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Radiological protection issues arising during and after the Fukushima nuclear reactor accident
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2013 J. Radiol. Prot. 33 497
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JOURNAL OF RADIOLOGICAL PROTECTION
J. Radiol. Prot. 33 (2013) 497–571 doi:10.1088/0952-4746/33/3/497
Radiological protection issues arising during and after
the Fukushima nuclear reactor accident
Abel J Gonz´ alez1, Makoto Akashi2, John D Boice Jr3,
Masamichi Chino4, Toshimitsu Homma4, Nobuhito Ishigure5,
Michiaki Kai6, Shizuyo Kusumi7, Jai-Ki Lee8, Hans-Georg Menzel9,
Ohtsura Niwa10, Kazuo Sakai2, Wolfgang Weiss11,
Shunichi Yamashita10,12and Yoshiharu Yonekura2,13
1Argentine Nuclear Regulatory Authority, Av. del Libertador 8520, (1429) Buenos Aires,
2National Institute of Radiological Science; 4-9-1, Anagawa, Inage-ku, Chiba-shi, 263-8555,
3Vanderbilt University and National Council on Radiation Protection and Measurements,
7910 Woodmont Avenue, Suite 400, Bethesda, MD 20814-3095, USA
4Japan Atomic Energy Agency, 2-4 Shirakata Shirane, Tokaimura, Nakagun, 319-1195
5Nagoya University, Graduate School of Medicine, 1-1-20, Daiko-minami, Higashi-ku, Nagoya,
6Oita University of Nursing and Health Sciences, 2944-9 Megusuno, Oita City, Oita Prefecture,
7Ex-Nuclear Safety Commission, Japan
8Nuclear Engineering, Hanyang University, 222 Wangsimni-rd, Seongding, Seoul 133-791,
9European Organization for Nuclear Research, CERN, CH-1211 Gen` eve 23, Switzerland
10Fukushima Medical University, 1 Hikariga-oka, Fukushima City 960-1295, Japan
11Federal Office for Radiation Protection (BfS), Department for Radiation Hygiene,
Ingolst¨ adter Landstrasse 1, DE-85764 Oberschleissheim/Neuherberg, Germany
12Nagasaki University, 1-1-4 Bunkyomachi, Nagasaki, Nagasaki Prefecture, 852-8521, Japan
E-mail: firstname.lastname@example.org and abel j email@example.com
Received 20 May 2013, in final form 22 May 2013, accepted for publication 24
Published 27 June 2013
Online at stacks.iop.org/JRP/33/497
Following the Fukushima accident, the International Commission on
Radiological Protection (ICRP) convened a task group to compile lessons
learned from the nuclear reactor accident at the Fukushima Daiichi nuclear
In this memorandum the members of the task group express their personal views
which was convened by the ICRP to collate the lessons learned from the nuclear reactor accident at the Fukushima
Daiichi nuclear power plant in Japan. The opinions expressed are those of the authors and do not necessarily reflect
the official view of the ICRP.
c ?2013 IOP Publishing Ltd Printed in the UK
498 A J Gonz´ alez et al
on issues arising during and after the accident, without explicit endorsement of
or approval by the ICRP.
While the affected people were largely protected against radiation exposure
and no one incurred a lethal dose of radiation (or a dose sufficiently
large to cause radiation sickness), many radiological protection questions
were raised. The following issues were identified: inferring radiation risks
(and the misunderstanding of nominal risk coefficients); attributing radiation
effects from low dose exposures; quantifying radiation exposure; assessing
the importance of internal exposures; managing emergency crises; protecting
rescuers and volunteers; responding with medical aid; justifying necessary
but disruptive protective actions; transiting from an emergency to an existing
of the public; caring for infants and children; categorising public exposures due
to an accident; considering pregnant women and their foetuses and embryos;
monitoring public protection; dealing with ‘contamination’ of territories,
rubble and residues and consumer products; recognising the importance of
psychological consequences; and fostering the sharing of information.
Relevant ICRP Recommendations were scrutinised, lessons were collected
and suggestions were compiled.
It was concluded that the radiological protection community has an ethical
duty to learn from the lessons of Fukushima and resolve any identified
challenges. Before another large accident occurs, it should be ensured that
inter alia: radiation risk coefficients of potential health effects are properly
interpreted; the limitations of epidemiological studies for attributing radiation
effects following low exposures are understood; any confusion on protection
quantities and units is resolved; the potential hazard from the intake of
radionuclides into the body is elucidated; rescuers and volunteers are protected
with an ad hoc system; clear recommendations on crisis management and
medical care and on recovery and rehabilitation are available; recommendations
on public protection levels (including infant, children and pregnant women
and their expected offspring) and associated issues are consistent and
understandable; updated recommendations on public monitoring policy are
available; acceptable (or tolerable) ‘contamination’ levels are clearly stated
and defined; strategies for mitigating the serious psychological consequences
arising from radiological accidents are sought; and, last but not least, failures
in fostering information sharing on radiological protection policy after an
accident need to be addressed with recommendations to minimise such lapses
1.1. The accident
On 11 March 2011, one of the most powerful earthquakes in recorded history set off a cascade
of events culminating in the nuclear reactor accident (hereinafter referred to as ‘the accident’)
at the Fukushima Daiichi nuclear power plant (NPP) in Japan. The catastrophic 2011 Great
East Japan earthquake and subsequent tsunami caused huge devastation in the eastern region of
Japan. The United Nations Environment Programme reported that the triple disaster left 15854
people dead and 3155 missing as at March 2012, according to official Japanese government
figures. Hundreds of thousands of houses and other buildings were damaged and more than
400000 people were displaced. With huge economic damage, this event is considered not
only tragic in terms of its human toll; it is the most economically devastating disaster in
history (UNEP 2012).
As a consequence of the accident, large amounts of radioactive substances, particularly
of volatile elements such as radioisotopes of iodine (131I,132I,133I), caesium (134Cs,136Cs,
137Cs) and tellurium (132Te), and inert gases such as xenon (133Xe), were released into the
environment, resulting in relatively high levels of ambient radiation, especially around the
plant. Notwithstanding this consequential radiological event, people were mostly protected
against radiation exposure and nobody received a lethal dose of radiation or a dose that
result in acute radiation sickness of any type. The World Health Organization (WHO) has
estimated that people near the damaged power plant received such low doses of radiation that
no discernible health effect could be expected (WHO 2012). A more recent WHO report (WHO
2013) suggested that slight increases in lifetime cancer risk might occur in any heavily
exposed subgroups of the population, although model estimates where based on conservative
(high-sided) assumptions of exposure to hypothetically exposed populations. Despite these
generally encouraging assessments of minimal future health effects on the population, many
concerns and questions related to radiation protection were raised not only in Japan but also
around the world. Addressing these concerns and questions is a main aspiration of this report.
1.2. The ICRP response
The International Commission on Radiological Protection (ICRP) does not normally comment
on events in individual countries; however, given the unusual circumstances, it reacted
promptly by offering advice and assistance in the hope that its recommendations would prove
helpful in dealing with the on-going radiological protection challenges. ICRP Task Group
84 (ICRP-TG84) was established to evaluate the radiological protection lessons from the
extraordinary situations created by the accident.
This memorandum reflects the report prepared by the ICRP-TG84 membership for the
ICRP Main Commission, a summary of which was posted by the ICRP Secretariat on the ICRP
web site (www.icrp.org/docs/ICRP%20TG84%20Summary%20Report.pdf). The authors wish
to emphasise that the issues, lessons and suggestions described in this report are their individual
assessments and, while based in their report to the ICRP and grounded in ICRP philosophy, are
not intended to express the views of the ICRP.
The aim of this memorandum is to describe radiological protection issues arising in the
aftermath of the accident vis-` a-vis the ICRP recommendations and guidance. It also attempts
to extract lessons learned and to provide suggestions for clarifying and improving existing and
future guidance in dealing with a severe radiological event. The memorandum is not intended
to be a critique of ICRP recommendations.
It was encouraging to note that measures adopted in a timely manner by the authorities
effectively reduced the dose received by people living in the affected area (Kai 2012). However,
dealing with the aftermath of the accident has provided suggestions on a number of relevant
issues that are addressed herein with a view to improving the effectiveness of radiological
It is not this report’s intention to evaluate the causes and consequences of the accident or
judge the appropriateness of the protective measures undertaken by the Japanese authorities.
500 A J Gonz´ alez et al
Several assessments on these issues are being developed, including by the government of
Japan (GOJ 2011a, 2011b, NDJ 2012), by international intergovernmental organisations (UN
2012, Weiss 2012, van Deventer et al 2012, IAEA 2011b, 2012a, MC 2011, Wondergem and
Rosenblatt 2012) and by non-nuclear and nuclear organisations (Fitzgerald et al 2012, Acton
and Hibbs 2012, TEPCO 2011, INPO 2011, ANS 2012, Greenpeace 2011).
The accident reinforced an important reality: nuclear accidents resulting in serious
radiological consequences can happen and, moreover, may occur in the future. The accident
confirmed that, in addition to the unlikely but foreseeable events that are usually considered
when developing measures for preventing nuclear accidents, unpredictable events may also
occur and may indeed be dominant for assessing outcomes (Taleb 2007). Preclusion of
‘maximum credible accidents’, ‘design basic accidents’ and any other imagined scenarios is
a necessary but not sufficient condition for protecting people against radiation. Preventive
measures against conceivable accidental conditions will no doubt remain a fundamental nuclear
safety objective, but occurrences of unexpected and largely unpreventable events should be
considered. The remaining safety tool for such unforeseeable events is the mitigation of
radiological consequences, which means: (i) reducing radioactive releases into the public
domain by containing radioactive substances as far as feasible and (ii) responding to the
emergency with prompt ad hoc radiological protection measures, in order to provide adequate
protection to emergency and recovery workers and the affected public.
A few years before the accident, the ICRP issued a revision and update to its
main recommendations (ICRP 2007a). They include renewed radiological protection
principles (Cooper 2012) providing the basis for a number of new national and international
regulatory instruments. Implementation of these recommendations is still on-going (IAEA
2011a, EC 2011).
Existing international obligations and intergovernmental requirements and guidance
documents generally follow ICRP recommendations. The Convention on Early Notification
of a Nuclear Accident (IAEA 1986b) and the Convention on Assistance in the Case of a
Nuclear Accident or Radiological Emergency (IAEA 1986c) were adopted in 1986, and place
legally binding obligations related to nuclear and radiological accidents on the parties to
these conventions and on the International Atomic Energy Agency (IAEA). Article 16 of the
Convention on Nuclear Safety (IAEA 1994), and Article 25 of the Joint Convention on the
Safety of Spent Fuel Management and the Safety of Radioactive Waste Management (IAEA
1997c) establish legally binding obligations related to emergency preparedness for the parties
to the conventions. In 2005, the IAEA established an Incident and Emergency Centre (IEC) to
serve as a global focal point for preparedness and response to nuclear and radiological incidents
and emergencies irrespective of their cause. Under the Early Notification and Assistance
Conventions, the IEC coordinates actions of international experts and efforts within the IAEA,
responses of Member States. Moreover, the IAEA statutorily establishes international safety
on Preparedness and Response for a Nuclear or Radiological Emergency (IAEA 2002a)
incorporates and establishes requirements for emergency preparedness and response so that
emergency management can be seen in its entirety by the bodies concerned. It elaborates on,
augments and structures all the requirements relating to emergency management established in
or Radiological Emergency (IAEA 2007b) and the International Safety Guide on Criteria for
use in Preparedness and Response for a Nuclear or Radiological Emergency (IAEA 2011c)
(which was adopted after the accident) are intended to assist Member States in the application
of the Safety Requirements on Preparedness and Response for a Nuclear or Radiological
Emergency (IAEA 2002a) and to help in the fulfilment of the IAEA’s obligations under the
Assistance Convention. Additionally, over the years the IAEA has issued a number of technical
documents providing advice on issues of emergency planning, preparedness and response,
including on procedures for determining protective actions following a reactor accident (IAEA
1997b), procedures for assessment and response during a radiological emergency (IAEA
2000c), procedures for monitoring in a nuclear or radiological emergency (IAEA 1999b),
methods for developing preparedness for a nuclear or radiological emergency (IAEA
1997a, 2003), medical preparedness and response (IAEA 2002b, 2005c), preparation, conduct
and evaluation of exercises to test preparedness for a nuclear or radiological emergency (IAEA
2005b), e-learning tools for first response to a radiological emergency preparedness and
response (IAEA 2009a), first response to a radiological emergency (IAEA 2006, 2009b),
portable digital assistant for first responders to a radiological emergency (IAEA 2009c), the
Joint Radiation Emergency Management Plan of the International Organizations (the so-called
JPLAN) (IAEA 2010), cytogenetic dosimetry: applications in preparedness for and response to
radiation emergencies (IAEA 2011d), IAEA response and assistance network (IAEA 2011e),
and communication with the public in a nuclear or radiological emergency (IAEA 2012b).
The Japanese authorities relied upon ICRP Recommendations in making radiological
protection decisions following the accident. Although at the time of the accident specific advice
on the application of the Recommendations to emergency situations had been issued by the
ICRP, the guidance was relatively new and had not been tested in practice. In fact, around year
before the accident, the ICRP had issued specific recommendations for the application of the
ICRP Recommendations to the protection of people in emergency exposure situations (ICRP
2009a) and of people living in long-term contaminated areas after a nuclear accident or
a radiological emergency (ICRP 2009b). The timeliness of this recent guidance has been
recognised (Lochard 2012). The decision by the Japanese authorities to follow ICRP guidance
facilitated the retrospective analyses presented in this report.
1.5. Identification and assembly of issues
The issues identified have been assembled in an arbitrary order and are treated in separate
(1) inferring radiation risks (and the misunderstanding of nominal risk coefficients);
(2) attributing radiation effects from low dose exposures;
(3) quantifying radiation exposure;
(4) assessing the importance of internal exposures;
(5) managing emergency crises;
(6) protecting rescuers and volunteers;
(7) responding with medical aid;
(8) justifying necessary but disruptive protective actions;
(9) transitioning from an emergency to an existing situation;
(10) rehabilitating evacuated areas;
(11) restricting individual doses of members of the public;
(12) categorising public exposures due to an accident;
(13) caring for infants and children;
(14) considering pregnant women and their foetuses and embryos;
502A J Gonz´ alez et al
(15) monitoring public protection;
(16) dealing with ‘contamination’ of territories, rubble and residues and consumer products;
(17) recognising the importance of psychological consequences; and
(18) fostering the sharing of information.
Each section will start by describing the major features of the issue and will follow with
a full discussion. It is noted that some of the issues were recognisable before the March 2011
accident as they had arisen after other accidents, notably in the aftermath of the 1986 accident
at the Chernobyl NPP (IAEA 1986a, 1988a, 1988b, 1991, 1996a, 1996b, 2001, UNSCEAR
2006a, 2006b, WHO 1995).
1.6. Environmental consequences
Radiological protection of the environment is specifically addressed by (ICRP 2003a, 2008,
2009c) and it is touched upon incidentally in this report. Following the accident the immediate
priority was the protection of people rather than the environment. It may take time to assess
the radiological environmental consequences of the accident. In the meantime, claims of
environmental damage will probably arise. For example, it was suggested that the accident
and releases of radioactive elements caused physiological and genetic damage to the pale grass
blue Zizeeria maha, a common lycaenid butterfly in Japan (Hiyama et al 2012). Studies will
be needed to evaluate the marine environmental impact of the accident because most of the
radioactivity released was deposited into the oceans. Increased radioactivity concentrations
have been reported in samples of animal plankton in the sea near the accident site (JAIF 2011)
and trace levels of radioactive caesium have been found in blue-fin tuna (Madigan et al 2012).
The ICRP has provided a framework for assessing the impact of ionising radiation on
non-human species (ICRP 2003a, 2003b) and recommendations on the concept and use of
reference animals and plants (ICRP 2008) and on the relevant transfer parameters (ICRP
2009c). The ICRP is currently working on a number of environmental protection issues,
including: collecting, reviewing and summarising studies that allow the derivation of radiation
weighting factors for alpha- and beta-radiation for application in dose assessment for reference
animals and plants; compiling a set of transfer factor data for reference animals and plants
within an internally consistent, documented format, for the more useful radionuclides with
respect to the relevant ICRP exposure situations; realistic dosimetry for non-human species;
and integrating a system for the protection of human and non-human species. The results of
these activities, which were not available at the time of the accident, should prove useful for
preliminary assessments of the potential environmental impacts of the accident.
Non-radiological environmental consequences appear to be surfacing as a result of
the accident. For example, all NPPs in Japan, which provide around 30% of the electric
energy consumed in the country, were shut down and replaced by fossil fuel generation,
therefore increasing significantly the release of greenhouse gases into the environment. Further,
the consequences of chemical contamination of the environment which resulted from the
widespread damage caused by the tsunami are yet to be determined (Bird and Grossman 2011).
1.7. International cooperation
Japan is a country that is naturally well-prepared to cope with disasters, inter alia due to
its location in a very active seismic region and its experience in dealing with earthquakes,
tsunamis, typhoons and other natural disasters over centuries. However, the consequences of
three catastrophic events occurring together (a large earthquake, a huge tsunami and a major
nuclear accident) left the country in need of assistance from other countries. This involvement
was extremely beneficial but did raise challenging issues.
The European Union responded swiftly with an assistance package to the affected
communities (EC 2012). Financial assistance (e.g. Kuwait 2012) and help to affected children
(e.g. Pravda 2012) was offered. The USA sent planes over the area to help monitor the
radioactive releases, and sent 60000 military personnel to help with the humanitarian efforts.
France, Russia and other countries provided robotics, cranes and expertise. The Assistant
Secretary for Preparedness and Response of the US Department of Health and Human Services
deployed a five-person advisory team to the US Embassy in Tokyo (Simon et al 2012). The
US Department of Energy’s National Atmospheric Release Advisory Center provided a wide
range of predictions and analyses including: daily Japanese weather forecasts and atmospheric
transport predictions; estimates of possible doses in Japan based on hypothetical scenarios
of the US Nuclear Regulatory Commission; predictions of possible plume arrival times and
dose levels at US locations; and source estimation and plume model refinement based on
Department of Energy/National Nuclear Security Administration’s Aerial Measuring System
deployed personnel and equipment to partner with the US forces in Japan (Craig and David
2012). The US Medical Radiobiology Advisory Team, which is the operations arm of the
US Armed Forces Radiobiology Research Institute, provided guidance and advice to the US
military leaders in Japan aimed at ensuring the safety of US service members, family members
and civilians and supported the humanitarian relief in a coordinated effort with the government
of Japan (Van Horne-Sealy et al 2012). A number of challenges were identified (Miller 2012),
particularly at the level of US states which were not always notified of outcomes by the US
federal agencies (Salame-Alfie et al 2012). The decision to issue an evacuation alert for US
citizens within 50 miles of the site by the US Nuclear Regulatory Commission (NRC 2011)
was not without controversy; this was based on calculations from a computer model for upper
bound radioactive material releases from severe reactor accidents, although its technical basis
was not entirely clear (ANS 2012, Musolino et al 2012). In one of the countries affected by
the fallout from the accident, the Republic of Korea, some over-reactions occurred and it was
concluded that significant radioactive contamination of a small country could lead to a severe
national crisis, the most important factor being the socio-economic damage caused by stigma,
which in turn is caused by a misunderstanding of the radiation risk (Lee 2012a). It is clear that
the Fukushima nuclear reactor accident has affected many countries throughout the world and
lessons are continually being learned that should be helpful in the event of any future nuclear
A generic lesson is that, while external assistance following a nuclear accident is
helpful and appreciated, foreign authorities should be careful and prudent in providing
contradictory public recommendations that might be unsuited to a local situation. The
distrust that hinder effective actions.
2. Issues identified
2.1. Inferring radiation risk and nominal risk coefficients
In the aftermath of the accident, claims were made that the risk of radiation-induced health
effects is much higher than the nominal risk coefficients recommended by the ICRP for
radiation protection. Further, the dose and dose-rate effectiveness factor used by the ICRP and
others for estimating radiation risk at low doses was questioned.
504 A J Gonz´ alez et al
This misunderstanding was reinforced during several television shows with a wide viewing
audience and added to the existing concern and confusion. The substantial biological and
epidemiological data supporting the basic notion of the nominal risk coefficients used for
radiological protection purposes were not understood and were misrepresented in the media. A
nominal risk coefficient is a sex-averaged and age-at-exposure-averaged lifetime risk estimate
for a representative population. Nominal risk coefficients are used in radiation protection to
provide an appropriate level of protection for people and the environment. They are based
on a substantial compendium of knowledge about radiation health effects accrued over the
past 100 years. Following a review of the biological and epidemiological information on the
health risks attributable to ionising radiation, the new ICRP Recommendations (ICRP 2007a)
reconfirmed the previous estimate of the combined detriment due to excess cancer and heritable
effects, which remain unchanged at around 5% per sievert of effective dose. This value is
consistent with international estimates of radiation risk. The concept of a dose and dose-rate
effectiveness factor (DDREF) also was not understood. This misunderstanding was due in
part to its rather convoluted wording, i.e. it is ‘a judged factor that generalises the usually
lower biological effectiveness (per unit of dose) of radiation exposures at low doses and low
dose rates as compared with exposures at high doses and high dose rates’. But the confusion
is particularly reinforced when translated into Japanese and other languages. The radiation
protection community must do a better job of explaining to the public and the media these
of science that has been synthesised by international committees throughout the world.
2.1.1. Radiation risk coefficients.
epidemiological data and provide the basis of radiological protection recommendations. Risk is
used to mean the probability of occurrence of a radiation-induced effect; it is a prospective
concept addressing the chance that an event will occur in the future. Risk coefficients are
numerical values that express the expected annual increase in the incidence or mortality rate per
unit dose. When multiplied by a specific dose, risk coefficients can be used for inferring risk,
namely for estimating the probability that such a dose might produce harm. Risk coefficients
are based on the latest epidemiological and biological information on radiation-induced cancer
and heritable effects. To estimate these coefficients the ICRP uses inter alia the evaluations of
the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) in
addition of its own assessments,.
Radiation risk coefficients are based upon direct human
2.1.2. Quantification of risk.
risk: (i) the detriment-adjusted risk, defined as ‘the probability of the occurrence of a
stochastic effect, modified to allow for the different components of the detriment in order
to express the severity of the consequence(s)’; and (ii) the nominal risk coefficient, defined
as the ‘sex-averaged and age-at-exposure-averaged lifetime risk estimates for a representative
population’, which is a stated value recommended for radiological protection purposes. The
a theoretical value of risk for the protection of populations without any distinctions based on
sex or age, as opposed to an actual risk coefficient that is derived from epidemiological studies
and is specific to population characteristics (such as age and sex) and the outcome of interest
(such as a specific cancer). The real risk coefficients show a distribution of values, which can
be presented as a cumulative distribution function, i.e. as a description of the probability that
a real-valued coefficient with a given probability distribution will be found at a value less than
or equal to it, or as a probability density function, i.e. a description of the relative likelihood
for the risk coefficient to take on a given value. The distributions are usually normal, i.e. a
continuous probability distribution that has a bell-shaped probability density function that is
Thus, the ICRP uses two fundamental concepts for quantifying
characterised by the mean risk coefficient (location of the peak) and its variance, i.e. a measure
of how far a set of risk coefficients is spread out. When modifier factors are applied to the data,
the distribution usually becomes log-normal. From these distributions of ‘real’ risk coefficients
extrapolated from epidemiological studies, the nominal risk coefficients are derived. Nominal
risk coefficients are used in radiation protection and are risk-informed, but since they are sex-
and age-averaged values for a representative individual or population they should not to be used
for inferring risk to an individual or specific population.
2.1.3. The dose–response model.
increase in the incidence of stochastic effects is assumed by the ICRP to occur with a small
probability and in proportion to the increase in radiation dose over the background dose. Use of
this so-called linear-non-threshold (LNT) model is considered by the ICRP to be a prudent and
practical approach to managing risk from radiation exposure. The LNT model is not universally
accepted as biological truth, but rather, because we do not actually know what level of risk is
associated with very-low-dose exposure, it is considered to be a prudent judgement for public
policy aimed at avoiding unnecessary risk from exposure (ICRP 2005a, 2007a).
At radiation doses below around 100 mSv in a year, the
2.1.4. The dose and dose-rate effectiveness factor.
by UNSCEAR (2000) that generalises the usually lower biological effectiveness (per unit of
dose) of radiation exposures at low doses and low dose rates as compared with exposures at
high doses and high dose rates. In general, cancer risk at low doses and low dose rates is
not directly apparent from epidemiological studies because the level of excess risk is just too
small in comparison with the high natural occurrence of cancer to observe directly. In order to
estimate risk in these dose ranges of uncertainty, a DDREF is applied to epidemiological data
obtained at higher doses and dose rates to reduce the estimate of risk. The DDREF is based on
judgement and considers a broad range of epidemiological, animal and cellular data obtained
at high doses and dose rates. In its 1990 Recommendations (ICRP 1991) the ICRP judged
that a DDREF of 2 should be applied for the general purposes of radiological protection. In
its new 2007 Recommendations, the ICRP continued to use broad judgements in its choice of
DDREF based upon dose–response features of experimental data, epidemiological data and the
results of probabilistic uncertainty analysis (NCRP 1997, EPA 1999, NCI/CDC 2003, ICRP
2005a). No compelling reason was found to change its 1990 recommendations for a DDREF
of 2, emphasising, however, that ‘this continues to be a broad whole number judgement for the
practical purposes of radiological protection which embodies elements of uncertainty’ (ICRP
2007a, section 73). The ICRP considers that the adoption of the LNT dose–response model
(combined with a DDREF) provides a prudent basis for the practical purposes of radiological
protection, i.e. for the management of risks from low dose radiation exposure (ICRP 2007a,
section 65). It is recognised that others have considered lower and higher values for the DDREF
and that DRREF evaluations are on-going as new data on radiation effects are accumulating.
The DDREF is a judged factor introduced
2.1.5. The detriment-adjusted nominal risk coefficients.
represents the expected total harm to health in an exposed group and its descendants as a result
of the group’s exposure. Detriment is a multidimensional concept used to quantify future harm.
It involves the incidence of radiation-related cancer or heritable effects, the lethality of these
conditions, quality of life and years of life lost owing to these conditions.
The ICRP recommends detriment-adjusted nominal risk coefficients (usually expressed as
% Sv−1or 10−2Sv−1), which are a combination of the notions of nominal risk coefficient
and detriment-adjusted risk. They are intended for establishing protection measures to limit
stochastic effects (after exposure to radiation at a low dose rate) over an adult population (i.e.
Detriment is distinct from risk; it
506A J Gonz´ alez et al
representative of an occupationally exposed population) and also over a whole population (i.e. a
generic population that includes adults and children).
Following a review of the biological and epidemiological information on the health
risks attributable to ionising radiation, the more recent ICRP Recommendations reconfirm
its previous estimates of the combined detriment due to excess cancer and heritable effects,
which remain unchanged at around 5% Sv−1of effective dose (ICRP 2007a, section e). The
ICRP has calculated the detriment-adjusted nominal risk coefficients used for inferring risk for
radiological protection purposes through the process described in its recommendations (ICRP
2005a, 2007a). The steps used for the estimations are as follows.
(1) For estimating risk of cancer: (a) the lifetime risk for radiation-associated incident cancers
is estimated. For 14 organs or tissues, male and female lifetime excess cancer risks are
estimated from epidemiological studies by using both the excess relative risk (ERR) and
excess absolute risk (EAR) models and these lifetime estimates of risk are then averaged
across sexes. (b) A DDREF is applied. The lifetime risk estimates are adjusted downward
by a factor of 2 to account for the assumed ameliorating effect when radiation is received at
a low dose and low dose rate, i.e. a DDREF of 2 is assumed (except for leukaemia, where
the linear-quadratic model for risk already accounts for the DDREF). (c) Risk estimates are
transferred across populations. In order to estimate radiation risk for each cancer site, a
weighting of the ERR and EAR lifetime risk estimates is assumed to provide a reasonable
basis for generalising across populations with different baseline cancer rates. (d) Nominal
risk coefficients. These weighted risk estimates, when applied to and averaged across seven
western and Asian populations, provided the nominal risk coefficients. (e) Adjustment for
lethality. The lifetime risks for respective cancer sites, which were based on excess incident
cancers, were converted to fatal cancer risks by multiplying by their lethality fractions, as
derived from representative national cancer survival data. (f) Adjustment for quality of life.
A further adjustment was applied to account the morbidity and suffering associated with
non-fatal cancers. (g) Adjustment for years of life lost. Average years of life lost for a
given cause was computed for each sex in each composite population as the average over
ages at exposure and subsequent attained ages of the remaining lifetime. The weights were
equal to the number of deaths from the cause of interest in each age group. These were
converted to relative values by division by the average years of life lost for all cancers.
An adjustment for years of life lost was then applied to the result of the previous steps.
(h) Radiation detriment. The results of the calculations above yielded an estimate of the
radiation detriment associated with each type of cancer. These, when normalised to sum to
unity, constitute the relative radiation detriments.
(It should also be underlined that the risk coefficients are mainly based on estimates
from epidemiological studies of the population cohorts exposed as a result of the atomic
bombing of Japan in 1945, although other populations exposed to medical radiation are
incorporated when applicable and available.)
(2) For estimating radiation risk for heritable diseases: (a) the baseline frequencies of human
genetic diseases of all classes (a set of values of P) is established. (b) The average
spontaneous mutation rate per generation for human genes is estimated. (c) Since no
human data are available to demonstrate heritable effects following radiation exposure,
the average rate of radiation-induced mutations in mice is estimated and it is assumed that
above, the genetic doubling dose (DD) is estimated. The DD is the radiation dose required
to produce as many mutations in the next generation as those that arise spontaneously in
the exposed generation. (e) The mutation component (MC) for different classes of genetic
diseases is estimated. MC is a relative measure of the relationship between change in
mutation rate and increase in disease frequency. (f) The potential recoverability correction
factor (PRCF) for different classes of mutation is estimated. The PRCF allows for differing
degrees of recoverability of mutations in live births, i.e. the fraction of mutations that is
the following equation, which uses the estimates from (a) to (f) above, provides the risk per
unit dose for heritable effects: P × (1/DD) × MC × PCRF.
In brief, the ICRP recommended that the following nominal coefficients should be used for
radiological protection purposes: for detriment-adjusted cancer risk, 5.5 × 10−2Sv−1for the
whole population and 4.1×10−2Sv−1for adult workers; for heritable effects, 0.2×10−2Sv−1
for the whole population and 0.1 × 10−2Sv−1for adult workers.
These values are consistent with current scientific knowledge about radiation risks
described in the UNSCEAR reports. UNSCEAR (2006a) estimated that, following radiation
exposure of 1 Sv, the excess lifetime risk of death (averaged over both sexes) is: (i) for all
solid cancers combined 4.3–7.2% Sv−1for an acute dose of 1 Sv; and (ii) for leukaemia
0.6–1.0 % Sv−1for an acute dose of 1 Sv (UNSCEAR 2006a, 2006b, 2010). Moreover, taking
into account available radiobiological information and epidemiological studies in animals,
UNSCEAR also estimated the risk of heritable diseases in one generation due to exposure of
an absorbed dose of 1 Gy and concluded that the risks in the first generation (per unit low-LET
dose) are: (i) for dominant effects (including X-linked diseases) ∼750–1500 per million per
gray vis-` a-vis a baseline frequency of 16500 per million; (ii) for chronic multifactorial diseases
∼250–1200 per million per gray vis-` a-vis a baseline frequency of 650000 per million; and
(iii) for congenital abnormalities ∼2000 per million per gray vis-` a-vis a baseline frequency
of 60 000 per million (chromosomal effects were assumed to be subsumed in part under
the risk of autosomal dominant and X-linked diseases and in part under that of congenital
abnormalities). Thus, as far as radiation-induced heritable diseases is concerned, UNSCEAR
concluded that for a population exposed to radiation in one generation only, the risks to the
progeny of the first post-radiation generation are estimated to be 3000–4700 cases per gray per
million progeny, which constitutes 0.4–0.6% of the baseline frequency of those disorders in the
human population (UNSCEAR 2001).
Thus, it can be concluded that the detriment-adjusted nominal risk coefficients
recommended by the ICRP for radiological protection purposes are consistent with
international estimates of radiation risk, e.g. the estimates of UNSCEAR (2001) and also
those of the US Committee to Assess Health Risks from Exposure to Low Levels of Ionizing
Radiation (BEIR VII) (National Research Council 2006). It seems therefore that the claims that
radiation risks have been underestimated by ICRP and others are not supported by the scientific
2.1.6. Misunderstanding the coefficients.
epidemiological and ethical foundations supporting the basic notion of the detriment-adjusted
nominal risk coefficients, these coefficients were misunderstood by the public. Granted that
trying to explain to the lay public the concept of ‘nominal’, much less ‘detriment-adjusted
nominal risk coefficients’, is a daunting challenge, false claims propagated by media coverage
that the ICRP intentionally provided low risk estimates because of a pro-nuclear bias
contributed to misunderstanding, confusion and anxiety. The concept of a DDREF was notably
misunderstood. A serious cause of confusion was the wording used for these concepts, which
is somewhat convoluted (even in English), particularly after translation into Japanese and other
Notwithstanding the substantial biological,
508 A J Gonz´ alez et al
with the public and press in more easily understood and transparent terms. Perhaps
public-friendly and easily understood brochures (and/or websites) should be develop that define
and describe the scientific basis, reasonableness and usefulness of the concepts of risk and
detriment used for radiological protection, and in particular the detriment-adjusted nominal
risk coefficients used for limiting the likelihood of stochastic effects occurring after exposure
to radiation at a low dose rate.
The radiation protection community should renew its efforts to communicate
2.2. Attributing radiation effects from low dose exposures
Since the accident, hypothetical estimates of future casualties due to the accident have been
made. They oscillated between some hundreds of cases in the peer reviewed literature to half
a million in reports in the media. These alarmist and misleading theoretical calculations have
caused anxiety and emotional distress in the Japanese population.
The inability of epidemiological health research to determine whether there are any health
consequences of exposures below about 100 mSv has led to the adoption of the LNT model
for the purposes of radiological protection. While prudent for radiological protection, the
LNT model is not universally accepted as biological truth, and its influence and inappropriate
use to attribute health effects to low dose exposure situations is often ignored. A clear
explanation of the limitations of epidemiology is essential for understanding the reasons
why collective effective doses aggregated from small notional individual doses should not
be used to attribute health effects to radiation exposure situations, neither retrospectively nor
prospectively. The ICRP, UNSCEAR, and others strongly urge that this misuse of collective
dose should be avoided. It is recognised, however, that collective dose is a very useful concept
which decision-making bodies may use to impose radiological protection measures even at low
doses, in part for reasons of social duty, responsibility, utility, prudence and precaution. But the
distinction between prudent practices for radiological protection and the misuse of protection
concepts to attribute adverse health effects is not always clearly enunciated and a much better
approach is needed.
2.2.1. Ascribing future deaths.
after accidents, nominal risk coefficients have been improperly used to ascribe hypothetical
future deaths. Speculative, unproven, undetectable and ‘phantom’ numbers are obtained by
multiplying the nominal risk coefficients by an estimate of the collective dose received by a
huge number of individuals theoretically incurring very tiny doses that are hypothesised from
radioactive substances released into the environment.
The same type of misleading attribution was made after the accident. One attempt
purported that total deaths will lie in the range 15–1300, while incident cases will number
24–2500—noting that these are cancers among the public (of the order of a million people
exposed) and not among the workers at the NPP (Ten Hoeve and Jacobson 2012a). The
estimates were rigorously criticised (Richter 2012), and responses to the critique were made
(Ten Hoeve and Jacobson 2012b). It has been noted that the uncertainties surrounding the crisis
itself, in addition to the absence of demonstrated risk at the tiny exposures to the population and
the uncertain validity of the linear extrapolation of risk down to such tiny doses, raise serious
questions about whether these calculations could provide even an order-of-magnitude guess as
to possible health consequences (Brumfiel 2012). Further, given the wide range of uncertainties
in the risk models used, it is likely that zero effects should be included as a lower bound to the
estimates, or even as a central estimate of the likely future effects.
It should be remembered that the exposures from the Fukushima releases are in large part
below radiation levels received annually from natural sources of radiation in the environment
In some low dose radiation exposure situations, particularly
or from the annual population exposures to medical radiation such as computed tomography
The media reporting on future cancer cases was dramatic and sensational. For instance,
on 20 March 2011 it was predicted that the death toll in the years ahead could exceed 500000
people (TCNN 2011).
These hypothetical computations of effects are based on assumptions that cannot be
validated because the estimated doses are substantially below the level where epidemiology has
the ability to detect increases above the natural occurrence. The large number of deaths reported
following these theoretical predictions, especially when not contrasted with the normal high
occurrence of death, is alarmist and unfounded and has caused severe anxiety and emotional
distress in the Japanese population
2.2.2. Previous misattributions.
serious after the Chernobyl accident and caused severe mental distress and significant
psychological harm to the affected population. A 2006 analysis (Cardis et al 2006)
concluded that Chernobyl may eventually cause 16000 thyroid cancers and 25000 other
cancers in Europe by 2065, and that 16000 of these cancers will be fatal (since thyroid
cancer is rarely fatal, most of the cancer deaths will be from other cancers), with the
caveat that these estimates do not consider the recovery-operation workers. Moreover,
according to a book published in 2009 (NYAS 2010) authored by three Russian scientists
including the former director of the Institute of Nuclear Energy of the National Academy
of Sciences of Belarus, the Chernobyl death toll amounted to 985000 people between
1986 and 2004. In the media it was claimed inter alia that the Chernobyl nuclear
accident caused as many as 170000 cancer deaths in North America alone (www.
huffingtonpost.com/john-rosenthal/level-7-major-nuclear-acc b 852666.html). The Union of
Concerned Scientist (UCS) released a revision to their previous estimates of deaths caused
by Chernobyl, which revises them slightly downward from their original posing (7 April
many-cancers-did-chernobyl-really-cause-updated). In spite of these apocalyptic predictions,
the only consistent evidence of harm from the Chernobyl reactor accident to the general
population has been the thyroid cancer epidemic that followed the ingestion of radioactive
iodine in contaminated milk by children. After 20 years of study, no other cancers have been
convincingly linked to Chernobyl radiation, even among the recovery workers (UNSCEAR
The confusing attribution of health effects was particularly
2.2.3. Misuse of the collective dose concept.
misinterpretation of the quantities used by the ICRP, particularly of the quantity collective
dose, coupled with the previously discussed misunderstanding of the detriment-adjusted
nominal risk coefficients. As discussed before, the coefficients are not applicable to actual
individuals because they are sex-averaged and age-at-exposure-averaged lifetime risk estimates
for a representative population. In fact, these coefficients are termed ‘nominal’ because
they relate to the exposure of a hypothetical population of women and men with a typical
age distribution and are computed by averaging over age groups and both sexes. They
are used to define the main radiological protection quantity, the effective dose, which is
computed by age- and sex-averaging. There are many assumptions inherent in the definition
of nominal factors to assess effective dose and the estimates are defined explicitly for
no other intent than radiological protection purposes. These coefficients should not be
used to estimate the mathematical expectations of harm in a real population exposed
Part of the confusion is triggered by a
510 A J Gonz´ alez et al
to small radiation doses, much less to attribute prospectively potential deaths in this
The ICRP has stressed that effective dose is a prospective protection quantity to be used
for the purposes of radiological protection in prospective dose assessments for planning and
optimisation of protection, and in demonstration of compliance with dose limits for regulatory
purposes. Effective dose is not recommended (and would be inappropriate) for epidemiological
evaluations, and should not be used for retrospective investigations of risk or health effects
(ICRP 2007a, section j).
The quantity collective effective dose is the summation of the individual effective doses
calculated for each person in an exposed population, and the ICRP recommends that the
collective dose should be used as an instrument for optimisation, for comparing radiological
protection options, predominantly in the context of occupational exposure (ICRP 2007a,
section k, and annex B, section B.234ff). The ICRP and UNSCEAR have stated that the
collective effective dose is not intended as a tool for epidemiological risk assessment, and it
is inappropriate to use it in risk projections. The ICRP and UNSCEAR have underlined that
the aggregation of very low individual doses over extended time periods is inappropriate, and
more importantly the calculation of a theoretical number of cancer deaths based on collective
effective doses from trivial individual doses should always be avoided (ICRP 2007a, section k;
2.2.4. Inferring risk compared with observing effects.
both detriment-related concepts, they have a distinct meaning in the ICRP Recommendations.
Risk is related to the probability (or chance) that an effect will occur, whereas effect is the
outcome of concern. Risk may be inferred, while effects should be observed. The distinction
is important for low radiation dose situations. Radiation-related cancer risks are inferred using
formal quantitative uncertainty analysis that combines the different components of estimated
radiation-related cancer risk, accounting for their uncertainties, with and without allowing for
an uncertain possibility of a low dose threshold below which no risk is assumed. Conversely,
actual cancers in specific cohorts of people may be revealed by epidemiological studies where
elevations in cancer occurrence are observed.
While the ICRP Recommendations imply that risks may be inferred for any prospective
assessment of generic radiation exposure situations, such inference of radiation risks should not
be automatically interpreted as meaning that effects, e.g. cancer deaths of specific individuals,
will be revealed by retrospective assessment. ICRP Publication 99 (ICRP 2005a, section
47) summarises the dilemma: ‘At low and very low radiation doses, statistical and other
variations in baseline risk tend to be the dominant sources of error in both epidemiological
and experimental carcinogenesis studies, and estimates of radiation-related risk tend to be
highly uncertain because of a weak signal-to-noise ratio and because it is difficult to recognise
or to control for subtle confounding factors. At such dose levels, and with the absence
of bias from uncontrolled variation in baseline rates, positive and negative estimates of
radiation-related risk tend to be almost equally likely on statistical grounds, even under the
LNT theory’. Following exposure to low radiation doses below about 100 mSv an increase of
cancer has not been convincingly or consistently observed in epidemiological or experimental
studies and will probably never be observed because of overwhelming statistical and biasing
In sum, theoretical cancer deaths after low dose radiation exposure situations are obtained
by inappropriate calculations based on the LNT model and misuse of the collective dose
concept. Any effects—if they occur at all—will be so small that they would fall within the
‘noise’ (scatter) of the ‘spontaneous’ cancer of unexposed people (Streffer 2008).
While radiation risks and effects are
2.2.5. Attribution of health effects.
to different levels of exposure to ionising radiation, and reached the following conclusions
UNSCEAR has addressed the attribution of health effects
(a) An observed health effect in an individual could be unequivocally attributed to radiation
exposure if the individual were to experience tissue reactions (often referred to as
‘deterministic’ effects), and differential pathological diagnoses were achievable that
eliminated possible alternative causes. Such deterministic effects are experienced as a result
of high acute absorbed doses (i.e. about 1 Gy or more), such as might arise following
exposures in accidents or in radiotherapy.
(b) Other health effects in an individual that are known to be associated with radiation
exposure—such as radiation-inducible malignancies (so-called ‘stochastic’ effects)—
cannot be unequivocally attributed to radiation exposure, because radiation exposure is
not the only possible cause and there are at present no generally available biomarkers that
are specific to radiation exposure. Thus, unequivocal differential pathological diagnosis
is not possible in this case. Only if the spontaneous incidence of a particular type of
stochastic effect were low and the radiosensitivity for an effect of that type were high
(as is the case with some thyroid cancers in children) would the attribution of an effect
in a particular individual to radiation exposure be plausible, particularly if that exposure
were high. But even then, the effect in an individual cannot be attributed unequivocally to
radiation exposure, owing to competing possible causes.
(c) An increased incidence of stochastic effects in a population could be attributed to radiation
exposure through epidemiological analysis—provided that, inter alia, the increased
incidence of cases of the stochastic effect were sufficient to overcome the inherent statistical
uncertainties. In this case, an increase in the incidence of stochastic effects in the exposed
population could be properly verified and attributed to exposure. If the spontaneous
incidence of the effect in a population were low and the radiosensitivity for the relevant
stochastic effect were high, an increase in the incidence of stochastic effects could at least
be related to radiation, even when the number of cases was small.
(d) Although demonstrated in animal studies, an increase in the incidence of hereditary effects
in human populations cannot at present be attributed to radiation exposure; one reason for
this is the large fluctuation in the spontaneous incidence of these effects.
(e) Specialised bioassay specimens (such as some haematological and cytogenetic samples)
can be used as biological indicators of radiation exposure even at relatively low levels of
radiation exposure. However, the presence of such biological indicators in samples taken
from an individual does not necessarily mean that the individual would experience health
effects due to the exposure.
(f) In general, increases in the incidence of health effects in populations cannot be attributed
reliably to chronic exposure to radiation at levels that are typical of the global average
background levels of radiation. This is because of the uncertainties associated with the
assessment of risks at low doses, the current absence of radiation-specific biomarkers for
health effects and the insufficient statistical power of epidemiological studies. Therefore,
UNSCEAR does not recommend multiplying very low doses by large numbers of
individuals to estimate numbers of radiation-induced health effects within a population
(g) UNSCEAR notes that public health bodies need to allocate resources appropriately, and
that this may involve making projections of numbers of health effects for comparative
purposes. This method, though based upon reasonable but untestable assumptions, could
be useful for such purposes provided that it were applied consistently, the uncertainties in
512 A J Gonz´ alez et al
the assessments were taken fully into account, and it were not inferred that the projected
health effects were other than notional.
2.2.6. Expectations on health effects.
understanding among scientists that public doses due to the accident are so low that:
(i) deterministic health effects have not and will not occur in the general population; and
(ii) epidemiological studies will not be able to reveal any stochastic effects. The limitations and
robustness of possible epidemiological studies have been recently discussed in the literature.
Statistical cancer risk models describing how the radiation-related risks of particular types
of cancer vary with the doses of radiation received by specific tissues, which are derived
from data gathered in epidemiological studies of exposed groups of people and guided by an
incomplete understanding of radiobiological mechanisms gleaned from experimental studies,
assume that at low doses or low dose rates the excess risk of cancer is directly proportional to
the dose of radiation received, with no threshold dose—the LNT dose–response model—and
the inferred summary estimate of the overall average lifetime excess risk of developing a
serious cancer is ∼5% Sv−1(Wakeford 2012). It is these cancer risk models and this inferred
nominal risk estimate that provide the technical basis of radiological protection. A preliminary
review of current plans necessary for risk evaluation of cancer and non-cancer diseases from
the accident have therefore been described mainly from the view point of inferring health
risk using epidemiological approaches rather than for attributing health effects (Akiba 2012).
Moreover, it was estimated that apart from the extreme psychological stress caused by the
horrific loss of life following the tsunami, the large-scale evacuation from homes and villages
and the fear of radiological consequences, such studies have limited to no chance of providing
information on possible health risks following low dose exposures received gradually over
the resultsof large-scaleradiation epidemiologicalstudies of thehealth effectsof the Chernobyl
accident, including radiation risks for emergency workers and the affected population (Ivanov
2012, UNSCEAR 2008). Apart from the excess of thyroid cancer among children who drank
contaminated milk and the increase in mental disorders following the Chernobyl accident, no
other adverse health effects have been convincingly reported despite much higher population
doses than at Fukushima (UNSCEAR 2008, Tokonami et al 2012).
While even at such low doses, the risk of stochastic health effects can be inferred and used
for radiological protection decisions, it should be clear for the Japanese people and authorities
that it will not be possible to obtain unequivocal scientific evidence for the expression of
such a risk in the future. For this reason, theoretically calculated radiation effects from the
low doses expected from the accident should not be used in notional projections of radiation
harm. Notwithstanding, it may be necessary for the Japanese decision-making bodies to ascribe
nominal radiation risks to prospective exposure situations and impose radiological protection
measures even at low doses, inter alia for reasons of social duty, responsibility, utility, prudence
There is a general though not universally accepted
2.2.7. Epistemological limitations.
the nature of knowledge, i.e. ‘how we know what we know’. The epistemological limitations
of the sciences of radiobiology and radioepidemiology, and their influence on the attribution
of health effects to low dose exposure situations are often ignored. A clear explanation of
the epidemiological limitations described above and the more fundamental epistemological
from small notional individual doses should not be used to attribute health effects to radiation
exposure situations, neither retrospectively nor prospectively. While there are reasons for the
Epistemology is the branch of philosophy that deals with
Japanese authorities to ascribe ‘detriment-adjusted nominal risk coefficients’ to prospective
exposure situations involving low radiation doses and impose commensurate radiological
protection measures, these coefficients should not be used for attributing prospective health
effects to radiation exposure situations at doses below the levels at which increased incidence
can be actually observed if they occurred at all. The reporting of theoretical future cancer deaths
due to the accident has already become an important ‘detriment’ (and inappropriate measure of
harm) to the Japanese people and any future pronouncements should be avoided.
to the public and press in more easily understood and transparent terms. Perhaps public-friendly
and easily understood brochures (and/or websites) should be develop that define and describe
the scientific basis, reasonableness and usefulness of the concepts used for radiological
protection, and in particular on the inappropriateness of attributing actual health effects to (in
contrast to inferring risk from) radiation exposure situations involving collective doses that
result from summing very low individual doses. The issue of radiation risk and effects will
need to be addressed comprehensively for people to understand, after an exposure has occurred,
the rationale of the protection levels applied. These suggestions point to the importance
of improved risk communication, radiation education and outreach in radiation exposure
The radiation protection community should renew its efforts to communicate
2.3. Quantifying radiation exposure
The quantities and units used in radiation science and radiation protection caused considerable
communication problems and confusion; these include the following:
• the differences between the quantities (e.g. effective dose and equivalent dose and absorbed
dose) are not well explained and are not well understood even by educated audiences;
• the distinction between the quantities used in the radiological protection system (e.g.
effective dose) and the operational quantities used for radiation measurement (e.g. personal
dose equivalent) are even more difficult to understand;
• the use of the same unit (i.e. sievert) for the quantities equivalent dose of an
organ and effective dose without specifying the quantity enhanced the confusion and
• it is not understood why there are so many different quantities used in radiation protection,
not only the many dosimetric quantities but also the many radiometric quantities (such as
activity and activity concentration).
There were great difficulties communicating radiological information to non-experts and
the public using the ICRP system and its quantities. This is probably the consequence of
the intricate system developed for protecting people which combines physical exposure data
to determine equivalent doses to organs and then uses scientific data on radiation risk to
specific organs and tissues to compute an effective dose that is used to monitor and control
human exposure. Although, the system of protection and its quantities are well suited for
operational radiation protection they are not easily understood by non-experts, particularly in
emergency situations. It was confusing that the quantities equivalent dose (to an organ or tissue)
and effective dose have a common unit, the sievert. The problem was particularly evident
in reporting thyroid doses to workers and the public from intakes of radioactive iodine. The
equivalent dose is the relevant quantity for reporting organ doses but, if the dose is reported
indicating only the unit, it can easily be confused with effective doses. The effective dose
514 A J Gonz´ alez et al
is a risk-related quantity for the whole body and can differ appreciably from the equivalent
dose to an organ for the same person. For example, the effective dose for workers with a
high intake of radioactive iodine would be much lower numerically than the equivalent dose
to the thyroid. One solution to minimise confusion is to always add the quantity when the unit
sievert is being used. Another solution would be to consider renaming the unit for effective
dose, but this would require careful deliberation. (It is noted that while the protection quantities
were developed by the ICRP, the operational quantities and the basic radiation quantities and
units were developed by the International Commission on Radiation Units and Measurements
(ICRU). It seems therefore that a close collaboration between the ICRP and ICRU is essential
for improving understanding of the quantification system.)
Although the quantities and units of the ICRP system of radiation protection have been
successfully applied in practical radiation protection, they are not easily explained and could
lead to problems for decision-makers in emergency and post-emergency situations. Simplified
dose reporting (e.g. organ dose, effective dose) might help to improve the situation in cases of
emergencies. The ICRP protection quantities are not to be used for individual or collective risk
assessment but rather for planning radiation protection in the low dose range and for verifying
compliance with individual dose restrictions.
2.3.1. The radiological protection quantities.
and units used in radiation protection. Interestingly, the history of radiation protection reflects
the attempts to identify quantities which measure human radiation exposures as well as provide
a metric for inferring the risk associated with the exposure.
After many decades, the ICRP converged upon a system of dosimetric protection quantities
which are risk related and are now used in the regulatory context to set exposure limits and to
enable the implementation of the optimisation of radiological protection (ICRP 1976). The
quantities used in the ICRP system of radiological protection and their selected names are as
There are problems in explaining the quantities
• The fundamental quantity is the mean absorbed dose in specified organs and tissues in the
human body, i.e. the mean energy deposited in an organ or tissue divided by its mass, with
the unit J kg−1and the special name gray (Gy) for this unit.
• To relate the quantity of absorbed dose better to radiation risk, the organ and tissue
absorbed doses are weighted by dimensionless radiation weighting factors to account for
the differences in biological effectiveness of different types of radiations from external and
internal sources. The radiation weighting factors are chosen on the basis of experimental
values of the relative biological effectiveness (RBE) of various radiation types for various
• The radiation-weighted organ and tissue absorbed doses are termed equivalent doses. The
equivalent dose is the mean absorbed dose from radiation in a tissue or organ weighted
by the radiation weighting factors. As radiation weighting factors are dimensionless, the
unit of equivalent organ or tissue dose is identical to absorbed dose, i.e. J kg−1. However,
to distinguish between absorbed dose, the special name sievert (Sv) is used for the unit
• The quantity effective dose is defined as the risk-related (or risk-informed) dose quantity
for the whole body. The effective dose is the sum of the equivalent doses in all specified
tissues and organs of the body, each weighted by tissue weighting factors representing the
relative contribution of that tissue or organ to the total health detriment. The calculation for
effective dose uses age- and sex-independent tissue weighting factors, based on updated risk
data applied to a population of both sexes and all ages. The sex-averaged organ equivalent
doses are applied to a reference individual rather than to a specific individual. It is the sum
of all (specified) organ and tissue equivalent doses, each weighted by a dimensionless tissue
weighting factor, the values of which are chosen to represent the relative contribution of that
tissue or organ to the total health detriment. As mentioned, the radiation weighting factors
are factors to account for the differences in effectiveness of different types of radiation
whereas the tissue weighting factors are factors to account for the differences in radiation
sensitivity (risk) of different types of organs or tissues. The definition for effective dose
uses age- and sex-averaged tissue weighting factors which are based on the most recent
human risk data. For a population of both sexes and all ages these tissue weighting factors
are applied to the sex-averaged organ equivalent doses of the reference person and not to a
specific individual (ICRP 2007a, section i). The values of each tissue weighting factors are
less than 1 and the sum of all tissue weighting factors is 1. The values are chosen by the
ICRP considering epidemiological studies of organ-specific detriment factors, in particular
of Japanese A-bomb survivors. As the tissue weighting factors are also dimensionless, the
unit for effective dose is also J kg−1. As effective dose is the (weighted) sum of equivalent
organ and tissue doses, the sievert is also used for effective dose.
In summary, quantification in the ICRP system of radiological protection is based on the
physical quantity absorbed dose and extended to the protection quantities equivalent dose
and effective dose. Central to the system of radiological protection is the quantity effective
dose which is a risk-related whole body quantity that allows for the summing of partial
body exposures and intakes of radionuclides. While effective dose is ‘risk-informed’ and is
a quantity used in protection to limit risks, it is not a quantity to be used for risk assessment
since it incorporates sex-, age- and tissue-specific averaging for a referent individual and not
for specific individuals or populations. The long search for such a dose quantity suitable for
setting exposure limits was completed in 1977. It is recognised, however, that the concept and
application of effective dose is not easily understood. Effective dose has nonetheless proven
to be successful for risk limitation and for risk management, in particular for occupational
exposure situations. Effective dose enables the summation of doses due to exposures from
external and internal exposures and takes account of scientific information on radiation risks.
Effective dose is the dose quantity used in the majority of countries for radiation protection.
2.3.2. The changing names of the radiological protection quantities.
the radiological protection quantities have evolved. ICRP Publication 26 (ICRP 1976) and
its amendment issued by the ICRP’s 1978 Stockholm statement introduced and defined the
quantities ‘organ or tissue dose equivalent’ and ‘effective dose equivalent’. ICRP Publication
60 (ICRP 1991) changed the terms to ‘equivalent dose in a tissue or organ’ and ‘effective dose’.
The reason for the change was that ‘the weighted dose equivalent (a doubly weighted absorbed
dose) has previously been called the effective dose equivalent but this name is unnecessarily
cumbersome, especially in more complex combinations such as collective committed effective
dose equivalent’. ICRP Publication 60 also states that ‘the Commission has decided to revert
to the earlier name of equivalent dose in a tissue or organ’. However, searching for the name
‘equivalent dose’ in previous ICRP reports failed to find clear evidence for this statement.
For example, in ICRP Publication 2 (ICRP 1959) the name ‘RBE dose’ was used and in
ICRP Publications 6 (ICRP 1962) and 9 (ICRP 1965) the name ‘dose equivalent’ was used.
Therefore, the coexistence of the names of equivalent dose and dose equivalent appears to be
due to changes introduced by the ICRP in Publication 60. The coexistence of the two different
names for the same quantity has added confusion and misunderstanding within an already
complex dosimetric system for radiological protection. Finally, ICRP Publication 103 (ICRP
The names used for
516A J Gonz´ alez et al
2007a) uses equivalent dose without the specification ‘in a tissue or organ’ which can add
to misunderstanding with effective dose if the quantity is not clearly specified since the unit,
sievert (Sv), is the same.
2.3.3. The operational quantities.
cannot be measured directly in body tissues, the ICRP decided to follow the recommendations
of the ICRU (1962, 1980), and proposed that the quantity dose equivalent be used as the
operational quantity for external radiations. Radiation monitors for external radiations are
calibrated in terms of the operational quantities derived from the dose equivalent (e.g. ambient
dose equivalent and personal dose equivalent). Measurements in terms of dose equivalent are
used to estimate effective dose.
Although it did not play a significant role after this Fukushima reactor accident, the use
of the operational quantity dose equivalent was another cause for uncertainty and difficulty
because it is easily confused with the quantity equivalent dose, i.e. the same words are used
but just in reverse order. The names of these quantities provide semantic problems in many
languages including Japanese. The usage is grammatically questionable in English because
while equivalent can be used as an adjective or noun, dose is a noun (or verb) and its forced use
as an adjective should be done with care (e.g. the expression ‘dose equivalent’ might be more
appropriately written as ‘equivalent dose’). Not surprisingly, the translation of equivalent dose
vis-` a-vis dose equivalent has been problematic in languages using ideograms such as Japanese.
The term dose equivalent is translated to Japanese as
dose is translated as. Namely, the character for dose,
beam,(here is the short form of
preserved as an adjective in the first case and as a noun in the second. But the term equivalent
is translated as (a combination of matching,
dose equivalent; and, as(a combination of same,
equivalent dose. If you are not versed in Japanese, these explanations may be difficult to
understand which in itself may provide an example of the difficulties that language translation
and inexact word usage might or does have on understanding and communicating.
Fortunately, the operational quantity dose equivalent is used primarily by dosimetrists
whereas the protection quantities, equivalent dose and effective dose, are used in
communication with the public and non-experts. Thus, this issue is of less importance than
others, although use of the same words to define different quantities remains problematic, and
it is not entirely uncommon for dose equivalent to be used incorrectly when equivalent dose is
the proper term.
Since the quantities equivalent dose and effective dose
, while the term equivalent
(a combination of
, meaning radiation) and amount,), is
, and amount,
, and value,
), in the expression
), in the expression
2.3.4. The units of the quantities.
and all the operational quantities derived from the quantity dose equivalent, use a common
unit—the sievert. The unit of the fundamental quantity absorbed dose is the unit corresponding
to energy per unit mass, namely joule per kilogram (J kg−1) in SI units. The protection
quantities equivalent dose and effective dose and the operational quantities derived from dose
equivalent also have the same unit, because both are obtained by multiplying absorbed dose
with dimensionless weighting factors. To avoid confusion, within the system of SI units it was
internationally agreed to use the special name gray for the J kg−1of absorbed dose and the
special name sievert for the J kg−1of all the other quantities (BIPM 2006); this policy was
endorsed by the Consultative Committee for Units (CCU) (Allisy-Roberts 2005).
The same unit, sievert, is used for both the radiological protection quantities equivalent
dose and effective dose and for all the operational quantities derived from dose equivalent.
The protection quantities equivalent dose and effective dose,
Therefore, if the name of the quantity is not specified together with the unit there could be
confusion and misunderstanding. Further complicating matters is that the older system of units
is used in some countries, expressing energy per unit mass in erg per gram, with the special
names rad for the absorbed dose and rem for the protection and operational quantities.
The confusion in the use of the unit sievert without stating whether it is equivalent dose
or effective dose seems to have been particularly evident in reporting of thyroid doses after
the accident and was related to the fact that incorporation of radioactive iodine into the body
results in radiation exposure almost exclusively to the thyroid. Usually the equivalent dose is
the relevant quantity for reporting organ doses but, if the dose is reported indicating only the
unit, it can easily be confused with effective doses. There can be a two orders of magnitude
difference in the risk to be inferred from the same number of sieverts of equivalent dose versus
effective dose. For example, a high effective dose might mask a high equivalent dose to the
thyroid; but even here, since the adult thyroid gland is less sensitive to the carcinogenic effects
of radiation than other organs, this ‘dose’ may or may not be of major health importance; unless
the dose were to children! As seen, this lack of specificity in using the sievert can be a major
source of confusion for decision-makers trying to interpret the potential impact of exposures
on workers and the public.
There are reasons to keep the same unit for equivalent dose and effective dose, since the
latter is just a weighted average of the first, although some have proposed a quick fix by creating
yet another name for effective dose. The confusion created by not specifying the dose quantity
when giving numerical values in terms of sieverts merits a careful analysis of the possibilities
of improving reporting and communication. The practice of not specifying the dose quantity
has produced confusion when reporting doses from radioiodine intakes, because whether the
number of sieverts reported are of thyroid equivalent dose or whole body effective dose makes
a difference of a factor of about 25 in terms of radiological protection. This is because the tissue
weighting factor for thyroid used in the computation of effective dose is 0.04 (i.e. the dose to
the thyroid is reduced by a factor of 0.04).
2.3.5. Radiation-weighted quantities for high doses.
applicable to very high doses is not available, as the equivalent dose is defined only for low
doses. Should the doses from the accident have been very high, this deficiency could have
caused problems of dose specification. Fortunately, the radiation doses from the Fukushima
accident were not high enough to cause any deterministic effects or acute radiation sickness
and thus the use of the equivalent dose was appropriate and valid. The problem created by the
lack of a formal quantity for a radiation-weighted dose for high doses was identified at the time
of the Tokai-Mura accident (Endo 2010) (when a de facto neutron weighted dose had to be
created to deal with the situation) but remains unsolved.
The dose limits for tissue effects (formally termed deterministic effects) for exposures at
higher doses are given in millisievert, usually without explicit specification of the quantity to
be used. In situations after accidental high dose exposures, health consequences have to be
assessed and decisions have to be made on treatments. The fundamental quantities to be used
for quantifying exposure in such situations are organ and tissue absorbed doses (given in Gy).
However, if high-LET radiation is also involved, absorbed dose weighted with an appropriate
‘relative biological effectiveness (RBE)’ is used (NCRP Report 167; NCRP Report 170). Such
RBE-weighted absorbed doses are not defined quantities, although they are being used in
clinical practice (ICRP 2007a, section B25). For the special situation of astronauts, the gray
equivalent (Gy-Eq) is also used (NCRP Reports 132, 142, 167). The ICRU is studying this
issue of iso-effective or equi-effective dose in the context of radiation therapy and the outcome
of this study could be of interest in addressing accidental exposures.
A radiation-weighted dose quantity
518 A J Gonz´ alez et al
successfully for more than 30 years in controlling occupational exposure and public exposure
in normal situations (prospectively in the design of facilities and planning of operations and
retrospectively for demonstrating compliance with regulations), the experience in the aftermath
of the Fukushima reactor accident revealed great difficulties in communicating radiological
information to non-experts and the public. These difficulties in understanding the units and
quantities appeared to be a consequence of the complexity of the system which uses more
than one quantity (organ doses and whole body dose) and combines physical exposure data
with scientific data on radiation risk for organs and tissues. Although the system and the
quantities have shown to be well suited for operational radiation protection, they is less
used internationally for radiological protection purposes and for measurement purposes are
somewhat sophisticated and their application requires professional knowledge. However,
radiological protection practitioners are not alone in using these quantities, as emergency
decision-makers—who do not necessarily know the details—rely on them for their choices
of intervention. Misunderstandings about the quantities in the aftermath of an accident may
lead to untoward difficulties, incorrect interpretations of potential consequences and incorrect
There are a number of possibilities for improving the situation in the short term. For
instance: (i) avoiding the use of equivalent dose without specification of the organ or tissue
concerned, e.g. a thyroid equivalent dose; and (ii) using the shorter and simpler term ‘organ
dose’ for organ equivalent dose in communications, e.g. thyroid dose, which is already usual in
many radiological protection practices.
As always, ways to improve and foster information exchange and education and to develop
‘easy-to-read’ material on the system of radiological protection quantities and units are sorely
While the system of radiological protection quantities has been used
2.4. Assessing the importance of internal exposures
doses from internal exposures have been incorrectly perceived as being more dangerous than
the same dose from external sources. There is compelling and consistent scientific evidence
that radiation effects depend on the amount of dose received by specific organs and tissues,
and not on whether the dose is received from internal or external sources. The ICRP and other
scientific committees conclude that for a given radiation dose the same radiation risk should be
expected, and the risk does not depend on whether the source of radiation comes from outside
or inside the body. The ICRP system of protection is somewhat more conservative for internal
than for external exposures because the limits for internal sources are based on the committed
dose (which could be delivered over a 50 year or longer period) rather than on the dose actually
recurringmisunderstandingafterthe accident.Alegalcase relatedtotheatomicbomb survivors
of Hiroshima and Nagasaki may have contributed to this confusion. Plaintiffs alleged that the
survivors had been exposed to radioactive fallout, so-called ‘black rain’, immediately after the
bombs exploded and that this internal exposure was not taken into account by the Radiation
Effects Research Foundation (RERF) that has provided quantitative estimates of health effects
for nearly 60 years (Ozasa et al 2012) . It was claimed that the effects of internal exposures
from intakes of tiny radioactive particles are more severe than those from external exposures
The perception that internal exposures were particularly dangerous was a
and that internal exposures were ignored in the RERF studies that form the basis of the ICRP
Recommendations (Sawada 2007). Despite decades of comprehensive dosimetry programmes
there remains little to no evidence that fallout contributed measurably to the radiation dose
received by survivors (Young and Kerr 2005). Nonetheless, the allegations of possible missed
dose from internal exposures among atomic bomb survivors have raised anxiety and stress
levels which will likely cause more harm to the population than conceivable from any exposure
to intakes of radionuclides which appear to be miniscule based on large-scale measurements of
children and adults (Hayano et al 2013). Further, any contribution of fallout from the atomic
bombs could not have had much of an impact on future cancer risk, since the total number of
excess cancers in the population is of the order of 600 deaths (Ozasa et al 2012).
There were also misrepresentations of the conclusions of the United Kingdom Committee
Examining Radiation Risks of Internal Emitters (CERRIE) (NRPB 2004), which have been
discussed elsewhere (Wakeford 2004). The CERRIE committee in fact concluded ‘To the
extent that ionising radiations from both internal emitters and external sources generate similar
physical and chemical interactions in living matter, there are no fundamental differences
between the two sources of radiation that suggest that their effects cannot be combined for
radiological protection purposes.’
2.4.2. The protection policy for internal exposures.
namely against exposure delivered by radioactive substances incorporated into the body,
is based on the concept of
committed dose. The committed dose from an incorporated
radionuclide is defined as the total dose expected to be delivered within a specified time period,
typically taken to be at least 50 or more years and often longer than the life expectancy of the
person exposed. The need to regulate exposures to radionuclides that remain in the body for
extended periods of time led to the recommendation that limits be based on committed dose,
i.e. the dose committed to be incurred over 50 or more years, rather than on the doses incurred
in a given period of time, usually in 1 year (as is the case for external exposures) .
For a given radiation dose the same radiation risk should be expected, whether irradiation
is from outside or inside the body, implying that the system for internal exposures is more
protective than that for external exposure. This intrinsic conservatism of the system of
protection against internal exposures is not generally appreciated (Mobbs et al 2011).
The protection against internal exposure,
globally accepted, there is widespread misunderstanding of the potential effects of internal
emitters and of the concept of committed dose, which takes into account that internal radiation
exposure is persistent for an extended period of time. The current scientific evidence from
human, animal and cellular studies indicates that radiation risk depends on the amount of dose
received and not on whether the dose is delivered from outside or inside the body. There is a
need, however, to address comprehensively the radiation risks from internal exposure compared
with the radiation risks from external exposure. It is encouraging that UNSCEAR is currently
discussing the biological effects of exposure to selected internal emitters (UNSCEAR 2012).
In addition, the perceived importance of internal exposure over external exposure points once
again to the importance of improved risk communication, radiation education and outreach in
radiation exposure situations.
While the protection system for internal exposures is well established and
2.5. Managing the emergency
Available international guidance to manage an emergency crisis involving large releases of
radioactive materials into the environment could be improved. Issues to be addressed include:
520 A J Gonz´ alez et al
• the management of an emergency radiological incident involving a prolonged release of
radioactive substances from multiple units rather than by an acute or brief release from a
• guidance on extending emergency planning zones to effectively manage changing exposure
situations and changing exposure scenarios;
• prioritising the emergency protective measures that could be taken;
• planning when and how to lift the emergency protective measures that were taken; and
• deciding when, why and how an emergency radiological incident should become an existing
2.5.1. Difficulties in managing.
incident that involved protracted and episodic releases of radiation into the environment over
a period of days and potentially longer periods of time was not adequate. Difficulties included
the need to extend the emergency planning zones to account for changing exposure scenarios
during the emergency response phase. However, this may not be a matter of radiological
protection per se, but rather of regulatory policy. Prioritising emergency protective measures
arose as an issue where guidance would have been welcomed. There was a need for clear
recommendations for when and how to lift the emergency protective measures that were taken
in response to the accident.
International guidance available for managing a radiological
2.5.2. International guidance.
the concept of emergency planning zones are available from IAEA (1997a, 1997b, 2002a,
2002b, 2003, 2011c). These were developed in the light of ICRP Recommendations which
advise that response actions should be planned because some potential emergency radiological
incidents can be assessed in advance depending upon the type of installation or situation
being considered; however, because actual emergency exposure situations are inherently
unpredictable, the exact nature of the necessary protection measures cannot be known in
advance but must flexibly evolve to meet actual circumstances (ICRP 2007a, section 274).
As discussed in Publication 96 (ICRP 2005b), three phases of an emergency are considered:
the early phase (which may be divided into a warning and possible release phase), the
intermediate phase (which starts with the cessation of any release and regaining control of the
source of releases) and the late phase. At any stage, decision-makers will have an incomplete
understanding of the future impact of the effectiveness of protective measures taken, and of the
concerns of those affected by the decisions made. An effective response must also include a
regular review of impact and effectiveness and make modifications accordingly (ICRP 2007a,
The ICRP has issued specific recommendations for the protection of people in emergency
exposure situations (ICRP 2009a), which are applicable to manage the emergency crisis arising
after a serious nuclear accident. The recommendations provide advice on the preparedness
for, and response to, radiological emergency situations, recognising that these situations may
evolve, in time, into an existing exposure situation. The ICRP recommends that reference
levels for emergency exposure situations should be set in the band of 20–100 mSv effective
dose (acute or per year), indicating that a dose rising towards 100 mSv will almost always
justify protective measures. The ICRP also recommends that an overall protection strategy
must be justified, resulting in more good than harm, and that, in order to optimise protective
measures, it is necessary to identify the dominant exposure pathways, the timescales over which
components of the dose will be received and the potential effectiveness of individual protective
options. Knowledge of the dominant exposure pathways will guide decisions on the allocation
Guidance on how to implement protective actions and on
of resources. Resource allocation should be commensurate with the expected benefits, of
which averted dose is an important component but not the only consideration. Other factors
of importance when managing resource allocation include individual and social disruption,
anxiety and reassurance and indirect economic consequences. Knowledge of the time periods
over which exposures will be received informs decisions about the lead times available to
organise the implementation of protective measures once an emergency exposure situation has
been recognised. The protection strategy takes into account the dose which an individual has
already received during an emergency when determining what constitutes optimum protection
in later response actions.
For the ICRP, decisions to remove protective measures should have due regard for the
appropriate reference level. The change from an emergency radiological incident to an existing
exposure situation will be based on a decision by the authority responsible for the overall
response. This transition may happen at any time during an emergency situation, and may
take place at different geographical locations at different times. Such a decision may be
accompanied by the setting of a radiological protection criterion above which it is mandatory
to relocate the population, and below which inhabitants are allowed to stay subject to certain
conditions. The transition should be undertaken in a coordinated and fully transparent manner,
and should be understood by all parties involved. Assessments based solely on potential future
and stakeholder desires among other consequences (ICRP 2007a, section 277).
are not clearly covered by international guidance. Specific issues to address include:
Several issues for crisis management following a serious radiological incident
• managing an emergency exposure situation created by a prolonged (rather than a brief)
release of radiation into the environment;
• extending emergency planning zones in the light of changing exposure scenarios over time;
• prioritising emergency protective measures;
• continuing assessment and modification as needed of the emergency protective measures
• lifting emergency protective measures and deciding when a radiological incident transitions
into an existing exposure situation.
2.6. Protecting rescuers and volunteers
The adequacy of occupational radiological protection recommendations for workers who are
not usually classified as ‘radiation’ workers needs to be addressed. Such workers include:
• rescuers, often the first responders to an emergency situation whose aim is to rescue people
from dangerous and life-threatening situations, recognising that their own well-being will
be at risk (e.g. fire-fighters, local police and members of the defence forces); and
• volunteers, often people who freely offer to help in the aftermath of an accident rather than
in the early phase.
The dose restrictions for rescuers had to be increased by the authorities above the limits
set for occupationally exposed ‘normal’ workers in order to maintain control of a potentially
catastrophic situation. Nonetheless, there was confusion as to why this was being done and
whether it resulted in a meaningful increase in health risk. For the volunteers, there was
confusion on what type of dose restriction should be applied, and how to address the fact that
522A J Gonz´ alez et al
some volunteers lived in proximity to the Fukushima plant and thus were already subjected to
increased doses due to the accident. Other volunteers came from outside the proximal area with
additional doses that were potentially very different.
The ICRP system of occupational protection is not specifically tailored to workers who
may be exposed to radiation only in special circumstances. The system of protection was not
conceived for people who willingly take high risks in order to save lives or control potentially
catastrophic situations. The system is even less tailored to volunteer workers, namely the casual
helpers in an emergency.
2.6.1. Emergency response personnel.
the Fukushima accident involved people who by profession engage in emergency response
activities as well as people who are usually classified as occupationally exposed workers
and controlled by occupational protection regulations. Some ad hoc helpers were professional
rescuers and others were volunteers.
As with other human-made or natural catastrophes,
rescuer is a specialised worker, usually employed by emergency organisations (e.g. fire-fighting
situation. They take risks that would be unacceptable in any other profession. Usually, they are
not employees of an employer engaged in activities that involve radiation exposure, because
radiation is rare in the daily disasters in which rescuers are engaged.
The differences between normal ‘radiation’ workers and rescuers were evident in the
recovery operations following the Chernobyl accident, where the rescuers received the
enigmatic name of ‘liquidators’. For Fukushima Daiichi, the combination of the improbable
events leading to the severe nuclear accident, plus the disruption caused by the accident
aftermath, resulted in an extreme state of affairs requiring an unexpected number of responding
rescuers working under extreme circumstances. They are the heroes of the situation, risking
their lives to undertake protective actions that could benefit millions of people. The prevailing
circumstances, both at Chernobyl and Fukushima Daiichi, were exceptional and the criteria to
be used for the protection of these rescuers are not easily delineated.
Rescuers are distinct from the normal occupationally exposed workers. A
intentions volunteered to perform remediation activities. International guidance is basically
silent in relation to ‘occupational’ protection of volunteers. Moreover, terming the exposure
from volunteer activities ‘occupational’ is somewhat questionable or at best unclear. The
approach to protecting such volunteers, however, may be similar to the approach for the
protection of health-care providers and comforters of patients who are diagnosed or treated
with nuclear medicine techniques. The ICRP recommends that for individuals directly involved
in comforting and caring for patients who are ‘radioactive’ because of nuclear medicine
procedures, other than young children and infants, a dose constraint of 5 mSv per episode
is acceptable (ICRP 2007a, section 351). On the other hand, given that informed consent is
obtained from the volunteers involved with remediation activities, there seems to be no reason
for not considering them as temporary occupational workers, e.g. they can be regarded as
temporary workers whose employer is the operation’s management. Should this be the case,
the dose constraint of 5 mSv imposed for health-care providers and comforters, except for
those from whom informed consent is not obtainable (e.g. children), may be considered over
In the aftermath of the accident, people with charitable and humanitarian
2.6.4. Occupational exposures.
exposures and medical exposures of patients, and also of comforters and carers of medically
treated patients, and volunteers in research. Occupational exposure refers to all exposure
incurred by workers during their work with the exception of: excluded exposures or exposures
from exempt activities; any medical exposure; and the normal local natural background
radiation. A worker is defined by the ICRP as any person who is employed, whether full time,
part time or temporarily, by an employer and who has recognised rights and duties in relation
to occupational radiological protection (a self-employed person is regarded as having the duties
of both an employer and a worker).
The ICRP recommendations on occupational protection refer to the classification of
working areas but they do not introduce any explicit classification of workers. It is nonetheless
implicit that the recommendations are aimed at workers whose activities customarily involve
exposure to radiation sources. In some countries, these occupationally exposed workers are
called ‘radiation workers’. However, because duration of employment is not a criterion for
classifyingan employeeas anoccupationally exposedworker fromthe view pointof protection,
temporary workers are not excluded from occupationally exposed individuals.
should not be applied in emergency radiological incidents, where an informed individual is
engaged in volunteered life-saving actions or is attempting to prevent a catastrophic situation.
For informed workers undertaking urgent rescue operations, the normal dose restriction may
be relaxed. However, workers undertaking recovery and restoration operations after the initial
crisis situation has passed should be considered occupationally exposed workers and should
be protected according to normal occupational radiological protection standards (ICRP 2007a,
section 247). This can be construed to imply that the exposure situation of these workers is a
planned exposure situation.
The absence of ad hoc recommendations for handling the emergency exposures of workers
has been recognised for over three decades (ICRP 1978). The distinction between ‘normal’
workers, whether working in normal or in emergency conditions, and ‘rescuers’ is not apparent.
This issue resurfaced when the ICRP issued recommendations for protecting people against
radiation exposure in the event of a radiological attack (ICRP 2005b). At that time, the ICRP
be subject to the usual international standards for occupational radiological protection, but that
restrictions may be relaxed for informed rescuers.
The ICRP distinguishes occupational exposures from public
2.6.5. International regulation.
of them under the International Labour Organization (ILO) Convention 105 (ILO 1960)
and its code of practice (ILO 1987), which are based on ICRP Recommendations. These
legal undertakings are often based on the 1990 ICRP Recommendations issued as ICRP
Publication 60 (ICRP 1991). Therefore, many national regulations, including the Japanese
regulations, establish the dose limit for radiation workers in ‘normal’ circumstances at an
effective dose of 100 mSv over 5 years and no more than 50 mSv in a single year. The
dose limit for women may be regulated separately, e.g. in Japan, as 5 mSv over 3 months.
These international standards (co-sponsored inter alia by the ILO) (IAEA 1996c), consider
occupational exposure outside ‘normal’ circumstances in two ways: workers occupationally
exposed in special circumstances and workers who are involved in emergency situations.
For special circumstances the Regulatory Authority may approve a temporary change in a
dose limitation requirement if appropriate consultation with the workers has taken place. For
emergencies, the standards specify that no worker undertaking an intervention shall be exposed
in excess of the maximum single-year dose limit for occupational exposure except: for the
Occupational protection is regulated by national laws, some
524 A J Gonz´ alez et al
purpose of saving life or preventing serious injury; if undertaking actions intended to avert
a large collective dose; or if undertaking actions to prevent the development of catastrophic
conditions. When undertaking intervention under these circumstances, all reasonable efforts
shall be made to keep doses to workers below twice the maximum single-year dose limit
(i.e. below 100 mSv), except for life-saving actions, in which every effort shall be made to
keep doses below ten times the maximum single-year dose limit (i.e. below 500 mSv) in order
to avoid deterministic effects on health.
The IAEA had addressed the issue of regulating occupational exposure after an accident
in a technical document on emergency response criteria (IAEA 2005d, p. 20, table 3, Guidance
levels for emergency workers), and in its Manual for First Responders to a Radiological
Emergency (IAEA 2006, p. 41, table 5). The latter provided dose guidance for those who
will be on the scene as emergency workers such as fire-fighters and law enforcement officers.
Dose guidance is different for different types of actions (e.g. life-saving actions that include
rescue from immediate threats to life; providing first aid for life-threatening injuries; and
preventing/mitigating any conditions that could be life threatening). Moreover, it was clarified
that the guidance is for ‘...emergency service personnel who would initially respond at the
local level...’. In other words, emergency workers are not considered typical radiation workers.
This guidance was developed further (IAEA 2011c (GSG-2); IAEA 2002a (GSR), part 3),
in which it was concluded that ‘...emergency workers may include workers employed by
registrants and licensees as well as personnel of responding organisations, such as police
officers, fire-fighters, medical personnel, and drivers and crews of evacuation vehicles’. While
there is still room for improving the guidance provided for emergency workers who are
not typical radiation workers and who perform rescue operations, it is noted that existing
international documents provide a good foundation to do so.
2.6.6. Unresolved issues.
and volunteers. The dose limits for the emergency workers had to be increased from 100 to 500
mSv by the authorities after the accident, which created anxiety among workers and questions
of appropriateness. It was seen as a relaxation of dose limits which, while necessary, was
considered by many as something the authorities should not do. In contrast there is rarely
an outcry when dose limits are lowered, even when unnecessary. For volunteers, there was
confusion on what type of dose restriction should be applied; moreover, it was not clear how
to address the fact that, while some volunteers lived in close proximity to the Fukushima plant,
and thus were already subjected to increased doses due to the accident, other volunteers came
from outside the proximal area where there was not a significant increase of the extant doses.
The main lesson learned is that the international system of occupational protection is not
specifically tailored to people who are not typical ‘radiation’ workers but who nevertheless may
be involved in radiation protection operations after an accident. The most obvious example is
presented by the ‘rescuers’ and ‘volunteers’ intervening in the aftermath of an accident. The
current system of radiation protection was not conceived for people who willingly take risks in
order to save lives and the system is even less tailored for volunteers helping in an emergency.
provided in international codes of practice seems to be not well-focused for severe situations.
The absence of guidance on these issues was apparent during the Chernobyl accident in 1986,
and in subsequent efforts dealing with planning in the event of a terrorist attack involving
radioactive or nuclear materials. It comes as no surprise that the absence of clear guidance for
rescuers and volunteers was also a problem during the Fukushima accident.
Nonetheless, there was confusion on how best to deal with rescuers
the protection of rescuers and of volunteers in the event of a serious radiological incident or
It might be appropriate to consider developing specific recommendations for
accident, distinct from the existing recommendations for the protection of workers who are
normally engaged in work involving occupational exposure to radiation.
A special category might be considered for people who are willing to engage in highly
dangerous work that threatens their own lives and safety (similar, perhaps, to soldiers who
willingly go into battle for their country and loved ones). Such an exposure category might
be for ‘heroic’ (intolerable) exposure. Volunteers from the public might also be ‘heroic’ in
the sense of self-sacrifice. A rigid dose restriction for this category of people is not relevant,
although every effort to reduce doses should be made.
Volunteers could therefore include many occupations such as plant employees,
fire-fighters, health professionals or compassionate citizens. Conceptually, all such volunteers
should be considered in one category. The current guidance sets 100 mSv as the upper bound
of a reference level while volunteer doses exceeding 100 mSv might still be tolerable. Hence,
it might be appropriate to have two sub-categories for volunteers: the first would include
volunteers planned to be exposed below 100 mSv and the other would include volunteers
planned to be exposed above 100 mSv but below an upper bound (e.g. about or even above
around 500 mSv).
2.7. Responding with medical aid
A number of medical management issues arose in the aftermath of the Fukushima accident.
• coping with a radiological accident in parallel with a tragic natural disaster that caused tens
of thousands of deaths and countless disrupted lives;
• personnel involved in emergency medicine and their understanding of radiation and
• dealing with people’s contamination, including the selection of a screening level for
decontamination and the consequences of removing clothing;
• the role of experts in health physics during emergencies;
• the appropriate core curriculum in medical schools for training in radiological science;
• risk communication and education; and
• medical preparedness, including drills and exercises.
Some of the more relevant lessons are the following:
• the complexity of the disaster that included damage to nuclear or radiological facilities in
addition to the damage and health consequences caused by the earthquake, increased the
need for multidisciplinary measures in the medical response;
• drills and exercises for medical radiological emergency professionals should be carried out
using scenarios that include a radiological/nuclear event caused by extreme natural events
such as earthquakes and tsunamis;
• medical professionals should have a basic understanding of radioactivity and radiation, of
their potential health effects and, particularly, of contamination with radionuclides;
• a basic understanding of radiation and its potential health effects is extremely important for
physicians, nurses, radiation technologists and first medical responders, because all of these
professionals might be called upon to respond to a radiological emergency; and
• the potential damage to community infrastructure such as water supplies and electrical
generators, as well as the monitoring and/or calculation system for radiation after an
earthquake or natural disaster, requires intense focus and vigilance.
526 A J Gonz´ alez et al
2.7.1. A combined disaster.
guidance provided (IAEA 2005c, 2006). However, the accident was a complex combined
disaster of a nuclear accident associated with a destructive earthquake and a calamitous
tsunami. This combination of catastrophes seriously affected the medical management
of people who were adversely affected. Earthquakes have a tremendous impact on the
infrastructure of public facilities, including hospitals, and public intercommunication. Indeed,
telecommunications infrastructures collapsed at the time of the accident, cutting off
communication between the local and general headquarters of health services. Essential
lifelines, such as water and electricity supplies, were also severely affected and impaired
medical management. The natural disaster resulted in deaths and serious injuries that required
immediate health care that was obstructed by damage to the basic infrastructure of the
In Japan, NPPs have been built on the coast in part because of the need for cooling systems.
Since primary medical facilities were located near the nuclear facilities, medical staff at these
facilities were also asked to evacuate. Thus, primary-level hospitals were unable to function,
and medical facilities not designated as radiological emergency hospitals had to replace them.
Unfortunately, these medical facilities did not or were not able to accept contaminated patients.
Some local ambulance services refused to transport injured workers because of the concern that
such workers were contaminated with radioactive materials and thus dangerous to others.
The local headquarters, located 5 km from the plant, were not able to function adequately
because community infrastructures such as water supplies and electricity generators were
severely damaged by the earthquake and tsunami. Therefore, even simple countermeasures for
decontamination, such as removing clothes and wiping the skin with wet towels, could not be
performed for evacuees at the shelters. Further, the local hospital system was dysfunctional;
hospitals designated as radiological emergency facilities lost their function because the
earthquake and tsunami caused severe structural damage, and they were also located in the
evacuation areas and the personnel left. Local fire departments were also asked to evacuate,
and a lack of knowledge prevented these personnel from transporting contaminated workers
from the plant. In addition, hospitals not designated for or trained in radiological measures
could not or would not receive patients from the plant because of concerns about health effects
of radiation on staff and other patients (Akashi et al 2013).
The evacuation itself also was not without severe consequences. The accident was in the
winter, and the evacuation of 840 patients or elderly people in nursing homes and health-care
facilities apparently resulted in 60 immediate deaths due to hypothermia, dehydration, trauma
and deterioration of serious medical conditions (Tanigawa et al 2012) and upwards of 100
deaths in subsequent months (Yasumura et al 2013).
Some medical management issues have been addressed and
2.7.2. Radioactive contamination of people.
important aspect of the nuclear reactor accident. Local officials had criteria for identifying
members of the public who should be decontaminated and were aware of the criteria
for contamination of skin and clothing. The cut-off criterion for screening of the public
below which decontamination was not deemed necessary was 40 Bq cm−2for beta/gamma
contamination. On 12 March 2011, however, the levels of body surface contamination on some
evacuees in shelters exceeded this level (Akashi et al 2013). Eleven workers were injured
at the Fukushima Daiichi NPP on 14 March 2011 and seven of them were transferred to
the Daini NPP by a TEPCO vehicle and a public ambulance. However, a worker needed
treatment for his injury at a hospital. At the Daini NPP, however, the local ambulance personnel
refused to transport the worker to a hospital, the reason stated was their belief that the worker
was significantly contaminated and, more importantly, that no hospitals could be found to
Dealing with people’s contamination was an
receive him. After extensive efforts, the worker was eventually admitted to the Fukushima
Medical University (FMU) Hospital, a second level hospital for radiation emergency, in
Fukushima City. The journey of the worker by ambulance was nearly 120 km from the
accident site to the hospital that accepted him. On 19 March, the Nuclear Safety Commission
of Japan (NSC) agreed to revise the screening level. According to the IAEA’s Manual for
First Responders to a Radiological Emergency, a dose rate of 1 µSv h−1at a distance
of 10 cm or a contamination level of 10000 Bq cm−2is a standard for decontamination
in the case of contamination on the surface of the body for general residents (Akashi
et al 2013).
Removal of the outer clothing has been shown to remove approximately 90% of a person’s
contamination. Unfortunately, residents were evacuated to shelters with only personal items
and did not have clothes to change into. The earthquake resulted in substantial damage, not
only to the nuclear facilities but also on the infrastructures of public facilities. The near
complete collapse of telecommunications infrastructures occurred, resulting in the inability
of health professionals and administrators to communicate between the local and general
headquarters. Moreover, public infrastructures such as water and electricity supplies were
severely compromised. People living or staying in the vicinity of the NPPs evacuated to
shelters immediately after being asked to do so. In the shelters, examinations for radiation
contamination showed elevated levels of contamination with radionuclides on the body surface
and hair. When contamination is found in residents, it should be removed with wet towels as
soon as possible. However, only drinking water was available and the supply of tap water was
shut down in most shelters, so decontamination was not possible. Moreover, the residents could
not stay in the shelters for long periods of time without warmer clothes and overcoats, because
the temperature was low and the heating systems were inadequate. Thus, the pre-accident
guidelines had to be revised by necessity (Akashi et al 2013).
2.7.3. Role of health physicists.
was another important aspect of the nuclear reactor accident. These experts are in a unique
position to assist first responders and medical personnel and to provide information as well
as to evaluate the true extent and potential impact of any contamination present. If these
procedures can be carried out properly, appropriate medical activities will occur in a timely
manner consistent with the safety of these personnel. From the experience gained after an
accident at Tokai-mura, Japan, in 1999, the NSC described the role of experts for radiation
safety in an emergency in the Medical Guidelines for Radiation Emergency issued in 2001
and revised in 2008. According to the guidelines, for smooth transportation and acceptance
of patients in hospitals, experts in radiation safety of NPPs or related companies should
accompany patients to hospitals. Moreover, they should be trained for emergencies (Akashi
et al 2013).
A hydrogen explosion occurred at the reactor building of Unit 3 on 14 March 2011, and
workers and JSDF personnel were injured. The JSDF members were brought to the local
headquarters by other JSDF personnel, but without experts in radiation safety; all of them
showed heavy contamination on their protective gear. After removal of their protective gear,
decontamination and showering, residual contamination was observed on their faces. One
JSDF member was transferred to the Fukushima Medical University Hospital, a secondary
emergency hospital in Fukushima prefecture, by ambulance. The patient had a contaminated
wound on his right thigh. He was then transferred to the National Institute of Radiological
Science by a JSDF helicopter. However, no expert on radiation safety accompanied the patient.
Fortunately, his fracture of the lumbar transverse process was not serious, although he was
internally contaminated with radioactive iodine and caesium (Akashi et al 2013).
The role of health physics professionals during emergencies
528A J Gonz´ alez et al
2.7.4. Medical school curricula.
in medical schools. Education and training are critical for physicians, nurses, radiation
technologists and first responders, because all of these professionals might be involved in
medical response activities after a radiation emergency. The Fukushima accident uncovered
the need for all medical professionals to have a basic knowledge of radiation exposure and
contamination from radionuclides. Such knowledge has not been provided in medical schools.
In March 2001, the model core curriculum for medical education, Guideline for Medical
Education, was published by the Japanese Ministry of Education, Culture, Sports, Science
and Technology (MEXT). The guideline presents what should be learned in medical schools
and is a reference for making up the curriculum; this was revised on 31 March 2011, just
after the earthquake. In this revision, the guideline recommended that the following topics
should be included in the curriculum: radiation, radioactivity, their characteristics, radiation
measurement and units; effects of radiation on humans (including the foetus) (acute and late
effects); radiation sensitivity in various tissues; and effects of radiation on genes, interaction
with cells, mechanisms of cell death due to radiation, local and whole body injuries. The
reason for this revision was to ensure that medical doctors know that people are continually
being exposed to natural sources of radiation and also the benefits of radiation used for medical
purposes (Akashi et al 2013).
Another related issue was the appropriate core curriculum
2.7.5. Communication of health risks.
challenges for medical emergency management, and communicating effectively with the
public about radiation effects is a key to its success. Radiation accidents can cause medical,
environmental, psychological and economic problems. Scientifically correct information about
health issues is critical for the prevention of psychological consequences, and explanation of
radiation risks and any countermeasures in plain language is a vital part of an effective risk
communication process. There are many ways to communicate today, including TV, radio,
newspapers, the internet, hot-lines, leaflets, social media (such as twitter) and public meetings.
There are also many ‘experts’ on radiation. Using these multiple sources of communication,
knowledgeable professionals can provide helpful information. Members of the general public
did not have sufficient knowledge about radiation and its effects before the Fukushima accident.
After the accident, an enormous amount of information, often conflicting, was suddenly
provided, and the public was not able to filter effectively which information was correct and
which was wrong and thus became confused and worried. There are some patients who refuse
medical tests using x-rays at hospitals, for the simple reason that radiation increases the risk
of cancer mortality. It is critical that scientifically correct information concerning radiation be
understood by the public, not just after a radiological incident has occurred but beforehand.
Accordingly, MEXT provided an auxiliary textbook for education on radiation and its effects
in primary, junior and senior high schools on 14 October 2011 (Akashi et al 2013).
Public communication is one of the most important
2.7.6. Medical preparedness.
was another important issue. Central and/or local governments have performed annual radiation
emergency drills in Japan. However, drills using the scenario of a radiation/nuclear event
caused by an earthquake have never been performed in Japan. This earthquake caused not only
deaths and life-threatening injuries, but also had a tremendous impact on public infrastructure
and the NPP. An earthquake measuring 6.8 on the Richter scale struck the Niigata-Chuetsu
region of Japan on 16 July 2007. The earthquake affected the Kashiwazaki-Kariwa NPPs,
the biggest NPP site in the world. The earthquake caused damage to the NPPs, resulting in
a small amount of radioactive material being released into the air and the sea. Fortunately, no
significant effects were observed in the public and the environment, and no damage was caused
Medical preparedness, including training, drills and exercises,
to the monitoring system of the NPPs, although infrastructure such as water supplies and roads
were affected. Similar to Fukushima, most of the members of the disaster medical assistance
team (DMAT) members who were sent to hospitals and first-aid care centres at the NPP site
had concerns about the effects of radiation, since adequate information about the problems
at the NPPs was not communicated to them (Akashi et al 2010). Although experiences
associated with this previous earthquake indicated the urgent need for an all-hazards approach
to address the complexity of medical issues, they were not incorporated into the planning
and response for future ‘combined disasters’ such as the one in 2011. The complexity of
disasters that include damage to nuclear or radiation facilities has increased the need for
multidisciplinary medical experts, and improved strategies to plan and respond to future
In response to a radiation emergency, the level of contamination from radionuclides has
to be evaluated for the public, patients, responders and medical staff. However, fixed screening
criteria set in advance are not applicable to everyone for all incidents and flexibility is required
to cope with the unique circumstances of each radiological incident. For example, when this
criterion was applied to a seriously injured but also contaminated patient with radionuclide lev-
els above the designated criteria, the patient could not be transported or admitted to a hospital.
For contamination with radioactive materials, unlike for chemical or biological contamination,
there is a general consensus that the first priority for medical response should always be life-
saving and that the main priorities of disaster rescue teams should be rescue and the provision
of emergency care for physical trauma. There are no reports showing significant effects of
radiation exposure upon receiving contaminated patients. Planning should be done in advance,
with some room for flexibility, and first responders have to have clear instructions to follow on
the basis of decisions by headquarters under specific circumstances (Akashi et al 2013).
2.7.7. International guidance.
exposure situations is limited but can be found in several IAEA documents co-sponsored by
the WHO dealing with medical surveillance issues (IAEA 2005c, 2005d), which preceded the
generalsystem ofprotective andother actionsestablishedin IAEAstandards (IAEA2011c) and
the long-term health surveillance programmes recommended by the WHO (WHO 2006). In its
that where prompt medical intervention has the potential to avert injuries, procedures and
measures should be included in the emergency response plan to enable those individuals who
may have received high exposures to be identified promptly and receive appropriate medical
treatment (ICRP 2009a, section e).
a nuclear accident or a radiological emergency (ICRP 2009b) addresses health surveillance.
Following a serious nuclear accident or radiological emergency, the exposed population should
have an initial medical evaluation, the first step being a census of the affected individuals,
possibly with an early dose assessment. It also recommends that, in addition, and regardless
of the level of dose, the affected population should also receive accurate and appropriate
information regarding their level of exposure and potential future health risks. If the level of
dose is sufficiently low, and below levels associated with natural background radiation, there
may be discussions as to the extent to which these recommendations are implemented. The
ICRP has also made recommendations on medical management in the event of a radiological
attack (ICRP 2005b). Action taken to avert exposures is a much more effective protective
measure than those taken after exposure has occurred.
A handbook on triage, monitoring and treatment of people exposed to ionising radiation
following a malevolent act is also available (Rojas-Palma et al 2009). European national
emergency response plans have long been focused on accidents at NPPs and other nuclear
International guidance on medical management in emergency
530A J Gonz´ alez et al
installations. Recently, possible threats by disaffected groups have shifted the focus to being
prepared for malevolent use of ionising radiation aimed at creating disruption and panic in
society. Although some countries may have adequate national plans for response, there is a
need for European guidelines on how to act in the event of malevolent use of radioactive
Moreover, some of the issues raised have been recognised previously, and some
recommendations incorporated in international standards (IAEA 2002a). Descriptions have
materials are available on the IAEA website (IAEA 2002b, 2009a, 2009b, 2009c).
Finally, the US National Council on Radiation Protection and Measurements (NCRP)
has also published a series of reports that are relevant to medical response, radionuclide
decontamination and emergency response during radiological incidents and emergencies
(NCRP 2001, 2004, 2005, 2006, 2008, 2010).
Fukushima accident, as follows.
Many issues concerning medical management were raised as a result of the
• It was fortunate that no workers from the plant or residents around the site incurred doses
that would have required medical treatment. That is, there were no severe tissue reactions
(deterministic effects) because the radiation exposures were far below the threshold doses
necessary to produce such effects.
• The complexity of disasters that involve not only damage to nuclear or radiological facilities
but also damage caused by natural forces such as earthquakes and ensuing tsunamis
increases the need for multidisciplinary measures in the medical response. Planning
operations after a complex disaster require an all-hazard approach.
• Training, drills and exercises for a medical radiological emergency should be carried out
using scenarios of a radiological/nuclear event caused by natural events such as earthquakes
• Medical professionals should have an understanding of radiation, radioactivity,
radionuclides, internal and external sources of radiation and their potential for causing future
health effects in the individuals exposed. Such training in medical and other professional
schools needs to be improved.
• Education and training in radiation-related issues is critical for physicians, nurses, radiation
technologists and first medical responders. All types of professionals are likely to be
involved during medical response to a radiological emergency. Basic knowledge of radiation
and its effects is extremely important for health-care providers, to provide understanding,
guidance and assurance as appropriate. Such professionals are on the front line with the
public and their opinions are highly valued.
• A system should be encouraged to improve, foster and educate health physics professionals
in radiation safety to assist first responders and medical personnel and to provide real-time
information and guidance as to the extent and potential impact of any contamination present.
• The potential to disrupt the infrastructure of society, such as electricity generation, sewers,
water supplies, hospitals, fire departments, as well as the monitoring and/or calculation
system for radiation necessitates an intense focus and vigilance to cope with the ensuing
myriad of unexpected consequences. There is an urgent need for a ‘combined disaster’
medical response strategy, which should be emphasised for current disaster planning and
It would be worthwhile to consider ad hoc recommendations addressing the issues
raised concerning the medical needs following a significant radiological incident that includes
compromised society infrastructures.
2.8. Justifying necessary but disruptive protective actions
Some of the decisions taken after the accident to protect the public were extremely disruptive
and caused significant social distress. For instance, evacuating people from their homes
obviously results in serious disturbance to normal life. Not all decisions were as clearly justified
and it is unclear whether they really produced more good than harm.
While the radiological protection principle of justification is usually applied to the
introduction of new sources of radiation, which are expected to increase exposure of people,
the principle is equally applicable to the introduction of disruptive protective actions, which
are expected to decrease the exposure of people. In the immediate emergency situation and in
the long-term existing exposure situation, decision-makers need to justify disruptive protective
actions from the perspective of the benefit obtained.
Applying justification in and after an emergency situation is particularly difficult. For
instance, decisions on whether to evacuate people from areas of elevated but not high doses
(or to allow them to return to such areas after evacuation) can present dilemmas. If people
remain they will incur some radiation doses and increase their theoretical chance of developing
radiation-induced harm in the future; if they are evacuated such a plausibility will disappear but
they will incur the immediate detriments associated with the evacuation itself.
Further guidance on the application of the justification principle in these challenging
situations would be welcomed. It should be recognised, however, that ‘balancing’ good and
harm is not confined to issues associated with radiation exposure. Other non-radiation-related
benefits and detriments arising from the protective action must also be considered, thus going
far beyond the scope of radiological protection.
2.8.1. The justification principle.
actions that may change the radiation exposure of people, has always been and continues
to be a fundamental ethical principle of the ICRP (ICRP 2007a, section 5). It is founded
on teleological ethics (from the Greek
to as consequentialism because it holds that the consequences of a particular action form
the basis for any valid moral judgement about that action, and argues that decision-makers
ought to be consequentialists. Protection-related consequentialism would therefore hold that
the ends or consequences of a protection-related action should determine whether such
action is good or evil. Thus, it is concerned with the overall outcomes or consequences of
protection-related actions, which would be morally right if they produce a good outcome or
consequence—namely, they turn out to have more absolute good than absolute harm for society.
The ICRP principle of justification simply states that ‘any decision that alters the radiation
exposure situation should do more good than harm’ (ICRP 2007a, section 203). In relation to
accidents, justification is precisely defined by the ICRP as the process of determining whether
a proposed remedial action in an emergency or existing exposure situation is likely, overall,
to be beneficial, i.e. whether the benefits to individuals and to society (including the reduction
in radiation detriment) from introducing or continuing the remedial action outweigh its cost
and any harm or damage it causes. The ICRP considers (ICRP 2009a) that more complete
protection is offered by simultaneously considering all exposure pathways and all relevant
protection options when deciding on the optimum course of action. While each individual
protective measure must be justified by itself in the context of an overall protection strategy,
the full protection strategy must also be justified, resulting in more good than harm.
The justification principle, namely the justification of
, ‘end, purpose’), which is usually referred
532A J Gonz´ alez et al
2.8.2. Approaches to justification.
principle of justification in exposure situations. The first approach is used in the introduction
of new activities where radiological protection is planned in advance. Application of the
justification principle to these situations requires that no planned exposure situation should
be introduced unless it produces sufficient net benefit to the exposed individuals or to society
to offset the radiation detriment it causes. The second approach is used where exposures can
be controlled mainly by action to modify the pathways of exposure and not by acting directly
on the source. The main examples are existing exposure situations and emergency exposure
situations such as those resulting from the accident. In these circumstances, the principle of
justification is applied in making the decision as to whether to take action to avert further
exposure. Any decision taken to reduce doses, which always have some disadvantages, should
be justified in the sense that it should do more good than harm.
There are two different approaches to applying the
2.8.3. Justification after the accident.
applicable to the protective actions to decrease exposure but surfaced as a relevant issue
of uncertainty. While the benefit of introducing new sources can be positive, the benefit of
introducing protective actions is indirectly gained by reducing harm. So the characteristics of
benefit (good versus harm) are different in these situations. It could be conceived that when
introducing a NPP, this process inherently includes the justification of decisions on protective
actions during emergency and existing exposure situations potentially caused by accidents.
However, once an accident occurs, in other words in the immediate emergency situation and in
the long-term existing exposure situation, people can only justify disruptive protective actions
from the perspective of the benefit obtained from the protective action.
In relation to accidents, the ICRP recommends that, when activities aiming at decreasing
the level of radiation exposure are being considered, the expected change in radiation detriment
should be explicitly included in the decision-making process (ICRP 2007a, section 205). The
consequences to be considered are not confined to those associated with the radiation—they
include other risks and the costs and benefits of the activity. Sometimes, the radiation detriment
will be a small part of the total. Justification thus goes far beyond the scope of radiological
protection. It is for these reasons that the ICRP only recommends that justification require that
the net benefit be positive. To search for the best of all the available alternatives is a task beyond
the responsibility of radiological protection authorities.
exposures can be controlled mainly by action to modify the pathways of exposure and not by
acting directly on the source, as was the case in the aftermath of the accident (ICRP 2007a,
section 207). In these circumstances, the principle of justification is applied in making the
decision about whether to take action to avert further exposure. Any decision taken to reduce
doses, which always have some disadvantages, should be justified in the sense that it should do
more good than harm.
The ICRP also recommends that every practicable effort should be made to avoid the
occurrence of severe deterministic injuries in an emergency exposure situation. This means
that it will be justified to expend significant resources, both at the planning stage and during the
response, if this is required, in order to reduce expected exposures to below the thresholds for
The ICRP has recognised that: (i) except for the case of medical exposure of patients,
the responsibility for judging the justification falls on governments or national authorities to
ensure an overall benefit in the broadest sense to society and thus not necessarily to each
individual; (ii) input to the justification decision may include many aspects that could be
informed by users or other organisations or persons outside of government, and justification
Following the accident, justification was theoretically
decisions may be informed by a process of public consultation; and (iii) there are many aspects
of justification, and different organisations may be involved and responsible (ICRP 2007a,
section 208). However, no clear guidance is available to governments and national authorities
on exercising their duties or whether other institutions should participate in the process.
2.8.4. Difficulties in the practical application of justification.
emergency situation triggered by the accident is particularly difficult. For instance, decisions
on whether or not to evacuate people from areas of elevated but not high doses can present
difficult dilemmas. If people remain they will incur some radiation dose and increase the
possibility of radiation-induced harm in the future; if they are evacuated such a possibility
will disappear but they will certainly incur the actual detriments associated with the evacuation
itself. Thus, applying justification to decide about actions to change the radiation exposure
situation of people in the aftermath of large radiological accidents should be done within
a self-critical attitude. This is the result of the extremely demanding nature of justification.
As there is no realm of moral permission, no realm of going beyond one’s moral duty
(supererogation), no realm of moral indifference, all actions are seemingly either required or
forbidden, and the approach might be deemed profoundly alienating. Justification seemingly
permits (or, more accurately, requires) difficult choices. If wrongly interpreted, it might be seen
to demand (and thus, of course, permit) that innocents be killed because of lack of protection, or
deprived of material goods because of excessive protection that may produce greater benefits
for others. Consequences stemming from decisions altering the radiation exposure situation
can conceivably justify any kind of act, no matter how harmful it is to some. Moreover, the
concept of justification gives little or no guidance for the decision-makers’ practical reasoning,
because the consequences (positive and negative) of any protective action, such as evacuation
or resettlement, stretch into the distant future, making them essentially unknowable. It should
be noted that the cultural situations of the country where justification is being applied have to
be considered (ICRP 2007a, section 284).
Applying justification in the
demanding situations created by a major accident would be welcomed and are needed. One
problem, however, is that there are often non-radiation-related benefits and detriments to deal
with that arise from the protective actions taken, i.e. the issues go far beyond the scope of
radiological protection. The search for the best of all the available alternatives is a task beyond
the responsibility of radiological protection professionals; their remit should be confined to
ensuring a positive net radiation-related benefit. In addition, it should be kept in mind that the
principle of optimisation of protection calls us to seek the best protection option among those
available, which is perhaps the most important task of radiological protection professionals and
it is a challenge.
Further guidance on the application of the principle of justification in the
2.9. Transitioning from an emergency situation to an existing situation
Deciding when to transition from an emergency radiological incident to an existing exposure
situation that will remain for many years to come is not always straightforward. One difficulty
is how to define and decide when the emergency situation has in fact ended and, accordingly,
when the existing exposure situation begins.
The process of transitioning from the emergency situation to an existing exposure situation
raised doubts about the credibility of the relevant authorities. Although there were engineering
guidelines as to when the reactors could be considered ‘safe’ and in cold shutdown, the
demarcation between the emergency crisis and an existing exposure situation was more
difficult. More quantitative guidance may have been helpful in making this judgement.
534 A J Gonz´ alez et al
2.9.1. The exposure situation.
situations involving the planned introduction and operation of sources), the ICRP has made
a distinction between what it termed emergency exposure situations and existing exposure
situations. Emergency exposure situations are defined as those that may occur during the
operation of a planned situation, or from any other unexpected situation, and require urgent
action in order to avoid or reduce undesirable consequences (ICRP 2007a, section 176).
Existing exposure situations are defined as those that already exist when a decision on control
has to be taken, including prolonged exposure situations after emergencies (ICRP 2007a,
These definitions may influence the difficulties experienced in transitioning from the
emergency exposure situation to an existing exposure situation. The definition of an emergency
exposure situation might be unnecessarily detailed and could have been clearer without the
initial qualifiers, e.g. simply stating that emergency exposure situations are those require
urgent action in order to avoid or reduce undesirable consequences (still a question would
remain: whether an emergency exposure situation requires urgent actions or urgent actions
create an emergency exposure situation). Furthermore, the differences between the common
understanding of ‘emergency’ and the connotation given to the qualifier ‘emergency’ in the
term ‘emergency exposure situation’ could have been another cause of confusion. For instance,
some questionable descriptions were made regarding all the exposure situations related to the
accident as emergency exposure situations: for example, many emergency responders to the
accident who participated in certain works at places distant from the plant, such as workers
restoring roads damaged by the earthquake, were certainly not subjected to an emergency
It has also to be noted (Homma 2013) that what transitions is the radiological
condition rather than the exposure situation. In fact, as defined, the three exposure situations
recommended by the ICRP are mutually exclusive; hence an emergency exposure situation
cannot become an existing exposure situation. (As an example, a teenager will eventually
become an adult, but this does not mean that teenager becomes adult as long as the definition
of the both teenager and adult are kept; what becomes an adult is the person considered,
not the category itself.) Thus what changes is the radiological condition, from variable and
quasi-uncontrollable into steady and basically controllable, rather than the defined situation.
In addition to traditional planned exposure situations (namely
2.9.2. Difficulties experienced in the aftermath of the accident.
situations created by the accident are tailored to the definition of an emergency exposure
situation, questions were raised on when the emergency condition could be considered
For the emergency workers and rescuers, the termination of the emergency situation is
self-evident: the emergency exposure situation is terminated when the assigned work expected
to cause doses exceeding the normal dose limits is over. This could be construed to mean
that an emergency exposure situation may be specific to the situations of the individuals being
subjected to the situation.
For the public, however, the concept of transition is unclear. Questions have been raised on
whether the concept of an emergency exposure situation is applicable to the public at all, and it
has even been suggested that the exposure of members of the public under an accident may fit
better to an existing exposure situation (Lee 2012b, 2013). Under this assumption the issue of
a transition point naturally vanishes.
The radiological conditions of members of the public residing in the affected area are
characterised by a measurable and prolonged incremental dose, which is higher than the
existing pre-accident background dose. This situation can be categorised as an ‘existing’ (or
While most exposure
long-term contamination resulting from an emergency situation should be treated as an existing
exposure situation (ICRP 2007a, section 283).
Transiting from the emergency exposure situation into an existing exposure situation,
defined by the ICRP, caused doubts among the Japanese authorities. On 30 March 2012, the
NSC judged that the reason for evacuation no longer existed in part of the evacuated area within
a 20 km radius of the Daiichi NPP, designated as ‘restricted area’ (
zone’, and termed 1F), because of inter alia the stabilisation of the nuclear reactor. The removal
of the designation ‘restricted area’ could be understood as a case where the emergency exposure
situation shifted to an existing exposure situation.
It is felt in Japan that the transition would be easier and clearer to judge if clearer and more
quantitative guidance were available.
2.9.3. International guidance.
from an emergency exposure situations to an existing exposure situation (ICRP 2009a).
Moreover, the ICRP noticed the commonalities between emergency and existing exposure
situations (and their differences from planned exposure situations), which could make it
difficult to define the transition. In its recommendations on protection of the public in situations
of prolonged radiation exposure (ICRP 1999) the ICRP recognised that, while in planned
exposure situations control was exercised over the additional doses that were expected to be
delivered due to the planned introduction of a source, the other possible exposure situations
(which are now described as emergency and existing exposure situation) were ‘interventional’
in the sense that control was aimed at reducing doses that originated in retrospective causes
rather than restricting additional doses that are inferred prospectively. The ICRP has recognised
that the concept of ‘intervention’ has become widely used in radiological protection and has
been incorporated into national and international standards to describe situations where actions
while the terms ‘emergency exposure’ or ‘existing exposure’ should be used to describe the
radiological exposure situations where such protective actions to reduce exposures are required
(ICRP 2007a, section 50).
In both emergency and existing exposure situations the system of radiological protection
could be conceived as follows: (i) the principle of justification is implemented by judging
it produce more good than harm; (ii) the principle of optimisation of protection, which aims at
the best protection under the prevailing circumstances by maximising the margin of benefit over
considerations being taken into account; and (iii) the restriction of individual doses is achieved
through comparison with reference levels of dose. (Establishing prospective limits, such as the
dose limits, is not appropriate under these circumstances, because the real exposure situation
is not fully predictable and can be very variable. The prevailing circumstances, particularly
the protection efforts and undesirable consequences from protective actions, are also variable
and furthermore may play a dominating role. In sum, limiting prospective additional doses can
be realistically exercised at the planning stage of the introduction of a source, where doses
can be forecast with reasonably certainty so as to ensure that these restrictions will not be
However, as indicated previously, there have been difficulties in deciding when and on
what grounds the transition from emergency to existing exposure situations should occur. The
ICRP expresses the time frame of transition as a grey area where the uncertainty in dose rates
The ICRP provides some recommendations on the transition
536 A J Gonz´ alez et al
decreases significantly, and leaves the decision on transition to the relevant authority (ICRP
2009a). The responsible authority may experience difficulties in deciding on transition because
of such ambiguities.
Another issue related to difficulties in the transition to an existing situation is the difference
between existing exposure situations created by an accident and existing exposure situations
created by nature (see the next section on the different public perception of these situations).
A distinction in control between these situations is implicitly recognised by the ICRP. While
reference levels in ‘natural’ existing exposure situations are conventionally expressed as an
annual effective dose (e.g. mSv in a year), in existing exposure situations remaining after an
emergency the reference levels are expressed as the total residual dose to an individual as
a result of the emergency that the regulator would plan not to exceed, either acute (and not
expected to be repeated) or, in case of protracted exposure, on an annual basis (ICRP 2007a,
2.9.4. Public perception.
two distinctive existing exposure situations, namely an existing exposure situation due to high
levels of natural radiation and an existing exposure situation remaining in the aftermath of an
accident. The long-term dose level in the aftermath of an accident will necessarily be higher
than the background dose level existing before the accident, which would however be taken by
the public as a reference for comparison. In this sense, people consider the difference between
both these levels as an additional dose and, unsurprisingly, expect that this additional dose be
controlled with the same criteria and levels used in planned exposure situations (see below
on the issue of categorising public exposure). This public perception is a major element in
the difficulties experienced by the authorities for transiting from an exposure situation that is
considered ‘emergency’ to a situation that is considered ‘existing’.
Recommendations for using the dose limit for planned exposure situation as a desired
objective during an existing exposure situation have increased the public’s misunderstanding.
People usually ignore the fact that millions of people are living in regions of elevated
background doses, which is an archetypal case of an existing exposure situation. In such
regions the public is exposed continuously to doses of tens of mSv year−1, far exceeding the
annual dose limit for the public of 1 mSv year−1, which is only applicable to the expected
additional doses resulting from a planned exposure situation. The crucial difference in the
public perception is that natural radiation exposure is imposed by nature while the exposure
remaining after the accident is imposed by a human act, i.e. there is someone responsible
and imputable for the exposure. This difference may be reflected in the course of selecting
the reference level value and in eventual legal actions, but does not alter the basic protection
concept of optimising protection under the prevailing circumstances. However, it is a major
component in the usual public claim that the dose limits for a planned exposure situation be
used for the additional dose (over the pre-existing background dose) in the existing exposure
situations remaining in the aftermath of the accident; this is not an issue in ‘natural’ existing
exposure situations because such a ‘previous’ levels does not exist.
The public seems to perceive an important distinction between
recommended characterisation of exposure situations, but it was noted by the public and the
authorities that the demarcation between planned, emergency and existing exposure situations
is subtle and its practical purpose not fully understood.
The protection paradigm for dealing with emergency and existing exposure situations
could be revisited. Consideration could be given as to whether the differentiation between
these situations should be more than conceptual or whether the concept of emergency exposure
situations fits the exposure of members of the public. A comprehensive practical approach
common to all interventional situations could be sought.
2.10. Rehabilitating evacuated areas
evacuated as a result of a nuclear accident. A large intergovernmental project was required to
tackle this problem after that accident. Rehabilitating and re-inhabiting areas in the Fukushima
Prefecture that were evacuated due to the accident are posing similar challenges.
Rehabilitating evacuated areas, for example allowing people who were evacuated to return
to their homes and constructing residential areas for both returning evacuees and new residents,
has proved to be extremely difficult. Evacuees from specific regions designated by the Japanese
government as ‘difficult to return’ (because of the levels of environmental contamination)
will be unable to return to their homes for some years to come. Some people do not wish
to return, either for economic reasons or because of concerns about potential health risks
for their families, or both, while others are not as concerned about living in areas where the
radiation exposure levels are just somewhat elevated and wish to return promptly. Issues being
addressed include how to characterise and classify the exposure situation, determining the type
of exposure, and deciding how the exposure situation should be remediated and controlled.
Existing recommendations have produced confusion among members of the public who
were evacuated, in large part to a misunderstanding the difference between a planned exposure
situation and an existing exposure situation. The ICRP recommended 1 mSv year−1as the
dose limit for a planned exposure situation. However, the reference level for existing exposure
situations can be higher where people are allowed to return to their homes and then optimisation
continues to lower the exposure levels. Depending on the circumstances and view point,
however, rehabilitation can be interpreted differently: as an existing exposure, as a planned
exposure of informed individuals or even as an exposure to background radiation that is
excluded from control if the residual dose is low enough. While ICRP Recommendations are
not explicit on how to handle this type of situation, it is generally, though not unambiguously,
understood that returning from a temporary evacuation changes the pre-existing status of the
affected areas and that the contaminated regions then become existing exposure areas.
2.10.1. The challenge of rehabilitation.
accident involving huge releases of radioactive materials into the environment continues to be a
serious test for the radiological protection profession. How to control the prospective exposure
of residents returning to rehabilitated areas is a major challenge.
Rehabilitating evacuated areas following a large
2.10.2. International guidance.
living in long-term contaminated areas after a nuclear accident or a radiological emergency
(ICRP 2009b) provide guidance for the protection of people living in those areas. They
consider the pathways of human exposure, the types of exposed populations and the
characteristics of exposures. Although the focus is on radiological protection considerations,
the recommendations also recognise the complexity of post-accident situations, which cannot
be managed without addressing all the affected domains of daily life, i.e. environmental, health,
economic, social, psychological, cultural, ethical and political aspects. The recommendations
emphasise the effectiveness of directly involving the affected population and local professionals
in the management of the situation, and the responsibility of authorities at both national and
local levels to create the conditions and provide the means to favour the involvement and
empowerment of the population.
The ICRP Recommendations for the protection of people
538A J Gonz´ alez et al
In these recommendations the ICRP considers that the situation at the rehabilitation stage
is an existing exposure situation. For existing exposure situations, the ICRP states that as the
long-term objective for existing exposure situations is ‘to reduce exposures to levels that are
close or similar to situations considered as normal’, it recommends that the reference level
for the optimisation of protection of people living in contaminated areas should be selected
from the lower part of the 1–20 mSv year−1band recommended in Publication 103 for the
management of this category of exposure situation (ICRP 2009b, section 50).
However, the recommendations also indicate that past experience has demonstrated that
a typical value used for constraining the optimisation process in long-term post-accident
situations is 1 mSv year−1. The recommendations encourage national authorities to take into
account the prevailing circumstances and use the timing of the overall rehabilitation programme
to adopt intermediate reference levels to improve the situation progressively. In addition, they
state that the principles of protection for planned situations also apply to planned work in
connection with existing and emergency exposure situations, once the emergency has been
brought under control (ICRP 2007a, section 253).
2.10.3. Confusion about dose limits.
some confusion among members of the public subjected to evacuation. It seems that they
interpret that returning to their homes is a planned exposure situation rather than a return to
an existing exposure situation. Therefore, they consider that they should be subjected to the
ICRP recommended dose limit of 1 mSv year−1for planned exposure situations, a level that
was suggested by the ICRP in Publication 111.
While rehabilitation is not yet an imminent issue in the severely affected areas in Japan, a
rehabilitation stage should be categorised as an existing exposure situation. The exposure
situation during rehabilitation is somewhat different from exposure in existing situations.
Rehabilitation is not a matter of coping with a given extant exposure situation, but it is
viewed as an intentional introduction of exposure by moving people into the area with elevated
exposure potential and hence formally regarded as a planned exposure situation of informed
Thus, the public has doubts about what type of exposure the inhabitants of the rehabilitated
area will be subject to when the rehabilitation starts. If these people are regarded as members
of the public and if the exposure situation is regarded as a planned one, the dose limit of
1 mSv year−1and the corresponding dose constraint could in principle be considered as
applicable, therefore requiring annual doses to the residents to be kept below a few tenths of
a millisievert, a restriction that might be considered unrealistic and furthermore rather strange
and unreasonable. Conversely, it could be assumed that the inhabitants returning to their homes
are to be subjected to a very special type of public exposure, namely exposure of people willing
to live in the area and who made their decision with informed consent.
These recommendations appear to have produced
guidance for rehabilitating evacuated areas after an accident, including clear numerical criteria
as appropriate. The categorisation of exposure situations involved in rehabilitation of the
relocated areas could also be revisited. While current international guidelines are not explicit
on how to handle this type of situation, it might be considered implicit that returning from a
temporary evacuation leads to an existing exposure situation rather than a planned exposure
situation. Notwithstanding, it would be appropriate to provide ad hoc recommendations on the
protection of the inhabitants’ children, including those unborn.
It seems advisable to explore the feasibility of issuing additional ad hoc
2.11. Restricting individual doses to members of the public
The nuclear reactor accident released large amounts of radioactive materials into the
environment. As such, the potential for members of the public to be exposed was greatly
increased and ways to restrict their exposures became critically important. The authorities
acted appropriately with ‘sheltering in place’ instructions, evacuation and food restrictions that
effectively reduced to low levels the dose received by people living in the affected area. The
naturally regarded the situation as an emergency exposure situation. The regulatory authority
selected a reference level of 20 mSv year−1, whereas the dose limit to members of the public
for planned exposure situations is (and continues to be) 1 mSv year−1.
Unfortunately, people living in the affected areas were confused by the logic behind
the restrictions applied to individual doses, in what was perceived as a mixture of the
pre-emergency, emergency and post-emergency protection policies. The fact that the reactor
conditions did not come under reasonable control for nine months after the accident did add
challenges and communication problems. Uncertainty and confusion arose among the public,
and even among some authorities, on the individual dose restrictions recommended for public
protection, particularly between the dose limit of 1 mSv year−1for a planned situation and the
various reference levels going up to 100 mSv for an emergency situation.
There was a particular misunderstanding about the appropriate use and application of the
dose value of 1 mSv year−1. The public tended to regard a dose above this value as dangerous,
which created challenges in coping with the aftermath of the accident. The fact that there is
little convincing evidence for human health effects below 100 mSv year−1(or 100 times the
dose limit) appeared to hold little sway over the level of concern.
Decisions on the levels used for restricting public doses are often debatable because by
necessity they involve judgements on possible future risk and individual acceptance of these
risks. The issue becomes exceptionally difficult in a radiological emergency, where doses are
levels of restrictions according to the prevailing circumstances is difficult to grasp and accept,
not only by the public but also by professionals and competent authorities.
While the current ICRP Recommendations take account of most of the difficulties
surrounding issues on individual dose restrictions, they may not adequately convey clearly the
assurance for protection under all circumstances requested by the public. For instance, it is not
entirely clear to the public that the reference levels recommended for dealing with emergencies,
while higher than the limits used for planned situations, still provide sufficient protection to
members of the public. Similarly, the rationale behind the numerical limits recommended by
the ICRP is also not entirely understood.
2.11.1. Dose restrictions at the time of the accident.
intergovernmental International Basic Safety Standards (or BSS) (IAEA 1996a, 1996b, 1996c)
were was being revised to take account of the new ICRP Recommendations in Publications 103,
109 and 111. The revision had reached a very advanced state but was not yet adopted (it was
finalised on 21 March 2011 and the new BSS was endorsed by the IAEA Commission on Safety
Standards (CSS) at its meeting from 25 to 27 May 2011). The relevant IAEA Safety Guide
GSG-2 which takes into account the most recent recommendations of the ICRP and provides
generic criteria for protective actions and other response actions in the case of a nuclear or
radiological emergency, including numerical values of these criteria, was published in May
2007 (IAEA 2007b). In essence this means that at the time of the accident the old BSS, which
was based on ICRP Publications 60 and 63, was still in force, while new approaches were under
At the time of the accident, the
540A J Gonz´ alez et al
Therefore, while confronting the emergency crisis immediately after the accident, the
Japanese authorities had to apply the dose restrictions recommended in the former ICRP
Recommendations in ICRP Publication 60 (ICRP 1991) and 63 (ICRP 1992), which were
internationally established as the global norm by the BSS and are still used in many national
standards. This implied, inter alia, the use of an intervention level of 50 mSv for deciding
on evacuation. It should also be noted that the protection of the public during emergencies is
still handled in many places following the recommendations of the ICRP in its Publication
63 (ICRP 1992), namely, the emergency is managed through decisions on intervention with
protective measures, following action levels, which are based on criteria of averted dose for
each protective action.
It seems, however, that the intervention criteria in terms of averted dose as recommended in
Publication 63 (ICRP 1992) and the BSS have not been so useful in implementing the protective
actions such as evacuation and shelter. In order to reduce potential radiation exposure to the
public, the Japanese authorities took the precautionary action of advising those within the first
3 km, then 10 km, and finally 20 km of the plant to evacuate and those between 20 and 30 km
to stay indoors and get ready to evacuate. In fact, this advice were given mainly on the basis of
the conditions at the Fukushima NPP at the time of the decisions.
Over time these criteria were adjusted to the newly recommended ICRP approach (ICRP
2007a) for restricting doses to the public by the use of reference levels with the selection of
a reference level of 20 mSv year−1, the bottom value of the recommended band for reference
levelsfor emergencyexposure situations,for interventionwith protectivemeasures. In selecting
the reference level, the authorities tried to follow the situation-based approach recommended
by the ICRP. It is to be noted that the regulatory public dose limit (emphasis added) for planned
exposure situations was and continues to be 1 mSv year−1in Japan.
The Japanese authorities applied the new recommendations to the decision to introduce
temporary relocation of people outside the 20 km zone. At this time it was also very difficult
to implement this protective action during the response phase because no operational criteria
had been enforced. When Japanese authorities had evaluated the monitoring data at the
contaminated area, the IAEA advised the Japanese government to carefully assess the situation
because one of the IAEA’s operational criteria for evacuation (temporary relocation) was
exceeded in the village of Iitate. The IAEA published this operational concept in GSG-2 just
after the accident in May of 2011. There was some confusion in moving from intervention
action levels to reference levels for the emergency situation, which may be caused by generic
statements in ICRP Publication 103 (ICRP 2007a, section 275). However, there is general
advice on how to use intervention levels described in Publication 103 (ICRP 2007a, table 8,
section g): ‘Intervention levels remain valuable for optimisation of individual countermeasures
when planning a protection strategy, as a supplement to reference levels for evaluation of
protection strategies; these refer to residual dose’. The intervention level may be useful as
an inputs to the planning and development of the overall response strategy in the optimisation
process. A detailed recommendation on how to use the intervention level is also described in
Publication 109 (ICRP 2009a, section 7.2.5). As described in Publication 109 (ICRP 2009a,
section 9), it is necessary to determine, in advance, a set of internally consistent criteria for
taking prompt actions, and based on these criteria to derive appropriate triggers expressed as
measurable quantities or observables for initiating them (see (IAEA 2002a and 2007a)). In the
accident, the triggers for initiating precautionary protective actions were the conditions at the
plant as measurable quantities or observables.
The real problem was that the Japanese authorities did not have enough time or experience
to issue emergency preparedness and response on the basis of the new ICRP Recommendations.
It is noted, however, that some confusion was caused by recommendations indicating that
the intervention levels are valuable for use as triggers for consideration of relevant protective
measures. The differences between the old and new approaches are significant, particularly for
emergency exposure situations and members of the public, and they have been summarised in
ICRP Publication 103 (ICRP 2007a, table 8).
2.11.2. Recommended dose restrictions.
other exposures and recommends specific individual restrictions on the dose expected to
be incurred by members of the public. It terms as public exposure any exposure incurred
by members of the public from radiation sources, excluding any occupational or medical
exposure and the normal local natural background radiation. It also recognises that public
exposure should be controlled coherently and consistently, although necessarily differently,
under different exposure situations, namely planned, emergency or existing exposure situations,
by a combination of three basic principles: justifying any decision that can change exposures;
optimising protection measures; and restricting individual doses. In planned exposure
situations, individual dose restriction is achieved through dose limits, expressed as the value of
the (additional) effective dose or the equivalent dose to individuals (from all regulated sources
that are able to generate planned exposure situations) that shall not be exceeded. The ICRP
also recommends the use of dose constraints, a prospective and source-related restriction on
the individual dose from a source, which provides a basic level of protection for the most
highly exposed individuals from a particular source, and serves as an upper bound on the dose
in optimisation of protection for that source, being an upper bound on the annual doses that
members of the public should receive from the planned operation of any controlled source. For
emergency situations, such as that caused by the accident, the source is not under control and
dose cannot be ‘limited’, either sensu stricto, sensu lato or sensu amplo. Therefore, individual
dose restrictions are achieved on a case-by-case basis using reference levels as guidance, which
are recommended for planning and responding with radiological protection measures. The
reference levels represent the level of dose above which it is judged to be inappropriate to
plan to allow exposures to occur, and below and above which optimisation of protection should
be implemented, the chosen value depending upon the prevailing circumstances of the exposure
of protection, namely selecting the best protection option under the prevailing circumstances,
but under restrictions on the expected individual doses. Three types of individual restrictions
are recognised: dose limits, dose constraints and reference levels. Dose limits are values
of the effective dose or the equivalent dose to individuals from (all controlled sources in)
planned exposure situations (emphasis added) that shall not be exceeded. Dose constraints
are upper bounds on the annual doses that members of the public receive from the planned
operation of any controlled source (emphasis added). Reference levels in emergency and
existing exposure situations (emphasis added) are levels of dose above which it is judged
to be inappropriate to plan to allow exposures to occur, the chosen value depending upon
the prevailing circumstances. While for public exposure in a planned exposure, the ICRP
recommends a dose limit of 1 mSv year−1(although in special circumstances a higher value
could be allowed in a single year, provided that the average over defined 5-year periods does not
exceed 1 mSv year−1), a framework for dose constraints and reference levels for all situations
is recommended with three bands: greater than 20–100 mSv year−1, for situations where
individuals are exposed to sources that are not controllable, or where actions to reduce doses
would be disproportionately disruptive; greater than 1–20 mSv year−1, for situations where
individuals will usually receive benefit from the exposure situation but not necessarily from the
exposure itself; and 1 mSv year−1or less, for situations where individuals are exposed to a
source that gives them little or no individual benefit but benefits society in general.
The ICRP distinguish public exposures from
542 A J Gonz´ alez et al
In its previous recommendations (ICRP 1991), the ICRP had calculated the cumulative
risk due to continuous lifetime exposure from birth at certain low dose rates and compared
the resulting maximum annual risk with a risk level considered to be acceptable to society
i.e. 10−4year−1. From this comparison, the annual dose limit for members of the public,
i.e. 1 mSv year−1, was derived and recommended. At the time of preparing the new
ICRP Recommendations, new information on radiation risk was taken into account in the
re-assessment of radiation risk. The dose limits were left unchanged because the changes in
radiation risk coefficients were minor so that a resetting of dose limits was not justifiable when
the inconvenience following the reset is considered. Perhaps the rationale behind the dose limit
of 1 mSv year−1was not sufficiently considered in the course of revising the recommendations.
In the previous recommendations, the unacceptable risk for the public, i.e. 10−4year−1, related
to ‘practices’, namely the introduction of human activities increasing radiation exposure. For
‘interventions’, the concept of unacceptable risk and consequently of the dose limit was not
relevant because intervention only reduces doses. In the formulation of the new system of
protection where dose restriction is based on the exposure situations, there is not a distinction
between intervention and practices but the dose limit, 1 mSv year−1for members of the public
is kept, without necessarily linking it to an acceptable risk.
2.11.3. Confusion among the stakeholders.
understanding the dose limit of 1 mSv year−1, which is used worldwide as a public dose limit
for planned exposure situations. The general public and society at large tend to regard a dose
emergencies.The public(andtosomeextent thenon-specialistauthorities)becameconfusedon
a fundamental issue: why they were permitted to receive during the emergency situation higher
doses than those that they were informed were a ‘limit’ before the accident occurred? Thus,
doubts arose on the coherence and consistency of the numerical restrictions recommended
for individual doses, namely the numerical values of dose limits, constraints and reference
levels. This issue created uncertainties in members of the public and their representatives. They
cannot understand why the dose limit of 1 mSv year−1, which was valid before the accident,
could be exceeded after the accident—at a time when people expect to be better protected.
They are confused about the rationale for tolerating individual doses based on reference levels
of 20–100 mSv year−1after the accident when doses above 1 mSv year−1(for the sum of
all regulated practices!) were unacceptable before the accident. In sum the relevant issue for
stakeholders was the rationality of the regulated values (e.g. a dose limit of 1 mSv year−1
vis-` a-vis a reference level of, for example, 20 mSv year−1) and, consequently, the perception
that double standards were being recommended (e.g. those suffering the accident being less
protected than neighbours of unaffected NPPs).
In addition there are semantic problems in the definitions of the levels of restriction,
which in turn create communication problems. An obvious semantic communication problem
occurred when the already confusing English terminology denoting the various individual dose
restrictions is translated into Japanese. The terms used for the individual restrictions applied
to dose (
) are blurred in English and, unsurprisingly, unclear in Japanese: sophisticated
explanations are required for understanding the concepts of dose limit,
constraintand reference level,
used as an adjective, and, which is used as the substantive, means limit, bound, boundary,
end, border, brim, edge, verge, etc. Namely,
exceeded under any circumstance; it is therefore unsurprising that the population was perplexed
There seems to be a considerable discrepancy in
. The Japanese expression for
means a level of dose that shall not be
with the use of dose restrictions higher than the dose limits. Moreover, the descriptors of dose
() are also unclear, both in English and in Japanese: dose (
() in the habitat, which is usually a total dose (
additional dose () added by a given source. In an emergency exposure situation, it
is possible to deal with projected dose (
dose ( ).
Part of the confusion is perhaps attributable to the fact that the differentiation between
additional doses () and extant doses (
semantics of these concepts is not clear in English and could be more confusing in other
languages, including Japanese. To the understanding of some, extant dose means the total dose
that is there and is incurred for whatever cause. To the understanding of others, it means ‘real‘
dose, a counter concept of hypothetical (or conceptual) dose, and under this understanding
an extant dose should not necessarily encompass all dose components including the natural
background. In this understanding, an occupational dose of a worker in a year is a kind of
extant dose. Equally, the natural background dose to the worker can constitute an extant dose.
The extent to which doses are summed into a total dose (
the purpose. The radiological protection recommendations imply as obvious that the level of
1 mSv year−1is not applied to a total dose incurred by individuals but rather to the additional
doses ( ) added by the introduction of (all) regulated sources. But this perception is
not necessarily apparent to the recipients.
An additional problem is that the ‘dose limit’ is not a factual ‘limit’ (despite this,
unfortunately, it is termed a limit, namely a point beyond which doses shall not pass), but rather
a restriction suggested that the regulatory authorities should take into account when they set the
authorised levels of individual dose for a given regulated source. This individual dose from each
specific regulated source is supposed to be restricted by dose constraints (
established by the regulatory authority. It should be noted that the concept of dose constraint
also applies to the additional dose (
doses. Namely, it applies to the dose expected to be added by the planned introduction of a
specific controlled source to the already existing extant dose.
It might be possible that in the Japanese situation, people and their representatives did not
necessarily realise the subtle differences between additional doses and extant doses in planned
exposure situations. Even if planned exposure situations in Japan and elsewhere are controlled,
so that the additional dose they deliver to individuals is below 1 mSv year−1, the exposed
individuals may still be incurring a much higher total dose due to the existence of an extant
dose caused by natural radiation, past human practices and releases into the environment from
other sources. They may not even be aware that the extant dose may vary by more than two
orders of magnitude: its minimum value is around 1 mSv year−1(in very few isolated places
of the world); its global average is well above 2 mSv year−1; its typical high value is around 10
mSv year−1(which is incurred by many people in many areas of the world); and, in some few
cases, its value may be as high as 100 mSv year−1or more. It is obvious, but not explicit, that
the rationale of the 1 mSv year−1restriction for all the additional doses from regulated practices
is base on the premise that the introduction of such practices should not change substantially
the de facto extant dose that individuals are incurring.
For emergency exposure situations, the scenario is necessarily different. At the stage of
emergency planning and preparedness it is still feasible to use the concepts of additional dose
(in this case it would be the additional dose expected to be delivered should the emergency
actually occur). When an emergency does in fact occur, like the accident in Japan, it is no
) can be an extant dose
), and it can also be an
), avertable dose () and residual
) is somehow blurred. The
) might be dependent on
) to be
) expected from the source, rather than to total
544 A J Gonz´ alez et al
longer feasible to plan for controlling the additional doses due to the accident. At that stage,
the relevant dose quantity is the extant dose in the aftermath of the accident—such doses
that already exist or are being delivered when control measures are decided—and they have
a pivotal role in deciding the justification for intervening with disruptive protective measures
or not. Another relevant quantity is the fraction of the extant dose which can be avoided by the
application of a protective measure or set of protective measures, namely the avertable dose
), which has a pivotal role in optimising the protection strategies. For the ICRP the
more important quantity for restricting individual doses is the dose that would be expected to
be incurred if no protective measure(s) were taken, namely the projected dose (
and the dose expected to be incurred after protective measure(s) have been fully implemented
(or a decision has been taken not to implement any protective measures), namely the residual
dose () 109 (ICRP 2009a).
The current framework for source-related dose restrictions, with examples for workers and
the public, does not indicate explicitly whether it refers to additional doses or extant doses. The
reader might suspect that the lower band around 1 mSv year−1refers to additional doses and
that the upper band towards 100 mSv year−1refers to extant doses, but this is not clear, and
potentially could be a source of confusion. Thus, the numerical values of annual limits vis-` a-vis
the numerical values of reference levels (e.g. 1 mSv vis-` a-vis 20–100 mSv) are not easily to
convey to a sceptical public. Furthermore, in addition to the conceptual confusion about the
quantities themselves, there may also be a lack of understanding of the epistemological basis
of the recommended levels.
2.11.4. Controversies and questions.
are naturally controversial because they involve judgements on individual acceptability of risks.
The issue becomes exceptionally difficult in a radiological emergency, where doses are difficult
to control but people expect to be particularly well protected. The logic behind different levels
of restrictions according to the prevailing circumstances is difficult to grasp and accept, not only
by the public at large but also by the competent authorities. After an accident occurs, people
hold a natural but equivocal expectation of being better protected than before the accident. It
is difficult for them to recognise that, because an accident has unfortunately occurred, they
will obviously be subjected to higher risks. Whatever good the wishes of the authorities, better
protection might simply be unfeasible: while in planned exposure situations authorities may be
they have to deal with the situation as it is and apply the best protection they can under the
The current system of protection does take account of most of the problems described for
individual dose restrictions, but it perhaps fails to convey clearly the assurance for protection
under any circumstance demanded by the public. For instance, it is not clear to the public that
the reference levels recommended for dealing with emergencies, while being levels of dose
higher than the limits used for planned situations, still provide sufficient public protection. It is
also not clear what the rationale is for the recommended numbers.
There are many questions related to exposure of people living in ‘contaminated areas’.
Questions are raised about the tentative reference level, 20 mSv in the first year, asking if the
level is not too high when the annual dose limit of 1 mSv year−1and especially exposures to
the projected dose exceeds 1 mSv year−1is inappropriate because the dose limit to an embryo
or foetus is only 1 mSv. This belief reflects a misinterpretation of the dose limit recommended
for members of the public or unborn children. The dose limit 1 mSv year−1is for planned
exposure situations. In existing exposure situations, people, residents in high background areas
Decisions on the levels used for restricting public doses
Memorandum545 Download full-text
for instance, are living with elevated doses much exceeding 1 mSv year−1. There is no question
that the exposure of current residents in an area with elevated residual radioactivity due to the
accident belongs to an existing exposure situation, and hence the concept of dose limit does not
apply. Instead, reference levels suitable for the prevailing circumstances are applied.
Contrary to this, ‘1 mSv year−1’ is referred to in almost every situation involving exposure
of the public, not only in planned exposure situations but also existing situations related to a
radiological event and even related to naturally occurring radioactive materials (NORMs). The
new criteria set for control of foodstuff in Japan, enforced on 1 April 2012, are also calculated
on the basis of 1 mSv year−1despite the situation not being a planned one.
The somewhat ambiguous presentation of the dose restriction of 1 mSv year−1may have
been partly due to misinterpretation. As described, the reference level for an existing exposure
situation can be selected in the dose band of 1–20 mSv year−1, with a long-term objective of
around 1 mSv year−1. While it is not explicitly indicated, it is implicit that the boundary doses,
20 mSv year−1and 1 mSv year−1, correspond to the dose limits for workers and the public,
respectively. Actually, the value of 1 mSv is explained as two orders of magnitude lower than
the maximum value for a reference level. However, they should mean the dose limits because,
for planned exposure situations, the dose constraints selected in the band should not exceed
the dose limits. The upper bound of the first band (<1 mSv) cannot have another value, for
example 3 mSv, because a dose constraint for members of the public should be set in this first
band and cannot exceed 1 mSv (the dose limit). This means that the upper bound should match
the dose limit for the public. This numerical link of 1 mSv year−1to the dose limit for the public
leads to confusion about the underlying concept and people believe that their dose should be
below 1 mSv year−1whatever the situation.
This problem of interpretation may have been caused by the fact that both occupational
and public exposures fall into a single set of bands. In reality, there are no obvious reasons why
the boundaries should be 20 and 1 mSv year−1for the reference levels. The second boundary
could well be a few mSv year−1for existing exposure situations of the public. The levels 20
and 1 mSv year−1are only appropriate for the dose constraints in planned exposure situations.
for better communication of the rationale behind the judgement as to whether and how an
individual dose should be averted. The current recommendations are to select a reference
level between 100 and 20 mSv year−1for emergency exposure situations and between 20 and
1 mSv year−1for existing exposure situations. The concepts of additional doses and extant
(existing) doses are misunderstood. The public and others do not completely understand the
reasons why different dose levels are recommended for different exposure situations, in large
part because they believe, incorrectly, that a ‘safe’ dose is below 1 mSv year−1, independent of
the exposure situation.
It would be worthwhile clarifying further the rationale and ethical foundations behind the
intended use of individual dose restrictions (dose limits, constraints and reference levels) for
protection of the public. The recommendations for the protection of the public in situations of
prolonged radiation exposure might sure as a useful guide in this regard (ICRP 1999).
An important lesson learned from the accident in Japan is to the need
2.11.6. Categorising public exposures due to an accident.
the previous sections, it can be concluded that some of the problems found in transitioning
from the emergency to an existing situation, in rehabilitating areas and in limiting public
doses might all be related to some confusion about the current characterisation of public
exposure during an accident. For such categorisation reference should be made to the relevant
definitions of exposure and situation. Public exposure is defined as exposure incurred by
From the issues reviewed in