A/68/46

United Nations

Report of the United Nations
Scientific Committee on the
Effects of Atomic Radiation
Sixtieth session(27-31 May 2013)

General Assembly
Official Records
Sixty-eighth session
Supplement No. 46

General Assembly
Official Records
Sixty-eighth session
Supplement No. 46

Report of the United Nations
Scientific Committee on the
Effects of Atomic Radiation
Sixtieth session(27-31 May 2013)

United Nations • New York, 2013

Note
Symbols of United Nations documents are composed of letters combined with
figures. Mention of such a symbol indicates a reference to a United Nations
document.

ISSN 0255-1373

[7 August 2013]

Contents
ChapterPage

I.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

II.

Deliberations of the United Nations Scientific Committee on the Effects of Atomic Radiation
at its sixtieth session . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3A.

Completed evaluations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3

B.

Present programme of work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

1.

III.

Radiation exposures from electricity generation and an updated methodology for
estimating human exposures due to radioactive discharges . . . . . . . . . . . . . . . . . . . .

42.

Biological effects from selected internal emitters . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

3.

Epidemiology of low-dose-rate exposures of the public to natural and artificial
environmental sources of radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

4.

Development of an evaluation of medical exposures . . . . . . . . . . . . . . . . . . . . . . . . .

45.

Outreach activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5C.

Strategic plan for 2014-2019 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5

D.

Future programme of work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6E.

Administrative issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6

Scientific findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

A.

Levels and effects of radiation exposure due to the nuclear accident after the 2011 greateast-Japan earthquake and tsunami . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

1.

The accident and the release of radioactive material into the environment . . . . . . . .

7

2.

Dose assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8

3.

Health implications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11

4.

Radiation exposures and effects on non-human biota . . . . . . . . . . . . . . . . . . . . . . . . .

13

Effects of radiation exposure on children . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13

Members of national delegations attending the fifty-eighth to sixtieth sessions of the United
Nations Scientific Committee on the Effects of Atomic Radiation . . . . . . . . . . . . . . . . . . . . . . .

17

Scientific staff and consultants cooperating with the United Nations Scientific Committee on
the Effects of Atomic Radiation in the preparation of its scientific report for 2013 . . . . . . . . .

19

B.
AppendicesI.
II.

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Chapter I
Introduction
1.
Since the establishment of the United Nations Scientific Committee on the
Effects of Atomic Radiation by the General Assembly in its resolution 913 (X) of
3 December 1955, the mandate of the Committee has been to undertake broad
assessments of the sources of ionizing radiation and its effects on human health andthe environment. 1 In pursuit of its mandate, the Committee thoroughly reviews andevaluates global and regional exposures to radiation. The Committee also evaluates
evidence of radiation-induced health effects in exposed groups and advances in theunderstanding of the biological mechanisms by which radiation-induced effects onhuman health or on non-human biota can occur. Those assessments provide thescientific foundation used, inter alia, by the relevant agencies of the United Nations
system in formulating international standards for the protection of the general public
and workers against ionizing radiation; 2 those standards, in turn, are linked toimportant legal and regulatory instruments.
2.
Exposure to ionizing radiation arises from naturally occurring sources (such as
from outer space and radon gas emanating from rocks in the Earth) and fromsources with an artificial origin (such as medical diagnostic and therapeutic
procedures; radioactive material resulting from nuclear weapons testing; energy
generation, including by means of nuclear power; unplanned events such as thenuclear power plant accidents at Chernobyl in 1986 and following the greateast-Japan earthquake and tsunami of March 2011; and workplaces where exposure
to artificial or naturally occurring sources of radiation may be increased).

__________________
1 The United Nations Scientific Committee on the Effects of Atomic Radiation was established by

the General Assembly at its tenth session, in 1955. Its terms of reference are set out in
resolution 913 (X). The Committee was originally composed of the following Member States:
Argentina, Australia, Belgium, Brazil, Canada, Czechoslovakia (later succeeded by Slovakia),
Egypt, France, India, Japan, Mexico, Sweden, Union of Soviet Socialist Republics (later
succeeded by the Russian Federation), United Kingdom of Great Britain and Northern Irelandand United States of America. The membership of the Committee was subsequently enlarged by
the Assembly in its resolution 3154 C (XXVIII) of 14 December 1973 to include the Federal
Republic of Germany (later succeeded by Germany), Indonesia, Peru, Poland and the Sudan. By
its resolution 41/62 B of 3 December 1986, the Assembly increased the membership of theCommittee to a maximum of 21 members and invited China to become a member. In its
resolution 66/70 of 9 December 2011, the Assembly further enlarged the membership of theCommittee to 27 and invited Belarus, Finland, Pakistan, the Republic of Korea, Spain andUkraine to become members.
2 For example, the international basic safety standards for protection against ionizing radiationand for the safety of radiation sources, currently co-sponsored by the International Labour
Organization, the Food and Agriculture Organization of the United Nations (FAO), the World
Health Organization (WHO), the International Atomic Energy Agency (IAEA), the Nuclear
Energy Agency of the Organization for Economic Cooperation and Development and the Pan
American Health Organization.

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Chapter II
Deliberations of the United Nations Scientific Committee on
the Effects of Atomic Radiation at its sixtieth session
3.
The Scientific Committee held its sixtieth session in Vienna from 27 to
31 May 2013. 3 Carl-Magnus Larsson (Australia), Emil Bédi (Slovakia) andYoshiharu Yonekura (Japan) served as Chair, Vice-Chair and Rapporteur,
respectively. The Committee took note of General Assembly resolution 67/112 on
the effects of atomic radiation.

A.

Completed evaluations
4.
The Committee discussed in detail two substantive scientific documents. The
principal findings of those two documents are summarized in a scientific report (seechap. III below) and, together with the two detailed scientific annexes that underpin
the findings, will be published separately in the usual manner, after comments fromthe Committee have been addressed.
5.
The first document reported the results of an assessment of the levels andeffects of radiation exposure due to the nuclear accident after the 2011 greateast-Japan earthquake and tsunami. The General Assembly, in its resolution 66/70,
had endorsed the Committee’s decision at its fifty-eighth session to conduct thatassessment. The Committee acknowledged that it had been a major undertaking that
had required efforts well beyond the resources normally available to the Committee
and its secretariat. Over 80 experts from 18 countries and 5 internationalorganizations had been involved in the work, constituting a major contribution in
kind, and prepared material for the Committee’s scrutiny at its sixtieth session. The
experts had collected and reviewed data and information, and defined
methodologies and processes for ensuring the quality of the data and for their use.
Germany, Sweden and Switzerland had made financial contributions to the generaltrust fund to support the work of the Committee in this regard. An expert (offered by
the Government of Japan under a non-reimbursable loan arrangement) had been
assisting the secretariat in Vienna.
6.
There were many sources of data: (a) specific datasets in electronic formats
and supplementary information requested of the Government of Japan and otherauthenticated Japanese sources; (b) results of measurements and evaluations madeby other United Nations Member States; (c) datasets made available by internationalorganizations, including the Preparatory Commission for the Comprehensive
Nuclear-Test-Ban Treaty Organization (CTBTO), the Food and Agriculture
Organization of the United Nations (FAO), the International Atomic Energy Agency(IAEA), the World Health Organization (WHO) and the World Meteorological__________________
3 The sixtieth session of the Committee was also attended by observers for FAO, WHO, theInternational Agency for Research on Cancer, the World Meteorological Organization (WMO),
IAEA, the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty
Organization (CTBTO), the European Commission, the International Commission on
Radiological Protection, and the International Commission on Radiation Units andMeasurements.

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Organization; (d) information and independent analyses published in peer-reviewed
scientific journals; and (e) measurements made by non-governmental organizations.
7.
The Committee also discussed a substantive scientific document that
represented an extensive review of the effects of exposure to ionizing radiation
during childhood. The Committee had decided at its fifty-seventh session(16-20 August 2010), in deliberations on its future programme of work, that itshould undertake to address radiation risks for and effects on children, to help
clarify how those risks and effects were different for children and adults. The
delegation of the United States of America had led the preparation of detailed
technical documents on this subject, which had been discussed at the fifty-eighth(23-27 May 2011) and fifty-ninth sessions (23-27 May 2012).

B.

Present programme of work

1.

Radiation exposures from electricity generation and an updated methodology for
estimating human exposures due to radioactive discharges
8.
The Committee discussed two progress reports, one on an evaluation ofradiation exposures from electricity generation and the other on updating theCommittee’s methodology for estimating human exposures due to radioactive
discharges into the environment. The Committee noted that the review and update of
the existing methodology was well advanced. It noted that electronic spreadsheets
were being developed that would implement the methodology for use in conducting
the assessment of radiation exposures of populations from various types ofelectricity generation. The Committee anticipated that both documents would beready for final scrutiny at its sixty-first session.

2.

Biological effects from selected internal emitters
9.
The Committee discussed progress on evaluations of the biological effects of
exposure to selected internal emitters, addressing two specific radionuclides: tritiumand uranium. It considered that further work was needed, but envisaged that thetwo components might be ready for detailed discussion at the Committee’s
sixty-first session.

3.

Epidemiology of low-dose-rate exposures of the public to natural and artificial
environmental sources of radiation
10. The Committee discussed progress on an evaluation of epidemiological studiesof low-dose-rate exposures of the public to naturally occurring and artificial
environmental sources of radiation. The Committee acknowledged that the work
was progressing but envisaged that it might not be completed before thesixty-second session.

4.

Development of an evaluation of medical exposures
11. The Committee took note of a progress report by the secretariat on developing
an evaluation of medical exposures. Because (a) exposures of patients undergoing
medical procedures represented the most significant source of artificial exposure toionizing radiation, (b) technology and practices in this area were changing rapidly

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and (c) this was a thematic priority of the Committee’s strategic plan (2009-2013),
the Committee had requested the secretariat to prepare a detailed plan for a reporton this subject. It had also requested the secretariat to initiate the Committee’s next
Global Survey of Medical Radiation Usage and Exposures and to foster close
cooperation with other relevant international organizations (such as IAEA andWHO), as appropriate. A web-based questionnaire on medical exposures had beendeveloped and was being tested. The secretariat planned to initiate the survey
during 2013 and to obtain feedback from the Committee at its sixty-first session on
preliminary findings, with a view to completing the evaluation thereafter.
12. The Committee suggested that the General Assembly might (a) encourage
Member States, the relevant organizations of the United Nations system and otherpertinent organizations to provide further relevant data about doses, effects and risks
from various sources of radiation, which would help greatly in the preparation of
future reports of the Committee to the Assembly; and (b) encourage IAEA, WHOand other relevant organizations to further collaborate with the Committee’s
secretariat to establish and coordinate the arrangements for the periodic collectionand exchange of data on radiation exposures of the general public, workers and, inparticular, patients.
5.

Outreach activities
13. The Committee took note of progress reports by the secretariat on outreachactivities, in particular plans for the dissemination of the Committee’s report on thelevels and effects of radiation exposure due to the nuclear accident after the2011 great east-Japan earthquake and tsunami. It took note of the progress that thesecretariat had made in enhancing the public website of the Committee, developing
leaflets and posters and updating a booklet to explain in plain language the findingsof its recent reports.

C.

Strategic plan for 2014-2019
14. The Committee discussed a strategic plan to provide vision and direction for
all its activities during the period 2014-2019, to facilitate results-based
programming by the secretariat, to help foster the management of sufficient, assured
and predictable resources and to improve planning and coordination among thevarious parties involved.
15. The Committee considered that its strategic objective for the period 2014-2019
was to increase awareness and deepen understanding among decision makers, thescientific community and civil society with regard to levels of exposure to ionizing
radiation and the related health and environmental effects as a sound basis for
informed decision-making on radiation-related issues.
16. The Committee identified its thematic priorities for the period: (a) the global
impact of energy production (including follow-up of the radiological consequencesof the 2011 accident at the Fukushima Daiichi nuclear power station) and of therapidly expanding use of ionizing radiation in medical diagnosis and treatment; and(b) radiation effects at low doses and low dose rates.

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17. Further strategic shifts were envisaged in order to better meet the needs ofMember States, including: (a) further streamlining the Committee’s scientificevaluation processes to complete both wide-ranging summary reports on the levels
and effects of radiation exposure and preparing special reports that respond to
emerging issues as the need arises; (b) further using intersessional expert groups todevelop assessment methodologies, conduct evaluations and maintain surveillanceon emerging issues; (c) developing networks of experts, scientific focal points in
Member States and centres of excellence to facilitate access to expertise; (d) further
enhancing mechanisms for data collection, analysis and dissemination; and(e) further raising awareness and improving dissemination of the Committee’sfindings in readily understandable formats for decision makers and the public.

D.

Future programme of work
18. At its previous session, the Committee had decided that the work to assess thelevels of exposure and radiation risks resulting from the nuclear accident following
the great east-Japan earthquake and tsunami of March 2011 and to complete an
extensive review of the effects of radiation exposure on children should take priority
over other evaluations and activities that had been initiated as part of the present
programme of work. Because those two studies were to be completed and publishedduring the following months, the Committee, in discussions about its future
programme of work, agreed to focus on completing other outstanding evaluations
that had been delayed owing to the unexpected work resulting from the accident at
the Fukushima Daiichi nuclear power station, and not to introduce further new
topics at this stage.

E.

Administrative issues
19. The Committee welcomed developments in streamlining procedures for
publishing the Committee’s reports as sales publications. Nevertheless theCommittee suggested that the General Assembly might request the United Nations
Secretariat to continue to streamline the procedures, recognizing that, while
maintaining quality, the timeliness of their publication is paramount to fulfil the
expected accomplishments approved in the programme budget, and expecting thatthe report ought to be published within the same year in which it is approved.
20. The Committee recognized that, because of the need to maintain the intensityof its work and particularly to improve dissemination of its findings, voluntary
contributions to the general trust fund established by the Executive Director of theUnited Nations Environment Programme to receive and manage voluntary
contributions to support the work of the Committee would be beneficial. The
Committee suggested that the General Assembly might encourage Member States toconsider making voluntary contributions to the general trust fund for this purpose or
to make contributions in kind.
21. The Committee agreed to hold its sixty-first session in Vienna from 26 to
30 May 2014.

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Chapter III
Scientific findings
22. Two scientific annexes (published separately) provide the rationale for theconclusions expressed in the present chapter.

A.

Levels and effects of radiation exposure due to the nuclear
accident after the 2011 great east-Japan earthquake and tsunami

1.

The accident and the release of radioactive material into the environment
23. On 11 March 2011, at 14.46 local time, a 9.0-magnitude earthquake occurred
near Honshu, Japan, creating a devastating tsunami that left a trail of death anddestruction in its wake. The earthquake and subsequent tsunami, which flooded over
500 square kilometres of land, resulted in the loss of more than 20,000 lives anddestroyed property, infrastructure and natural resources. They also led to the worst
civil nuclear disaster since the one at Chernobyl in 1986. The loss of off-site andon-site electrical power and compromised safety systems at the Fukushima Daiichi
nuclear power station led to severe core damage to three of the six nuclear reactors
on the site; this resulted in the release, over a prolonged period, of very large
amounts of radioactive material into the environment.
24. As an immediate response, the Government of Japan recommended theevacuation of about 78,000 people living within a 20-km radius of the power plant
and the sheltering in their own homes of about 62,000 other people living between
20 and 30 km from the plant. Later, in April 2011, the Government recommended
the evacuation of about 10,000 more people living farther to the north-west of theplant (referred to as the deliberate evacuation area), because of the high levels ofradioactive material on the ground. The evacuations greatly reduced (by up to afactor of 10) the levels of exposure that would otherwise have been received bythose living in those areas. However, the evacuations themselves also hadrepercussions for the people involved, including a number of evacuation-related
deaths and the subsequent impact on mental and social well-being (for example,
because evacuees were separated from their homes and familiar surroundings, andmany lost their livelihoods).
25. The information reviewed by the Committee implies atmospheric releases ofiodine-131 and caesium-137 (two of the more significant radionuclides from theperspective of exposures to people and the environment) in the ranges of 100 to
500 petabecquerels (PBq) and 6 to 20 PBq, respectively; for its further work, theCommittee used estimates that lie within those ranges. These estimates are lower,
indicatively, by a factor of about 10 and 5, respectively, than corresponding
estimates of atmospheric releases resulting from the Chernobyl accident. Windstransported a large portion of the atmospheric releases to the Pacific Ocean. In
addition, liquid releases were discharged directly into the surrounding sea. The
direct discharges amounted to perhaps 10 and 50 per cent of the corresponding
atmospheric discharges for iodine-131 and caesium-137, respectively; low-level
releases into the ocean were still ongoing in May 2013.

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2.

Dose assessment
26. Iodine-131 (with a short half-life of 8 days) and caesium-137 (with a much
longer half-life of 30 years) were found to be the two most important radionuclides
for dose assessment. For those two radionuclides, the affected tissues and the timespan of the exposure were quite different. Iodine-131 tended to accumulate in the
thyroid gland for a few weeks after the release and delivered a dose primarily to thatorgan. Caesium-137 was deposited on the ground; it delivers a dose to the wholebody over many years following the release.
27. The Committee has made estimates of the radiation exposures of various
categories of people, namely: members of the public exposed as a result of therelease of radioactive material into the environment; occupationally exposed
workers employed at the Fukushima Daiichi nuclear power station at the time of theaccident and those subsequently involved in on-site recovery operations; andemergency personnel involved in on-site and/or off-site activities. Where
practicable, the Committee based its evaluations on results of individual monitoring.
Occupationally exposed workers and emergency personnel were generally
monitored for exposure to sources of radiation external to the body (external
exposures) and for exposures from intakes of radioactive materials into the body(internal exposures) where these may have been significant.
28. At the time the Committee’s evaluation began, few direct measurements ofinternal exposures were available for members of the public. These were insufficientfor the Committee to estimate doses for the areas in Japan most affected by theaccident. Therefore, the Committee had to rely on the use of various models toestimate doses on the basis of measured, or predicted, levels of radioactive material
in the environment and their transfer through the environment to humans (forexample, the figure illustrates the pattern — derived from measurements — of
caesium-137 deposition in the areas of Japan most affected as a result of theaccident). Of necessity, modelling had to be used to forecast potential doses in the
future.

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FigureDeposition of caesium-137 on the ground in the Fukushima Prefecture andneighbouring prefectures based on measurement data adjusted to 14 June 2011
This map is derived by interpolating between measurements; its aim is toportray the overall pattern of deposition levels and extent rather than to indicate
precise demarcation areas.

29. The estimated effective doses resulting from the accident at the Fukushima
Daiichi nuclear power station can be put in perspective by comparing them withthose received from exposures to radiation sources of natural origin (such as cosmic
rays and naturally occurring radioactive material in food, air, water and other partsof the environment). The Japanese people receive an effective dose of radiation

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from naturally occurring sources of, on average, about 2.1 millisieverts (mSv)
annually and a total of about 170 mSv over their lifetimes. The Committee’s latest
estimate for the global average annual exposure to naturally occurring sources ofradiation is 2.4 mSv and ranges between about 1 and 13 mSv, while sizeable
population groups receive 10 to 20 mSv annually. 4 Absorbed doses to individualorgans are expressed in milligrays (mGy). The average annual absorbed dose to thethyroid from naturally occurring sources of radiation is typically of the order of
1 mGy.
(a)Members of the public
30. The districts with the highest average estimated doses for members of the
public were within the 20-km evacuation zone and the deliberate evacuation area.
For adults, the effective dose estimated to have been received before and during theevacuation was, on average, less than 10 mSv and about half of that level for thoseevacuated early on 12 March 2011. The corresponding estimated average absorbed
dose to the thyroid was up to about 30 mGy. For 1-year-old infants, the effective
dose was estimated to be about twice that for adults and the dose to the thyroid wasestimated to be up to about 70 mGy, as much as one half of which arose from theingestion of radioactivity in food. However, there was considerable variation
between individuals around this value, depending on their location and what foodthey consumed.
31. Adults living in the city of Fukushima were estimated to have received, on
average, an effective dose of about 4 mSv in the first year following the accident;
estimated doses for 1-year-old infants were about twice as high. Those living inother districts within the Fukushima Prefecture and in neighbouring prefectures
were estimated to have received comparable or lower doses; even lower doses were
estimated to have been received elsewhere in Japan. Lifetime effective doses(resulting from the accident) that, on average, could be received by those continuing
to live in the Fukushima Prefecture have been estimated to be just over 10 mSv; thisestimate assumes that no remediation measures will be taken to reduce doses in the
future and, therefore, may be an overestimate. The most important source
contributing to these estimated doses was external radiation from depositedradioactive material.
32. Doses higher or lower than the average values above can be estimated forpeople with habits or behaviour significantly different from the average, and/or for
those living in areas where the levels of radioactive material were or are
significantly different from the average for a particular district or prefecture. Within
a district the individual doses related to inhalation and exposure to externalradiation typically range from about one third of the average up to three times theaverage. Larger doses cannot be totally discounted for some individuals — inparticular, if they consumed certain locally produced foodstuffs in the aftermath of
the accident despite governmental advice or continued living in evacuation areas foran extended period. Some infants may have received thyroid doses of 100 mGy or
more.

__________________
4 Official Records of the General Assembly, Sixty-third Session, Supplement No. 46 (A/63/46),

table 1.

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33. Some information on internal doses, based on direct measurements ofradioactivity in people, was available shortly after the accident, but more
information became available after the Committee completed its dose estimations.
Collectively, these measurements of radioactive content of the thyroid and of thewhole body indicated doses due to internal exposure lower than those estimated by
the Committee, by a factor of about 3 to 5 for thyroid doses and up to about 10 for
whole-body doses. Thus, the Committee considers that its dose estimates may
overestimate actual exposures.
34. Radiation exposures in neighbouring countries and the rest of the world
resulting from the accident were far below those received in Japan; effective doses
were less than 0.01 mSv, and thyroid doses were less than 0.01 mGy; these levels
would be of no consequence for the health of individuals.
(b)

Fukushima Daiichi nuclear power station workers, emergency personnel,
municipal workers and volunteers
35. By the end of October 2012, about 25,000 workers had been involved in
mitigation and other activities at the Fukushima Daiichi nuclear power station site;
about 15 per cent of them were employed directly by the plant operator (Tokyo
Electric Power Company (TEPCO)), while the rest were employed by contractors or
subcontractors. According to their records, the average effective dose of the
25,000 workers over the first 19 months after the accident was about 12 mSv. About
35 per cent of the workforce received total doses of more than 10 mSv over that
period, while 0.7 per cent of the workforce received doses of more than 100 mSv.
36. The Committee examined the data on internal exposure for 12 of the most
exposed workers and confirmed that they had received absorbed doses to the thyroidin the range of 2 to 12 Gy, mostly from inhalation of iodine-131. The Committee
also found reasonable agreement between its independent assessments of effective
dose from internal exposure and those reported by TEPCO for those workers forwhom there were measurable levels of iodine-131 in the body. No account was
taken of the potential contribution from intakes of shorter-lived isotopes of iodine,in particular iodine-133; as a result, the assessed doses from internal exposure could
have been underestimated by about 20 per cent. For many workers, because of thelong delay before monitoring, iodine-131 was not detected in their thyroids; forthose workers the internal doses estimated by TEPCO and its contractors are
uncertain.
37. Apart from those groups, in vivo monitoring of 8,380 personnel affiliated with
the United States Department of Defense was carried out between 11 March 2011
and 31 August 2011. About 3 per cent of those monitored had measurable activity
levels with a maximum effective dose of 0.4 mSv and a maximum absorbed dose to
the thyroid of 6.5 mGy.

3.

Health implications
38. No radiation-related deaths or acute diseases have been observed among theworkers and general public exposed to radiation from the accident.
39. The doses to the general public, both those incurred during the first year andestimated for their lifetimes, are generally low or very low. No discernible increased
incidence of radiation-related health effects are expected among exposed members

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A/68/46of the public or their descendants. The most important health effect is on mental andsocial well-being, related to the enormous impact of the earthquake, tsunami andnuclear accident, and the fear and stigma related to the perceived risk of exposure toionizing radiation. Effects such as depression and post-traumatic stress symptoms
have already been reported. Estimation of the occurrence and severity of such healtheffects are outside the Committee’s remit.
40. For adults in Fukushima Prefecture, the Committee estimates average lifetime
effective doses to be of the order of 10 mSv or less, and first-year doses to be
one third to one half of that. While risk models by inference suggest increased
cancer risk, cancers induced by radiation are indistinguishable at present from othercancers. Thus, a discernible increase in cancer incidence in this population that
could be attributed to radiation exposure from the accident is not expected. An
increased risk of thyroid cancer in particular can be inferred for infants andchildren. The number of infants that may have received thyroid doses of 100 mGy is
not known with confidence; cases exceeding the norm are estimated by model
calculations only, and in practice they are difficult to verify by measurement.
41. For the 12 workers whose exposure data were scrutinized by the Committee
and who were estimated to have received absorbed doses to the thyroid fromiodine-131 intake alone in the range of 2 to 12 Gy, an increased risk of developing
thyroid cancer and other thyroid disorders can be inferred. More than 160 additional
workers received effective doses currently estimated to be over 100 mSv,
predominantly from external exposures. Among this group, an increased risk ofcancer would be expected in the future. However, any increased incidence of cancer
in this group is expected to be indiscernible because of the difficulty of confirming
such a small incidence against the normal statistical fluctuations in cancer
incidence. Workers exposed to doses above 100 mSv will be specially examined,
including through annual examinations of the thyroid, stomach, large intestine andlungs for potential late radiation-related health effects.
42. In June 2011, a health survey of the local population (the Fukushima HealthManagement Survey) was initiated. The survey, which began in October 2011 and isplanned to continue for 30 years, covers all 2.05 million people living in Fukushima
Prefecture at the time of the earthquake and reactor accident. It includes a thyroid
ultrasound survey of 360,000 children aged up to 18 years at the time of theaccident, using modern high-efficiency ultrasonography, which increases the ability
to detect small abnormalities. Increased rates of detection of nodules, cysts andcancers have been observed during the first round of screening; however, these are
to be expected in view of the high detection efficiency. Data from similar screening
protocols in areas not affected by the accident imply that the apparent increased
rates of detection among children in Fukushima Prefecture are unrelated to radiation
exposure.

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4.

Radiation exposures and effects on non-human biota
43. Exposures of selected non-human biota in the natural environment were also
estimated. The doses and associated effects of radiation on non-human biota
following the accident were evaluated against the Committee’s previous evaluationsof such effects. 5 Exposures of both marine and terrestrial non-human biota
following the accident were, in general, too low for acute effects to be observed,
though there may have been some exceptions because of local variability:(a) Effects on non-human biota in the marine environment would be
confined to areas close to where highly radioactive water was released into theocean;(b) Continued changes in biomarkers for certain terrestrial organisms, inparticular mammals, cannot be ruled out, but their significance for population
integrity of those organisms is unclear. Any radiation effects would be restricted to alimited area where the deposition of radioactive material was greatest; beyond thatarea, the potential for effects on biota is insignificant.
44. While it was not within the scope of the Committee’s evaluation, it isimportant to note that the effects of the protective actions and any remediation
conducted to reduce human exposure have a significant impact on, inter alia,
environmental goods and services, resources used in agriculture, forestry, fisheries
and tourism, and amenities used in spiritual, cultural and recreational activities.

B.

Effects of radiation exposure of children
45. Epidemiological studies reported in the literature vary with regard to thespecific age groups they consider. For the purposes of the Committee’s evaluation of
the effects of radiation exposure on children, the term “children”, in contrast to“adults”, included those exposed as infants, children and adolescents. The
evaluation did not specifically address effects of in utero exposure to radiation
because such information is contained in other comprehensive reports. The
evaluation also did not address the many beneficial uses of radiation exposure forchildren, such as in medical diagnosis and therapy, which are outside the mandate of
the Committee.
46. Sources of exposure to children that are of particular interest include
accidental exposures, and specific regions with enhanced levels of natural
background radiation, as well as diagnostic and therapeutic procedures. The data
reviewed by the Committee were derived from studies covering a wide range ofdoses, variable dose rates, whole and partial body exposure and children of different
ages. The effects described in the annex are often very specific to a given exposure
scenario.
47. At its sixtieth session the Committee considered the effects of radiation
exposure of children and reached the following conclusions:(a) For a given radiation dose, children are generally at more risk of tumour
induction than are adults. Cancers potentially induced by exposure to ionizing__________________
5 See Official Records of the General Assembly, Fifty-first Session, Supplement No. 46 (A/51/46),

and Sixty-third Session, Supplement No. 46 (A/63/46).

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radiation at young ages may occur within a few years, but also decades later. In its
report on its fifty-fourth session, the Committee stated that estimates of lifetime
cancer risk for those exposed as children were uncertain and might be a factor of
2 to 3 times as high as estimates for a population exposed at all ages. 6 That
conclusion was based on a lifetime risk projection model combining the risks of all
tumour types together;(b) The Committee has reviewed evolving scientific material and notes thatradiogenic tumour incidence in children is more variable than in adults and depends
on the tumour type, age and gender. The term “radiation sensitivity” with regard tocancer induction refers to the rate of radiogenic tumour induction. The Committee
reviewed 23 different cancer types. Broadly, for about 25 per cent of these cancer
types, including leukaemia and thyroid, skin, breast and brain cancer, children wereclearly more radiosensitive. For some of these types, depending on thecircumstances, the risks can be considerably higher for children than for adults.
Some of these cancer types are highly relevant for evaluating the radiologicalconsequences of accidents and of some medical procedures;(c) For about 15 per cent of the cancer types (e.g. colon cancer), children
appear to have about the same radiosensitivity as adults. For about 10 per cent ofcancer types (e.g. lung cancer), children appear less sensitive to external radiation
exposure than adults. For about 20 per cent of cancer types (e.g. oesophagus
cancer), the data are too weak to draw a conclusion regarding any differences inrisk. Finally, for about 30 per cent of cancer types (e.g. Hodgkin’s disease andprostate, rectum and uterus cancer), there is only a weak relationship or none at all
between radiation exposure and risk at any age of exposure;(d) At present, projections of lifetime risk for specific cancer types
following exposure at young ages are statistically insufficient. Estimates currently
do not adequately capture the known variations, and additional studies are needed;(e) For direct effects that occur after high (either acute or fractionated) doses(so-called deterministic health effects), the differences in outcome between
exposure in childhood and in adulthood are complex and can be explained by theinteraction of different tissues and mechanisms. These effects may be seen afterradiation therapy or following high exposures in accidents. The difference between
the radiation sensitivity of children and that of adults for deterministic effects in a
specific organ is often not the same as the difference for cancer induction. There aresome instances in which childhood exposure poses more risk than adulthood
exposure (e.g. risk of cognitive defects, cataracts and thyroid nodules). There areother instances where the risk appears to be about the same (e.g. risk ofneuroendocrine abnormalities), and there are a few instances where children’s
tissues are more resistant (e.g. lungs and ovaries);(f) Because of all the above considerations, the Committee recommends thatgeneralizations on the risks of effects of radiation exposure during childhood should
be avoided. Attention should be directed to specifics of the exposure, age at
exposure, absorbed dose to certain tissues and the particular effects of interest;__________________
6 Official Records of the General Assembly, Sixty-first Session, Supplement No. 46 andcorrigendum (A/61/46 and Corr.1) paras. 21-22.

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A/68/46(g) There have been many studies of possible heritable effects following
radiation exposure; such studies were reviewed by the Committee in 2001. It has
been generally concluded that no heritable effects in humans due to radiation
exposure have been explicitly identified (specifically in studies of offspring ofsurvivors of the atomic bombings). Over the past decade, there have been additional
studies that have focused on survivors of childhood and adolescent cancer following
radiotherapy, where gonadal doses are often very high. There is essentially noevidence of an increase in chromosomal instability, minisatellite mutations,transgenerational genomic instability, change in sex ratio of offspring, congenital
anomalies or increased cancer risk in the offspring of parents exposed to radiation.
One reason for this is the large fluctuation in the spontaneous incidence of theseeffects;(h) Health effects and risks are dependent on a number of physical factors.
Because children have smaller body diameters and there is less shielding by
overlying tissues, the dose to their internal organs will be larger than for an adult fora given external exposure. Because they are also shorter than adults, children may
receive a higher dose from radioactivity distributed in and deposited on the ground.
These factors are important when considering doses to populations in some areas
with high levels of radionuclides in and on the ground. In diagnostic medical
exposure, children may receive significantly higher doses than adults for the same
examination if the technical parameters for delivering the dose are not specifically
adapted;(i) Regarding internal exposure, because of the smaller size of infants andchildren, and thus because their organs are closer together, radionuclides
concentrated in one organ irradiate other organs of children’s bodies more thanoccurs in adults. There are also many other age-related factors involving metabolism
and physiology that make a substantial difference in dose at different ages. Several
radionuclides are of particular concern regarding internal exposure of children.
Accidents involving releases of radioactive iodines (for example, in a nuclear power
plant accident) can be significant sources of exposure of the thyroid gland, and thus
have the potential to induce thyroid cancer. For a given intake, the dose to thethyroid for infants is eight or nine as large as that for adults. For intakes of
caesium-137, there is very little difference in dose between children and adults.
Internal exposure of children also occurs in the medical use of radionuclides. The
spectrum of procedures normally performed on children is different from that
performed on adults. Potentially higher doses in children are offset in practice by
the use of a lower amount of administered radioactive material.
48. The Committee recognizes that continued research is needed to identify thefull scope and expression of the differences in effects, mechanisms and risk fromexposure to ionizing radiation for children and for adults. This is necessary because
for a number of studies (such as of the atomic bombing survivors, children exposed
to radioiodine after the Chernobyl accident and those who have had computed
tomography scans), the lifetime results remain incomplete. Future long-term studies
following childhood exposure will face significant difficulties owing to unlinked
health records, administrative and political barriers and ethical and privacy
considerations.
49. Important areas of future research and work also include evaluation ofpotential radiation effects for children: (a) in areas of high natural background

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exposure; (b) after high-dose medical procedures involving interventional
fluoroscopy; and (c) after cancer radiotherapy (including evaluation of potential
interactions with other therapies). The Committee has identified the following areas
for future research as well: development of databases on radiation doses for children
who can be tracked in the long term; and evaluation of effects following whole andpartial irradiation of juvenile organs. Studies at the molecular, cellular, tissue andjuvenile animal level are potentially informative.

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Appendix I
Members of national delegations attending thefifty-eighth to sixtieth sessions of the United Nations
Scientific Committee on the Effects of Atomic Radiation

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Argentina

A. J. González (Representative), A. Canoba, M. di Giorgio

Australia

C. M. Larsson (Representative), C. Baggoley, G. Hirth,
S. B. Solomon, R. Tinker

BelarusJ. Kenigsberg (Representative), A. Stazharau, V. Ternov

Belgium

H. Vanmarcke (Representative), S. Baatout, H. Bijwaard,
H. Bosmans, G. Eggermont, H. Engels, F. Jamar,
L. Mullenders, H. Slaper, P. Smeesters, A. Wambersie,
P. Willems

BrazilJ. Hunt (Representative), D. R. Melo (Representative),
M. Nogueira Martins (Representative), M. C. Lourenço,
L. Holanda Sadler Veiga

CanadaC. Purvis (Representative), B. Pieterson (Representative),
N. E. Gentner (Representative), D. Boreham, K. Bundy,
D. B. Chambers, J. Chen, S. Hamlat, R. Lane, C. Lavoie,
E. Waller

China

Pan Z. (Representative), Chen Y., Du Y., Gao H., Liu J.,
Liu S., Pan S., Su X., Sun Q., Wang Y., Yang H., Zhang W.,
Zhu M.

Egypt

T. S. El-Din Ahmed (Representative), M.A.M. Gomaa(Representative)

Finland

S. Salomaa (Representative), A. Auvinen, E. Salminen

FranceL. Lebaron-Jacobs (Representative), A. Rannou(Representative), E. Ansoborlo, M. Bourguignon,
J.-R. Jourdain, F. Ménétrier, M. Tirmarche

Germany

W. Weiss (Representative), A. A. Friedl, K. Gehrcke,
P. Jacob, T. Jung, G. Kirchner, J. Kopp, R. Michel,
W. U. Müller

India

K. B. Sainis (Representative), B. Das, P. C. Kesavan,
Y. S. Mayya, K. S. Pradeepkumar

Indonesia

S. Widodo (Representative), Z. Alatas, G. B. Prajogi,
G. Witono, B. Zulkarnaen

Japan

Y. Yonekura (Representative), S. Akiba, T. Aono, N. Ban,
M. Chino, K. Kodama, M. Kowatari, M. Nakano, O. Niwa,
K. Ozasa, S. Saigusa, G. Suzuki, T. Takahashi, Y. Yamada,
H. Yamagishi

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MexicoJ. Aguirre Gómez (Representative)

Pakistan

M. Ali (Representative), Z. A. Baig

Peru

A. Lachos Dávila (Representative), B. M. García Gutiérrez

PolandM. Waligórski (Representative), L. Dobrzyński, M. Janiak,
M. Kruszewski

Republic of Korea

K.-W. Cho (Representative), S. H. Na (Representative),
K.-H. Do, D.-K. Keum, J.-I. Kim, J. K. Lee, S. Y. Nam

RussianFederation

M. Kiselev (Representative), A. Akleyev, R. Alexakhin,
T. Azizova, V. Ivanov, N. Koshurnikova, A. Koterov,
I. Kryshev, B. Lobach, O. Pavlovskiy, A. Rachkov,
S. Romanov, A. Sazhin, S. Shinkarev

Slovakia

E. Bédi (Representative), M. Chorváth, Ž. Kantová,
K. Petrová, L. Tomášek, I. ZachariášováSpain

M. J. Muñoz González (Representative), M. T. Macías
Domínguez, B. Robles Atienza, E. Vañó Carruana

Sudan

M.A.H. Eltayeb (Representative), I. Salih Mohamed Musa
(Representative), E.A.E. Ali (Representative)

SwedenL. Hubbard (Representative), L. Moberg (Representative),
A. Almén, L. Gedda, J. Johansson Barck-Holst

UkraineD. Bazyka (Representative)

United Kingdomof Great Britain
and Northern
Ireland

J. Harrison (Representative), J. Cooper (Representative),
S. Bouffler, J. Simmonds, R. Wakeford

United States ofAmerica

F. A. Mettler Jr. (Representative), L. R. Anspaugh,
J. D. Boice Jr., N. H. Harley, E. V. Holahan Jr.,R. J. Preston

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Appendix II
Scientific staff and consultants cooperating with the United
Nations Scientific Committee on the Effects of Atomic
Radiation in the preparation of its scientific report for 2013
G. N. Kelly
V. Golikov
L. S. Constine
H. D. Nagel
D. Nosske
R. Shore
Secretariat of the United Nations Scientific Committee on the Effects of Atomic
Radiation
M. J. Crick
F. Shannoun
H. Yasuda (seconded)

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