggesting that organisms in their natural environment were moresensitive to radiation than those tested under laboratory conditions [G1].
C.

Potential implication of new publications

85.
The Committee has concluded that its findings in this area of the 2013 Fukushimareport remain broadly supported by the available evidence. However, it recognizes potential
limitations in its approach (e.g. the benchmarks used) owing to reliance largely onlaboratory-based rather than field studies. Field studies, tailored to analyse the impacts of
exposure to ionizing radiation on populations of wild organisms interacting under theconditions prevalent within contaminated ecosystems, are required. Such studies would
need to be multidisciplinary, involving not just radioecologists and radiation specialists but
also ecologists, population biologists and geneticists.

IX. CONCLUSIONS
86.
Of the 79 new sources of information appraised for this first annual digest, morethan half confirmed one or other of the major assumptions in the 2013 Fukushima report.
None materially affected the main findings in, or challenged the major assumptions of, the2013 Fukushima report but twelve were identified that had the potential to do so, albeit
subject to further analysis or confirmation from studies of better quality. Those publications
judged to have the potential to challenge one or other assumption or finding in the2013 Fukushima report are summarized in table 2. In each case an indication is given ofwhat further work or analysis may be needed before informed judgements could be reachedon the significance or otherwise of an identified potential challenge.
87.
Eight of the publications highlighted in table 2 relate to a series of field studies
reporting population-level effects on invertebrates and birds that were different from what
could be inferred from the Committee’s assessment. The results from these studies are notconclusive, and the findings in this area of the 2013 Fukushima report remain broadly
supported by the available evidence. Further research would be needed to resolve theseapparent differences.

DEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 23

88.
One publication on levels of radionuclides in foods (supplemented by further wholebody measurements reported elsewhere) has provided support to the statement already madein the 2013 Fukushima report (based on the then limited whole-body measurements
available) that doses to the public from ingestion may have been significantly overestimatedin the 2013 Fukushima report. The magnitude of any overestimation needs to be further
investigated. Any overestimation, in the 2013 Fukushima report, of doses via ingestion
would, in general, have little impact on estimates of total doses as these are dominated byexternal exposure to radiation from deposited radionuclides.
89.
Two of the twelve new sources of information concern two re-evaluations of doses
to workers requested by the Japanese Ministry of Health, Labour and Welfare. These haveresulted in significant changes (generally increases) to the doses estimated for someworkers. These changes are judged unlikely to materially affect the main findings of the2013 Fukushima report, but this would need to be confirmed by a fuller review of the data
and methodologies adopted.
90.
The final new publication concerns the latest in a series of estimates of the source
term for releases to atmosphere by a group of researchers at the JAEA. In any further or
updated assessment by the Committee, the use of this latest estimate would be preferable tothat used in the 2013 Fukushima report. However, its use would not be expected to altersignificantly the doses estimated in the 2013 Fukushima report, with the possible exceptionof estimated doses to evacuees. The impact on the estimated doses to evacuees would
depend on detailed differences between the source terms over the periods before and during
evacuation when people may have been exposed at levels depending on their locations. This
would need more detailed analysis.
91.
The Committee encourages the Japanese authorities to carry out a detailed
evaluation of the doses received by those evacuated using this new source term, withconsistent meteorological data and atmospheric transport, dispersion and deposition
modelling, and a detailed analysis of the movements and behaviours of those residents ofevacuated communities.
92.
Table 3 summarizes those publications that have been judged to make a significant
contribution to addressing the research needs identified in the 2013 Fukushima report. Manyof the research needs identified in that report have yet to be addressed (at least in peerreviewed publications). Through this and subsequent digests, the Committee intends to keep
under review progress in addressing its identified research needs. Progress made may
influence the Committee’s decision on when it would be most appropriate to update the2013 Fukushima report.

Reference

Challengea to assumptions / findingsof [U6]

Potential challengeb to assumptions /findings of [U6]

Further work required to assess
potential challenge

Comments

RELEASES TO ATMOSPHERE, DISPERSION AND DEPOSITION
[K4]

None

Further refinement of source term
estimate used in [U6] with detailed
different temporal pattern that may
have implications in particular for dose
estimates for evacuees

Need to assess the implications of
the temporal distribution of releasefor estimates of doses to evacuees

Based on source term estimation of
Terada et al. [T4] but uses improved
ATDM and additional and extensive
data sets, some not published or used
before. Methodology seems
appropriate

RELEASES TO WATER, DISPERSION AND DEPOSITION (NO PUBLICATIONS IDENTIFIED)
Doses to the public
[S2]

None

Food measurement data are consistent
with those reported [U6], strengthening
the statement that doses for ingestion
estimated using the database on foodmeasurements may be significant
overestimates

Needs to be confirmed by further
studies

Methodological deficiencies cannot
be ruled out

Findings of the 2013 Fukushimareport not likely to be materiallyaffected, but further detailed
evaluation is needed

The need for this re-analysis arose
inter alia from the shortcomings inindividual monitoring discussed in
the 2013 Fukushima report

Doses for workers[M3, Y4]

None

Dose estimates have been revised for
621 workers

HEALTH IMPLICATIONS (NO PUBLICATIONS IDENTIFIED)
Doses and effects for non-human biotaab[H7, N4, T1]

None

Observations of population-level andtransgenerational effects ininvertebrates reported, which is notconsistent with 2013 Fukushima report

Needs confirmation throughmultidisciplinary field studies

Concerns over quality of Taira et al.
[T1] and Nohara et al. [N4] becauseof lack of or poor dosimetry andreference to non-applicable models[M2, M6, M7, M8, M9]

None

Observations of population-level effects
in invertebrates and birds reported,which is not consistent with
2013 Fukushima report

Needs confirmation throughmultidisciplinary field studies

Concerns over quality because of
insufficient dosimetry and unclear
accounting for confounding factors

Denotes a challenge to the assumptions and findings set out in the 2013 Fukushima report sufficient to warrant the Committee considering issuing an addendum to the report.
Denotes a potential challenge to the assumptions and findings set out in the 2013 Fukushima report that, if confirmed, would be sufficient to warrant the Committee considering issuing an addendum to the report.

24 2015 WHITE PAPER

Table 2. Publications identified as challenging or potentially challenging the assumptions and/or findings of the 2013 Fukushima report [U6]

DEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 25

Table 3. Publications considered to make a significant contribution to one or other identified
research need
Research need

Publications making ahigh contribution toresearch need

Publications making a
medium contribution toresearch need

RELEASES TO ATMOSPHERE, DISPERSION AND DEPOSITION
Improve estimates of amount and characteristics of releases toatmosphere as function of time

[A3, K4, T12, W3, Z1][S3, T5]

RELEASES TO WATER, DISPERSION AND DEPOSITION
Measure and improve characterization of leaks of radioactive waterand releases to aquatic environment over time

[Y2]

[B7, K3, T11]

Forecast and quantify long-term transport and mixing of releases
and consequent exposures through aquatic pathways[A2, B4, K7, O2][K1, K10, O3, R1, R2,
T6]

DOSES TO THE PUBLIC
Measure dose rates due to external exposure to deposited material
in various environments, forecast and track changes over time andquantify impact of environmental remediation programmes[H1, T2, T7]

Conduct in vivo measurements of radionuclides in people tosupport refinement in the estimation of doses and their distribution,and to estimate current and future levels of exposure[N1]

DOSES FOR WORKERS
Elucidate the reasons for the differences between internal dose
assessments performed by TEPCO and its contractors for someworkers[Y4]

HEALTH IMPLICATIONS
Analyse and quantify the impact of ultrasonographic surveys on
the apparent incidence of thyroid cancer in Fukushima Prefecture(surveys of thyroid cancer incidence in areas unaffected by theaccident would be useful in this regard)[H4][I7, N2, W1]

DOSES AND EFFECTS FOR NON-HUMAN BIOTA
Measure and assess the environmental exposures typical for certain
species of non-human biota, and further analyse whether radiation
exposure was an important factor in causing environmental effects
reported in field studies but which were inconsistent with theCommittee’s assessment[H7, S4, T1][H2, K5, K6, O1]

262015 WHITE PAPER

Acknowledgements
In approving this white paper, the Committee wishes to acknowledge with gratitude thehelp of the experts directly involved in undertaking follow-up activities relating to levels
and effects of radiation exposure due to the nuclear accident after the 2011 great east-Japan
earthquake and tsunami.
Senior technical advisers
W. Weiss (Germany) and K. Kodama (Japan)
Critical reviewers
N. Harley (United States), G. Hirth (Australia), L. Hubbard (Sweden), P. Jacob (Germany),
J.-R. Jourdain (France), B.I. Min (Republic of Korea), S. Solomon (Australia), K.S. Suh(Republic of Korea)
Project manager (consultant)
G.N. Kelly
Expert group (consultants)
M. Balonov, C. Estournel, G. Etherington, F. Gering, R. Shore, P. Strand
Japanese working group
T. Aono, N. Ban, K. Ozasa, S. Saigusa, T. Takahashi, H. Yasuda

APPENDIX A. COMMENTARY ON COMMON THEMES IN CRITIQUES OF THE 2013
FUKUSHIMA REPORTI.

INTRODUCTION

A1.
The responses to the 2013 Fukushima report [U6] have been generally positive.
However, some critiques have been published. This appendix sets out a commentary by theCommittee that addresses common themes in these critiques. Its aim is to promote better
understanding of the scope, purpose and findings of [U6].
A2.
Some of the critiques were based on the relevant findings in the Committee’s report to
the United Nations General Assembly9 and/or the associated press release rather than on theCommittee’s full report [U6], which was published later, and some reflected amisunderstanding of the Committee’s mandate. In most cases, the 2013 Fukushima report itself
provides an answer to the critique, and, where relevant, the commentary below includes areference to the relevant paragraph number of the full report where more detail can be found.
A3.
The Committee recognized that there were uncertainties associated with many aspectsof its assessment. The 2013 Fukushima report included a review of the main uncertainties, andidentified some of the key priorities for scientific research to extend, corroborate and increase
confidence in the Committee’s evaluations (see paragraph 230 in [U6]).

II.

ESTIMATES OF THE RELEASES OF RADIONUCLIDES FROM
THE ACCIDENTA.

Validity of choice of estimate of releases to the atmosphere

A4.
The 2013 Fukushima report has been criticized for choosing the estimate of releases ofradionuclides to the atmosphere over time developed by scientists from the Japan Atomic
Energy Agency rather than other available, and arguably more impartial, estimates,
particularly those with larger estimates of the release [B1, I2, I4].
A5.
The Committee had based its estimates of doses to the public in the 2013 Fukushimareport primarily on measurements of the levels of radionuclides deposited on the ground and infoodstuffs in Japan. It only used its chosen estimate of the magnitude, time profile and natureof the release of radionuclides to the atmosphere (the “source term”), together with calculationsof the subsequent dispersion of the radionuclides in the environment using atmospherictransport, dispersion and deposition modelling (ATDM) for the following purposes:
9

Official Records of the General Assembly, Sixty-eighth Session, Supplement No. 46 and corrigendum (A/68/46
and Corr.1).

28

2015 WHITE PAPER− Directly to estimate levels of radionuclides in the air and on the ground to which
evacuees were exposed during the early stages of the accident;− To estimate ratios of levels of radionuclides in the air to their levels on the ground inorder to scale measured densities of radionuclides on the ground to infer concentrationsof radionuclides in the air.
A6.
The Committee had reviewed estimates of the source term published up to the end of
March 2013, and made its choice in the light of how it intended to use the source term estimate(see paragraphs 45 and B11 to B16 in [U6]). It had chosen a source term derived by reverse
modelling from, and optimized to fit, measurements of radioactive material in the terrestrial
environment of Japan.
A7.
The Committee acknowledged (see paragraphs 45 and B15 to B16 of [U6]) that it had
adopted a source term for which the total releases of iodine-131 and caesium-137 were both atthe lower end of the ranges of published values. However, if a larger source term had beenused with ATDM, the resulting levels of radioactive material in the terrestrial environment
would have been overestimated and this would have been contrary to the Committee’s intent ofmaking realistic estimates.
A8.
The Committee recognized the uncertainties associated not only with the choice ofsource term but also with the subsequent ATDM. Its 2013 Fukushima report included ananalysis of the robustness and implications of its choice of source term and ATDM
(see paragraphs B52 to B59 and C118 to C119 in [U6]).
A9.
Several more recent estimates of the source term tend to favour the lower ends of theranges of releases given by the Committee in the 2013 Fukushima report (see chapter III of thiswhite paper).
B.

Validity of choice of radiologically significant radionuclides forreleases to the atmosphereA10. The 2013 Fukushima report has been criticized for not including other potentiallysignificant radionuclides (such as isotopes of strontium and plutonium) in the source term forreleases to the atmosphere [B1, I3].
A11. The Committee had based its choice of radiologically significant radionuclides on aconsideration of the chronology of the accident, the conditions in the three reactors that led toreleases, measured levels of radionuclides in the environment, and knowledge and experiencefrom extensive theoretical and experimental investigations of a wide range of postulated
accident conditions (see paragraphs 46 and B17 to B18 of [U6]). The significance of very
short-lived radionuclides in the FDNPS accident was greatly reduced by the delay between
reactor shutdown and when the releases occurred. The fractional release (and therefore
significance) of isotopes of elements such as strontium, barium and plutonium was much lower
than those of isotopes of elements that were included because of their much lower volatilities.
This has been confirmed by measurements in the environment.
A12. The Committee’s quantitative analysis had explicitly included all radionuclides that
could have made a material contribution to the doses estimated and presented in [U6]. This isfurther supported by more recent evidence (see chapter III of this white paper).

DEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 29

III.

SOURCES OF DATA AND THEIR IMPARTIALITY

A13. The 2013 Fukushima report has been criticized for its use of data from organizations(such as the Tokyo Electric Power Company (TEPCO), the operator of the FDNPS, and theInternational Atomic Energy Agency (IAEA)), which are claimed not to be impartial, inparticular being perceived by some as having an interest in minimizing the impacts of theaccident [I2, I3, J1].
A14. The Committee described the sources of data and the processes used to assure thescientific quality and relevance of each dataset for its purposes in its 2013 Fukushima report(see paragraph 4 and appendix A of [U6]). The sources included non-governmentalorganizations as well as a wide range of national and international bodies. The processes
included reviewing the methods used to collect the data and the quality assurance procedures
followed, as well as comparisons and cross-checking between datasets from different sources.
Only information that had been deemed of acceptable quality and fit for the purpose of theCommittee’s assessment was used.
A15. In the few specific instances for which the Committee had any reason to question thevalidity of the data, it had clearly indicated this in its report (e.g. see below – reliability ofdoses to workers).

IV. AVERAGE DOSES AND VARIABILITY BETWEEN INDIVIDUALS
A16. The 2013 Fukushima report has been criticized for presenting average doses to broadgroups of the population of Japan and not indicating the variability about the average or thehigher doses to which many people would have been exposed [B1, I2, I3, J1, P1].
A17. The 2013 Fukushima report made clear that the Committee’s aim was to make realistic
estimates of doses and, to that end, its main focus had been on estimating doses to definedgroups of individuals considered to be representative of the different subsets of the Japanese
population. Accordingly, the report generally presented average doses, at different spatial
resolutions, to different age groups in the population.
A18. The report also included a discussion of the variation about these average doses
between individuals depending on their location and habits. In particular, the spatial variability
in both the measured radionuclide deposition densities and the concentrations of radionuclides
in air was such that the estimates of both effective doses and the absorbed doses to the thyroidfrom inhalation could be from 30–50% of the district-average dose up to about two to threetimes higher than the district-average dose (see paragraph 98 in [U6]).
A19. The Committee also stated that there was significant variability in measured levels ofradionuclides in different foodstuffs. It could not exclude the possibility that some individuals,
particularly those in the deliberate evacuation areas, might have consumed locally-grown food orcollected mushrooms or wild plants, or caught or hunted local fish and game with highconcentrations of radionuclides before their evacuation. Such food habits had the potential toincrease the estimates of effective dose from ingestion for these individuals by up to perhaps ten
times, however there was no evidence of such higher doses in the extensive sets of in vivo
whole-body measurements of the general public. Also, because of the time of year of theaccident, locally-grown food was limited, and many people in Japan took measures to reduce302015 WHITE PAPER

their intake of radionuclides in food by avoiding fresh produce or anything that might have comefrom Fukushima Prefecture. For those people, doses due to ingestion would have beensignificantly lower than those estimated by the Committee (see paragraphs 100–101 in [U6]).

V.

FETAL DOSES AND EFFECTS

A20. The 2013 Fukushima report has been criticized for not specifically assessing doses andeffects to the fetus [I2, I3].
A21. The Committee had not explicitly estimated doses to the fetus but did provide anindication of their magnitude. This was considered sufficient because the doses to the fetus
would have been similar to those to other age groups for which doses were explicitly assessed(adults, children and infants, where 1-year-old infants were used to represent all infants
younger than 5 years old). The Committee had judged that the doses to the fetus from external
exposure were approximately the same as those to adults, and that those from internal exposure
were lower than, or within the range of, doses estimated for the three main age groups(see paragraphs 80, C32, C80 and C97 in [U6]).
A22. In discussing the health implications of the estimated doses, the Committee hadrecognized that relative risks in certain population groups (notably following exposure as fetus,
or during infancy and childhood) are higher than for the population average, and had
considered the risk to those exposed as fetuses during pregnancy (see paragraphs 221 to 224
and E37 in [U6]).

VI. RELIABILITY OF WORKER DOSES
A23. The 2013 Fukushima report has been criticized for basing its assessment of doses toworkers on data provided by the Tokyo Electric Power Company (TEPCO), the operator of
FDNPS, which should not be relied on because of the company’s perceived interest in minimizing
the impacts of the accident. In addition, the 2013 Fukushima report did not adequately address
numerous reports of shortcomings in TEPCO’s monitoring arrangements, including missing
dosimeters, tampering with dosimeters and faulty radiation measuring instruments, or the lack of
information about possible intakes of shorter-lived radionuclides [I2, I3].
A24. The Committee had to rely on data provided, not only by TEPCO, but also by theJapanese authorities, for the assessment of doses to workers, because there were no other,
independent, sources of relevant information. One of the aims of the Committee’s work was tojudge the extent to which the individual doses reported in Japan provided a true and reliablemeasure of the doses actually incurred. The Committee’s assessment therefore comprised,
firstly, a review of the methodologies used in Japan for assessing doses and, secondly,
independent dose assessments for defined groups of workers (including individuals randomly
selected by the Committee) which were then compared with the values reported in Japan.
A25. Further details of its approach and the results were set out in the 2013 Fukushima report(see paragraphs 145 to 155, and appendix D of [U6]). In general, the process had resulted in good
agreement between the dose assessments of the Committee and the Japanese government, butbetter information was needed in some areas. The Committee also made clear that, because of theuse of shared dosimeters and a lack of information about whether conditions for the use of shareddosimeters had been met, it had some reservations about the reliability of the external dosimetry
carried out before 1 April 2011. The Committee also provided an indication of the impact on theDEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 31

assessed doses of the delay in starting in vivo monitoring based on a detailed assessment of thepotential additional doses arising from intakes of shorter-lived radionuclides (see paragraphs D38
to D40 and attachment D−1 of [U6]).

VII. INCONSISTENCIES BETWEEN FINDINGS AND PUBLISHED
FIELD STUDIES ON NON-HUMAN BIOTA
A26. The 2013 Fukushima report has been criticized for not taking adequate account ofevidence from field studies from both the Fukushima-Daiichi and Chernobyl accidents ofobserved effects on non-human biota [I4].
A27. The 2013 Fukushima report included a summary of the findings of a few field studies
published up to December 2012 (see paragraphs 197 and F4 to F6 of [U6]). However, theCommittee noted that uncertainties with regard to dosimetry and possible confounding
factors (including the impact of the tsunami itself) made it difficult to substantiate firm
conclusions on a causal relationship with radiation exposure. Furthermore, the main body ofexisting scientific data did not support the appearance of the observed effects at the dose
rates recorded. The Committee identified the need for further analyses of whether radiation
exposure was an important factor in causing the environmental effects reported in fieldstudies as a priority for future research. This need is reinforced by more recent publications(see chapter VIII of this white paper).

VIII. HEALTH RISKS
A.

Discernibility

A28. The 2013 Fukushima report has been criticized for stating that no discernible increases in
the future incidence of health effects due to radiation exposure would be expected either among
workers or the public. Some critics stated that the concept of “no discernible increase” in risk is
not valid from a public health perspective and is inconsistent with the international scientificconsensus that there is no threshold below which radiation poses no harm [B1, I2, I3, P1]. At thesame time, other critics [S1] called on the Committee to make a firm, unconditional statement to
the Fukushima residents that returning to their homes would not increase their risk of cancer andthereby overcome the “disastrous consequences” of the use of the linear no-threshold model forradiation-induced cancers and its associated no-safe-dose mantra.
A29. The 2013 Fukushima report included a commentary on the immediate and long-term
health implications of exposures to ionizing radiation resulting from the accident at FDNPS(see paragraphs 156 to 167 and appendix E in [U6]). The Committee estimated risks due toexposure for members of various exposed groups based on its own dose estimates, its estimatesof disease risks from exposures to ionizing radiation, and the results of the WHO report [W2].
The Committee’s commentary considered qualitative and quantitative estimates of potential
disease outcomes among the exposed populations that may or may not be observable in future
disease statistics. Further analysis of the power of epidemiological studies to detect increases in
the frequency of disease occurrence given the numbers of people exposed as a result of the
FDNPS accident can be found in electronic attachment 1 to this white paper.
A30. In its commentary, the Committee used the phrase “no discernible increase” to express
the idea that currently available methods would most likely not be able to demonstrate an322015 WHITE PAPER

increased incidence in the future disease statistics (i.e. an increased frequency of disease
occurrence) due to irradiation. The 2013 Fukushima report made clear that the use of thisphrase did not equate to absence of risk or rule out the possibility of excess cases of disease
due to irradiation, nor to the possibility of detection of a biomarker for certain types of cancer
in certain subgroups being identified in the future that could be associated with radiation
exposure; moreover, it was not intended to disregard the suffering associated with any suchcases should they occur.
A31. The Committee is a body dealing with science alone; it does not have the mandate totake that science and develop public health policy. It has recognized that public healthauthorities may calculate risks based on certain assumptions at doses well below the levels at
which effects have been observed.
B.

Non-cancer diseases and hereditary effects

A32. The 2013 Fukushima report has been criticized for not assessing the risks of noncancer health effects, such as cardiovascular diseases, endocrinological and gastrointestinal
disorders, infertility, genetic mutations in offspring and miscarriages [I2, I3].
A33. The 2013 Fukushima report included a brief recapitulation of knowledge on healtheffects and risks from exposure to ionizing radiation that covered all known effects (seeparagraphs 164 and E4 to E14 in [U6]). The Committee had concluded that exposure ofmembers of the public fell well below the thresholds for deterministic effects (see paragraph
168 in [U6]). It had also concluded that exposure during pregnancy was not expected toincrease the incidence of spontaneous abortion, miscarriages, perinatal mortality, congenitaleffects or cognitive impairment (see paragraphs 178 and 224 in [U6]).
A34. No early deterministic health effects had been observed among the workers with thehighest doses to the thyroid, but the Committee could not preclude the possibility of
hypothyroidism among the most exposed workers. The Committee had concluded that risks forcirculatory disease resulting from radiation exposure were very low for those most exposed.
However, the Committee had had insufficient information on exposures of the eye lens to reachan informed judgement on the risk of cataracts (see paragraphs 184 and 186 in [U6]).
A35. An increased incidence of hereditary effects has not been reliably demonstrated inhumans for any level of exposure, and it was not expected to be possible to demonstrate thisamong the general public or workers following the FDNPS accident (see paragraph 166 in [U6]).
C.

Effects from combined exposure to radiation and other pollutants

A36. The 2013 Fukushima report has been criticized for not considering the possibility that
exposure to hazardous chemical contamination, resulting from the effects of the earthquake
and tsunami on other industrial facilities, may severely confound the relationship between
radiation exposure and carcinogenic effects [I4].
A37. The Committee considered the issue of the combined effect of ionizing radiation withother physical, chemical and biological agents in its reports of 1982 and 2000 [U2, U4]. The
2000 report [U4] included a detailed review of the available evidence on combined effects. It
concluded that, except for radiation and smoking, there was no evidence that low-level
exposures to multiple agents yielded combined effects far from additivity (i.e. from what

DEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 33

would be expected from adding the effects of each agent separately), or above the estimates
resulting from linear extrapolation of single agent effects to lower doses.
D.

Thyroid anomalies

A38. The 2013 Fukushima report has been criticized for deficiencies in its discussion of theapparently high prevalence of thyroid anomalies that are being found in the health screening
being carried out in Fukushima Prefecture, specifically over “assurances” based oncomparisons with a cohort of Ukrainians and the results of a survey carried out in prefectureslargely unaffected by the accident [I2, I3].
A39. In the 2013 Fukushima report, the Committee concluded that most of the absorbed doses
to the thyroid of members of the public were in a range for which an excess incidence of thyroid
cancer had not been observed in epidemiological studies, although doses towards the upperbounds of the ranges could imply an increased risk for individuals that among sufficiently large
population groups might lead to discernible increases in the incidence of thyroid cancer due toradiation exposure. The Committee concluded that a large number of radiation-induced thyroid
cancers as had been observed after the Chernobyl accident, could be discounted because doses
were substantially lower (see paragraph 175 in [U6]).
A40. The Committee did not provide any “assurances”. It reviewed the information available
at the time from the thyroid ultrasound examinations that were being carried out for individuals
in Fukushima Prefecture and noted that thyroid nodules had been detected in about 1% of thosesurveyed and thyroid cysts in about 40% of those surveyed. It further noted that, in a survey
using similar equipment that had been made in prefectures largely unaffected by the accident,
the observed prevalence of thyroid nodules and cysts was even larger, suggesting that theintensive screening and the highly sensitive nature of the equipment being used could explain
the high detection rate of nodules and cysts. The prevalence of some types of asymptomatic
thyroid cancers (that would remain latent, but would be detectable in the surveys being
conducted) could be as high as 35% in many parts of the world, according to findings from
autopsies (see paragraphs 180 to 181 and E48 in [U6]). This interpretation is supported bymore recent evidence (see chapter VII of this white paper).
E.

Collective dose

A41. The 2013 Fukushima report has been criticized for presenting estimates of thecollective doses to the Japanese population from the accident, but not presenting estimates ofthe expected cancer cases that would result based on “internationally accepted”, no-thresholdmodels [B1, I3, I4, J1, P1].
A42. The Committee’s views on the usefulness of collective dose estimates were recently
summarized in its report to the sixty-seventh session of the United Nations General Assembly. 10
The Committee had concluded, inter alia, that “an increased incidence of stochastic effects in a
population could be attributed to radiation exposure through epidemiological analysis —provided that, inter alia, the increased incidences of cases of the stochastic effect were sufficient
to overcome the inherent statistical uncertainties. In this case, an increase in the incidence ofstochastic effects in the exposed population could be properly verified and attributed to
10

Official Records of the General Assembly, Sixty-seventh Session, Supplement No. 46 (A/67/46).

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exposure”. “In general, increases in the incidence of health effects in populations cannot be
attributed reliably to chronic exposure to radiation at levels that are typical of the global averagebackground levels of radiation. This is because of the uncertainties associated with theassessment of risks at low doses, the current absence of radiation-specific biomarkers for healtheffects and the insufficient statistical power of epidemiological studies. Therefore, the ScientificCommittee does not recommend multiplying very low doses by large numbers of individuals [i.e.
estimating collective dose, and using this] to estimate numbers of radiation-induced health effects
within a population exposed to incremental doses at levels equivalent to or lower than natural
background levels.” The Committee noted, however, that “public health bodies need to allocate
resources appropriately, and that this may involve [estimating collective dose and/or] making
projections of numbers of health effects for comparative purposes. This method, though based
upon reasonable but untestable assumptions, could be useful for such purposes provided that it
was applied consistently, the uncertainties in the assessments were taken fully into account, and it
were not inferred that the projected health effects were other than notional”.

IX. UNSCEAR COMMITTEE
A.

Composition

A43. The Committee has been criticized for not being balanced in respect of pro- and antinuclear sympathies and for not being clearly free from conflicts of interest or bias [B1, C2].
A44. The Committee’s mandate in the United Nations system (as set out by the General
Assembly in resolution 913 (X) of 3 December 1955) is the science of the matter – it is neither
pro- nor anti-nuclear nor, indeed, pro- nor anti- any other activity that involves the use or
production of radiation or radioactive material (e.g. in medicine, research or industry). The
Committee assesses and reports on the levels and effects of exposure to ionizing radiation fromall sources, including natural sources.
A45. The governing principles of the Committee place expectations on its members to be freeof conflict of interest. All those working on the 2013 Fukushima report signed a formal
declaration of any potential conflicts of interest. The selection of those involved in theassessment work was based on proposals made by the national representatives to UNSCEAR; thekey selection criteria were scientific excellence and competence in the relevant scientific fields.
B.

Japanese funding

A46. The Japanese government made a voluntary contribution to support “the vital role
UNSCEAR plays in the safety of nuclear energy” [U1]. This contribution has been claimed to havebeen made for the purposes of “removing unnecessary concerns about radiation effects” [I3].
A47. The Secretariat of the Committee is financed by the United Nations and administeredthrough its environment programme (UNEP). In May 2007, in response to a resolution of theUnited Nations General Assembly urging UNEP to review and strengthen the funding of
UNSCEAR, the Executive Director of UNEP, in common with practice in other areas of UNEP’swork, had established a general trust fund to receive and manage voluntary contributions to
support the work of the Committee. Since the establishment of this trust fund, the United Nations
General Assembly had regularly encouraged Member States to consider making voluntaryDEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 35

contributions to the trust fund. Several countries have contributed (namely, Australia, Canada,
Germany, Indonesia, Sweden, and Switzerland) and Japan and Spain are recent additions.
A48. The trust fund is intended to support the Committee in fulfilling its mandate, which isto undertake scientific assessments of the sources of ionizing radiation and its effects on humanhealth and the environment. The Committee’s reports are based on science and are neutral withrespect to policy. The Committee does not develop policy or provide advice to governments orregional or international bodies. However, many governments and relevant bodies choose to
make use of the Committee’s scientific evaluations for their own development of policies andthus the Committee may be considered to play a “vital role” in the safety of nuclear energy.
A49. For the purposes of the 2013 Fukushima report, the contributions in kind of more than
80 experts at no cost to the United Nations, and their support staff in national institutes, weremore significant than the financial contributions to the trust fund.
C.

Delay in publishing the report

A50. The Committee has been criticized because of the delay between the review of thereport by the Committee and its publication, which has been attributed to “disputes between
members of the committee” and “the need for the report to be worded correctly” [B1].
A51. The main findings of the assessment were approved by the Committee and submitted
to the United Nations General Assembly in October 2013. This was in line with theCommittee’s planned schedule. The full report with supporting scientific annex andappendices was published in April 2014. The six-month period was taken up with further
extensive and detailed checking of the data, the assumptions and the methods used to assure
the quality and robustness of the assessment, and publication matters. This period was notexcessive, given that the report extended to nearly 300 pages, was supported by 28 electronic
attachments and involved the work of more than 80 scientific experts from around the world,a significant number of whom were involved in reviewing and checking drafts of the
document for quality assurance purposes.

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150*1507428*unscear.org

In 1955 the United Nations General Assembly established the Scientific Committee on
the Effects of Atomic Radiation (UNSCEAR) in response to concerns about the effectsof ionizing radiation on human health and the environment. At that time fallout fromatmospheric nuclear weapons tests was reaching people through air, water and food.
UNSCEAR was to collect and evaluate information on the levels and effects of ionizing
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prohibiting atmospheric nuclear weapons testing was negotiated in 1963.

15-07428 (V.15-05060)

Over the decades, UNSCEAR has evolved to become the world authority on the global
level and effects of atomic radiation. UNSCEAR’s independent and objective evaluationof the science are to provide for—but not address—informed policymaking and decisionmaking related to radiation risks and protection.