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 2016 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 2016 white paper
to guide the Scientific Committee’s
future programme of work

UNITED NATIONSNew York, 2016

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.
© 2016. United Nations for the English edition.
© 2016. 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 ................................................................................... 3IV.

UPDATES ON RADIONUCLIDE RELEASES TO WATER,DISPERSION AND DEPOSITION ................................................................................... 8V.

UPDATES ON TRANSFER OF RADIONUCLIDES IN TERRESTRIAL
AND FRESHWATER ENVIRONMENTS ..................................................................... 11

VI.

UPDATES ON EVALUATION OF DOSES FOR THE PUBLIC .................................. 14VII. UPDATES ON EVALUATION OF DOSES FOR WORKERS ..................................... 21
VIII. UPDATES ON HEALTH IMPLICATIONS FOR WORKERS AND PUBLIC ................. 23
IX.

UPDATES ON EVALUATION OF DOSES AND EFFECTS FOR NONHUMAN BIOTA .............................................................................................................. 28

X.

CONCLUSIONS .............................................................................................................. 32

ACKNOWLEDGEMENTS ....................................................................................................... 34
REFERENCES ........................................................................................................................... 35

The attachment cited in this white paper is electronically available for download fromhttp://www.unscear.org/unscear/en/publications/Fukushima_WP2016.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 seventy-first session of the United Nations General Assembly.1[…]
9.
The Committee recalled its assessment of the exposures and effects due to the
nuclear accident after the 2011 great east-Japan earthquake and tsunami, as presented in its
report to the sixty-eighth General Assembly in 2013 (A/68/46) and the supporting detailed
scientific annex. 2 It had concluded in that report that, in general, doses were low and that
therefore associated risks were also likely to be low. Cancer rates were expected to remain
stable. Nevertheless, in the report the Committee had noted a possibility that the risk ofthyroid cancer among those children most exposed to radiation could increase. However, italso noted that the likelihood of a large number of radiation-induced thyroid cancers inFukushima Prefecture—such as after the Chernobyl accident—could be discounted because
absorbed doses to the thyroid after the Fukushima accident were substantially lower. It hadconcluded that no discernible changes in the incidence of birth defects and hereditarydisease were expected, and that the effects on terrestrial and marine ecosystems would betransient and localized. Cancer rates for workers were expected to remain stable.
10.
Following its assessment, the Committee put in place arrangements for follow-up
activities to enable it to remain abreast of additional relevant information as it was published.
The Committee’s report of its sixty-second session to the seventieth General Assembly
included the findings from the follow-up activities it had conducted up to that time.
11.
The Committee continued to identify further information that had become available
up to the end of 2015, and systematically appraised relevant new publications to assess theirimplications for its 2013 report. A notable publication was the report by the International
Atomic Energy Agency (IAEA) on the accident at the Fukushima Daiichi nuclear power
station. 3 It describes the accident and its causes, evolution and consequences based on an
evaluation of data and information from a large number of sources available at the time it
was written. That report and a large proportion of the new publications again confirmed themain assumptions and findings in the Committee’s 2013 report. None of the publications
materially affected the main findings in the 2013 report or challenged its major assumptions.
Several publications were identified for which further analysis or more conclusive evidence
from additional research was needed. On the basis of the material reviewed, the Committee
saw no need, at the current time, to make any change to its overarching conclusions.
However, several of the research needs identified by the Committee had yet to be addressed
fully by the scientific community.
12.
The Committee plans to continue to identify and systematically appraise new
information on the accident, and evaluate the outcomes periodically at its annual sessions. It
also plans to actively engage with those responsible for formulating, implementing andadvising on major research programmes in Japan, in order to rapidly assimilate emerging
1

Official Records of the General Assembly, Seventy-first session, Supplement No. 46 (A/71/46).
United Nations publication, Sales No. E.14.IX.1.
3
International Atomic Energy Agency, The Fukushima Daiichi Accident: Report by the Director General(GC(59)/14), accompanied by technical volumes 1-5.
2v

issues, and highlight questions needing further research. At an appropriate time, dependent
on the outcomes, the Committee expects to consider the need to update its 2013 report.
13.
The Committee requested the secretariat, subject to available resources, to publish
the findings of its systematic review of new scientific literature as a non-sales publication in
English and also to foster its publication in Japanese.

vi

I.

INTRODUCTION

1.
The Committee had assessed radiation exposures of the public, workers and non-humanbiota that resulted from the 11 March 2011 accident at the Fukushima Daiichi nuclear power
station (FDNPS), considered 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 scientific annexes
underpinning them on 2 April 2014 [U3]. The publication (referred to hereafter as the “2013report”) 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 theforeseeable future. The Committee intends to remain abreast of such developments because
they may have implications for the results of its assessment (for example in corroborating,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 previous findings. The Committee expects that providing sound scientificappraisal of new material will also help (a) those affected by the accident to better understandthe situation and (b) inform decision-making.
3.
Accordingly, at its sixty-first session (21–25 July 2014), the Committee had requested
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 radiological consequences of the
Fukushima Daiichi accident”. It also asked the secretariat to “promptly develop a standing
mechanism to stay aware of new scientific developments in the follow-up to the accident. Thatmechanism should be based on the ad hoc arrangements that had been developed for
conducting its recent assessment of the accident. The Committee also asked the secretariat toreport annually on the implications for the Committee’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 twophases: Phase I, a systematic and ongoing review of new information; and Phase II, an updateof the 2013 report at an appropriate time. The overall aim of Phase I (up to at least 2016 andbeyond) is to “keep the Committee regularly apprised of the implications of new publications
and research activities related to the accident with a view to initiating a formal update of the2013 report (i.e. Phase II) at an appropriate time”. 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

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2016 WHITE PAPER(c)
To promptly identify inconsistencies between information issued after October 2012
and the 2013 report;(d) To conduct ad hoc analyses to help clarify the situation and which could be usedsubsequently in any update of the 2013 report;(e)

To respond to questions and critiques of the 2013 report;(f)

To report annually to the Committee at its regular sessions on the outcomes of the above.

5.
At its sixty-second session, the Committee agreed to the publication of a white paper 5
setting out: (a) an assessment of the implications of new scientific developments (up till theend of 2014) for the findings of the 2013 report; and (b) a commentary on general themes
raised in the few critiques made of the 2013 report. In addition, two electronic attachments
were made available providing additional technical information that supplemented the 2013
report. This first white paper was published in October 2015 [U4].
6.
This second white paper sets out a further assessment of the implications of newscientific developments (since the first white paper and up to the end of 2015) 6 for the findingsof the 2013 report. It provides a summary of the main outcomes of the follow-up activities that
underpin the findings reported by the Committee to the General Assembly.

II.

EVALUATION OF NEW INFORMATION

7.
The scope of new information analysed by the Committee in its first white paper was,in general, restricted to publications in English in peer-reviewed journals which had not been
included or referenced in the 2013 report (i.e. published after October 2012, the cut-off datethat had been generally adopted for information analysed in the report), but which had become
available or published before the end of 2014. This second white paper covers information notpreviously considered that has become available or published before the end of 2015. In
principle, the scope of the second white paper was extended to include not only publications inpeer-reviewed journals, but also peer-reviewed conference papers, reports issued byregional/national institutes/organizations, government departments/ministries, learned societies,
utilities, and similar bodies, 7 reports issued by intergovernmental organizations, and major
compilations 8 (and/or analyses) of data from official and other sources. In practice, only one
publication was identified for review from these additional categories: the report on the
Fukushima accident published by the International Atomic Energy Agency (IAEA) [I2].
8.
The approach the Committee used to identify, screen and appraise new information was
as described in the first white paper, with the exception of the introduction of a new topicalarea, that of transfer through the terrestrial and freshwater environments. Introducing this5

White papers are documents developed for the Committee to guide its future programme of work and that theCommittee has decided to share with the wider community.
6
Publications considered for this white paper comprised those which had not been reviewed in the previous white
paper and which had become available up to the end of 2015, including publications which had been made available
online. This white paper therefore includes some publications with an earlier publication date than 2015 and somewith a final publication date in 2016.
7
In exceptional cases, the scope was extended to scientific reports issued by non-governmental organizations.
8
Large volumes of data continue to be generated and published at relatively frequent intervals by various
Japanese organizations, and it would not be practicable to include all of these for review within this project.
Consideration has, therefore, been limited to more substantive compilations of data that have the potential to be
useful in the context of any future reassessment or in extending the scope of any such reassessment.

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

additional topical area enabled the Committee to explicitly consider the implications of theincreasing number of publications in this field. In screening potentially relevant publications
and selecting those which should be subject to more detailed appraisal, particular consideration
was given to whether the publication had the potential to:− Challenge 9 the assumptions in the 2013 report;− Materially affect the conclusions of the 2013 report; or− Address research needs either identified in the 2013 report or in topical areas where awide consensus was emerging.
As a result, this white paper has a greater focus on new information that may potentiallychallenge the assumptions and conclusions of the 2013 report, rather than on new information
which confirms these assumptions and conclusions. It also highlights some of the more
relevant information which has become available that would be valuable to any futureassessment of the impacts of the accident at FDNPS. However it is not intended to provide acomprehensive overview of all new information relating to the FDNPS accident.
9.
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 isprovided of the findings of the 2013 report, because these provide the context for the review, as
well as of the conclusions of the previous white paper. This is followed by a summary of theoutcomes of the appraisals, and conclusions about the implications both for the 2013 report andany follow-up activities. Finally, chapter X sets out overall conclusions from this second white
paper and includes a tabular summary of those sources of new information deemed to make asignificant contribution to addressing identified research needs.

III. UPDATES ON RADIONUCLIDE RELEASES TO ATMOSPHERE,DISPERSION AND DEPOSITIONA.

Recapitulation of the 2013 report

10.
The Committee had reviewed estimates of total releases to the atmosphere of 131I and137
Cs (the two most significant radionuclides from the perspective of exposures of people andthe environment). These estimates had ranged generally from 100 to 500 petabecquerels (PBq)
for 131I and from 6 to 20 PBq for 137Cs. The averages of the published estimates were about
10% and 20%, respectively, of the corresponding releases to the atmosphere estimated for the
Chernobyl accident. Much of the released material was dispersed over the Pacific Ocean, but,depending on the meteorological conditions, a fraction was dispersed over eastern mainland
Japan, and radioactive material was deposited on the ground by means of (a) dry deposition,and (b) wet deposition with rain and snow. The main deposition on land occurred to the northwest of the FDNPS site, but significant deposition also occurred to the north, south and west of
the FDNPS site.
9

A publication would be considered to challenge an assumption in the 2013 report or materially affect its
conclusions if its implications were sufficient to warrant the Committee considering issuing an addendum to the2013 report.

42016 WHITE PAPER

11.
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, 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 and resulting doses to people. The Committee had chosena published source term for this purpose [T12]. The releases of the radiologically dominantradionuclides 131I and 137Cs in this source term were 120 and 8.8 PBq, respectively. While atthe 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 result of dispersion over the land mass of Japan (see paragraphs B15–B16
in [U3]).
B.

Findings of review of new publications

12.
The first white paper concluded that no publications had been identified in this area thatmaterially affected the main findings or challenged the major assumptions of the 2013 report;
several publications confirmed the assumptions in whole or part. One publication was
identified that provided a refinement of the source term estimate used in the 2013 report [K3],and the Committee recommended the use of this refinement in preference in any subsequentstudies, although it did not expect that its use would alter significantly the doses estimated in
the 2013 report.
13.
Of the publications considered in this second white paper, 12 peer-reviewed journal
papers and the IAEA report [I2] have been reviewed in detail. Many confirmed theassumptions and findings of the 2013 report in whole or in part. The main implications of thefindings of these publications are summarized below.
14.
The IAEA report [I2] included reviews of numerous peer-reviewed papers and otherrelevant data sources published up to the first quarter of 2015. It provided estimates of the total
amount and characteristics of releases to the atmosphere. It did not provide any further detailed
information on the releases as a function of time beyond what was available for theCommittee’s assessment in the 2013 report. Excluding the very early estimates made inMarch/April 2011 on the basis of limited information, the IAEA report estimated the ranges of
releases of 133Xe, 137Cs and 131I to atmosphere to be 6,000–12,000 PBq, 7–20 PBq and100-400 PBq, respectively. These ranges agree well with those set out in the Committee’s 2013
report of about 7,000 PBq for 133Xe, 6–20 PBq for 137Cs and 100–500 PBq for 131I. Most of theradioactive material released to the atmosphere was blown eastward by the prevailing winds,
depositing onto and dispersing within the northern Pacific Ocean. Uncertainties in estimationsof the amount and composition of the radioactive substances released were difficult to resolve
for reasons that included the lack of monitoring data on the deposition of the atmosphericreleases on the ocean [I2].
15.
Lebel et al. [L2] analysed available measurements of the forms in which iodine wasreleased from FDNPS and how these forms changed during dispersion in, and deposition from,the atmosphere. They estimated that, overall, about one half of the iodine had been released ina volatile or gaseous form, with the other half released as a particulate. They analysed thevariation in the ratio of measured levels of airborne iodine and caesium with distance fromFDNPS, and concluded that iodine released in a volatile or gaseous form comprised bothelemental and organic forms, although the relative amounts released of each remainedDEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 5

uncertain. This is contrary to the assumption in the 2013 report that one half of the iodine wasreleased in an elemental form with the other half as a particulate (i.e. release of iodine in an
organic form was not assessed).
16.
In light of the conclusions of Lebel et al. [L2], explicit account should be taken, forcompleteness and additional rigour, of releases of iodine in organic forms in any future updateof the 2013 report. For plausible assumptions as to the fraction of iodine released in organic
forms, the thyroid doses estimated in the 2013 report for those evacuated would decrease by asmall amount (i.e. perhaps about ten to twenty per cent). For those not evacuated, the estimateddoses would increase by a factor depending on distance from FDNPS. At short distances,where doses were highest, any underestimation would be unlikely to exceed several tens of
per cent. At larger distances, the potential underestimation would be larger but the estimatedlevels of dose at such distances were very small. Katata et al. [K3], in updating the source term
[T12] used in the 2013 report, have provided an indication of the amount of iodine that may
have been released in organic forms, based on experimental and other evidence.
17.
Leadbetter et al. [L1] investigated the impact of different meteorological datasets anddifferent wet scavenging coefficients on the model predictions of radionuclide deposits
following the accident at FDNPS. Saito et al. [S1] described improvements in macro-scaleatmospheric transport models that included new approaches to modelling deposition, e.g.
newly implemented algorithms for simulating dry deposition, wet scavenging, and gravitational
settling of radionuclide aerosol particles. With this work both groups of authors addressed theneed for further improvement in modelling wet deposition in atmospheric transport models,
which had been highlighted in the 2013 report.
18.
Christoudias and Lelieveld [C1] and Evangeliou et al. [E1] confirmed that winds
transported a large portion of the atmospheric releases over the Pacific Ocean, as noted in the2013 report. Evangeliou et al. estimated that around 23% of the released 137Cs was depositedover Japan and 76% over the oceans (North Pacific and North Atlantic); Christoudias andLelieveld estimated that about 80% of the radioactive material released from FDNPS was
deposited on to the Pacific Ocean. The data presented on the deposition of radionuclides invarious countries and regions of the world may be useful for subsequent assessments.
19.
Hirayama et al. [H8] assessed the time distribution of 131I concentration in air frommeasurements made at several monitoring posts in Fukushima Prefecture in March 2011 using
peak count rates and the calculated response of NaI(Tl) detectors. The data provide a newsource of information on 131I concentrations in air during the first days of the accident and thus
have the potential to improve knowledge about radioiodine concentrations in air, for whichvery few direct measurements have previously been published. Hirayama et al. have compared
the concentrations of 131I in air integrated over time derived from these monitoring data withinformation set out in the 2013 report (table B10) based on ATDM predictions for particularlocations and times. No firm conclusions could, however, be drawn from this comparison
because of differences between the locations of the monitoring posts and the few locations forwhich relevant ATDM predictions had been presented in the 2013 report.
20.
The Committee has carried out a more rigorous comparison of the measurements ofHirayama et al. with its own estimates of 131I concentrations in air at nearby locations; the latterhad been used to underpin the 2013 report. An electronic attachment has been developed toprovide the detailed comparison. For some of the monitoring posts (i.e. those at Okuma andFutaba), the time series of measurements presented by Hirayama et al. were incomplete, with

6

2016 WHITE PAPER

no measurements 10 over time periods when the ATDM analysis indicated high levels of 131I
concentration in air; thus, no valid comparisons could be made for these locations (other thanfor more limited time periods when 131I concentrations in air based on measurements werelow). For three other monitoring posts (Shoukan/Naraha, Futatunuma/Hirono, andMomijiyama/Fukushima City), the time-integrated 131I concentrations in air that had been
estimated using ATDM ranged from a factor of about 2 times higher to about 8 times lower
than the corresponding measurements presented by Hirayama et al. Such differences are notsurprising given the uncertainties in ATDM predictions, uncertainties in the methods used (andacknowledged) by Hirayama et al., and differences between the exact location of themonitoring posts and where ATDM estimates had been made. For two of these locations, timeintegrated 131I concentrations in air (and doses via inhalation) in the 2013 report had been
estimated, not from ATDM alone, but by using ATDM estimates to scale measurements ofdeposition densities. For these two locations, the time-integrated 131I concentrations in air
estimated in this way were only a few tens of per cent lower than those estimated by Hirayama
et al. The good agreement between the measured levels and those predicted using ATDM in
combination with measured deposition levels—albeit for only a few locations—provides added
confidence in the robustness of the methodological approach used in the 2013 report toestimate radionuclide concentrations in air and doses via inhalation.
21.
The data presented by Hirayama et al. also provide support for the estimates made in
the 2013 report of 131I concentrations in air (and subsequently doses via inhalation) to which
evacuees were exposed prior to their evacuation from Futaba and Okuma. These evacuations
were completed before 12 March 2011 and the ATDM estimates indicated that there would
have been no exposures prior to this time. The measurements at Futaba and Okuma show thearrival of air masses with elevated concentrations of 131I at varying times during the day of
12 March (i.e. after the evacuation had been completed) and, as such, confirm the dose
estimates in the 2013 report.
22.
Muramatsu et al. [M16] confirmed the understanding summarized in the 2013 reportthat the plume containing higher 131I/137Cs ratios moved in a southerly direction. Furthermore,they concluded that there was good agreement between the 131I deposition map as constructedfrom the direct measurements of 131I [S2] and that reconstructed from later measurements of
129
I. The newly reconstructed data for 131I deposition (based on measurements of 129I in soil
samples) has the potential to further improve estimations of the 131I source term and also to
improve assessments of doses to inhabitants and evacuees from inhalation. Analysis of theremaining soil samples from the very large soil sampling campaign has the potential to provide
valuable additional data in the future about the initial deposition of 129I and 131I.
23.
Oura et al. [O7] presented a comprehensive new dataset of hourly concentrations of
Cs and 137Cs in air, derived from samples automatically collected on filter tapes at 99 air
quality monitoring stations from 12 to 23 March, 2011, in eastern Japan. This dataset provides
a new and unique source of information about radiocaesium concentrations in air at a large
number of monitoring stations and with a high resolution in time. The dataset could enableimproved source term estimates, an improved assessment of the levels of radionuclides in air,and an improved assessment of inhalation doses which could potentially challenge the findingsof the 2013 report. This can only be judged by a more detailed comparison with theassumptions and data used in the 2013 report. The authors stated that they are in the process of134

10

The reasons for the absence of measured levels during these periods are not fully clear (an additional publication by
Hirayama et al. [H7] stated that data for these monitoring posts after 14 March 20:00 JST “could not be analysed because of adrastic increase or a lack of data”), but may have resulted from failure of the equipment or saturation due to the passage of air
masses with highly elevated concentrations of radionuclides.

DEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 7

carrying out similar analysis of the remainder of the approximately 400 air quality monitoring
stations and providing information about concentrations in air for many more locations, and forother radionuclides in the future.
24.
Steinhauser et al. [S10] reported the results of an analysis of weekly air filter
measurements, which revealed sporadic releases of radionuclides long after FDNPS wasstabilized. This article indicated that secondary releases of radioactive materials werepossible—even years after the accident—because of decommissioning and dismantling
activities on the FDNPS site. The estimated size of these secondary releases was small incomparison with the releases in the immediate aftermath of the accident, and their impact forassessed doses (both in the past and in the future) is therefore negligible.
25.
Akimoto [A3] reported on measurements of radiocaesium concentration in the air anddeposited on the ground in Fukushima City during the period from June 2011 until July 2013.
These measurements showed that resuspension of deposited radiocaesium led to only very low
concentrations in air, confirming the assumption made in the 2013 report that the contributionof resuspension to doses was negligible.
C.

Potential implication of new publications

26.
The Committee has noted the new data that are becoming available on concentrations in
air of 131I, 134Cs and 137Cs as a function of time, on 131I deposition based on measurements of
129
I in soil samples, and on the chemical form of the iodine released. These data have thepotential to significantly improve source term estimates, and estimates of the levels ofradionuclides in the air and deposited on the ground. Similar analyses of other existing samples
are expected to yield further data in the near future. A detailed comparison of these new datawith those used in the 2013 report would be needed to fully understand their implications.
27.
The Committee has identified that research in the following specific areas would havethe greatest potential to contribute to addressing the needs identified in the 2013 report:(a) Continuing to investigate the modelling of wet deposition in atmospheric transportand dispersion models;(b)Continuing to improve inverse and reverse modelling to estimate the source term;(c) Improving current estimates of the source term making use of all available
measurement data, in particular the new data on 131I deposition reconstructed frommeasurements of 129I deposition, on 131I concentrations in air and on 134Cs and 137Csconcentrations in air;(d) Extending the reconstruction of 131I deposition based on 129I measurements to theremaining soil samples;(e) Extending the measurements of radionuclide concentrations on filter tapes from air
quality monitoring stations to the remaining filter samples;(f) Analysing and comparing the new data on 131I, 134Cs and 137Cs concentrations in air
against previous monitoring and modelling results;(g) Analysing emerging data on aerosol particle size and speciation measurements for137
Cs to better determine inhalation characteristics for the purposes of estimating doses.

82016 WHITE PAPER

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

Recapitulation of the 2013 report

28.
The Committee had concluded that the direct discharges 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 threedimensional modelling. In addition, the Committee had concluded that the release to the ocean
from deposition from the atmosphere was about 60–100 PBq for 131I and 5−8 PBq for 137Cs,
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 (6.8 × 107 Bq/m3) on 7 April 2011 and weregenerally below 200 Bq/L (2 × 105 Bq/m3) 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, than near 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.
29.
At the time the 2013 report was finalized, radioactive water had still been leaking on
the site, and groundwater had been transporting radionuclides into the aquatic environment.
The Committee had also noted the appearance of significant amounts of fission and activation
products in stagnant water in the basements of the reactor and turbine buildings. The
Committee had identified that key priorities for scientific research were to improve thecharacterization of the leaks and releases to the aquatic environment, and forecasting andquantifying the long-term transport and mixing of these releases.
B.

Findings of review of new publications

30.
The Committee concluded in the first white paper that its findings in this area of the2013 report remained valid and were largely unaffected by new information that had since been
published.
31.
Of the publications considered in this second white paper, 14 peer-reviewed journal
articles and the IAEA report [I2] were reviewed in detail. None contradicted the findings of the2013 report, and several confirmed the assumption of a general decreasing trend of the directdischarge to the ocean. Several publications addressed identified research needs. Their
contributions are summarized in the following paragraphs.
32.
The IAEA report noted that there was considerable variation between different
estimates of the direct discharge to the ocean published between 2011 and 2013. Thisvariability was considered to be due to the large uncertainties in the different oceanic
circulation and radionuclide dispersion models and in the different modelling approaches usedby each study, and the lack of spatially distributed observations in the surrounding region. The
report noted that the direct discharges and releases of 137Cs were generally estimated to be in
the range 1–6 PBq, but that there were assessments that had reported estimates up to 26.9 PBq.
Estimates of this magnitude had also been noted in the 2013 report, but the Committee had

DEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 9

considered them to be less reliable because they had generally been derived with extrapolation
methods assuming constant dispersion rates.
33.
Aoyama et al. [A7] derived estimates of the total release to the atmosphere and then to
the ocean by deposition. The authors estimated the inventory of 137Cs in the ocean frommeasurements of concentrations of 134Cs and 137Cs in surface water made across the North
Pacific Ocean in April and May 2011. They then compared this estimate of the inventory with
one derived using atmospheric dispersion and deposition models and a particular source term
for the release to the atmosphere [T12], as well as the estimate of the direct release to the ocean
derived by Tsumune et al. [T18]. The authors reported that the comparison suggested that thedeposition of 137Cs released to the atmosphere on to the ocean surface was in the range of
11.7-14.8 PBq, somewhat higher than the estimate of 5–8 PBq given in the 2013 report.
However, the range quoted by Aoyama et al. does not appear to take account of the uncertainty
associated with the assumptions made about the vertical profile of radiocaesium with water
depth, or the uncertainty in the estimate of the direct release to the ocean. Including these
uncertainties would give a much wider range of estimates for deposition on to the ocean
surface, which would encompass the range given in the 2013 report. In addition, as had been
noted in the 2013 report and in the first white paper, the Terada et al. source term was derived
from measurements of radionuclide deposition levels on land and would not be the mostreliable source term to use to assess deposition on to the ocean. More recently, Katata et al. [K3]and Kobayashi et al. [K9] have made use of a wider range of measurements on land and in theocean, and used coupled models to make better estimates of both total releases to theatmosphere and releases as a function of time, although they did not estimate deposition on tothe ocean (see [U4]).
34.
The contribution of inputs from rivers to the discharge of radiocaesium into the Pacific
Ocean has been studied in several papers. The annual discharge of 137Cs from rivers has been
estimated to be between 5 and 10 TBq [A1, K8], representing of the order of 1 to 2% of theinitial deposition on to the catchment area of the rivers most affected by the FDNPS accident.
These catchments would be expected to be a continuing source of radiocaesium to the Pacific
Ocean. Takata et al. [T7] estimated the fraction of 137Cs bound to particles in different rivers
that became desorbed in the presence of cations (especially K+) in estuaries. This is of interest
because radiocaesium in the dissolved phase is more easily taken up by marine biota. Takata et
al. found that this fraction ranged from a few per cent to more than 50% under conditions ofhigh river discharge (e.g. floods).
35.
The general decrease of the direct releases to the ocean has been confirmed by thecontinuous monitoring at the outlets of FDNPS. However, this monitoring has also shown
sporadic increases of 137Cs levels as a result of exchanges of water between the harbour and theocean [H9]. Most of these sporadic increases correspond to heavy rainfall events. Hirose has
concluded that there are two main pathways by which radionuclides are continuing to bedischarged into the ocean. One is a continuous release due to exchange of waters between the
harbour and the open ocean, and the other is a sporadic discharge of contaminated water via
drainage because of rainfall.
36.
Several publications have reported the decrease of concentration of radiocaesium insurface seawater at different distances from FDNPS. These studies have found the following
results:(a) In 2014, the 137Cs concentration in the north canal of Units 5 and 6 and at thenorthern outlet of FDNPS was around 1,000 Bq/m3 [A6, H9];

10

2016 WHITE PAPER(b) Within the 20 km zone, 137Cs concentrations in 2014 were between 10 and 100 Bq/m3,
one to two orders of magnitude higher than background levels [H9];(c) In a series of three cruises from June 2011 to June 2012 in the northwest Pacific(hundreds to thousands of kilometres from FDNPS) there was about a 40-fold decrease in
the average 137Cs concentration during this one-year period, with average concentrations of
137
Cs of 3.4 Bq/m3 in June 2012 [M8];(d) During winter 2012, the average 137Cs inventory between 42°N and 4°S along the
149°E meridian (region extending between 400 and 4,000 km from FDNPS) was estimatedto be about 1.3 times the residual inventory from nuclear weapons testing [K16].
37.
Several publications have documented the transport of 134Cs and 137Cs in the Pacific
Ocean, and some of these have discussed the physical processes responsible for this transport.
These studies have found the following results:(a) Lateral inputs of 137Cs transported via suspended particulate matter have been
observed on the continental shelf break, 115 km south-east of FDNPS [B7]. Buesseler et al.
have suggested that these particles, originating from shallower regions and possibly
resuspended during typhoons, transported only small amounts of 137Cs relative to theinventory buried nearshore, and therefore that this transport process did not significantly
reduce the levels of 137Cs in the coastal sediment;(b) Mesoscale oceanic eddies (approximately 200 km diameter), which develop in thesubarctic frontal zone of the northwest Pacific (on the northern side of the Kuroshio
Extension), accumulated and transported radiocaesium downward to a depth of 500 m [B6];(c) Radiocaesium was also transported into deeper water (water depth: 100–400 m) in
the ocean during winter by the action of wind [A6].
38.
The long-distance eastward transport of radiocaesium by oceanic currents has beenmonitored in the Pacific as far as the North American coast. Radiocaesium released from the
FDNPS accident was first detected in June 2012 at 1,500 km from the British Columbia coast
at a concentration of 0.3 Bq/m3. Subsequent observations at the same point in February 2014
revealed an increase to 2 Bq/m3 throughout the upper 150 m of the water column. In June 2013,137
Cs attributable to the FDNPS accident was detected on the Canadian continental shelf at aconcentration of 0.5 Bq/m3 [S8]. These concentrations are similar to concentrations of 137Cs of
1 Bq/m3 found prior to the accident, which were due to fallout from weapons testing.
39.
Concerning the westward transport of radiocaesium, observations south of Java,
Indonesia in September 2012 [S12] did not detect any increase in radiocaesium concentrations
that could be attributed to the accident, nor did regular monitoring around Sri Lanka between
September 2011 and April 2013 [W5].
C.

Potential implication of new publications

40.
The Committee has concluded that its findings in this area of the 2013 report remain
valid and are largely unaffected by new information that has since been published. The
Committee has noted several publications that will contribute to an improved understanding of
the release and subsequent dispersion of radionuclides in the marine environment.

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

V. UPDATES ON TRANSFER OF RADIONUCLIDES INTERRESTRIAL AND FRESHWATER ENVIRONMENTS
A.

Recapitulation of the 2013 report

41.
In the 2013 report, the Committee had modelled transfers through terrestrial andfreshwater environments to estimate doses to members of the public from ingestion offoodstuffs for the second year after the FDNPS accident onwards. The Committee had
estimated these doses using the FARMLAND model [B5]. This model was used to predict the
migration of deposited radionuclides into the soil and their subsequent uptake into foodproducts. Some modifications had been made to the model to account for East-Asian
agricultural conditions (especially for rice, vegetables and fruit), but many radiological andagricultural parameter values based on Northern European data had been retained.
42.
In the 2013 report, the food categories with the highest per capita intake by weight for
adults, included in the assessment of doses from ingestion for the second year onwards, hadbeen rice, “other vegetables” (assumed to be in the leafy green vegetables category), wheat andwheat products (assumed to be in the cereals category), fruit and milk. The aim had been to
make realistic estimates of doses and the focus had been on assessing average doses torepresentative groups in the population, therefore consumption of wild food products, such as
game animals or mushrooms, had not been considered.
43.
On the basis of these assumptions, and that food restrictions remained in place, theCommittee had estimated doses from ingestion for periods after the first year that were one totwo orders of magnitude lower than those from external exposure to deposited radionuclides.
Several subsequent studies, in which the internal exposure of people has been measured
directly, have confirmed the dominance of the external exposure pathway, and have indicatedthat doses from ingestion estimated using the FARMLAND model were more likely
overestimates than underestimates (see section VI below).
44.
The Committee had identified the need to better characterize the distributions of doses
to the public and to better quantify the uncertainties in the dose estimation as priorities for
future research. In this context, notwithstanding the minor contribution ingestion of foodstuffs
had made to estimated doses, better information on the transfer of radionuclides to foodstuffs,
and specifically regional and national parameters for models would be useful for futureassessments of the consequences of the FDNPS accident. In addition, such information would
be helpful to improve understanding of the potential impact of environmental remediation
programmes.
B.

Findings of review of new publications

45.
The Committee did not explicitly consider new publications on transfers through theterrestrial and freshwater environments in the first white paper. For this second white paper theCommittee gave priority to the transfer pathways of radiocaesium (which had made the dominant
contribution to ingestion doses after the first year) to food products and to information publishedin 2015.
46.
Of the publications considered in this second white paper, 25 have been reviewed indetail. The main implications of the findings of these publications are summarized below.

122016 WHITE PAPER

1.

Radiocaesium fixation and migration in soil

47.
In the 2013 report, migration of radiocaesium into deeper layers of well-mixed soil used
for crop production had been assumed to be slow, with, for example, only about 7% migrating
below the top 30 cm of well-mixed soils after 10 years (based on a migration rate constant of
1.9 × 10−5 per day). No data have been identified (in publications reviewed in this white paper)
which show radiocaesium attributable to the FDNPS accident at soil depths below 30 cm.
48.
Rates of radiocaesium migration were measured in soils from locations excluding
forests and residential areas by Lepage et al. [L3] and in an extensive survey by Matsuda et al.
[M5]. In both studies, most radiocaesium remained in the upper 5 cm, despite high cumulative
rainfall, some of which was associated with typhoons.
49.
Uematsu et al. [U1] and Nakao et al. [N5] measured the ability of soils to bindradiocaesium and the influence of different soil characteristics. Both studies found that theamounts of micaceous clay minerals and organic matter present were key factors influencing
the extent of binding of radiocaesium in soil. There was some evidence that the binding of theradiocaesium in soils developed from volcanic ash may be lower (and, therefore, that theuptake of radiocaesium by plants and its migration rate down the soil profile may be higher)
than that of other soil types.
2.

Radiocaesium transfer from soil to crops

50.
Seven of the reviewed papers [F1, F2, I4, K4, K11, O2, S3] have reported values ofconcentration ratio (the ratio of the concentration of a radionuclide in the food product to its
concentration in soil) for the transfer of radiocaesium from soil to brown rice, derived fromboth pot and field experiments conducted between 2011 and 2013. These publications suggestthat the concentration ratio for brown rice may have been higher (by up to around an order ofmagnitude) in the first one or two years than assumed in the 2013 report, but declined between
2011 and 2012 at a similar rate to that predicted in the 2013 report.
51.
Sato et al. [S5] reported concentration ratios for the transfer of radiocaesium from soil
to six different types of fruit in 2011. The values reported were all higher (by between 1.6 and16 times) than that assumed in the 2013 report, with the highest values for Japanese cherry.
Two studies by Kusaba et al. [K17, K18] on blueberries and chestnuts suggested thatradiocaesium adhered to bark surfaces was an important source of radiocaesium for the fruit in
the first three years after deposition, rather than radiocaesium in soil. The reductions inradiocaesium concentration in chestnuts and blueberries reported in the two studies [K17, K18]
were faster than those predicted using the FARMLAND model. In contrast, Tagami and
Uchida [T2] found that the rate of decline in the concentration of 137Cs in persimmon at a
specific site in Chiba was similar to that which would be predicted by the FARMLAND model,
whereas for persimmon collected in Fukushima Prefecture it was slower.
52.
For leafy green vegetables, Aung et al. [A9, A10] reported concentration ratios for
Cs which were consistent with that used in the 2013 report, with some values up to twotimes lower and others two or three times higher. Ohse et al. [O2] also reported higher
radiocaesium concentration ratios (by up to a factor of 20) for a range of crops, including
eggplant, pumpkin, soybean and cabbage, grown in soil with high radiocaesium concentrations
in Okuma town in 2012. Tagami and Uchida [T1] reported a reduction in the concentration of137
Cs in giant butterbur, which occurred at a faster rate than would be predicted for leafy green
vegetables using the assumptions of the 2013 report.
137

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

53.
Kubo et al. [K12] reported mean concentration ratios for radiocaesium in buckwheat,and Hoshino et al. [H13] reported concentration ratios for rye. The concentration ratios initially(in 2011 and 2012) were around an order of magnitude higher than that assumed for cereal andpasture in the 2013 report but had declined by 2013 to a similar value. Sunaga et al. [S11]reported limited data showing concentration ratios ranging from 20% lower to 40% higher thanthat assumed in the 2013 report for cereal and pasture.
54.
The Committee identified no papers published in 2015 on the transfer of radiocaesium
to wheat crops or agricultural animal products.
3.

Radiocaesium transfer to food products not considered in the 2013 report

55.
Hiraide et al. [H6] and Nakai et al. [N4] showed that the transfer of radiocaesium toforest mushrooms in Japan was as high as that reported in other countries (e.g. [I1]).
56.
Tsuboi et al. [T13] reported a correlation between the radiocaesium concentration in
Ayu fish internal organs (which are often eaten by Japanese people), and that in soils of thecatchment, for five rivers in 2012–2013. Matsuda et al. [M3] measured the radiocaesium
concentration in 11 freshwater fish species from three lakes with different radiocaesium levels.
The radiocaesium concentrations in lake water, sediments and fish were correlated with that of
surface soil near the lakes.
57.
The Committee identified no papers published in 2015 on the transfer of radiocaesium
to wild animals.
C.

Potential implication of new publications

58.
The Committee has concluded from this preliminary review that its assumptions andfindings in this area of the 2013 report remain broadly valid. New information that is specific
to Japanese conditions has become available on transfers of radioactive material in soils andinto foods. This information would be more appropriate for any future assessment of the
FDNPS accident than parameter values based on European conditions, which had been used in
the 2013 report in the absence of more relevant alternatives. Use of this information may leadto detailed changes in the time-dependence of the doses from ingestion of foods predicted forthe second year after the accident onwards and in the relative importance of different foodstuffs.
However, the Committee expects that the overall effect on predicted ingestion doses for thesecond year onwards would be minor, mainly because of the continued application of foodrestrictions. In addition, measurements on people (see section VI below) have confirmed thatinternal exposure was very small compared with external exposure, and suggested that thedoses from ingestion of foods predicted using the FARMLAND model were likely to beoverestimates.
59.
The following areas of research would be particularly beneficial in providing better
regional and national parameters on the transfer of radionuclides to foodstuffs for futureassessments and in improving understanding of the potential impact of environmental
remediation programmes:(a) Identification and quantification of the long-term impact of fixation mechanisms forradiocaesium in Japanese soils and demonstrate the effect of fixation in different soils on plant
uptake;142016 WHITE PAPER(b) Continued study of the migration of radiocaesium in agricultural and forest
environments and their transfer into various agricultural and wild foods (especially in the
categories of rice and “other vegetables”, wild boar, wild plants and mushrooms);(c) Development of a spatial and temporal model of environmental transfer processes
specific to the diversity of food produced and consumed in Japan to support prediction of
long-term ingestion doses, addressing, in particular:− Variation in radiocaesium uptake from different soil types and the mechanistic basis
for the differences;− Feeding and management regimes of key domestic agricultural animals and wild
animals;− The potential long-term contribution of transfer of radiocaesium in rivers and lakes tofood products;(d) Measurement of long-term changes with time in radiocaesium concentrations invarious agricultural and wild foods;(e) Continued study of the effectiveness of remediation measures in reducing
radiocaesium transfer from soil to agricultural products.

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

Recapitulation of the 2013 report

60.
The Committee’s aim had been to make realistic estimates of doses to defined groups ofindividuals considered representative of the different subsets of the Japanese population. For
the assessment of doses from external exposure, the Committee had used models withparameter values mostly derived from European studies after the Chernobyl accident, andvalidated with numerous individual thermoluminescent dosimeter measurements conducted in
the affected Bryansk region of Russia. The Committee had used these models in its 2013 reportin combination with population-averaged deposition densities of radionuclides for Japanesedistricts or prefectures, derived by combining measurements of radionuclide deposition
densities with the density of population. Data on population densities as well as on age
compositions and occupancy factors for different groups of the Japanese population had been
based on the 2010 Japanese census.
61.
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
inhalation of resuspended radionuclides considered insignificant. Exposure from inhalation ofradionuclides in the passing plume had been estimated from measurements of deposition
density using ratios of the concentrations of radionuclides in air to deposition density levels
derived using the assumed source term and ATDM.
62.
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DEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 15

with the sampling: samples with potentially elevated activity concentrations were more likely
to have been selected. However, at the time of preparation of the 2013 report, no other foodmeasurements had been available.
63.
For subsequent years, a modified form of the FARMLAND model [B5] had been
applied for estimating the transfer of radionuclides through terrestrial food chains, with sometransfer coefficients adjusted for the conditions and agricultural practices of contemporary
Japan. The model had been used in combination with input data on population-averaged
deposition densities of radionuclides for Japanese districts or prefectures.
64.
For residents of evacuated communities, where it had not been possible to use
measurements of radionuclide concentrations in the environment, the Committee had estimatedtime-varying concentrations of radionuclides in the environment using the assumed source
term for releases to the atmosphere and ATDM. Doses from external exposure and frominhalation had then been estimated for the periods before, during and after evacuation using
scenarios representing the movements of residents derived from the results of a survey using
questionnaires.
65.
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 report, the number of thyroid measurements had been
limited (about 1,100 persons) and these data could only be used to corroborate modelled doses
to the thyroid in a few settlements. In addition, data from WBC measurements had only
become available to the Committee at a late stage of the 2013 report preparation, andcomprehensive data analysis had not been possible. Nevertheless, some assessment of doses
from internal exposure based on human measurements had been carried out by the Committee
and were presented in the 2013 report (see paragraphs 116–118 of [U3]). These had indicatedthat estimates of dose from internal exposure based on whole-body measurements were
substantially lower than those based on modelling.
B.

Findings of review of new publications

66.
In the first white paper, the Committee concluded that its findings in this area remained
valid and were largely unaffected by new information that had been published subsequently.
By far the majority of the new publications broadly supported or confirmed the main
assumptions made in, and the findings of, the 2013 report. Further whole body measurements
had given added weight to the statement made in the 2013 report that effective doses fromingestion of radionuclides in foodstuffs may, in practice, have been much lower than thoseestimated theoretically.
67.
Of the publications considered in this second white paper, 16 peer-reviewed journal
papers and the IAEA report [I2] have been reviewed in detail. None materially affected themain findings of the 2013 report, while nine of them provided confirmation of the main
assumptions in whole or part. The main implications of the outcome of this review aresummarized below.
68.
The IAEA report [I2] included reviews of numerous peer-reviewed papers and otherrelevant data sources published up to the first quarter of 2015. The contributors to the IAEA
report undertook in-depth analysis of the available data, including stochastic analysis of publicdose distributions and comparison of available dose parameters with those from the 2013

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2016 WHITE PAPER

report [U3]. In all cases they came to conclusions that the available information did notcontradict the findings of the 2013 report.
1.

External exposure

69.
The Fukushima Health Management Survey (FHMS), 11 including the Basic Survey fordose estimation from external exposure, was launched after the FDNPS accident. Information
was collected from questionnaires completed by more than 500,000 individuals (representing
26% of all residents of Fukushima Prefecture in 2011) on the behaviour of residents during thefirst four months after the accident [I7]. In combination with information on space- and timedependent dose rates, 12 these data enabled the assessment of individual effective doses fromexternal exposure over the four-month period. Ishikawa et al. presented the distribution ofdoses over the first four months for 421,394 individuals from all of Fukushima Prefecture, by
seven areas, several particular districts, and by age and gender.
70.
The full dataset of dose estimates for the first four months had a distribution as follows:
62% received less than 1 mSv; 94% less than 2 mSv; and 99% less than 3 mSv. The arithmetic
mean and maximum value of all the individual doses from external exposure were 0.8 and
25 mSv, respectively. The larger mean doses were assessed as being received by residents ofareas located to the north and west of FDNPS, namely Kempoku (1.4 mSv), Kenchu (1.0 mSv)
and Soso (0.8 mSv). Among the districts, the largest mean dose (more than 4 mSv) was
assessed as being received by residents of Iitate Village. Somewhat larger doses were assessed
as being received by senior people (50–79 y) compared to other adults (20–49 y) and especiallyto children and adolescents (0–19 y). This is in contrast with the 2013 report [U3], where doses
to infants and children were assessed to be larger than doses to adults. Doses to men wereassessed as generally slightly larger than doses to women.
71.
Although some comparisons can be made of the FHMS dose estimates with the doses
estimated in the 2013 report (on the basis that the doses from external exposure in the first year
for people not leaving the area would be about double those in the first four months), moredetailed comparisons would require special analysis. The 2013 report presented doses forparticular social groups and towns, whereas the FHMS has reported doses for larger areas andpopulations. However, both studies concluded that estimated doses from external exposure
were generally low [I7, U3].
72.
Naito et al. [N3] compared the individual doses from external exposure of 26 residents
of various affected areas of Fukushima Prefecture measured by means of personal electronic
dosimeters (D-shuttle) between 20 September and 7 November 2013. Doses were assessedfrom ambient dose rate measurements with account taken of daily activity patterns, quantified
by means of geographic information system detectors worn by each volunteer. The results haveshown that, on average, effective doses to the individuals were 29% of the ambient equivalentdose rate, integrated over time, as the volunteers moved around. This is in reasonableagreement with the assessments in the 2013 report [U3].
11

The Fukushima Health Management Survey is a large programme of health questionnaires and health screening
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.
12
In this and subsequent paragraphs, the terminology used by the authors of the reviewed publication has been
followed, while recognizing that it can be imprecise.

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

73.
Nomura et al. [N6] demonstrated a statistically significant correlation between(a) individual doses from external exposure measured during a three-month period in 2012 by
520 school children in Minamisoma City and (b) dose rates measured outside their homes. In
contrast, no statistically significant correlation was found between individual dose and age or
gender, or behaviour during outdoor activities at school. This can be partially explained by thefact that dose rates outside homes (0.19–1.38 μSv/h) were generally higher than dose rates inthe school grounds (0.06–0.22 μSv/h).
74.
In Minamisoma City, 881 school children took part in a screening programme aimed atdetermining individual doses from internal and external exposure in 2012–2013 [T14]. All thechildren wore individual glass dosimeters over three months during various seasons and eachof them had the content of radiocaesium in the body measured by WBC. The total annual
effective doses ranged from 0.025 to 3.5 mSv with a median of 0.7 mSv. Caesium
radionuclides were detected (at levels above 220 Bq for 134Cs and 250 Bq for 137Cs) in only
three children out of the 881, and it was estimated that 90.3% of the total dose was the result of
external radiation exposure. This finding is consistent with the 2013 report [U3]. The study
also showed that annual effective doses among children in Minamisoma City during the second
year after the FDNPS accident were low.
75.
Mikami et al. [M9] constructed maps of the air dose rates around FDNPS using theresults of measurements obtained from approximately 6,500 locations for three different time
periods. Temporal changes in the air dose rates were examined. The reduction of the air dose
rate in the 18-month period from June 2011 to December 2012 was found to be 10% greaterthan that resulting solely from radioactive decay of radiocaesium during that interval, in
reasonable agreement with the modelling of radiocaesium migration into soil carried out for the2013 report [U3]. The trend in the reduction of the air dose rate was observed to be
independent of land use.
76.
Yoshida-Ohuchi et al. [Y7] measured dose rates indoors in 69 detached wooden houses
and outside in an open field in the evacuated village of Iitate and in the Odaka district ofMinamisoma City. From 522 survey results, they calculated the ratio of the indoor dose rate tothe outdoor dose rate, i.e. the dose reduction factor (DRF). The median DRF value found was
0.43 with an interquartile range of (0.34–0.53). This is in agreement with parameters used by
the Committee for public dose assessment in its 2013 report [U3]. The authors found nodifference in the DRF for the first and second floors. However, the location of the room within
the house, the area topography, and the use of cement roof tiles did influence the DRF. The
median DRF for living rooms (usually located on the front side of the house) was 0.38 (0.31–0.47),
and that for the rooms facing the backyard was 0.49 (0.41–0.62).
77.
Satoh et al. [S6] calculated the age-dependent dose conversion coefficients for external
exposure to deposited radiocaesium using Monte Carlo simulation to estimate the dose
received by babies, children and adults. The work extended previous studies and the results
were consistent with those studies. Although the effective dose rates for younger people were
estimated to be higher than those for adults, they were numerically less than the ambient dose
equivalent rate that is continuously monitored around FDNPS. The authors also proposed amethod to derive the dose conversion coefficients for a volumetric source by using theconversion coefficients for planar sources. They used this method to estimate the dose received
from radiocaesium distributed with an assumed depth profile in the soil. They also derived theconversion coefficients for the effective dose accumulated over the first and second months,
the first year, and over a lifetime (assumed to be 50 years) following the deposition of theradiocaesium. These data are helpful to estimate doses received by people remaining in areas

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with enhanced levels of radioactive material as a result of the accident or for those returningand staying in remediated areas.
2.

Internal exposure

78.
Orita et al. [O5] reported on WBC screening of 2,839 residents of Iwaki City in 2012and of 2,092 residents in 2013. The results showed that 99% of subjects registered below
300 Bq of radiocaesium in their bodies in the first screening, and all subjects registered below
300 Bq in the second screening. The corresponding ranges of the estimated committed
effective dose from internal exposure were 0.01–0.06 mSv for the first screening and0.01-0.02 mSv for the second screening. Long-term follow-up studies will be useful to confirm
these very low chronic internal exposure levels and “to reduce anxiety among the residents bycommunicating radiation health risks”. The results are in line with the estimates of the 2013
report [U3].
79.
Tsubokura et al. [T15] presented further evidence of the small contribution of internal
exposure to the effective dose of children living in Minamisoma City in 2013. Of 3,299
elementary and middle school students in the city, 3,255 individuals (98%) were screened by
WBC measurements during school health check-ups. Not a single student was detected withlevels of radioactive caesium above the detection limit of 220 Bq of 134Cs or 250 Bq of 137Cs.
The detection limits correspond to annual effective doses from internal exposure to 134Cs and137
Cs together of 66, 40, and 25 μSv for those aged 6, 10, and 15 y, respectively, assuming a
constant daily intake of radiocaesium. The children included those who consumed foodstuffs
from outside Fukushima Prefecture, those who consumed foodstuffs produced in unspecified
areas, and those who consumed locally produced foodstuffs (including foodstuffs not tested forpossible radionuclide content).
80.
Further evidence of low-level internal exposure of the public in 2013–2015 has been
provided by Hayano et al. [H2]. Three WBCs (Babyscan), suitable for scanning infants andchildren less than 130 cm tall, operated between December 2013 and March 2015 in threehospitals located to the north, west and south of FDNPS. During that period, 2,707 children
between one and twelve years of age from Fukushima, Miyagi and Ibaraki prefectures were
measured. The body content of radiocaesium in all children was less than the minimum
detection level of 3 Bq/kg. The minimum detection level corresponded to a radiocaesium
intake rate of less than 1–2 Bq/day (depending on age) and an annual dose due to internal
exposure from radiocaesium of 8–16 µSv, assuming a constant daily intake. This is consistent
with the assessment in the 2013 report which estimated doses from internal exposure after the
first year to be very low.
81.
The parents of the infants and children scanned were asked to complete a questionnaire
regarding the family’s dietary habits. The percentage of families which avoided drinking any
local water and consuming any rice or vegetables produced in Fukushima Prefecture varied
between 1% and 4% in Daigo Town and Miharu Town, and between 57% and 65% in
Minamisoma City and Soma Town. These differences were attributed to different perceptionsof radiation risk, but did not reflect differences in documented local radiation levels, whichwere similar in Miharu Town, Minamisoma City and Soma Town [H2].
82.
In order to reveal the possible radiological role of 90Sr as a potential source of longerterm post-accident public exposure, Nabeshi et al. [N1] carried out an analysis of 53 samples ofvegetable and animal foods collected from all over Japan between 2011 and 2013. They
detected 90Sr in 25 out of 40 samples in which radiocaesium had been previously detected, andDEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 19

also in 8 out of 13 samples in which radiocaesium had not been detected. The 90Sr
concentrations in sea fish, freshwater fish, rice, grains, beans, beef, and other foods did not
significantly exceed concentrations reported before the FDNPS accident. There was also no
difference between the 90Sr concentrations in the samples in which radiocaesium was detected
and those in the samples in which it was not. Thus, 90Sr concentrations in food samples wereconcluded to be indistinguishable from the background 90Sr concentrations arising from global
fallout from nuclear weapons testing, suggesting that no marked increase of 90Sr concentrations(nor exposures resulting from them) has occurred as a result of the FDNPS accident. The
authors intend to continue to analyse the 90Sr in various food samples, including samples
harvested from neighbouring areas to FDNPS in order to collect more data for future reference.
3.

Remediation

83.
Decontamination of settlements in the evacuated Special Decontamination Area (SDA)
and inhabited Intensive Contaminated Survey Area (ISCA) has been in progress since 2012. In
some of the remediated towns in the SDA, evacuation orders were lifted in 2014, and the returnof residents began. Dose rate measurements have been carried out on a regular basis before andafter remediation, but are yet to be published in the peer-reviewed literature. It is important thatthe effectiveness of decontamination is assessed in terms of the reduction not only in dose rate
but also in the annual effective dose of residents, both individual and collective. The latter canbe assessed either by estimating the dose from external exposure from dose rate measurements
or by measuring the personal dose of residents before and after decontamination.
84.
Following remediation, the method of estimating doses from external exposure fromradionuclide ground depositions, as used in the 2013 report, may be less valid, and prospective
doses would be better assessed from outdoor and indoor dose rate measurements. Yajima et al.
[Y1] measured ambient dose rates at many residential and occupational sites throughout anumber of study areas in Fukushima Prefecture and also individual doses with personal
dosimeters. The measurement results indicated that the ratio of individual dose based on a
personal dosimeter to the weighted ambient dose rate from external exposure was 0.7. The
paper also presented some national human occupancy parameters and building shielding
parameters that can be compared with those used in the 2013 report [U3]. For all areas
investigated, the estimated effective dose to outdoor workers was substantially higher than thatto indoor workers.
85.
Martin et al. [M2] developed a low-altitude unmanned aerial vehicle equipped with alightweight gamma-spectrometer and height normalization system and tested it at three sites
within Fukushima Prefecture. The aim was to produce high spatial resolution (of less than 1 m)
maps of deposition levels of radioactive material. The system provides a valuable method torapidly examine both areas with enhanced deposition levels and those which have been
remediated, whilst greatly reducing the dose received by the operator. The availability of such
equipment will be important for accurate characterization with high spatial resolution of thedeposition levels of radioactive material, verification that areas have been remediated, andassessment of the effectiveness of remediation.
C.

Potential implication of new publications

86.
The Committee has concluded that its findings in this area of the 2013 report remain
valid and are largely unaffected by new information that has since become available. The

202016 WHITE PAPER

majority of the new publications broadly support or confirm the main assumptions made in,and the findings of, the 2013 report, in particular:(a) Radiation doses to the general public in Japan continue to decline in line with thefindings of the 2013 report;(b) Doses to the general public in Japan from external exposure, determined by personaldose measurements or dose rate measurements combined with national shielding factors forbuildings and exposure scenarios, are in general agreement with the findings of the 2013
report;(c) Doses to the general public in Japan from ingestion of radiocaesium in foods asdetermined by WBC measurements are small and do not contradict the findings of the 2013
report for 2012 and subsequent years;(d) Progress has been made in clarifying the radiological role of radionuclides other thancaesium and iodine, e.g. 90Sr, the contribution of which to dose from internal exposure
seems to be insignificant.
87.
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 report:(a) Continue to measure the dose rates due to external exposure to deposited material invarious environments, forecast and track changes over time;(b) Determine regional and national values necessary for refinement of dosimetricmodels, such as the following parameter values:− Shielding parameters of buildings;− Time spent outdoors and indoors in various building types in different seasons, andas a function of age and social group;− Parameters related to the system of food distribution, and consumption habits ofcultivated and wild foods);(c) Measure individual doses from external exposure to residents of towns with elevateddeposition of radionuclides in order to validate dosimetric models and obtain anexperimental basis for uncertainty analysis;(d) Further conduct in vivo measurements of radiocaesium in people with different food
habits to support refinement in the estimation of doses and their distribution;(e) Clarify the role of soil-to-plant transfer, the food distribution system of Japan,
national food consumption habits, and the system of inspecting foods in Japan forradioactive material, in influencing the levels of exposure from ingestion of radionuclides
in food;(f) Measure radiocaesium concentrations in various foods (agricultural and wild) as afunction of time after the FDNPS accident;(g) Quantify the impact of environmental remediation programmes (decontamination,
agricultural measures and others) both in terms of reduction of environmental radiation
indicators (such as dose rate and activity concentrations) and their impact on averted dosefrom external and internal exposure of residents;

DEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 21(h) Better characterize the distributions of modelled doses to the public, expressing
variability between individuals, using probabilistic approaches, and compare them withhuman measurements.

VII. UPDATES ON EVALUATION OF DOSES FOR WORKERS
A.

Recapitulation of the 2013 report88.
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 the accident 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 had also received the highest reported committed effective dose due tointernal exposure (590 mSv). Dose statistics had been reported separately for a few hundred
emergency services workers.
89.
The Committee’s independent assessments of the doses due to internal exposure for
12 workers (out of a total of 13) who had committed effective doses due to internal exposure
higher than 100 mSv had confirmed that they had received absorbed doses to the thyroid due toinhalation of 131I in the range of 2 to 12 Gy.
90.
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.
91.
The Committee had confirmed the reliability of the assessments reported by TEPCO for
those of its workers where 131I in the body had been detected. However, for most of theworkers, 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 shorter-lived radionuclides such as
132
Te and 133I could not be reliably assessed. The Committee had been unable to confirm thereliability of the assessments reported by TEPCO for those of its workers for whom 131I had notbeen detected in the body, nor the reliability of the internal exposure assessments reported bycontractors for their workers.
92.
The Committee had judged that the major factor potentially affecting the reliability of
external exposure assessments had been the sharing of electronic personal dosimeters during
March 2011 (because the majority of the dosimeters had been lost in the tsunami flood), with
only one worker in a team wearing a dosimeter for many missions.
93.
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 [U3]).

222016 WHITE PAPER

B.

Findings of review of new publications

94.
The Committee concluded in the first white paper that, while significant changes had
been made to doses estimated for some workers since the 2013 report, the Committee did not
expect that these would materially affect its main findings. However, this would need to be
confirmed by a fuller analysis of the data and methodologies adopted in the re-evaluations.
95.
Of the publications considered in this second white paper, six peer-reviewed journal
articles and the IAEA report [I2] have been reviewed in detail. One publication [Y6] provides
information on improved monitoring procedures, and a second [K10] provides data andanalyses. Both publications might be relevant to any follow-up assessment to the Committee’s
2013 report. None of the publications confirm or challenge major assumptions of the 2013
report, nor do they materially affect its main findings.
96.
The IAEA report [I2] presented a statistical analysis of doses to workers which tookaccount of the reassessments of doses to TEPCO workers and contractors, which became
available after the publication of the 2013 report. The personal dose equivalent values for both
TEPCO workers and contractor workers were statistically analysed to derive probability
density distributions and cumulative probability distributions of personal dose equivalent forworkers for 2011. The estimates of the occupational exposures of these on-site workers are
consistent with the findings of the 2013 report.
97.
Yasui [Y6] presented lessons learned from a fact-finding study conducted by theJapanese Ministry of Health, Labour and Welfare (MHLW). This study was carried out in
response to cases where personal alarm dosimeter readings at FDNPS had been deliberately
manipulated, by the use of lead shielding placed over the dosimeter, to give lower values fordoses arising from external exposure. The fact-finding study was conducted “to identify similarcases and determine measures to prevent a recurrence of this incident” using methods specified
by MHLW [Y6]. If it were to be found that such cases were widespread, this could affect theCommittee’s evaluation of the reliability of doses from external exposure reported in Japan.
MHLW has stated that its study found no further cases with intentionally tampered data. The
focus of Yasui was on lessons learned that could improve radiation protection of FDNPS
workers by making improvements to practical external exposure monitoring procedures, rather
than the issue of deliberate manipulation of readings. However, Yasui comments that, becauseof the mutual interest of workers and employers in concealing the manipulation of exposure
data, “… The MHLW did not expect to discover additional incidents of dosimeter
manipulation through its screening and interviews, but, rather, intended to use them to gather
information to construct systems to detect future manipulation of dosimeter data and minimize
worker motivation to participate in the manipulative behaviour.” Given these comments, there
remain some questions about the robustness of the findings of the survey relating to the extent
of deliberate manipulation. Considering the evidence that it had access to, the Committee
judges that, if any further deliberate manipulation did occur, it was probably not widespread,and that the findings of the 2013 Fukushima assessment would remain valid.
98.
There have been few peer-reviewed publications reporting dose assessments for healthcare workers who were involved in the treatment of casualties during the emergency phase of
the accident. Kodama et al. [K10] reported the results of in vivo monitoring conducted for
101 hospital employees at Minamisoma Municipal General Hospital (25 km north of FDNPS)
in July and August 2011. The measurements were part of a broader study to investigate theimpact of a nuclear power plant accident on nearby medical centres. The monitored health-care
workers had provided care to outpatients and hospitalized patients during the period
11-20 March 2011, after which all hospitalized patients had been evacuated. The health-careDEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 23

workers could potentially have been exposed to patients with external and/or internal
radionuclide contamination. On 14 March, working employees took stable iodine and were
instructed to wear chemical protective clothing. Measurements were made of radionuclides in
the whole body for the health-care workers, and estimates were made of committed effective
dose. Caesium-134 was detected in 24 of the 101 employees, and committed effective doses
from intakes of 134Cs were reported as less than 1 mSv in all cases. It is unclear why results arereported for 134Cs in the body, but not for 137Cs, since 137Cs in detectable amounts would be
expected to accompany 134Cs. These relatively low doses are consistent with findings for otheroff-site workers reported in the 2013 report. This appears to be only the second peer-reviewed
publication in English that reports committed effective doses assessed from in vivo monitoringmeasurements for health-care workers (Results for five members of a Radiation Emergency
Medical Assistance Team (REMAT) from Nagasaki University were reported in Matsuda et al.
[M4]. Committed effective doses from intakes of 131I, 137Cs and 134Cs were reported as lessthan 0.1 mSv for all five members of the REMAT). Further peer-reviewed publications relating
to health-care workers at different locations are available in Japanese.
C.

Potential implication of new publications

99.
The Committee has concluded that its findings in this area of the 2013 report remain
valid and are largely unaffected by new information that has been published so far.
100. 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 report. Further research in these areas
would be particularly valuable.

VIII.

A.

UPDATES ON HEALTH IMPLICATIONS FOR WORKERS AND
PUBLIC
Recapitulation of the 2013 report101. The Committee had found that health risks resulting from the FDNPS accident were
expected to be far lower than those for the Chernobyl accident, owing to the substantially lower
doses received by the public and workers. No deterministic effects from radiation exposure had
been observed among the public and none had been expected. No increase in spontaneousabortions, 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 the accident” (paragraph 224 of [U3]) been
expected. No discernible radiation-related increases in rates of leukaemia or breast cancer (twoof the most radiogenic cancer types), nor in other types 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, could 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 andsolid nodules, including a number of thyroid cancers “that would not normally have been
detected without such intensive screening” (paragraph 225 of [U3]). However, similar evenslightly higher rates of cysts and nodules had been found in the prefectures of Aomori,
Yamanashi and Nagasaki that had not received significant radionuclide deposition from the242016 WHITE PAPER

accident. The substantial numbers that had already been observed in the FHMS had been
considered likely to be due to the sensitivity of the screening and not to radiation effects.
102. Among FDNPS emergency workers, deterministic effects had been considered unlikely,
but the Committee had been unable to preclude the possibility of hypothyroidism, or to assess
the risk of cataracts because of insufficient information on doses to the lens of the eye frombeta irradiation. Although 2−3 excess cancers could be inferred over the lifetime among the
173 workers with doses greater than 100 mSv (mainly from external exposure), the Committee
had considered it unlikely that such increased incidence of cancer due to irradiation would bediscernible. The Committee had judged the magnitude of any inferred risk of thyroid cancer
among workers to be such that any increase in incidence due to radiation exposure would likely
not be discernible.
103. The Committee had noted that the major health impacts that had been observed among
the general public and among workers were mental health problems and impaired social wellbeing [U3]. The Committee did not assess health effects unrelated to radiation exposure:estimation of the occurrence and the severity of such health effects was outside of theCommittee’s mandate.
B.

Findings of review of new publications

104. The Committee concluded in the first white paper that its findings in this area of the2013 report remained valid and were largely unaffected by new information that had since been
published.
105. Of the publications considered in this second white paper, 11 peer-reviewed journal
articles and the IAEA report [I2] have been reviewed in detail. Only one report, discussed
below, appeared to challenge the assumptions or findings of the 2013 report; the others served
to strengthen or complement the report findings. Three publications provided information on
thyroid cancer screening among those who were young at the time of examination, including
information on the detection rates of thyroid cysts, nodules and cancers in groups exposed or
not exposed to radiation in order to provide a perspective on the rates found in the FHMS. Twomore provided insights from radiation biology that were pertinent to interpreting the childhood
thyroid cancers detected by screening. The remaining publications provided information onheart and other non-cancer diseases or on the health of workers.
106. The IAEA report [I2] described health surveys initiated in Japan following the accident
at FDNPS, including both the FHMS of the general population and the monitoring of the healthof workers involved in remediation. The report concluded that, at the time of its publication,
there were no health effects among workers or members of the public that could be diagnosed
by a physician and confirmed by pathology and that could be attributed to exposure to radiation
arising from the accident at FDNPS.
107. The IAEA report compared estimates of the Lifetime Attributable Risk Fraction (LARF)(the fraction of the incidence of cancer that is estimated to be attributable to radiation exposure)associated with the reported doses to FDNPS workers for the period March 2011–August 2014
for various forms of malignancy. LARFs were derived using both the ICRP risk model and the
WHO risk model [W4]. The IAEA report determined that the inferred LARFs for solid cancer,
leukaemia and all cancer were all less than 1%. The LARF for thyroid cancer varied among
workers according to the thyroid dose received, but the LARF for the entire worker population
for whom thyroid doses were available was of the order of 3% or less with either risk model.

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

108. The IAEA report also provided LARF estimates for the public at a range of locations
and for various populations, including children, in the areas where higher doses were received.
These groups received lower doses than emergency workers, so the values of LARF werelower, at 0.1 to 1%. The LARF for thyroid cancer in young children was of the order of 1% orless for all of the areas for which thyroid dose information was available.
109. The IAEA report provided a preliminary update of thyroid screening results in the
FHMS, including 121,997 children/adolescents from Fukushima Prefecture who had received asecond round of thyroid screening. Of these, 1,043 were referred for confirmatory testing
because of detected thyroid solid nodules or cysts. Five children had new diagnoses ofpapillary thyroid cancer, with a mean age of 13.1 y (range 6–18 y) at the time of the accident.
However, 10 more children were awaiting fine needle aspiration biopsy or surgery, so an
accurate estimate of cancer incidence/prevalence was not yet available. 13 The IAEA reportobserved that similar results were obtained when the same screening was carried out onchildren living far away from the areas affected by the accident, and that the proportion of
suspicious or malignant cases was almost the same among regions in Fukushima Prefecture. In
many cases, thyroid cancers were found in children in the late teenage years, but no cases were
found in the most vulnerable group of children who were aged under five years at the time of
the accident. The IAEA report concluded that the thyroid abnormalities detected in the survey
were unlikely to be associated with radiation exposure due to the accident.
110. In three areas of Japan with negligible radiation exposure as a result of the accident,
investigators conducted a 2–15 month follow-up examination of 31 children who had been
diagnosed as having a thyroid nodule or cyst at initial thyroid ultrasound screening [H4]. They
found that a third of the cases had a diagnosis of “normal” upon re-examination, while one wasdiagnosed with thyroid cancer and the others with various benign lesions. A similar analysis in
the FHMS screening programme of initially diagnosed thyroid nodules and cysts would be ofinterest for comparison.
111. One paper [T17] (and a subsequently published response to criticisms [T16]) claimed todemonstrate that there had been a radiation-induced increase in thyroid cancer incidence: theauthors reported a 50-fold (95% CI: 25, 90) excess in Fukushima Prefecture. However, thestudy design and methods were too susceptible to bias [J2] to warrant this interpretation. Tsudaet al. [T17] did not adequately account for the impact of the sensitive ultrasound screening of
the thyroid upon the observed rate of thyroid cancer. Their conclusions were based on acomparison of the rate of thyroid cancer among those people screened by FHMS with the rates
found elsewhere in Japan where few children had undergone thyroid screening. Studies ofother populations screened in childhood, particularly those who underwent ultrasoundscreening in three unexposed Japanese prefectures [H3], as well as other screening studies ofyoung people in Japan [T6], found baseline rates of thyroid cancer in the absence of radiation
exposure that were similar to the FHMS rates. Similarly, the Republic of Korea experienced anapparent large increase in thyroid cancer rates once they instituted universal screening [A2]. It
is also likely that some of the cancers detected by screening may have existed before theradiation exposure [T5].
112. Wakeford et al. [W2] carried out an analysis of the data in the Tsuda et al. paper bycomparing the thyroid cancer prevalence among children studied by FHMS who were residing
13

The first white paper indicated that 51 thyroid cancers had been found by FHMS screening up to that time, as
stated in a published paper [N2]. This figure appears to have been an error (the correct figure was 50 cancers plus
one benign tumour), as indicated elsewhere in the same paper.

262016 WHITE PAPER

in localities with relatively low, medium, and high exposures as a result of the accident, as
defined by Tsuda et al. The analysis by Wakeford et al. did not show any dose–response trend.
In fact, the ratio of thyroid cancer prevalence between the localities with the highest and lowest
exposures was only 1.08 (95% CI: 0.60, 1.96) [W2]. Other inconsistencies between Tsuda et al.
and the substantial body of data on radiation-induced thyroid cancer in childhood include:(a) the Tsuda et al. paper reported excesses within 1–2 years after radiation exposure, whereas
studies after the Chernobyl accident and other studies with much larger doses to the thyroid did
not show excesses within 3–4 years; (b) all the thyroid cancers in the FHMS occurred among
those 6–18 years old at radiation exposure, while other studies show the greatest incidence of
thyroid cancer induction was among those with early childhood exposure (before age 5); and(c) the measured doses to the thyroid were much too low to be consistent with the highprevalence they reported [T6, W2]. Because of these weaknesses and inconsistencies, theCommittee does not consider that the study by Tsuda et al. presents a serious challenge to thefindings of the 2013 report.
113. Williams [W6] presented a biological theory of the development of clinical thyroid
cancer which implies that only a small percentage of thyroid cancers identified in tissue
samples taken in childhood would be likely to develop into clinically significant cancer (i.e.
associated with the uncontrolled growth of cancer cell clones) in years ahead if left untreated.
Thyroid follicular cells divide much more rapidly in early childhood than in adolescence or
adulthood, and this could increase the opportunity for cancer development due to radiationinduced mutations primarily in those exposed in early childhood. The anticipated chain of
events would include the mutations that lead initially to a clone of cells that is identifiablemicroscopically as a thyroid cancer in a tissue sample, followed by mutations at subsequentcell divisions that lead to uncontrolled growth of the cancer cell clone, resulting in a clinicalcancer. However, cancers associated with exposure in early childhood were not found in the
FHMS. On the contrary, all the cancers occurred among those exposed at ages six years orabove (mean age 13.1 years), suggesting that the thyroid tumours may not be radiogenic.
Research is ongoing to find new biomarkers that identify mutations or gene expression patterns
that differentiate radiogenic from sporadic thyroid cancers (e.g. [D1, S7]), with the goal of
improving estimations of the risk of radiation-induced thyroid cancer and the ability to attributecases to their cause. Progress is being made, but much yet needs to be done before viablebiomarkers are likely to be established. Given its potential implications, research in this area
should be actively pursued.
114. Regarding other health parameters, Ishii et al. [I6] performed a range of clinicalexaminations and laboratory tests on a population whose residences were in areas with some ofthe highest radiation exposures but that had not been evacuated. They concluded there were no
substantial adverse effects upon basic physiological and metabolic parameters for those withradiation exposure. However, because the number of children under the age of 16 years was
small, and their results were not broken down by age, the effects in children were not welladdressed. The IAEA report [I2] summarized a study suggesting an increase in body massindex, glycated haemoglobin (HbA1c), elevated blood pressure and abnormal liver function
among residents of Fukushima Prefecture, and another study indicating increases in obesity,
hypertension and hyperlipidaemia in Iitate Village. However, the IAEA report concluded thatthese changes were attributable to stress and changes in lifestyle. Similarly, the triple disasterand perceptions of hazards have led to stresses with consequent psychological effects [G2, O3],
but such psychological stresses are common to most disasters and are not due to radiation
exposure [O4], so have not been considered further by the Committee.

DEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 27

115. White blood cell, neutrophil and lymphocyte counts were compared in various localities
of Fukushima Prefecture within a year of the accident; the counts for persons in the localities
with the highest levels of radiation exposure did not differ from those in localities with lower
exposure [S4].
116. There were few published data on the health of FDNPS workers. The IAEA report [I2]indicated that MHLW had sponsored ultrasound examinations of the thyroid for
627 emergency workers whose equivalent dose to the thyroid was more than 100 mSv in 2011,
along with 1,437 who had lower exposures. There were no significant differences in thyroid
findings between the two groups, which is consistent with expectations, given (a) the relatively
low exposures, (b) that those exposed were adults, and (c) the short time interval after exposure.
117. In 1976, under the Industrial Accident Compensation Insurance scheme provided by thethen Ministry of Labour (now the MHLW), the Japanese government had established the basis
for the award of compensation to occupationally exposed workers. Under this establishedscheme, leukaemia may be deemed eligible for medical compensation by a medical review
panel if the dose was at least 5 mSv times the number of years between exposure and diagnosisof the malignancy. A similar scheme applies for certain other lympho-haematopoietic
malignancies with modification based on their comparative radiosensitivity. One person who
worked at FDNPS in 2012 and 2013 and developed leukaemia was granted compensation
under this scheme during 2015. The granting of this compensation claim is the result of theapplication of the pre-existing policy on the granting of compensation claims. It does not imply
a scientifically proven cause–effect relationship between radiation exposure and the healtheffect (see annex A [U5]).
118. An expert group was convened by the International Agency for Research on Cancer(IARC) and Fukushima Medical University to consider future health risks in Fukushima
Prefecture and plan strategies to address them [I5]. Their recommendations generally paralleledthose in the 2013 report, but with added emphasis on collaborations and data-sharing toenhance the scientific and public health value of the studies.
C.

Potential implication of new publications

119. The Committee has concluded that its findings in this area of the 2013 report remain
valid and are largely unaffected by new information that has since been published. A study
which appeared to challenge the Committee’s findings regarding radiogenic thyroid cancer risk
was found to be seriously flawed.
120. The Committee has noted, and will remain abreast of, ongoing research andinvestigations into the health implications of the accident and, in particular, the health survey
being carried out in Fukushima Prefecture. It has identified the following specific areas where
further data or information would have the greatest potential to contribute to addressing the
research needs identified in the 2013 report:(a) In order to properly understand the findings of the thyroid screening programme in
Fukushima Prefecture it is highly desirable to be able to place these findings in the context
of the results from an adequately-sized study of an equivalent Japanese population that was
unaffected by the releases from the FDNPS accident. Such a study would provide definitive
evidence to evaluate the current assessment that the Fukushima Prefecture findings are areflection of the fundamental nature of thyroid disease in this age range, rather than any

282016 WHITE PAPER

effect of exposure to radiation, although the study would clearly require appropriate ethicalapproval;(b) More detailed publication of the numbers of people screened by FHMS, and of
thyroid nodules and thyroid cancers broken down by age and sex, because this would
permit more accurate comparisons with the existing data from people screened but
unexposed;(c) Completion of dose estimation for the young people in the FHMS screening study;
this would permit a dose-related analysis which could provide a stronger basis for inference
than comparisons with other populations who may differ from the FHMS study in age, sex,
screening protocols, and other factors;(d) Well-standardized outcome information, including mortality and incidence of cancer
and non-cancer diseases and birth defects, together with clinical and laboratory findings
with good quality control. Provision should be made to link these with radiation exposureand harmonized information on lifestyle to permit the most informed assessment of healthexperience and risk, in order, in time, to address important questions that both scientists
and the public may have;(e) Systematic collection and analysis of data pertaining to the health of FDNPS
emergency workers, especially among those who received higher doses.

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

Recapitulation of the 2013 report121. The Committee had estimated radiation doses due to the accident to non-human biota
by applying suitable models. The corresponding estimates of effects due to the radiation
exposure had then been inferred by synthesizing the Committee’s generic evaluations of dose–
effects relationships. Exposures of both marine and terrestrial non-human biota following theaccident had been, in general, too low for acute effects to be observed, 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 to where highly radioactive water wasdischarged and released into the ocean. Although the Committee had been unable to exclude arisk 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 a limited area where the deposition density ofradioactive material was greatest, and that, beyond this area, the potential for effects on biota
was insignificant.
122. The Committee had made reference to studies in which effects in various terrestrial
biota had been observed in areas with enhanced levels of radioactive material as a result of the
FDNPS accident [H10, M12, M13]. It had noted that the substantial impacts reported for
populations of wild organisms from these studies 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 [...] 29

B.

Findings of review of new publications

123. The Committee concluded in the first white paper that its findings in this area of the2013 report remained broadly supported by the available evidence. However, it recognized
potential limitations in its approach owing to reliance largely on laboratory-based rather thanfield studies. It identified a need for multidisciplinary field studies tailored to analyse theimpacts of ionizing radiation on populations of wild organisms interacting under the conditions
prevalent within ecosystems in areas with enhanced levels of radioactive material.
124. Of the publications considered in this second white paper, 52 peer-reviewed journal
articles and the IAEA report [I2] have been reviewed in detail. The main implications of thefindings of these publications are summarized below.
125. The IAEA report [I2] included an impact assessment for all ecosystems. The IAEA
assessment used a somewhat different methodology to that adopted by the Committee in the2013 report (which incorporated dynamic transfer models, enabling the estimation of
maximum dose rates occurring over shorter time periods). The overall results were largely
consistent, although the IAEA was more definite on whether population-level effects observedin field studies may be linked to radiation exposure, concluding that no impacts on populations
and the ecosystems (both terrestrial and marine environments) were expected. Furthermore, the
IAEA concluded that long-term effects were not expected, given that the estimated short-term
doses were generally well below levels at which highly detrimental acute effects might beobserved, and dose rates declined relatively rapidly after the accident.
126. Several papers reported concentrations of radionuclides in, and their transfer to, nonhuman biota [A8, B1, H1, H5, K5, K13, M3, T9, T10, T11, T13, W1]. The results presented
were generally consistent with the input datasets used for the environmental impact assessment
carried out for the 2013 report, having, in some cases, been drawn from the same or related
information sources. Data have also been presented for a number of new organism groups orlife stages that had not been considered by the Committee [A11, A12, K1, S9, T8, Y3, Y8] but
for which a broad comparison of radionuclide concentrations could be made (e.g. values can becompared for species falling under generic categories such as invertebrates). The radionuclide
levels reported in these publications also appear to be consistent with those used in the 2013
report. All of the above-mentioned, and other publications [B2, M6, Y4] of less direct
relevance, may facilitate a refinement of the models applied in the 2013 report. Where
exposures to terrestrial organisms have been derived [F4] and, in some exemplary studies,
where these have been supported by experimental determinations in the field [F5, K14], dose
rates generally correspond well with those presented in the 2013 report.
127. Several papers [B3, K19, M10, O6, Y2] appeared to support the finding of the 2013
report that the contribution of radionuclides in marine sediment to exposures of marine biota in
the initial period of the accident were negligible compared to other sources, whereas others (e.g.
[K7]) do not. Some studies [I3, K2, M1] suggest that steady state transfer models (as assumed
in the 2013 report) may not be appropriate for a few components of some ecosystems (e.g. fishin rivers and trees in forests), even several months after the accident.
128. Sublethal effects on biota in the Fukushima area have been observed in some studies.
Chromosomal aberrations increased in wild mice inhabiting areas with elevated radionuclide
concentrations in Fukushima Prefecture, and were correlated with the estimated doses [K15].
In a study on wild carp, Suzuki [S13] observed deleterious impacts on various blood
parameters for fish taken from areas with elevated radionuclide concentrations, although it was
not possible to demonstrate negative impacts on fish health due to the radiation. Fujita et al.

302016 WHITE PAPER[F3] observed that earthworms from a “high-dose” region (defined in the study as one with
ambient dose equivalent rates of around 3 μSv/h — notably using units not appropriate forwildlife) had a significantly greater extent of DNA damage than those from the “low-dose”
region (defined in the study as those with dose rates around 0.3 μSv/h), whereas differenceswere not apparent for wild boar. This study is not consistent with the expectation (as inferred in
the 2013 report) that mammals would be more at risk of harm than invertebrates because of thegreater radiosensitivity of the former. Nonetheless, as noted elsewhere [F3, U2], DNA damage
does not necessarily correspond to impairment of biological functions, and ultimately fitness,of wildlife. Similarly, Ochiai et al. [O1] observed low blood cell counts in monkeys from
Fukushima City, and speculated that, because the animal’s immune system had been
compromised to some extent, individual animals and the entire troop were potentiallysusceptible to infectious disease.
129. Matsushima et al. [M7] observed no clear abnormalities in the gonadal tissues of frogs,
collected from sites with elevated levels of radionuclide concentrations. In contrast, Watanabe
et al. [W3] showed that Japanese fir tree populations near FDNPS exhibit a significantly
increased number of morphological defects, compared to a control population far from FDNPS.
The frequency of the defects corresponded to the deposition densities of radioactive material at
the study sites, although numerous other confounding factors (e.g. accidental damage orenvironmental stress, such as frost) could account for the observation of morphologicalchanges. Accumulated doses to vegetation in areas with relatively high deposition densities
were estimated for the 2013 report. The estimated doses for trees were similar to those at which
disturbances in growth, reproduction and morphology of conifers had been observed following
the Chernobyl accident (albeit that this inference was not made explicitly in the 2013 report).
130. Murase et al. [M17] observed that the reproductive performance of a top avian predator,
a goshawk, had declined markedly following the FDNPS accident and deteriorated
progressively for three study years after the accident. The authors concluded that impacts wereprimarily caused by an increase in the ambient dose equivalent rate, as measured undergoshawk nests, as a result of the nuclear accident, rather than by other factors. Whilst thereported change to reproductive performance appears to be a sound observation, given thelength of time the goshawk had been studied (owing to its protected status), the study area was
100–120 km south-west of FDNPS in North Kanto, an area not significantly affected byreleases from the accident. Murase et al. [M17] noted dramatic impacts on reproduction atambient dose equivalent rates not greatly elevated above natural background levels, andcertainly substantially below any of the thresholds generally considered to be detrimental at theindividual level.
131. The studies of Hiyama et al. [H12] and Taira et al. [T4] have built upon earlier work by
the same group [H11, T3] studying the pale grass blue butterfly, as reported in the 2013 report
and the first white paper. The authors found stronger correlations of abnormality rates with
distance from FDNPS than with radiation dose (for the offspring generation), but argued that
this reflected (unsubstantiated) elevated irradiation of study sites south of FDNPS by shortlived radionuclides in the early phase. Hiyama et al. [H12] contended that butterfly populations
were severely disturbed as a result of radiation exposure, although abnormality rates had
returned to levels existing before the accident by 2013. Taira et al. [T4] examined thegeographical, temporal and temperature-dependent changes of the forewing size of butterflies.
After accounting for all factors, the authors maintained their conclusion that the size reduction,observed only in Fukushima Prefecture in 2011, was caused by radiation exposures.
Perturbations to specific biological end points such as wing-size may be caused by manyenvironmental factors and complex interactions between them, as illustrated by this paper.

DEVELOPMENTS SINCE THE 2013 UNSCEAR REPORT [...] 31

Akimoto [A4] noted that abnormalities and mortality of aphids were significantly higher in theregion affected by the accident compared to controls shortly after the accident, but that theviability and healthiness of the insects were significantly improved by 2013. Confounding
factors, including the removal of human management activities, can have substantial negative
impacts on populations of some insect species such as bees [Y9], and need to be accounted forin assessments of stressor impacts.
132. Møller et al. [M14] provided an analysis of bird abundance data, based on census
methods in regions around Fukushima and Chernobyl, which appeared, at least in part, to be
based on information published earlier. The study demonstrated a negative impact of exposure
to ionizing radiation on abundance and on a number of ecological characteristics in birds,
whilst accounting for potentially confounding variables (such as coverage by vegetation andagricultural habitat). For the period 2011–2014, Møller et al. [M15] found that the abundanceof birds in regions of Fukushima Prefecture decreased with increasing levels of backgroundradiation (as reported in their earlier publications [U4]), with significant variation between
species. The authors argued that their findings were consistent with the hypothesis that thenegative effects of radiation exposure on abundance and species richness accumulate over time.
The work is supported by the dose reconstruction presented by Garnier-Laplace et al. [G1],drawing on the same census datasets. Reconstructed dose rates were commensurate with a levelconsidered by Garnier-Laplace et al. to induce physiological disturbances in birds. The authors
also reproduced the result that overall bird abundance in Fukushima Prefecture decreased withincreasing total doses, albeit that no dose rates exceeded the benchmark of 100 µGy/h used in
the 2013 report. Even though there are improvements in dose reconstruction of this type, someweaknesses remain in the approaches applied. In a related study by Bonisoli-Alquati et al. [B4]on barn swallows, exposure to radiation was observed not to correlate with higher genetic
damage in nestlings, although, at higher levels of radiation exposure, numbers of birds declined
and the fraction of juveniles decreased. The above studies suggest that the traditional view, thatthe absence of cytogenetic damage would rule out elevated risk at the population level, may be
too simplistic, and that environmental disturbances induced by stressors might not be entirely
understandable from knowledge of the stressor's effects on individual organisms [U4].
133. Full environmental impact assessments have been reported by some authors for themarine environment in proximity to FDNPS [J1, K6, K7] and at more distant locations [Y5,
Y10]. These assessments confirm the finding of the 2013 report that marine biota populations
were not at significant risk of severe impact from radiation exposure. In contrast, Aliyu et al.
[A5] concluded that the exposure models and dose/dose-rate benchmarks applied in the 2013
report were inappropriate for inferring possible impacts on population integrity.
C.

Potential implication of new publications

134. The Committee has concluded that its findings in this area of the 2013 report remain
valid and are broadly supported by much of the new information that has since been published.
In particular, several publications confirm the validity of the dose rates for non-human biota
derived in the 2013 report. More questions may arise in relation to how these dose-rates arethen interpreted, and, in particular, whether it is sufficient to focus on endpoints that do nottake full account of the complexity of ecosystem interactions. As noted in the first white paper,a large proportion of available dose–response data pertain to exposures of small groups ofindividuals, maintained in isolation and under controlled laboratory conditions. From these
data, and a much more limited set of field observations, dose rates at which populations are
considered to be at risk can be derived. However, under real conditions, exposure to stressors
might potentially trigger non-linear changes in ecosystem function and structure that cannot be322016 WHITE PAPER

predicted from effects on individual organisms. There remains a clear requirement for followup studies investigating the dose response at high levels of biological organization (e.g.
population) that take due account of biota interactions within ecosystems. A multidisciplinary
approach would be essential to achieve this.

X. CONCLUSIONS
135. Of the new sources of information appraised for this second white paper, a large
proportion confirmed one or other of the major assumptions in the 2013 report. Nonematerially affected the main findings in, or challenged the major assumptions of, the 2013
report. Those that had the potential to do so, albeit subject to further analysis or confirmationfrom studies of better quality, are summarized briefly below.
A.

Potential challenges to 2013 report136. New data [H8, M16, O7] are becoming available on measured concentrations in air ofI, 134Cs and 137Cs as a function of time, and on 131I deposition from 129I measurements in soil
samples. These data have the potential to significantly improve estimates of the source termand of the levels of radionuclides in the air and deposited on the ground. Similar analyses ofother existing samples should yield further data in the near future. There is also more, albeit
limited, information [L2] emerging on the chemical form in which iodine was released andtransported in the atmosphere. A detailed comparison of these new data with the data used in
the 2013 report would be needed to fully understand their implications.

131137. The latest in a series of estimates of the source term for releases to atmospheredeveloped by a group of researchers at the Japan Atomic Energy Agency [K3] was highlighted
in the first white paper. In addition to providing improved estimates of the temporal pattern of
the release, this source term estimate also takes account of the release of iodine in threedifferent physico-chemical forms (elemental, organic and particulate). This further strengthens
the Committee’s view that use of this latest estimate would be preferable to that used in the2013 report, where only two forms (elemental and particulate) were considered. As made clear
in the first white paper, the use of this source term would not, in general, be expected to altersignificantly the doses estimated in the 2013 report, with the possible exception of estimateddoses to evacuees. Estimated doses to the thyroid may also increase when account is taken of
the release of iodine in organic forms, but any significant increases would be confined to large
distances from FDNPS where doses are small. The possible implications for the estimateddoses to evacuees and for estimated doses to the thyroid at larger distances would need moredetailed analysis.
138. One publication [T17] claimed to demonstrate that there had been a radiation-induced
increase in thyroid cancer rates. This study was found to be seriously flawed. The weaknesses
and inconsistencies of this study were confirmed by a considerable body of evidence.
139. Further publications [B4, H12, M14, M15, T4] have been identified, in addition to
those reviewed in the first white paper, reporting population-level effects on non-human biota
that would not be expected from the Committee’s assessment. In the Committee’s view, theresults from these studies remain inconclusive, and the findings in this area of the 2013 reportremain broadly supported by the bulk of the available evidence. Further, multidisciplinary
research is still needed to resolve these apparent differences.

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

B.

Contributions to research needs

140. Table 1 summarizes those publications that have been judged to have made asignificant contribution to addressing the research needs identified in the 2013 report. However,
several of those research needs have yet to be addressed fully by the scientific community (atleast in peer-reviewed publications).
Table 1. 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 a function of time

[M16, O7]

[L2, S1, S10]

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

[A1, H9, K8, K16]

Forecast and quantify long-term transport and mixing of releases
and consequent exposures through aquatic pathways[A6, M8, S8][B6, B7]

TRANSFER THROUGH TERRESTRIAL AND FRESHWATER ENVIRONMENTS
Collate relevant information on transfer parameter values for foodchain pathways[K11, N5, O2, U1][A9, F1, F2, H6, H13, K4,
K12, L3, M3, N4, S3, S5,
S11, T1, T2, T13]

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[Y7][I7, M2, M5, M9, N3, S6,
T14, Y1]

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[I2, O5, T14, T15]

Quantify possible contribution to dose from internal exposure ofradionuclides other than iodine and caesium[N1]

HEALTH IMPLICATIONSContinue the ongoing health survey in Fukushima Prefecture
Analyse and quantify the impact of ultrasonographic surveys on
the apparent incidence of thyroid cancer in Fukushima Prefecture[I2, S4][H4]

Consider the feasibility of establishing a cohort for
epidemiological study with members whose individual doses could
be adequately assessed[M11, W6]
[I5]

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[B4, F3, F5, G1, H12,
J1, K2, K13, K14,
M1, M7, T4, W3, Y9][A11, A12, B2, B3, F4,
H5, I3, K7, K19, M3, M6,
M10, M14, M15, M17, O1,
O6, S9, S13, T11, T13,
W1, Y3, Y8]342016 WHITE PAPER

Acknowledgements
In approving this white paper for publication, the Committee wishes to acknowledge withgratitude the help of the experts directly involved in undertaking follow-up activities relating tolevels and effects of radiation exposure due to the nuclear accident after the 2011 great EastJapan earthquake and tsunami.
Senior technical advisers
W. Weiss (Germany) and K. Kodama (Japan)
Expert group
M. Balonov (Russian Federation), C. Estournel (France), G. Etherington (United Kingdom),
F. Gering (Germany), B. Howard (United Kingdom), R. Shore (United States), S. Solomon(Australia), P. Strand (Norway)
Japanese working group
T. Aono (Japan), K. Ozasa (Japan), S. Saigusa (Japan), T. Takahashi (Japan), H. Yasuda (Japan)
Critical reviewers
J. Chen (Canada), N. Harley (United States), G. Hirth (Australia), J.-R. Jourdain (France),
F. Mettler (United States), B.I. Min (Republic of Korea), S. Shinkarev (Russian Federation),
J. Simmonds (United Kingdom), K.S. Suh (Republic of Korea), H. Vandenhove (Belgium)
Project manager
G.N. Kelly (United Kingdom)

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