This Safety Report explains how thec o ncept s o f a t t ri but ion of he alth e ffects
and i nf erence o f ri sks can be t aken into
acco unt i n t he a ppl i c ation of IAEA s afetys t a nda rds, so a s t o i mple me nt them mor ee ff ect i vel y. In pa r t i cular, this publicationd emo nst ra t es expl i ci tly w hat the r ele vantprovisions of the safety standards are
fo r hi gh a nd mo dera t e le vels of ex pos ur e ,w here hea l t h eff ect s might be able to bea t t r i b u t e d t o t h e ex p o s u r e , a n d f o r l ow
and ver y l ow l evel s of ex pos ur e , w he r erisks can only be inferred. This Safety
Repo r t a l so a i ms t o su ppor t mor e e ffective
c o mmuni ca t i o n by cl a rify ing the pr ope r us eof cer t a i n co ncept s d e t aile d in the s afetys t a n d a r d s a n d p r ov i d i n g p l a i n l a n g u a g e
expl a na t i o ns o f t he concepts of attr ibutionof eff ect s a nd i nf erenc e of r is k.

Safety Repor ts Series
N o. 1 2 2Attribution ofRadiation Health
Effects and Inferenceof Radiation Risks
Considerations for Application of
the IAEA Safety Standards

INTERNATIONAL ATOMIC ENERGY AGENCY
VIENNAAtoms for Peace

IAEA SAFETY STANDARDS AND RELATED PUBLICATIONSIAEA SAFETY STANDARDSUnder the terms of Article III of its Statute, the IAEA is authorized to establish or adopt
standards of safety for protection of health and minimization of danger to life and property, andto provide for the application of these standards.
The publications by means of which the IAEA establishes standards are issued in the
IAEA Safety Standards Series. This series covers nuclear safety, radiation safety, transport
safety and waste safety. The publication categories in the series are Safety Fundamentals,
Safety Requirements and Safety Guides.
Information on the IAEA’s safety standards programme is available on the IAEA Internet
site
https://www.iaea.org/resources/safety-standards
The site provides the texts in English of published and draft safety standards. The texts
of safety standards issued in Arabic, Chinese, French, Russian and Spanish, the IAEA Safety
Glossary and a status report for safety standards under development are also available. For
further information, please contact the IAEA at: Vienna International Centre, PO Box 100,
1400 Vienna, Austria.
All users of IAEA safety standards are invited to inform the IAEA of experience in theiruse (e.g. as a basis for national regulations, for safety reviews and for training courses) for the
purpose of ensuring that they continue to meet users’ needs. Information may be provided via
the IAEA Internet site or by post, as above, or by email to Official.Mail@iaea.org.
RELATED PUBLICATIONSThe IAEA provides for the application of the standards and, under the terms of Articles III
and VIII.C of its Statute, makes available and fosters the exchange of information relating
to peaceful nuclear activities and serves as an intermediary among its Member States for thispurpose.
Reports on safety in nuclear activities are issued as Safety Reports, which provide
practical examples and detailed methods that can be used in support of the safety standards.
Other safety related IAEA publications are issued as Emergency Preparedness andResponse publications, Radiological Assessment Reports, the International Nuclear Safety
Group’s INSAG Reports, Technical Reports and TECDOCs. The IAEA also issues reports
on radiological accidents, training manuals and practical manuals, and other special safety
related publications.
Security related publications are issued in the IAEA Nuclear Security Series.
The IAEA Nuclear Energy Series comprises informational publications to encourage
and assist research on, and the development and practical application of, nuclear energy forpeaceful purposes. It includes reports and guides on the status of and advances in technology,
and on experience, good practices and practical examples in the areas of nuclear power, thenuclear fuel cycle, radioactive waste management and decommissioning.

ATTRIBUTION OF
RADIATION HEALTH
EFFECTS AND INFERENCE
OF RADIATION RISKSThe following States are Members of the International Atomic Energy Agency:
AFGHANISTANALBANIA
ALGERIAANGOLA
ANTIGUA AND BARBUDA
ARGENTINA
ARMENIA
AUSTRALIA
AUSTRIAAZERBAIJAN
BAHAMAS
BAHRAINBANGLADESHBARBADOSBELARUSBELGIUM
BELIZEBENIN
BOLIVIA, PLURINATIONAL
STATE OFBOSNIA AND HERZEGOVINABOTSWANABRAZILBRUNEI DARUSSALAM
BULGARIA
BURKINA FASO
BURUNDI
CABO VERDECAMBODIACAMEROONCANADACENTRAL AFRICAN
REPUBLIC
CHAD
CHILE
CHINA
COLOMBIACOMOROSCONGOCOSTA RICA
CÔTE D’IVOIRECROATIACUBACYPRUSCZECH REPUBLIC
DEMOCRATIC REPUBLIC
OF THE CONGO
DENMARKDJIBOUTIDOMINICADOMINICAN REPUBLICECUADOREGYPTEL SALVADORERITREAESTONIA
ESWATINIETHIOPIAFIJI
FINLANDFRANCEGABONGAMBIAGEORGIAGERMANYGHANA
GREECE
GRENADAGUATEMALAGUYANAHAITI
HOLY SEE
HONDURASHUNGARYICELAND
INDIA
INDONESIA
IRAN, ISLAMIC REPUBLIC OFIRAQIRELANDISRAELITALY
JAMAICAJAPANJORDANKAZAKHSTANKENYAKOREA, REPUBLIC OFKUWAITKYRGYZSTANLAO PEOPLE’S DEMOCRATIC
REPUBLICLATVIALEBANONLESOTHO
LIBERIA
LIBYA
LIECHTENSTEIN
LITHUANIALUXEMBOURG
MADAGASCARMALAWI
MALAYSIAMALI
MALTA
MARSHALL ISLANDS
MAURITANIA
MAURITIUS
MEXICOMONACOMONGOLIAMONTENEGRO
MOROCCOMOZAMBIQUE
MYANMAR
NAMIBIANEPAL
NETHERLANDSNEW ZEALANDNICARAGUANIGERNIGERIANORTH MACEDONIANORWAYOMANPAKISTAN
PALAU
PANAMAPAPUA NEW GUINEAPARAGUAYPERU
PHILIPPINESPOLANDPORTUGALQATARREPUBLIC OF MOLDOVAROMANIARUSSIAN FEDERATIONRWANDASAINT KITTS AND NEVISSAINT LUCIA
SAINT VINCENT AND
THE GRENADINESSAMOASAN MARINOSAUDI ARABIASENEGALSERBIASEYCHELLESSIERRA LEONESINGAPORESLOVAKIASLOVENIA
SOUTH AFRICASPAIN
SRI LANKA
SUDAN
SWEDENSWITZERLANDSYRIAN ARAB REPUBLICTAJIKISTANTHAILANDTOGO
TONGA
TRINIDAD AND TOBAGOTUNISIATÜRKİYETURKMENISTANUGANDAUKRAINE
UNITED ARAB EMIRATESUNITED KINGDOM OFGREAT BRITAIN ANDNORTHERN IRELAND
UNITED REPUBLICOF TANZANIAUNITED STATES OF AMERICAURUGUAYUZBEKISTANVANUATU
VENEZUELA, BOLIVARIAN
REPUBLIC OFVIET NAMYEMEN
ZAMBIA
ZIMBABWE

The Agency’s Statute was approved on 23 October 1956 by the Conference on the Statute of the
IAEA held at United Nations Headquarters, New York; it entered into force on 29 July 1957.
The Headquarters of the Agency are situated in Vienna. Its principal objective is “to accelerate and enlarge
the contribution of atomic energy to peace, health and prosperity throughout the world’’.

SAFETY REPORTS SERIES No. 122

ATTRIBUTION OF
RADIATION HEALTH
EFFECTS AND INFERENCE
OF RADIATION RISKSCONSIDERATIONS FOR APPLICATION OF THE IAEA
SAFETY STANDARDSINTERNATIONAL ATOMIC ENERGY AGENCY
VIENNA, 2023

COPYRIGHT NOTICEAll IAEA scientific and technical publications are protected by the terms of
the Universal Copyright Convention as adopted in 1952 (Berne) and as revisedin 1972 (Paris). The copyright has since been extended by the World Intellectual
Property Organization (Geneva) to include electronic and virtual intellectual
property. Permission to use whole or parts of texts contained in IAEA publicationsin printed or electronic form must be obtained and is usually subject to royalty
agreements. Proposals for non-commercial reproductions and translations arewelcomed and considered on a case-by-case basis. Enquiries should be addressedto the IAEA Publishing Section at:
Marketing and Sales Unit, Publishing Section
International Atomic Energy Agency
Vienna International Centre
PO Box 100
1400 Vienna, Austria
fax: +43 1 26007 22529
tel.: +43 1 2600 22417
email: sales.publications@iaea.org
www.iaea.org/publications© IAEA, 2023
Printed by the IAEA in Austria
October 2023
STI/PUB/2026

IAEA Library Cataloguing in Publication Data
Names: International Atomic Energy Agency.
Title: Attribution of radiation health effects and inference of radiation risks :considerations for application of the IAEA safety standards / International Atomic
Energy Agency.
Description: Vienna : International Atomic Energy Agency, 2023. | Series: IAEA
safety report series, ISSN 1020-6450 ; no. 122 | Includes bibliographicalreferences.
Identifiers: IAEAL 23-01603 | ISBN 978–92–0–134523–3 (paperback : alk. paper) |ISBN 978–92–0–134323–9 (pdf) | ISBN 978–92–0–134423–6 (epub)
Subjects: LCSH: Radiation — Health aspects. | Radiation — Safety measures. |Radiation — Safety regulations.
Classification: UDC 614.876 | STI/PUB/2026

FOREWORD
In 2012, the United Nations Scientific Committee on the Effects of Atomic
Radiation (UNSCEAR) presented a report to the United Nations General
Assembly in which it clarified the scientific knowledge regarding the attributionof health effects to radiation exposure and the inference of risks from a radiation
exposure that has been received. The UNSCEAR 2012 report distinguishedbetween three types of radiation exposure: (i) radiation exposure at a high level,
for which a health effect in an individual can be attributed to the exposure;(ii) radiation exposure at a moderate level, for which an increased incidence of
health effects in a population can be attributed to the exposure; and (iii) radiation
exposure at low and very low levels, where effects — either at an individual or at
a population level — cannot be attributed to the exposure, and instead the risks
can only be inferred.
The IAEA safety standards provide principles, requirements andrecommendations that are intended to be used to protect people and theenvironment from harmful effects of ionizing radiation. They do this on thebasis of inferred risks — both risks that exist in normal circumstances and risks
that could arise as a consequence of an accident — but they are generally not
formulated in terms of health effects that could be attributed to radiation exposure.
This Safety Report explains how the concepts of attribution of healtheffects and inference of risks can be taken into account in the application of thesafety standards, so as to implement them more effectively. In particular, thispublication explains the relevant provisions of the safety standards for high andmoderate levels of exposure, where health effects might be able to be attributed
to the exposure, and for low and very low levels of exposure, where risks canonly be inferred. This Safety Report also supports more effective communication
by clarifying the proper use of certain concepts relating to radiation risks and byproviding a plain language explanation of the concepts of attribution of effects
and inference of risks.
The IAEA is grateful for the contributions of all those who were involvedin the drafting and review of this report. The IAEA officer responsible for thispublication was K. Asfaw of the Office of Safety and Security Coordination.

EDITORIAL NOTE
Although great care has been taken to maintain the accuracy of information containedin this publication, neither the IAEA nor its Member States assume any responsibility forconsequences which may arise from its use.
This publication does not address questions of responsibility, legal or otherwise, for acts
or omissions on the part of any person.
Guidance provided here, describing good practices, represents expert opinion but does
not constitute recommendations made on the basis of a consensus of Member States.
The use of particular designations of countries or territories does not imply any
judgement by the publisher, the IAEA, as to the legal status of such countries or territories, of
their authorities and institutions or of the delimitation of their boundaries.
The mention of names of specific companies or products (whether or not indicated asregistered) does not imply any intention to infringe proprietary rights, nor should it be construed
as an endorsement or recommendation on the part of the IAEA.
The IAEA has no responsibility for the persistence or accuracy of URLs for external or
third party Internet web sites referred to in this book and does not guarantee that any content
on such web sites is, or will remain, accurate or appropriate.

CONTENTS
1.

2.

3.

4.

5.

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

1

1.1.
1.2.
1.3.
1.4.

Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
Structure  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

1
2
3
4

RISK RELATED CONCEPTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

5

2.1.
2.2.
2.3.

Attribution of health effects to past radiation exposures  . . . . 
Inference of health risks from radiation exposures . . . . . . . . . 
Estimation of health effects for comparative purposes . . . . . . 

5
10
15

BASIS OF THE SAFETY STANDARDS . . . . . . . . . . . . . . . . . . . . 

16

3.1.
3.2.
3.3.
3.4.

Purpose of the safety standards . . . . . . . . . . . . . . . . . . . . . . . . 
Development and use of the safety standards . . . . . . . . . . . . . 
Scope of the safety standards  . . . . . . . . . . . . . . . . . . . . . . . . . 
The fundamental safety principles  . . . . . . . . . . . . . . . . . . . . . 

16
17
17
19

PRACTICAL APPLICATION OF RISK RELATEDCONCEPTS FOR DIFFERENT CATEGORIES OF EXPOSURE

25

4.1.
4.2.
4.3.

Public exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
Occupational exposure  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
Medical exposure  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

25
32
39

IMPLICATIONS OF THE CONCEPTS OF ATTRIBUTION
OF HEALTH EFFECTS AND INFERENCE OF RISK FOR
COMMUNICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

42

5.1.
5.2.

Communication about the safety standards . . . . . . . . . . . . . . . 
Communication about risk and health effects . . . . . . . . . . . . . 

4245

A PLAIN LANGUAGE EXPLANATION OF THE
CONCEPTS OF ATTRIBUTION AND INFERENCE
TO SUPPORT PUBLIC COMMUNICATION

51

APPENDIX:REFERENCES  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
CONTRIBUTORS TO DRAFTING AND REVIEW  . . . . . . . . . . . . . . . 

5359

1. INTRODUCTION
1.1. BACKGROUND
The IAEA safety standards are based on the scientific knowledge of thehealth effects associated with radiation exposure that has been gained overdecades by the studies of the United Nations Scientific Committee on the Effectsof Atomic Radiation (UNSCEAR), and on the recommendations of international
expert bodies, notably the International Commission on RadiologicalProtection (ICRP).
UNSCEAR was established by the United Nations General Assembly on
3 December 1955 by its resolution 913 (X). Its mandate is to undertake broad
assessments of sources of ionizing radiation and of the effects of ionizing radiation
on human health and the environment. In pursuit of this mandate, UNSCEAR
reviews and evaluates exposures to radiation at global and regional levels andevaluates evidence for radiation induced health effects in exposed persons.
UNSCEAR also reviews advances in the understanding of the radiobiologicalmechanisms by which radiation induced effects on human health or on nonhuman biota can occur.
In its resolution 62/100 of 17 December 2007 (A/RES/62/100), theUnited Nations General Assembly requested UNSCEAR “to clarify further theassessment of potential harm owing to chronic low-level exposures among large
populations and also the attributability of health effects” and encouraged it “tosubmit a report on that issue at its earliest convenience”. This was subsequently
provided by UNSCEAR in its 2012 Report to the General Assembly (A/67/46),
in particular in annex A to that report [1]. The report sets out the concepts ofretrospective attribution of radiation health effects to past radiation exposuresand the prospective inference of health risks from radiation exposures.
UNSCEAR 2012 [1] also raises questions about understanding among experts
and communication with the public regarding issues such as radiation exposure,
health effects and risks. The report focuses on “the sum of the relevant incremental
exposures above that from normal background exposure to natural sources,
because that is usually the characteristic considered in epidemiological studies(and is also of interest to those who might use the Committee’s information as thebasis for policy and decision-making)” [1].
The ICRP was established in 1928 at the Second International Congress onRadiology in Stockholm, Sweden. Its purpose is to advance for the public benefit
the science of radiological protection, in particular by providing recommendations
and guidance on all aspects of protection against ionizing radiation. The ICRP’s

1latest recommendations for a system of radiological protection were published in2007 as ICRP Publication 103 [2].
Following the issue of UNSCEAR 2012 [1], the IAEA Safety Standards
Committees and the Commission on Safety Standards (CSS)1 considered whether
the report could have implications for the IAEA safety standards — both thosepublished and those still under development. The CSS did not identify any safety
standards that warranted revision as a result of UNSCEAR 2012 [1]; however,there was general consensus in the CSS that a better understanding among users of
the safety standards of the concepts of attribution of health effects and inferenceof risks could enhance the application of the standards and communication onradiation risks. Consequently, the CSS requested that a Safety Report be preparedon how to apply the concepts of: (a) retrospective attribution of radiation healtheffects to past radiation exposures; (b) prospective inference of health risks fromradiation exposures; and (c) prediction of notional health effects for comparative
purposes (e.g. the use of collective dose).

1.2. OBJECTIVE
The objective of this Safety Report is to explain how the concepts
of attribution of health effects and inference of risks, as set out in
UNSCEAR 2012 [1], can be taken into account in applying the safety standards
and in more effectively communicating concepts relating to radiation risks in thesafety standards.
The safety standards are not intended to be used in estimating health effects,
either retrospectively or prospectively. This Safety Report also explains that it isappropriate to use the safety standards to infer risks for the purposes of protection
and safety (of the public, workers and patients), but it is not appropriate to usethem to attribute health effects to radiation exposures, in particular after exposure
to low and very low doses.
The target audience of this Safety Report comprises experts on radiation
protection and safety and individuals who might need to communicate on matters
1
The five Safety Standards Committees are standing bodies of senior representatives
in the areas of emergency preparedness and response, nuclear safety, radiation safety, transport
safety and waste safety. They are open to all IAEA Member States and were established tomake recommendations on the IAEA’s programme for the development, review and revisionof safety standards and on activities to support the use and application of these standards. The
Commission on Safety Standards is a standing body of senior government officials, appointed
by the IAEA Director General, holding national responsibilities for establishing standards andother regulatory documents relevant to nuclear, radiation, transport and waste safety, and to
emergency preparedness and response.

2

of radiation protection and safety in regulatory bodies, other relevant authorities,
operating organizations, technical support organizations and internationalorganizations.

1.3. SCOPE
This Safety Report addresses matters relating to radiation health effects,
radiation risks and radiation protection. It is relevant for all circumstances coveredby the safety standards that give rise to radiation risks, including the entire
lifetime of all facilities and activities — existing and new — utilized for peacefulpurposes, as well as existing or unregulated radiation risks (see Section 3.3).
This Safety Report does not address nuclear safety, nuclear security or theprotection of the environment.
This Safety Report does not provide guidance on assessing prospective
cancer risks from exposure to radiation, or on assessing the attributability ofhealth effects to radiation exposure for purposes of determining legal liability incompensation programmes for individuals who have cancer.2
The terms used in this Safety Report are to be understood as they aredefined in the IAEA Nuclear Safety and Security Glossary [5]. The purpose of the
IAEA Nuclear Safety and Security Glossary is to define and explain the usage ofterms in the safety standards as a whole, and as such, some of the definitions areintentionally not consistent with the definitions included in UNSCEAR 2012 [1],which are for the purposes of that report alone.
The terms ‘attribution’ and ‘inference’ are defined in UNSCEAR 2012 [1].
Attribution is: “The ascribing of an actual or manifest outcome to a cause. In
the context of this report, attribution refers to the ascribing of an outcome—inparticular a health effect—to radiation exposure” [1]. The health effect might
be a deterministic effect evident in an individual or a stochastic effect evident
via observation of an increase of the incidence of that effect in a population.
Inference is: “The process of drawing conclusions from scientific observations,evidence and reasoning in the presence of uncertainty” [1].
The use of the term ‘risk’ warrants some additional explanation. In thesafety standards, ‘risk’ is used in different ways depending on the context. For
the purposes of this Safety Report, the relevant definition is: “The probability ofa specified health effect occurring in a person or group as a result of exposure toradiation” [5]; the health effect could be, for example, skin reddening or cancer(see Section 2.1). In UNSCEAR 2012 [1], “risk refers to the probability that an
event of interest (e.g. onset of cancer) will occur (i.e. it is prospective) during a2

Such matters are addressed in Refs [3, 4].

3

TABLE 1. TERMINOLOGY FOR BANDS OF RADIATION DOSE
(adapted from table 1 of annex A of UNSCEAR 2012 [1])Terminology
for dose bands

Range of absorbed dose
for low LET radiation

Scenarios

High

Greater than ~1 Gy

Typical dose (whole or partial body) toindividuals after severe radiation
accidents or from radiotherapy

Moderate~100 mGy to ~1 Gy

Doses to about 100 000 of the recovery
operation workers after the Chernobyl
accident

Low~10 to ~100 mGy

Dose to an individual from multiple wholebody computed tomography (CT) scans

Very lowLess than ~10 mGy

Dose to an individual from conventional
radiology (i.e. without CT or fluoroscopy)

given time period (e.g. the rest of life following an exposure)”. This is considered
consistent with the definition used in this Safety Report. More general meaningsof the word ‘risk’ as used in the safety standards, such as the risk of an accident
occurring or the risk to ecosystems in the environment, are not intended here.
For the purposes of discussing health effects, UNSCEAR has adopted aterminology to indicate bands of radiation exposure, expressed as approximate
ranges of total absorbed dose. The terminology is intended to foster a consistentinterpretation of the terms ‘high’, ‘moderate’, ‘low’ and ‘very low’ with reference
to total doses of low linear energy transfer (LET) radiation (e.g. gamma
radiation). Table 1 indicates, in approximate ranges, bands of total absorbed dose
(to the whole body or to a specific organ or tissue of an individual) received inaddition to that from normal background exposure to natural sources of radiation.
The dose bands do not account for the rate at which the dose is delivered.

1.4. STRUCTURE
Sections 2 and 3 summarize the relevant concepts from UNSCEAR 2012 [1]and the safety standards. Section 2 draws a clear distinction between three concepts
that are not always distinguished clearly in practice: data on actual effects; models
used to estimate the occurrence of health effects; and models used for purposes ofradiation protection. Section 3 addresses the basis of the IAEA safety standards
4and sets out their purpose (i.e. protection of people and the environment fromharmful effects of ionizing radiation) and also makes connections between thefundamental principles of justification, optimization and limitation of risks andthe concepts of attribution and inference.
Section 4 considers doses that have occurred in the past and whether
health effects were able to be attributed to these doses, either at an individual orat a population level, for each of the three categories of exposure (occupational
exposure, public exposure and medical exposure). For each exposure category,it also considers how exposure is to be controlled, in accordance with the IAEA
safety standards, in dose ranges where individual effects can be attributed, where
effects can be attributed at a population level and where risks can only be inferred.
Section 5 provides suggestions on how the concepts of attribution andinference can support communication about certain concepts in the safety
standards that are sometimes misunderstood and also sets out an approach thatcan be applied to communicate with the public about radiation risks.
The Appendix provides a plain language explanation of the concepts of
attribution and inference to support public communication.

2. RISK RELATED CONCEPTS
2.1. ATTRIBUTION OF HEALTH EFFECTS TO PAST RADIATIONEXPOSURES
Basic aspects of radiation health effects are set out in UNSCEAR 2012 [1].
In the context of radiation protection, harmful health effects of radiation exposure
are categorized into the following two groups3:— Deterministic effects, which are described as injury in populations of cells
and are also termed ‘tissue reactions’;— Stochastic effects, which include malignant disease, benign tumours andheritable effects.

3

There are some health effects, such as circulatory diseases and cataracts, that havenot been possible to classify as either deterministic or stochastic effects. For the purposes of
UNSCEAR 2012 [1], such effects are included in the term ‘tissue reactions’.

52.1.1. Deterministic effects
2.1.1.1.

Characteristics of deterministic effects

When the human body is exposed to ionizing radiation, a process ofionization occurs that might alter the structure of molecules in cells. If suchmolecules are affected, cells might be damaged. This damage might kill thecell, or it might result in a viable but modified cell, including a cell in which
the capacity for reproduction is affected. If a critical number of cells in an organor tissue is killed, or if a critical number of cells is prevented from reproducing
and functioning normally, there might eventually be a loss of function of
the organ or tissue, resulting in detrimental health effects, which are termed‘deterministic effects’.
Deterministic effects are, with few exceptions (e.g. fibrotic processes), acuteand occur early in individuals exposed to radiation at high doses. Examples ofdeterministic effects include hair loss, skin burns, damage to the haematopoietic
system, acute radiation syndrome (i.e. radiation sickness) and death.
A deterministic effect can occur only if the individual radiation dose exceeds
a certain threshold. At increasing doses above this threshold level, the deterministic
effect becomes more severe. The level of the threshold dose is different for different
deterministic effects. The threshold is also related to the duration of exposure, andit depends (to some extent) on the individual who is exposed.
2.1.1.2.

Attribution of deterministic effects

As stated in annex A of UNSCEAR 2012 [1]:“In the context of deterministic effects, one can very often observe many
characteristics (e.g. damage evolution and severity) in a differential
pathological diagnosis, so that a health effect in an individual can beunequivocally attributed to a radiation exposure.”
2.1.2. Stochastic effects
2.1.2.1.

Characteristics of stochastic effects

Exposure to ionizing radiation can also induce a modification of the genetic
material in a cell in such a way that the cell remains viable. If the damaged
cell is not killed by the body’s immune system, this might eventually lead tothe development of cancer or benign tumours in the exposed tissue or organ. If
the cell that is modified by exposure to radiation is a reproductive cell, it might
6

transmit altered genetic information to the descendants of an exposed individual
and thus cause health effects in those descendants. Radiation induced heritableeffects have been demonstrated in animal studies but have not been demonstrated
for human populations exposed to any level of radiation [1]. Such health effects,
including heritable effects, are termed ‘stochastic effects’.
The latency period for the manifestation of stochastic effects might be a
few years (e.g. in the case of most types of leukaemia) to tens of years (e.g. forother malignant conditions, such as solid cancers). The probability of occurrenceof a stochastic effect increases with increasing radiation dose; the severity of theeffect (if it occurs) is independent of dose.
2.1.2.2.

Attribution of stochastic effects

At present, it is not possible to attribute with certainty a stochastic effectin an individual to radiation exposure. This is because similar health effects
also occur in the absence of radiation exposure (i.e. due to other carcinogens),
and there are currently no specific biomarkers for stochastic radiation healtheffects. Even if such a biomarker were discovered, it would not be possible
to distinguish between the effects of exposure to low levels of radiation from
artificial sources and the effects of exposure to natural background radiation.
Unlike for deterministic effects, therefore, in the case of stochastic effects ofradiation exposure, unequivocal differential pathological diagnosis of individuals
is not currently possible.4
By means of epidemiological studies of populations of exposed persons, it
is possible, under certain conditions, to attribute an increase in the incidence ofstochastic effects to radiation exposure. Such attribution at the population levelis possible only where the observed change in incidence of the stochastic effectis high enough to be clearly distinguished from the normal incidence of such
effects, taking into account the inherent uncertainties in epidemiological studies.
An example is the incidence of thyroid cancer among children. Thyroid
cancer has a very low normal incidence in children, and the high radiosensitivityof the thyroid makes this radiation induced effect easier to attribute. Therefore,
epidemiological studies have shown an increased frequency of thyroid cancer
among children that can be attributed with confidence to radiation exposure [7];however, thyroid cancer in an individual still cannot be attributed unequivocallyto radiation exposure.
In many other situations — for example, where the change in the incidence ofa stochastic effect is small or where the dose is low — it is not possible to attributesuch effects to radiation exposure, either for individuals or for a population.
4

See Ref. [6] for further discussion.

7

2.1.2.3.

Uncertainties in attributing stochastic effects

Estimates of the incidence of stochastic effects are uncertain, particularly at
low doses. There are two types of uncertainty: aleatory uncertainties (also calledstatistical uncertainties), which are due to the random variations of the estimates(i.e. in comparison with the ‘true’ value) and are inherent to a phenomenon;
and epistemic uncertainties, which are due to incomplete knowledge about aphenomenon, which affects the ability to produce a reliable estimate [5].
Annex B of UNSCEAR 2012 [1] addresses uncertainties in risk estimatesfor radiation induced cancer. The dominant uncertainty is the statistical (oraleatory) uncertainty, due to the dose distributions and the sample size consideredin epidemiological studies. For low and very low doses, these statistical variations
are normally large enough to obscure any small increase in the incidence ofstochastic effects. As stated in annex A of UNSCEAR 2012 [1]:“It is extremely difficult to detect excess frequency of occurrence ofcancer by studying population exposures limited to low dose and very low
doses” [8]. “As a result, extremely large sample sizes (typically millions ofpeople) would theoretically be required in these dose ranges for a statisticallysignificant increase in frequency to be observed.”
In other words, as a consequence of these uncertainties, it might
never be possible to demonstrate the effects of low and very low doses using
epidemiological studies.
2.1.3. The dose‒response relationshipThe dose–response relationship presents the increase in probability of healtheffects for an increase in radiation dose. UNSCEAR 2012 [1] notes “the current
limitations to knowledge…regarding health effects from radiation exposure” andhighlights the distinctions between the attributability of effects for three different
ranges of dose (see Fig. 1), as follows:— The high dose range (i.e. above 1 Gy; see Table 1), for which deterministic
effects are clinically observable in individuals by means of a diagnosis. The
dose‒response relationship for deterministic effects in a population follows
a sigmoid function distribution (the red line in Fig. 1), but in practice, atthe individual level, it is assumed to be a threshold function: below thedose threshold for the occurrence of a particular deterministic effect, theprobability of that effect is taken to be zero; above the threshold, it isassumed to be one.
8

— The moderate dose range (i.e. about 100 mGy to about 1 Gy; see Table 1), forwhich radiation induced stochastic effects are observable (i.e. statistically)
only in populations by means of epidemiological studies; such effects cannot
be unequivocally attributed to radiation exposure of individuals. The dose‒
response relationship for stochastic effects observed in large populations
forms a roughly linear function (the blue line in Fig. 1). Therefore, it isimportant to note that the extent to which health effects in this dose range
can be observed depends not only on the dose received but also on the sizeof the exposed population.
— The low dose and very low dose range (i.e. less than about 100 mGy; see
Table 1), for which health effects might be scientifically plausible but are
not observable in either individuals or an exposed population.

FIG. 1. Relationship between radiation dose and risk of health effects. (Adapted withpermission from figure A–VI of annex A of UNSCEAR 2012 [1].) 			

9

2.2. INFERENCE OF HEALTH RISKS FROM RADIATIONEXPOSURES
2.2.1. Frequentist risk and subjective risk
The mathematical quantification of risk (or probability) was originally basedon retrospective analysis of the frequencies of past occurrences. The concept ofrisk later evolved to also include subjective risks estimated on the basis of expert
judgement. The distinction between frequentist risk and subjective risk, and thefact that risk estimates in radiation protection are generally derived values basedon expert judgement, are not always made explicit, and an expression such as‘estimated increased risk of cancer of 5% per sievert’ (see Section 2.2.3) could
refer either to a frequentist risk or a subjective risk.
In the context of radiation induced health effects, a frequentist risk can bederived from the results of epidemiological studies. This is generally the case onlyin the moderate and high dose ranges (see Section 2.1.3). Such epidemiologicalstudies have also usually involved moderate to high dose rates (e.g. the Life Span
Study of the survivors of the atomic bombings in Hiroshima and Nagasaki [1]).
Subjective risks in the context of radiation induced health effects are
generally derived from a consensus opinion of experts. Such expert judgement
has mainly involved extrapolation of the results of epidemiological studies of
populations exposed to moderate and high doses, and moderate and high dose
rates, to derive subjective risk estimates for situations in which the inherent
uncertainties make obtaining frequentist risk estimates impossible (seeSection 2.1.2.3). Such extrapolation involves the use of appropriate modifying
factors and is also based on knowledge of the biological mechanisms that underly
such effects. There are various situations in which expert judgement is necessary
to extrapolate epidemiological data, including: “(i) extrapolation of risks overlifetime, (ii) transference to another population; (iii) transference from one typeof radiation to another; (iv) inferring risks from low-dose-rate exposure and (v)inferring risks from low and very low doses” [1].
2.2.2. Inferring radiation risks for purposes of estimating health effects
For exposure to high doses, received in a short period of time, there isnormally sufficient evidence “to be able to predict relatively accurately whether
or not there will be a deterministic effect in an exposed individual and, if so, thelikely severity of that health effect” [1] (see Sections 2.1.1 and 2.1.3).
For exposure to moderate doses or to high doses, there is epidemiologicalevidence “to be able to predict with some confidence an increased risk ofstochastic effects in an exposed population similar to that for which evidence
10exists” [1] (see Sections 2.1.2 and 2.1.3). UNSCEAR’s latest major evaluationsof epidemiological studies of radiation induced cancer were issued in annex A of
UNSCEAR 2006 [9] and in UNSCEAR 2010 [10]. These evaluations provided
a statistically significant estimate of the excess lifetime risk of mortality
for doses in the moderate to high dose ranges. Therefore, the risk of a healtheffect occurring following a dose in the moderate or high dose range could beconsidered a frequentist risk.
For exposures in the ranges of very low and low doses, annex A of
UNSCEAR 2012 [1] states that “there have been no studies that unequivocallyindicate statistically significant increases…in the frequency of occurrence ofcancer in epidemiological studies of the general population”. Therefore, only
subjective risks can be inferred for very low and low doses, and the values
derived will depend on the models and assumptions used to project and predictthe possible consequences of these doses for individuals. The cumulative
uncertainties and margins of error in the values derived from the use of models
may be significant.
Annex A of UNSCEAR 2012 [1] notes that there are several plausibledose‒response relationships for the very low and low dose ranges, although it“considers that risks are unlikely to change dramatically just below the doselevels at which a statistically significant increased frequency of occurrence has
been established”. In particular, the risks in the upper part of the low dose range
in Fig. 1 (i.e. where no population level data are available) are unlikely to behigher than the risks in the lower part of the moderate dose range in Fig. 1 (where
population level data are available).
Figure 2 shows some possible dose‒response relationships for the risk ofcancer from exposures at very low, low and moderate doses, all of which areplausible in terms of known mechanisms for cancer induction. The values forrisks obtained from any of these relationships are subjective risks — that is, they
are based on expert judgement and not on actual epidemiological data.
The plausible dose‒response relationships illustrated in Fig. 2 are as follows:
(a)

(b)

(c)

The risk of radiation induced cancer from exposure in the very low and low
dose range is substantially greater than expected from a linear no threshold(LNT) relationship (a supralinear relationship — curve a in Fig. 2).
The risk of radiation induced cancer from exposure in the moderate dose
range is extrapolated linearly down to zero additional dose (line b in Fig. 2).
A linear relationship is commonly used in modelling the risk of cancers otherthan leukaemia [11] and is also the model used for purposes of radiation
protection (see Section 2.2.3).
The risk of radiation induced cancer is lower than that predicted by thelinear dose–response relationship at very low doses and follows a quadratic
11

(d)

relationship (curve c in Fig. 2). Such a linear–quadratic relationship isgenerally preferred for estimating the risk of leukaemia [11].
The risk of radiation induced cancer from exposure in the very low and low
dose ranges is substantially lower than expected from a linear dose–response
relationship and is a threshold relationship or a hormetic relationship (line dand curve e in Fig. 2, respectively).

The relatively large uncertainties in determining whether stochastic
effects occur at low and very low doses (see Section 2.1.2.3) are such that allof these dose‒response relationships are scientifically plausible. Annex A of
UNSCEAR 2012 [1] states that the relationships in Fig. 2 “cannot be convincingly
verified or falsified at the moment”.

FIG. 2. Schematic presentation of plausible dose‒response relationships for the risk ofradiation induced cancer in the ranges of very low, low and moderate doses (see text for
definitions of curves a–e). The data points and confidence intervals marked on the graphrepresent observations of increased frequency of occurrence of a specific cancer type in
populations exposed to moderate doses. (Reproduced with permission from figure 1 of annex A
of UNSCEAR 2012 [1].)122.2.3. Inferring radiation risks for purposes of radiation protection
The inference of radiation risks for the purposes of radiation protectionneeds to consider exposure to high doses and high dose rates, exposure to low
doses and low dose rates, as well as acute exposures and chronic exposures. It
is also necessary to provide a system of protection that is workable in practice.
On the basis of these considerations, the model used for inferring risks for the
purposes of radiation protection is based on the LNT hypothesis. This is the
hypothesis that the risk of stochastic effects is assumed to increase in direct
proportion to the radiation dose (i.e. as per line b in Fig. 2). The LNT model
is designed to be applied for all levels of dose below the relevant thresholdvalues at which deterministic effects occur; that is, the LNT hypothesis makes
no distinction between moderate doses that lead to attributable stochastic effects(at a population level) and low and very low doses for which health effects due
to radiation exposure cannot be attributed. The LNT model also does not take
into account the dose rate or the rate of change of dose rate. Within the LNTmodel, any additional dose above background levels implies a non-zero risk ofstochastic effects.
The ICRP first used the LNT model in its recommendations published in1966 [12]. In Ref. [2], the ICRP continues to apply and promote the LNT modelfor the purposes of radiation protection and states:“The central assumption of a linear dose–response relationship for the
induction of cancer and heritable effects, according to which an incrementin dose induces a proportional increment in risk even at low doses, continues
to provide the basis for the summation of doses from external sources ofradiation and from intakes of radionuclides.”In Ref. [2], the ICRP also reviews the latest biological and epidemiologicalstudies on the health effects of ionizing radiation and states:“The distribution of risks to different organs/tissues is judged to havechanged somewhat since Publication 60, particularly in respect of the risksof breast cancer and heritable disease. However, assuming a linear response13

at low doses, the combined detriment due to excess cancer and heritableeffects remains unchanged at around 5% per Sv.”5
The LNT hypothesis is not based on objective observation of health effects;
that is, it does not represent a frequentist risk estimate at low and very low doses.
Instead, it represents a subjective risk estimate, based on extrapolation from thehigh and moderate dose ranges and on expert judgement. Although the LNT
hypothesis is consistent with known mechanisms for induction of cancer (seepara. A82 of annex A of UNSCEAR 2012 [1]), it is only one of several possiblemodels for what could be assumed to happen at low and very low doses (seeFig. 2). Nevertheless, it is still considered by the ICRP to be scientifically thebest model for the purposes of radiation protection [2].
The purpose of adopting the LNT hypothesis is to facilitate the practicalapplication of the system of radiation protection. The LNT hypothesis provides
the basis for the aggregation and summation of equivalent and effective doses
from external radiation and from intakes of radionuclides while maintaining asimple approach to calculations.
In addition, the LNT hypothesis is considered an ethical approach toradiation protection. With regard to this, Ref. [2] states:“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 verylow-dose exposure, it is considered to be a prudent judgement for public
policy aimed at avoiding unnecessary risk from exposure.”
Therefore, the LNT hypothesis may be considered to be commensuratewith the ‘precautionary principle’6 [14] and is a prudent basis for prevention andprotection [15].
Annex A of UNSCEAR 2012 [1] also states that the LNT and the associatedradiation risk coefficients are “coherent with radiobiological knowledge, adhere
to epidemiological information, and incorporate ethical judgements on therelative harm associated with different health effects”.

5

The ICRP defines detriment as “The total harm to health experienced by an exposedgroup and their descendants as a result of the group’s exposure to a radiation source. Detrimentis a multi-dimensional concept. Its principal components are stochastic quantities: probabilityof attributable fatal cancer, weighted probability of attributable non-fatal cancer, weighted
probability of severe heritable effects, and potential years of life lost if the harm occurs” [13].
6
See http://www.precautionaryprinciple.eu/

14

In conclusion, it is considered that the use of LNT for the inference of risk
at low and very low doses remains the most reasonable and practical approach toradiation protection.

2.3. ESTIMATION OF HEALTH EFFECTS FOR COMPARATIVEPURPOSES
Possible health effects that might result from radiation exposure, even atvery low doses, sometimes need to be estimated for comparative purposes. For
example, authorities with responsibilities for public health have to appropriately
and effectively allocate resources for radiation protection. This might involve
making estimates of theoretical numbers of postulated stochastic effects forcomparative purposes.
The concept of collective dose [16, 17] was introduced as a tool for use
in optimization, namely, for comparing protection and safety options (seeSection 3.4.2). The collective dose is calculated as the sum of all individual doses
over the time period of exposure being considered. The concept of collective doseis consistent with the use of the LNT model, which enables the summation ofdoses. For example, the collective dose due to occupational exposure of a groupof workers is sometimes used in the optimization of protection and safety whenassessing various options to carry out a maintenance task in a nuclear power
plant [18]. Collective dose is also used for comparing alternative options for
managing discharges from facilities [19]. The use of collective dose is describedin more detail in Ref. [20].
Care needs to be taken when multiplying low doses with a large numberof exposed persons to derive a collective dose. Such a calculation conceals
large uncertainties: for example, the increased uncertainties in modelling bothindividual doses and the size of the exposed population (especially far into the
future) mean that the concept of collective dose cannot be used to reliably infer
the risks that might be associated with the post-closure period of a waste disposal
facility [21].
The assumptions that underpin calculations of collective dose, as well as
the associated uncertainties and limitations on its applicability, have to be madeexplicit and taken into account. Annex A of UNSCEAR 2012 [1] states:“[P]ublic health bodies need to allocate resources appropriately, and…
this may involve making projections of numbers of health effects…forcomparative purposes. This method, though based upon reasonable but
untestable assumptions, could be useful for such purposes provided that itwere applied consistently, the uncertainties in the assessments were taken
15

fully into account, and it were not inferred that the projected health effects
were other than notional.”
The estimation of cancer deaths on the basis of collective effective doses
involving trivial exposures to large populations is not reasonable, and the ICRP,UNSCEAR and the IAEA have all strongly recommended that such use ofcollective dose is scientifically not justified and should be avoided [1, 2, 19].
Specifically, UNSCEAR 2012 [1] states:“[T]he Scientific Committee does not recommend multiplying very low
doses by large numbers of individuals to estimate numbers of radiationinduced health effects within a population exposed to incremental doses atlevels equivalent to or lower than normal natural background levels.”

3. BASIS OF THE SAFETY STANDARDS
3.1. PURPOSE OF THE SAFETY STANDARDSArticle III.A.6 of the IAEA Statute [22] states:“[The IAEA is authorized to] establish or adopt, in consultation and, whereappropriate, in collaboration with the competent organs of the United
Nations and with the specialized agencies concerned, standards of safety forprotection of health and minimization of danger to life and property…andto provide for the application of these standards.”
The safety standards provide principles, requirements and recommendations
that are intended to be used to protect people and the environment from harmful
effects of ionizing radiation. The safety standards are regulatory in nature, and assuch, they need to be practical and provide requirements and recommendations
for a broad range of facilities and activities. As well as including measures forprotection — namely, for controlling exposures to both high doses of radiation(e.g. exposures following an accident) and very low doses at levels typicalof the global average background levels of radiation (e.g. exposures from thenormal operation of a facility or normal use of a radioactive source) — thesafety standards also include measures for safety, that is, for the prevention ofincidents or accidents.

16

The safety standards are not intended to be used for attributing healtheffects to radiation exposure, either individually or collectively, or retrospectively
or prospectively. Moreover, the safety standards are not intended to be cited incourt (e.g. in the context of occupational compensation claims).

3.2. DEVELOPMENT AND USE OF THE SAFETY STANDARDSThe safety standards reflect an international consensus on what constitutes
a high level of safety for protecting people and the environment from harmful
effects of ionizing radiation. They are based on the practical experience of Member
States and are produced through a process of international consensus building,through consultation with Member States by means of a system of standing
bodies of senior representatives of Member States, selected intergovernmentalorganizations and international non-governmental organizations. Many safety
standards are sponsored jointly by several agencies of the United Nations systemand other intergovernmental organizations. As such, the IAEA safety standards
are intergovernmental, international standards for safety. The regulation of safety
is a national responsibility, and the safety standards are not legally binding on
States. However, they are widely applied, and many States decide to adopt
these standards for use in national regulations. The standards are also appliedby designers and manufacturers of nuclear and radiation technologies and bylicensees around the world to enhance nuclear and radiation safety in power
generation, medicine, industry, agriculture, research and education. The safety
standards are binding on the IAEA in relation to its own operations and also on
States in relation to IAEA assisted operations.

3.3. SCOPE OF THE SAFETY STANDARDSThe safety standards cover all situations that give rise to radiation risks andare applicable for the entire lifetime of all facilities and activities — both existingand new — utilized for peaceful purposes and protective actions to reduce
unregulated radiation risks.
The safety standards are concerned with both risks that exist in normal
circumstances and risks that could arise as a consequence of incidents, including
loss of control over a nuclear reactor core, nuclear chain reaction, radioactive
source or any other source of radiation. The risks addressed in the safety standards
are intended to include both risks to persons and risks to the environment.

17

The IAEA Safety Standards Series is based on a hierarchy of three typesof publication: Safety Fundamentals, Safety Requirements and Safety Guides, as
explained below:— The Safety Fundamentals present the fundamental safety objective andprinciples for protection and safety [23]. They are formulated in a way thatis understandable to non-specialist readers, and they convey the basis andrationale for the safety standards to those at senior levels in government andregulatory bodies (see Section 3.4).
— The Safety Requirements establish the requirements that shall be met toensure the protection of people and the environment, both now and in the
future. The requirements are governed by the objective and principles of
the Safety Fundamentals. The requirements are formulated in a mannerthat facilitates their use in establishing a national regulatory framework.
The requirements represent the international benchmark for protection andsafety, and thus they have major implications for regulatory policy and for
decision making.
— The Safety Guides provide recommendations and guidance on how tocomply with the safety requirements. They are based on internationallyrecognized good practices to help users to achieve high levels of protection
and safety.
The safety standards cover radiation protection and nuclear safety(also termed ‘protection and safety’), namely the protection of people and theenvironment against risks and the safety of facilities and activities that give rise torisks. ‘Protection and safety’ includes the safety of nuclear installations, radiation
safety, the safety of radioactive waste management and safety in the transportof radioactive material, and emergency preparedness and response7. The safety
standards also address the interface between nuclear security and safety.8
For the purpose of establishing practical requirements for protection andsafety, the safety standards distinguish between three different types of exposure
situation: planned exposure situations, emergency exposure situations andexisting exposure situations. In addition, for the protection of persons, three basic
7

Safety standards for preparedness and response for a nuclear or radiologicalemergency apply irrespective of the cause of the emergency, including a natural event, humanerror, mechanical or other failure, or a nuclear security event.
8
Measures that are specific to nuclear security (e.g. measures of physical protection)
are not established in the safety standards, although both safety and nuclear security have thecommon aim of protecting people and the environment. The IAEA issues guidance on nuclear
security in the IAEA Nuclear Security Series.

18

categories of exposure have been considered: occupational exposure, public
exposure and medical exposure.
There are some situations involving radiation exposure that are considered
not to be amenable to control9 (see para. I.42 of IAEA Safety Standards
Series No. GSR Part 3, Radiation Protection and Safety of Radiation Sources:
International Basic Safety Standards [24]). These are excluded from the scope ofthe safety standards.
The safety standards are intended to be applied for situations whereradiation exposure could occur. Such situations involve exposures that are
anticipated (e.g. the exposures expected to be incurred in normal operation) and‘potential exposures’ (i.e. that are not expected to be incurred with certainty,
but that may potentially result from an incident involving a source of radiationor owing to an event or sequence of events of a probabilistic nature, including
equipment failures and operating errors [5]).
In accordance with the risk related concepts presented in Section 2 of this
Safety Report, it can be seen that the safety standards apply to situations in which
exposures could lead to health effects that can be attributed at an individual level(deterministic effects), situations in which exposures could lead to health effects
for which an increase in incidence of the effect in a population can be attributed
to exposure (stochastic effects) and situations in which risks can only be inferred.
Notwithstanding this, the safety standards are generally not formulated in termsof health effects, either individually attributable or attributable at a populationlevel. Instead, the requirements and recommendations in the safety standards are
more generally aimed at the restriction of risks, from facilities and activities andfrom unregulated or existing situations.

3.4. THE FUNDAMENTAL SAFETY PRINCIPLES
Many of the fundamental concepts used throughout the IAEA safety
standards are set out in IAEA Safety Standards Series No. SF-1, Fundamental
Safety Principles [23]. SF-1 [23] is presented in language that is understandable
to the non-specialist reader, and the intention is to convey the basis and rationale
for the IAEA safety standards to those at senior levels in government andregulatory bodies.
SF-1 [23] states that: “The most harmful consequences arising fromfacilities and activities have come from the loss of control over a nuclear reactor
core, nuclear chain reaction, radioactive source or other source of radiation.” The
9

It is generally accepted that it is not feasible to control 40K in the body or cosmic
radiation at the surface of the Earth.

19safety standards require that measures be taken to make sure that the likelihoodof such a loss of control is extremely low. The intention is that high doses anddeterministic effects, as well as moderate doses and possible stochastic healtheffects, will be avoided.
SF-1 [23] also states that: “For the purposes of the IAEA safety standards,
it is assumed that there is no threshold level of radiation dose below which there
are no associated radiation risks.” Therefore, the safety standards make use of the
LNT hypothesis for the inference of risk at very low and low doses.
SF-1 [23] establishes the fundamental safety objective of protecting people
and the environment, as well as a coherent set of ten fundamental principles
that represent a common safety philosophy across all areas of application of thestandards. Although the fundamental safety principles are applicable in their
entirety, four of the fundamental safety principles are directly related to theprotection of people, and hence to the purpose of this Safety Report, as follows:
(a)

(b)

Principle 4 on justification of facilities and activities states that: “Facilities
and activities that give rise to radiation risks must yield an overall
benefit”.
Principle 5 on optimization of protection states that: “Protection must be
optimized to provide the highest level of safety that can reasonably beachieved”. Paragraph 3.23 of SF-1 [23] states:“The optimization of protection requires judgements to be made about therelative significance of various factors, including:— The number of people (workers and the public) who may be exposed
to radiation;— The likelihood of their incurring exposures;— The magnitude and distribution of radiation doses received;— Radiation risks arising from foreseeable events;— Economic, social and environmental factors.”

(c)

(d)

20

Principle 6 on limitation of risks to individuals states that: “Measuresfor controlling radiation risks must ensure that no individual bears
an unacceptable risk of harm”. Paragraph 3.25 of SF-1 [23] states that:“Consequently, doses and radiation risks must be controlled within specified
limits”.
Principle 10 on protective actions to reduce existing or unregulated radiation
risks states that: “Protective actions to reduce existing or unregulated
radiation risks must be justified and optimized”.

3.4.1. The concepts of attribution and inference and the principle ofjustification
Justification involves a balancing of benefits and harm to determine whether
an action is expected to yield a net benefit to the exposed individuals or to society.
Justification has to be applied, for example, in making decisions on whether tointroduce a new facility or activity in a State and on whether to take actions to
reduce radiation exposures in an emergency exposure situation or in an existing
exposure situation. Decisions on justification may fall within the authorityof a broad spectrum of stakeholders, from the highest levels of government to
day to day practitioners; therefore, the concept needs to be well understood byall. The main aim of justification is “to do more good than harm” [2].
Justification means that the detriments that might be caused by the
introduction of a new source of radiation or by the reduction of an existing or
emergency exposure would be outweighed by the benefits. In some cases, thepotential detriments and benefits are to the same person(s); in other cases,
the detriments and benefits are received by different (groups of) persons. The
comparison of the benefits and detriments often goes beyond the considerationof protection and safety and entails a consideration of economic, societal,
environmental and other factors. Medical exposures, whether for diagnosis or fortreatment, are a special case, in that the benefit is primarily to the patient. The
justification for such exposures is therefore considered first with regard to thespecific procedure to be used. The justification decision for individual patients
is a clinical decision made by medical practitioners. In all cases, justification
involves the prospective inference of risks as a key element in assessing
possible detriments.
Justification needs to be performed in all exposure situations, irrespectiveof whether or not radiation exposures are at a level for which health effects might
be attributable. This is of particular importance in the justification of protective
actions and the protection strategy in a nuclear or radiological emergency.
Protective actions are almost always justified in situations involving high andmoderate doses (e.g. when projected doses are above the generic criteria provided
in annex II of IAEA Safety Standards Series No. GSR Part 7, Preparedness
and Response for a Nuclear or Radiological Emergency [25]). However, inemergency exposure situations and in existing exposure situations involving low
and very low doses, particular care is needed to ensure that protective actions,which could have significant societal, economic or environmental impacts, domore good than harm.

21

3.4.2. The concepts of attribution and inference and the principle of
optimization of protection and safety
Optimization of protection and safety is the process for determining whatlevel of protection and safety would result in the magnitude of individual doses,
the number of individuals (workers and members of the public) subject toexposure and the likelihood of exposure being as low as reasonably achievable(ALARA), economic and social factors being taken into account [2, 5]. The goal
is to achieve the best protection under the circumstances and with the resources
available, which does not necessarily mean achieving the lowest dose.
Optimization of protection and safety is a prospective, iterative processthat examines the available options for protection [2]. Depending upon thecircumstances, the process can include the use of a variety of quantitative andqualitative techniques, for example the use of ‘collective dose’ (see Section 2.3).
Optimization is conducted within a set of boundary conditions on the rangeof available protection options. These boundary conditions are referred to as‘dose constraints’ or ‘risk constraints’ in the case of planned exposure situations
and as ‘reference levels’ in the case of emergency exposure situations or existing
exposure situations [2].
Dose constraints and reference levels are not dose limits. Exceeding a dose
constraint or a reference level does not necessarily represent non-compliancewith regulatory requirements; rather, these are regarded as values that are not to
be exceeded for planning purposes.
Table 2 summarizes the ranges of values for dose constraints and forreference levels applicable for each exposure situation, as established in
GSR Part 3 [24]. The values in Table 2 all lie in the very low and low dose ranges
shown in Table 1. This means that if protection and safety is optimized, the dose
received by workers and members of the public will not be in the ranges in which
health effects could be attributed at an individual or population level.
In certain situations, decisions might need to be taken regarding theapplication of limited resources in optimizing protection for different groups
of individuals, some of whom might be subject to higher doses than others.
This may be of particular importance in emergency exposure situations andin existing exposure situations. In optimizing protection and safety in planned
exposure situations and optimizing protection strategies and protective actions
in emergency exposure situations and in existing exposure situations, particularconsideration needs to be given to those groups of individuals that receive higher
doses, particularly if such doses could be in the moderate or even high dose
ranges, where health effects can be attributed to exposure at the population oreven the individual level.

22

TABLE 2. DOSE CONSTRAINTS AND REFERENCE LEVELS [26]Range in which the value
for a dose constraint
or reference level is set

Category of exposure and type of exposure situation

20–100 mSva,b,cReference level for public exposure in an emergency
exposure situation

1–20 mSv per year

Dose constraint for occupational exposure in a planned
exposure situation
Dose constraint for medical exposure of carers andcomforters in a planned exposure situation
Reference level for workers in an existing exposure
situation
Reference level for public exposure in specific existing
exposure situations (e.g. exposure due to radon in
dwellings, areas with residual radioactive material)

Not greater than 1 mSv
per year

Dose constraint for public exposure in planned exposure
situations
Reference level for public exposure in specific existing
exposure situations (e.g. exposure due to radionuclides incommodities such as food, drinking water or construction
materials)abcAcute dose or annual dose.
In exceptional situations, informed volunteer workers may receive doses above this range
to save lives, to prevent severe deterministic effects or to prevent the development ofcatastrophic conditions.
Situations in which the dose threshold for deterministic effects in relevant organs or tissues
could be exceeded always require action.

3.4.3. The concepts of attribution and inference and the principle oflimitation of risks to individuals
Paragraph 3.25 of SF-1 [23] states: “Justification and optimization ofprotection do not in themselves guarantee that no individual bears an unacceptablerisk of harm. Consequently, doses and radiation risks must be controlled within
specified limits.”
In addition, para. 3.26 of SF-1 [23] states:“Conversely, because dose limits and risk limits represent a legal upperbound of acceptability, they are insufficient in themselves to ensure the23

best achievable protection under the circumstances, and they therefore
have to be supplemented by the optimization of protection. Thus both the
optimization of protection and the limitation of doses and risks to individuals
are necessary to achieve the desired level of safety.”
The dose limits that have been adopted in the safety standards (i.e. in
GSR Part 3 [24]) were originally recommended by the ICRP [17]. The dose limit
for exposure of workers is an annual effective dose of 20 mSv, and for exposureof members of the public it is an annual effective dose of 1 mSv. Dose limits do
not apply for medical exposure of patients. The selection of the dose limit forworkers was based on expert judgement on the level of dose above which theconsequences for the worker would be widely regarded as unacceptable [17]. The
dose limit for the public, in contrast, was set at a similar order of magnitude tonatural background levels, based on uncertainties, the lack of measurement andthe lack of direct benefit from the radiation [17].
Dose limits apply only for planned exposure situations, namely from theplanned operation of a source or from a planned activity that results in exposure
from a source.10 Dose limits do not apply for emergency exposure situations orfor existing exposure situations, where reference levels are used as criteria. This
complexity could lead to misunderstandings (see Section 5).
The dose limits are in the very low and low dose bands shown in Table 1.
Thus, the dose limits are lower than the dose levels at which health effects could
be attributed at an individual or population level to radiation exposure; indeed,
the attributability of health effects is not a criterion for limitation of doses.

10

In some cases, dose limits for workers for planned exposure situations are applied toemergency exposure situations (see para. 4.21 of GSR Part 3 [24]) and to existing exposure
situations (see paras 5.26 and 5.29 of GSR Part 3 [24]).

24

4. PRACTICAL APPLICATION OF RISKRELATED CONCEPTS FOR DIFFERENTCATEGORIES OF EXPOSURE

4.1. PUBLIC EXPOSURE
4.1.1. Doses and health effects associated with public exposure
Members of the public are continuously exposed to radiation, resulting
in very low or low doses. UNSCEAR periodically summarizes the radiation
exposure of the public due to natural and artificial sources of radiation[7, 9, 27–31]. The global average annual effective dose received by the public isapproximately 2.4 mSv [7]. Table 3 and Fig. 3 summarize the doses associatedwith public exposure from different natural and artificial sources.

TABLE 3. GLOBAL ANNUAL DOSES [7, 28]
Source or mode

Average annual effective dose (typical range) (mSv)

Inhalation (radon gas)

1.26 (0.2–10)

External terrestrial

0.48 (0.3–1)

Ingestion

0.29 (0.2–1)

Cosmic radiation

0.39 (0.3–1)

Nuclear fuel cycle

0.0002(<0.02 mSv for critical groups at 1 km fromsome nuclear reactor sites)

Atmospheric testing of nuclear
weapons

0.005

Chernobyl accident

0.002 — globally dispersed radionuclides

Fukushima Daiichi accident<0.01 — first year, countries outside Japan

Total from all sources

2.44 (1–13)

25

FIG. 3. Estimated contributions to public exposure from different sources, in millisievert. (Datataken from table 1 of UNSCEAR 2008 [7].)The largest component of the global average annual effective dose arises
from the indoor inhalation of naturally occurring radon gas and its short lived
decay products (on average 1.26 mSv in a year). Other natural sources ofradiation include cosmic radiation (high energy protons, X rays and gamma rays
produced in space and arriving at the surface of the Earth), terrestrial sources(rocks and soil) and other materials containing radionuclides of natural origin,such as food. The average annual exposure to natural radiation sources has notchanged significantly over time, although individual exposures, particularly
to radon, can differ significantly, both spatially and temporally. Annex B of
UNSCEAR 2008 [7] provides information on the global range of exposures toeach of these components, which tends to follow a log-normal distribution.
The public is also exposed to artificial sources of radiation from current
and past facilities and activities. Examples include nuclear power plants; research
reactors; radioactive waste disposal facilities; releases into the air and into thegroundwater from installations; sources used in medical and veterinary facilities(X rays and radionuclides used in nuclear medicine) and in education and researchfacilities; sources used for industrial purposes, such as industrial radiography andnuclear gauges; consumer products; and non-medical human imaging. Exposure
also results from atmospheric nuclear weapons testing. These contributions are
all included under ‘other’ in Fig. 3.

26

From Table 3 and Fig. 3, it can be seen that the exposure of the large
majority of members of the public due to natural and artificial sources of radiation
falls in the range of very low levels of dose.
UNSCEAR has published several reviews of the health effects associatedwith public exposure, including a review of epidemiological studies of cancer
risk due to low dose rate radiation exposure from environmental sources (seeannex B of UNSCEAR 2017 [29]). This includes reviews of the Techa River
cohort (TRC) studies in the Russian Federation and studies of environmental
exposure to high natural background radiation (HNBR) in Karunagappally, India,
and Yangjiang, China. UNSCEAR 2017 [29] concludes:“The TRC study has demonstrated dose-dependent increases in occurrenceof solid cancer and leukaemia, though associations with radiation exposure
were also found for cancer types that have not been commonly increased
following radiation exposure in other studies. No discernible increases werereported for solid cancer or leukaemia in the Karunagappally or Yangjiang
HNBR studies, though the low precision of the risk estimates does not ruleout either absence of an excess risk of cancer or substantially higher risks
per dose unit than those reported in high-dose and dose-rate studies.”
UNSCEAR’s reviews of epidemiological studies of people living near
nuclear installations have not shown an increase in attributable effects [9]. For
disposal of low and intermediate level solid waste, UNSCEAR 2008 [7] estimatesthat the worldwide average annual individual effective dose is minimal, at about
1 nSv per year for each facility. UNSCEAR 2006 [9] also reviews studies ofgroups of persons exposed to atmospheric nuclear weapons testing and does not
identify an increased incidence of leukaemia among such groups.
There are cases where radiation induced health effects in members of the
public are attributable at the population level; for example, reviews of the healtheffects from exposure to radon are published in annex E of UNSCEAR 2006 [9]and annex B of UNSCEAR 2019 [30]. These studies indicated a significant
association (at a population level) between the risk of lung cancer and exposure
to radon in homes. The World Health Organization concludes [32]:“Recent studies on indoor radon and lung cancer in Europe, North Americaand Asia provide strong evidence that radon causes a substantial number oflung cancers in the general population. Current estimates of the proportionof lung cancers attributable to radon range from 3 to 14%, dependingon the average radon concentration in the country concerned and thecalculation methods.”

27

UNSCEAR 2012 [1] also considers a case study on lung cancer fromexposure to radon in 117 homes in Winnipeg, Canada, and concludes:“[I]ncreased frequency of lung cancer is unlikely to be observable among
the people living in the Winnipeg homes sampled because of the small
numbers involved; however, if the size of the population exposed at thesame levels were large enough, then the predicted increased frequency ispotentially observable.”
UNSCEAR 2012 [1] concludes that: “An observed lung cancer in an
individual cannot be unequivocally attributed to exposure to radon”.
Some persons have also been exposed as a result of accidents at nuclear
power plants or with orphan sources [7, 28]. These exposures range from highdoses for a few individuals to moderate doses for groups of individuals and low
and very low doses for some population groups. Annex D of UNSCEAR 2008 [7]summarizes the doses and health effects for members of the public from the
Chernobyl accident. More than 300 000 individuals received effective doses inexcess of 10 mSv. The average thyroid dose to evacuees was about 500 mGy;that is, in the moderate range of doses as shown in Table 1, whereas the average
thyroid dose to 6 million people living in contaminated areas was about 100 mGy.
UNSCEAR 2008 [7] concludes:“The contamination of milk with 131I, for which prompt countermeasures
were lacking, resulted in large doses to the thyroids of members of thegeneral public; this led to a substantial fraction of the more than 6000 thyroid
cancers observed to date among people who were children or adolescents atthe time of the accident (by 2005, 15 cases had proved fatal). To date, there
has been no persuasive evidence of any other health effect in the general
population that can be attributed to radiation exposure.”
UNSCEAR 2012 [1] also includes a case study on thyroid cancer after the
Chernobyl accident and concludes that there is “strong support for attributing,at least in part, the observed increased frequency to radiation exposure” in thispopulation. UNSCEAR also states:“In the absence of a biomarker to distinguish a radiation-related thyroid
cancer from one that occurs due to other causes, an observed thyroid cancer
in an individual among the population of those exposed as children oradolescents at the time of the accident cannot be unequivocally attributed toradiation exposure from the accident” [1].

28

UNSCEAR summarizes the doses and health effects from the Fukushima
Daiichi nuclear power plant accident in annex A of UNSCEAR 2013 [28] andannex B of UNSCEAR 2020/2021 [31]. In the first year following the accident,
for adult evacuees the average thyroid dose ranged from 16 to 35 mGy; for adults
living in Fukushima prefecture, the average thyroid dose ranged from 7.8 to
17 mGy; and for adults living in the rest of Japan the average thyroid dose ranged
from 0.5 to 0.9 mGy [28]. UNSCEAR 2013 [28] concludes:“No radiation-related deaths or acute diseases have been observed among
the workers and general public exposed to radiation from the accident. The
doses to the general public, both those incurred during the first year andestimated for their lifetimes, are generally low or very low. No discernible
increased incidence of radiation-related health effects are expected among
exposed members of the public or their descendants.”
UNSCEAR 2020/2021 [31] states:“[T]he rates of diagnosed, suspected or confirmed thyroid cancer among
the approximately 300 000 individuals who were children or adolescents(ages 0–18) at the time of the [Fukushima Daiichi] accident were foundto be much higher than those documented in the cancer registries of otherprefectures of Japan.
…….
“[T]he increased incidence rates may be due to over-diagnosis (i.e., detectionof thyroid cancer that would not have been detected without the screening
and would not have caused symptoms or death during a person’s lifespan).”Members of the public have also been exposed to radiation from exposure
to orphan sources. There have been situations in which members of the public
suffered deterministic effects, which are attributable at an individual level. For
example, following an accident with an abandoned teletherapy device in Goiânia,Brazil, containing a 137Cs source, 21 people received doses in excess of 1 Gy [7].
Annex C of UNSCEAR 2008 [7] summarizes accidents involving orphan sourcesthat led to the exposure of members of the public to high doses, with information
on 34 accidents involving orphan sources that resulted in 42 early deaths anddisfiguring injuries to both children and adults. The details of many of these
accidents have been published by the IAEA, for example in Refs [33–37].

29

4.1.2. Control of public exposure in the safety standards
Requirements for establishing governmental, legal and regulatory systems
for the control of radiation sources are established in IAEA Safety Standards
Series No. GSR Part 1 (Rev. 1), Governmental, Legal and Regulatory Framework
for Safety [38]. Requirements for control of public exposure are established in
GSR Part 3 [24] and GSR Part 7 [25]. Detailed guidance for control of public
exposure is provided in many IAEA Safety Guides: for planned exposure
situations [19, 26, 39, 40]; for emergency exposure situations [41–43]; for existing
exposure situations [26, 44, 45]; for regaining control over orphan sources [46];and for control of orphan sources in the metal recycling industry [47].
Exposure due to some sources of radiation is excluded from the scope ofthe safety standards because the sources are not amenable to control; examples
include exposure due to cosmic rays at the surface of the Earth and exposure due
to globally dispersed artificial radionuclides, such as from atmospheric testing of
nuclear weapons. Excluded exposures in fact make up a certain fraction of those
exposures incurred by the public, shown in Table 3 and Fig. 3.
4.1.2.1.

Control of public exposure at low and very low doses

For planned exposure situations, the control of public exposures is generally
focused on low and very low doses and is achieved through optimization ofprotection and safety and by applying dose constraints and the public dose limit
to representative persons.
GSR Part 3 [24] establishes various criteria for the control of public
exposures, such as the dose limit for public exposure (i.e. an effective dose of
1 mSv in a year), dose constraints (i.e. 0.1 to less than 1 mSv in a year) or risk
constraints to be used in optimization of protection and safety, and exemption
and clearance criteria (of the order of 10 µSv in a year). All these values arevery low doses.
The government or the regulatory body is required to establish or approvedose constraints (see para. 3.222 of GSR Part 3 [24]) and is expected to take into
account the characteristics of the facility or activity, the scenarios for exposureand the views of interested parties. The government or regulatory body is also
required to ensure that the dose limit is not exceeded in case members of the
public are exposed to several sources of radiation from different authorizedpractices; see footnote 25 of GSR Part 3 [24]. In practice, through optimizationof protection and safety, the actual doses that members of the public receive as aresult of the operation of facilities and the conduct of activities are expected to besignificantly lower than the annual effective dose limit of 1 mSv.

30

Dose limits are not applied in emergency exposure situations and existing
exposure situations. Rather, the safety standards require that the protection of
all individuals be optimized; this applies to persons incurring doses above thereference level, as well as doses below the reference level, with the priority given
to those persons who receive doses above the reference level. Indeed, para. 5.8 of
GSR Part 3 [24] states that: “All reasonable steps shall be taken to prevent doses
from remaining above the reference levels”.
As shown in Table 2, for emergency exposure situations, the reference levelspecified in GSR Part 3 [24] is in the range 20–100 mSv in a year, whereas forexisting exposure situations, the reference level is in the range of 1–20 mSv in a
year; that is, values that are in the low dose range in Fig. 1. The actual value ofthe reference level within these ranges is required to be established or approvedby the government, regulatory body or another relevant authority (see paras 4.8
and 5.8 of GSR Part 3 [24]), and it will depend on the prevailing circumstances
for the exposure situation under consideration.
4.1.2.2.

Control of public exposure at moderate and high levels of dose

For emergency exposure situations, para. 4.7 of GSR Part 3 [24] states:“The government shall ensure that protection strategies are developed,
justified and optimized at the planning stage, by using scenarios based on
the hazard assessment, for avoiding deterministic effects and reducing the
likelihood of stochastic effects due to public exposure.”
In emergency exposure situations, high doses and moderate doses to the
public might occur. Generic criteria for use in emergency preparedness andresponse are specified in appendix II of GSR Part 7 [25]. On the basis of a hazard
assessment, a protection strategy and associated emergency arrangements are
required to be established at the preparedness phase [25]. The higher the expected
doses, the more comprehensive the strategy and associated arrangements need to
be to ensure effective response, with priority given to taking protective actions
aimed at avoiding or minimizing severe deterministic effects and reducing therisk of stochastic effects. Table II.1 of GSR Part 7 [25] sets out generic criteria
for doses received within a short period of time and for which protective actions
and other response actions are expected to be taken under any circumstances inan emergency to avoid or minimize severe deterministic effects. Table II.2 of
GSR Part 7 [25] sets out generic criteria for protective actions and other response
actions to reduce the risk of stochastic effects. Such actions are expected to beundertaken only if this can be done safely.

31

In existing exposure situations, it is possible that moderate doses to the
public might occur, for example, in an area that has been contaminated by a past
activity or event. To prevent such exposures, the safety standards recommendthat the planning and implementation of remediation be such that greater efforts
are directed to areas where the highest contributions to doses and risk might
be expected [45]. This might be accomplished through the removal of a source
and/or the reduction of its magnitude, such as through engineered barriers,
restrictions or other mechanisms that disrupt exposure pathways [45].

4.2. OCCUPATIONAL EXPOSURE
4.2.1. Doses and health effects associated with occupational exposure
UNSCEAR [7], the IAEA [48] and the OECD Nuclear Energy Agency [49]have conducted studies on occupational exposure. Typical occupations in which
workers are monitored individually to assess their occupational exposure arethose associated with the nuclear fuel cycle and research, as well as industrial andmedical facilities involving radiation sources. However, there are other workers,
especially those exposed to natural sources of ionizing radiation, who are notindividually monitored.
TABLE 4. GLOBAL AVERAGE ANNUAL OCCUPATIONAL EXPOSURE
FOR DIFFERENT PRACTICES [7]Practice

Average annual effective dose (mSv)

Nuclear fuel cycle

1.0

Uranium mining

2.1–2.3

Uranium milling

1.1

Fuel fabrication

1.6

Reactor operations

1.0 (2% >10 mSv)

Fuel reprocessing

0.9

Decommissioning

1.9

32

TABLE 4. GLOBAL AVERAGE ANNUAL OCCUPATIONAL EXPOSURE
FOR DIFFERENT PRACTICES [7] (cont.)
Practice
Aircrew

Average annual effective dose (mSv)
2.5

Industrial radiography

1.5 (1% > 15 mSv)

Industrial irradiators

0.63 (1% >15 mSv)

Luminizing
Radioisotope production

0.72
2 (2% >15 mSv)

Well logging

0.96

Accelerator facilities

0.74

All other industrial uses

0.26

Veterinary medicine

0.15

Educational

0.08

Coal mining

2.4

Other mining

3.0

Medical0.5

Diagnostic radiology

1.2 (0.3–3.1)

Interventional cardiology

3.1 (0.4–29.5)

Dental0.06

Nuclear medicine

0.7Radiotherapy

0.5

Table 4 shows the global average annual doses for occupational exposurefor different practices. Apart from interventional cardiology, annual effective
occupational exposures lie within the very low dose range.
33

4.2.1.1.

Nuclear fuel cycle workers

Nuclear fuel cycle workers include those involved in the mining andprocessing of uranium and thorium ores, enrichment of uranium, manufacturingof nuclear fuel, operation of nuclear reactors (including research and test reactors)
and reprocessing of spent nuclear fuel, as well as those involved in waste
management and decommissioning activities relating to operations associatedwith the production of nuclear energy. Average exposures are 1–2 mSv per year,with about 2% of workers receiving doses above 10 mSv [7]; consequently,
occupational exposures tend to lie within the range of very low and low doses.
Annex A of UNSCEAR 2006 [9] contains a review of a study of 21 500
workers at the Mayak nuclear complex in the former Soviet Union between 1948
and 1972. The average cumulative external dose among those monitored was
0.8 Gy. Some workers had the potential for significant internal exposure frominhaled plutonium. UNSCEAR 2006 [9] notes that the estimates of radiationinduced risks from this study are lower than those derived from other studies, butthat any comparisons have to be regarded as tentative in view of the dosimetric
uncertainties.
An international worker study is also described in annex A of
UNSCEAR 2006 [9] and is based on over 400 000 workers from 15 countries
working in 154 nuclear facilities, who were individually monitored for external
exposure. UNSCEAR 2006 [9] concludes that “there are substantial uncertainties
in the risk estimates derived from the 15-country study. Consequently, not too
much should be made of the apparent discrepancies with risks observed inother studies”.
Annex C of UNSCEAR 2008 [7] summarizes accidents at nuclear facilities
that led to high doses to workers as follows:“Of the 35 reported accidents, 24 were in facilities related to nuclear weapons
research, development and production, and to the reprocessing of nuclear
fuel for weapons programmes. Other accidents occurred in power reactor
research, development and operation, and in the reprocessing of nuclear
fuel. Excluding the 1986 accident at Chernobyl, 32 deaths are known tohave occurred as a result of radiation exposure in accidents at nuclear
facilities, and 61 workers suffered radiation injuries requiring medical care.
The incidence of accidents in these facilities has fallen; most of the deaths
and injuries occurred in the early years of research and development in thecontext of nuclear weapons programmes. Only one criticality accident,with the death of two workers, has occurred in the past 20 years” (in the
period 1988 to 2008).

34

Annex D of UNSCEAR 2008 [7] summarizes the radiation induced healtheffects from the Chernobyl accident and concludes the following:“The observed health effects currently attributable to radiation exposure
are as follows:— 134 plant staff and emergency workers received high doses of radiationthat resulted in acute radiation syndrome (ARS), many of whom also
incurred skin injuries due to beta irradiation;— The high radiation doses proved fatal for 28 of these people;…….
— Skin injuries and radiation-induced cataracts are major impacts for the
ARS survivors;— Other than this group of emergency workers, several hundred thousandpeople were involved in recovery operations, but to date, apart fromindications of an increase in the incidence of leukaemia and cataracts
among those who received higher doses, there is no evidence of healtheffects that can be attributed to radiation exposure.”
Regarding emergency workers involved in the Fukushima Daiichi accident,
UNSCEAR 2020/2021 [31] concludes that “No deterministic health effects ordeaths have been observed among workers engaged in emergency work that
could be attributed to radiation exposure” and that UNSCEAR “expects nodiscernible increase in health effects among the overall group of emergency
workers that could be attributed to their radiation exposure”. Regarding the
174 workers who received effective doses above 100 mSv within the first year,
UNSCEAR 2020/2021 [31] states that “it is unlikely that an increased incidenceof cancer due to irradiation would be discernible, because the normal variability
in baseline rates of cancer incidence is much larger than the inferred radiationassociated cancer rates”.
4.2.1.2.

Miners

The worldwide average annual exposure of the approximately 13 million
workers exposed to natural sources of radiation is estimated to be 2.9 mSv [7].
The level of exposure in mines depends on several factors, including the typeof mine, the geology and the working conditions, particularly the ventilation.
For coal mines, the estimated average effective dose is 2.4 mSv; for non-coalmines, it is estimated to be 3 mSv [7]. Thus, the average annual radiation doses
35are in the very low dose range, especially for those underground mines withgood ventilation.
Annex E of UNSCEAR 2006 [9] contains a review of the health effects
from exposure to radon. UNSCEAR reviewed 11 miner cohorts and evaluated thenumber of excess lung cancers, the quality of the exposure data and confounding
factors such as smoking and exposure to arsenic. UNSCEAR combined theestimated excess relative risks for miners and obtained values close to those frompooled studies of exposure to radon in homes.
4.2.1.3.

Medical workers

Radiological medical practitioners, medical radiation technologists, medical
physicists and nurses constitute the largest single group of workers occupationally
exposed to human-made sources of radiation [7]. For conventional diagnostic
imaging techniques, the average annual effective dose is about 1.2 mSv (range
0.33‒3.14 mSv) for medical workers subject to individual monitoring [7]. Forinterventional procedures, the average annual effective dose is about 3.1 mSv(range of 0.4‒29.5 mSv) for individually monitored workers [7].
Annex A of UNSCEAR 2006 [9] also describes a study involving a cohortof 146 022 ‘radiologic technologists’ in the United States of America certified
between 1926 and 1982. UNSCEAR 2006 [9] notes: “As with most working
populations, the rates of death from all cancers were lower than expected in
the general population, for both sexes. No specific cancer type showed an
overall excess risk.” UNSCEAR 2006 [9] also notes that there were substantial
methodological concerns with the epidemiological data.
A study of Chinese radiologists and technologists is also described inannex A of UNSCEAR 2006 [9]: “The study group consisted of 27 011 medical
diagnostic workers, including both radiologists and technicians, employed
between 1950 and 1980 in 24 provinces of China. A control group consistedof 25 782 workers from other medical specialties who did not use X rayequipment in their work.” Retrospective dose assessment was performed.
An excess of total cancers and a significant excess of leukaemia was found.
UNSCEAR 2006 [9] concludes:“The reported statistical significance of the results in this study, however,should be treated cautiously, as it appears that calculations were performed
without taking into account the variance contributed by the control group.”36

4.2.1.4.

Workers in industrial facilities

There are many uses of radiation sources in industry, including industrial
radiography, industrial irradiators, radioisotope production, well logging, nuclear
gauges and accelerators. The average annual dose to workers in these industries
is less than 1 mSv, except for industrial radiography (average annual dose of
1.5 mSv) and radioisotope production (average annual dose of 2 mSv). There isalso a wide range of individual doses received in some industries. For example,
30% of industrial radiography workers receive annual doses over 1 mSv and
1% receive annual doses over 15 mSv; 55% of radioisotope production workers
receive annual doses over 1 mSv and 2% receive annual doses over 15 mSv; and
29% of industrial irradiator workers receive annual doses over 1 mSv and 1%
receive annual doses over 15 mSv [7].
Annex C of UNSCEAR 2008 [7] lists 80 accidents at industrial
facilities and states:“Nine deaths were reported in these accidents. They all occurred atindustrial irradiation facilities using high-activity sealed sources, primarily
because of improper entry into the hot cell, and a lack or failure of safetymechanisms. At least 84 other people were excessively overexposed inthese facilities. In other industries, 36 workers were injured during theuse of radiography sources, X-ray devices and accelerators, and during
manufacturing procedures.”
Details of several industrial accidents affecting workers have also been
published by the IAEA, for example in Refs [50–53].
4.2.2. Control of occupational exposure in the safety standards
Requirements for control of occupational exposure are established in
GSR Part 3 [24] and in GSR Part 7 [25]. Recommendations on meeting therequirements for control of occupational exposure are provided in IAEA
Safety Standards Series No. GSG-7, Occupational Radiation Protection [18].
Recommendations specific to control of occupational exposure in an emergency,with a focus on the transition to an existing exposure situation, are provided in
IAEA Safety Standards Series No. GSG-11, Arrangements for the Terminationof a Nuclear or Radiological Emergency [43], and those specific to controlof occupational exposure in medical facilities are provided in IAEA Safety
Standards Series No. SSG-46, Radiation Protection and Safety in Medical Usesof Ionizing Radiation [54].

37

4.2.2.1.

Control of occupational exposure at low and very low levels of dose

For planned exposure situations and existing exposure situations, the samerequirements for control of occupational exposures apply, and the control ofoccupational exposures is generally focused on low and very low doses.
Dose limits (i.e. an effective dose of 20 mSv per year averaged over fiveconsecutive years and of 50 mSv in any single year) are part of the requirements
for the control of occupational exposure in planned exposure situations andexisting exposure situations. To the extent practicable and if circumstances allow,
dose limitation is applied also for emergency workers in emergency exposure
situations (see also Section 4.2.2.2).
Dose constraints are used in the optimization of protection and safety. Dose
constraints for occupational exposure are established by operating organizations(see footnote 25 of GSR Part 3 [24]). The value of the dose constraint is lessthan the applicable dose limit, and occupational exposures are required to be
optimized below the dose constraint (see paras 1.22–1.28 of GSR Part 3 [24]).
As a result, most occupational exposures are a small fraction of the dose limits(typically below 1 mSv in a year), namely in the very low dose range.
However, in some workplaces, occupational exposures might still not be
as low as this, even after options to optimize protection and safety have been
implemented. For example, workers using interventional radiological equipment
need to stand next to the patient and even with radiation protection measures inplace might receive certain exposures, especially to the extremities and to thelens of the eye. Workers who carry out certain maintenance activities in nuclear
power plants might need to work in high dose rate environments. As a result, theannual effective doses received by some of these workers can exceed 10 mSv in a
year, namely a dose within the low dose range.
4.2.2.2.

Control of occupational exposure at moderate and high levels of dose

Although doses from occupational exposure in a single year can beconsidered to be low, over a working life of 40 or more years, the lifetime
effective dose of some workers might be several hundred millisievert: thisis in the moderate dose range in Table 1. However, it may still not be possible
to attribute stochastic effects to such exposures owing to the small numbers ofworkers who receive doses in this range.
For emergency workers, GSR Part 3 [24] and GSR Part 7 [25] requirethat the relevant requirements for occupational radiation protection in planned
exposure situations be applied, unless there are exceptional circumstances. The
exceptional circumstances are defined in para. 5.55 of GSR Part 7 [25], whichstates (see also para. 4.15 of GSR Part 3 [24]):
38

“The operating organization and response organizations shall ensure that no
emergency worker is subject to an exposure in an emergency that could giverise to an effective dose in excess of 50 mSv other than:
(1)
(2)

(3)

For the purposes of saving human life or preventing serious injury;
When taking actions to prevent severe deterministic effects or actions
to prevent the development of catastrophic conditions that could
significantly affect people and the environment;
When taking actions to avert a large collective dose.”

For emergency workers carrying out such actions, guidance values are
required to be applied to restrict the exposure of emergency workers. These
guidance values are set out in appendix I of GSR Part 7 [25] and are in therange of moderate doses (see Table 1), as the benefit to an individual and thesociety from carrying out these actions significantly outweighs the risks to which
emergency workers are subjected while taking assigned actions. It is only forlifesaving actions that an individual dose to an emergency worker may exceed
these doses (possibly even entering the high dose range in Table 1), and only
“under circumstances in which the expected benefits to others clearly outweighthe emergency worker’s own health risks, and the emergency worker volunteers
to take the action and understands and accepts these health risks” [25]. Becauseof this, it is of paramount importance that risks associated with the radiation
exposure of emergency workers be factored into the justification and optimizationof the protection strategy. Further recommendations for the protection of workers
in an emergency are provided in section 4 of GSG-7 [18] and in section 4of GSG-11 [43].

4.3. MEDICAL EXPOSURE
4.3.1. Doses and health effects associated with medical exposure
Medical exposure is the exposure incurred by patients for the purposes of
medical or dental diagnosis or treatment; exposure of individuals as part of healthscreening programmes; by carers and comforters; and by volunteers subject
to exposure as part of a programme of biomedical, diagnostic or therapeutic
research [5]. Medical exposure is the largest human-made type of exposure toionizing radiation, although the increases in annual effective dose per caputdue to medical exposure that had been seen in previous decades appear to havelevelled off [31]. According to UNSCEAR 2020/2021, the global average annual
individual effective dose received by the public in 2020/2021 from medical
39

TABLE 5. WEIGHTED DOSE PER PROCEDURE FOR VARIOUS
PROCEDURES [31]Medical application

Typical effective dose per procedure (mSv)

Diagnostic procedures
Conventional radiology (excluding dental)

0.37

Dental radiology

0.01

Computed tomography

6.4

Interventional radiology

14.9

Nuclear medicine procedures

6.8

exposure was approximately 0.6 mSv [31]. The estimated worldwide annual
number of medical radiological procedures was 4.2 billion, the estimated numberof nuclear medicine procedures was 40 million, and the estimated number ofradiation therapy procedures was over 6 million [31].
Table 5 shows the weighted effective dose per examination for somediagnostic and interventional medical procedures. The average effective doses
from most diagnostic procedures are very low. As can be seen from Table 5,computed tomography (CT) scans deliver significantly higher doses, but thesestill fall within the low dose range as defined in Table 1.
As the dose to the patient from diagnostic medical procedures is in thevery low to low dose range, it is very difficult to attribute any adverse healtheffect to a single radiation exposure from diagnostic medical procedures.
UNSCEAR 2012 [1] provides a case study of 72 million CT scans performed in
the United States of America in 2007. The report states that: “The published casestudy made conditional predictions of the risk to the population taking accountof the doses to individual organs and tissues, age at exposure and the inferredrisks for each cancer type for people exposed at moderate or high doses” [1].
UNSCEAR 2012 [1] concludes:“[T]he inferred increase in the number of cancers would be of the order of
2% above the normal frequency in the general population, although morethan 2% of the population [are] subjected to CT. An epidemiological study todemonstrate such an increase would involve following hundreds of thousandsof people over many years and a similar-sized, matched-control group.”
40

The doses from interventional procedures are also in the low dose
range. However, for some patients, the interventional procedure might not be
straightforward, and the dose to the skin of the patient might be in the high dose
range — in some cases high enough for the patient to receive a skin burn — which
can be attributed with confidence to the particular exposure [55].
Therapeutic medical procedures are associated with high doses. In radiation
therapy, the intent is to kill (shrink or eradicate) the tumour while sparing thenormal surrounding tissue. This killing of the tumour is itself an observable,
deterministic effect that can be directly attributed to the radiation exposure.
Depending on the area being irradiated, deterministic side effects, such as nausea,
vomiting and diarrhoea, can also occur.
Unintended and accidental exposures might also occur during medical
procedures. There have been occasions when patients have been accidentally
exposed during diagnostic procedures to cause deterministic effects, particularlyskin reddening and loss of hair. For example, Ref. [56] describes a case in which
over 200 patients received eight times the normal dose of radiation during a
specific type of brain scan. Forty per cent of the affected patients experienced
skin redness and hair loss, which could be attributed to the exposure they
had incurred [56].
Annex C of UNSCEAR 2008 [7] reviews accidents from medical
procedures and considers that accidents associated with the medical useof radiation in diagnosis and treatment may have been underreported. The
IAEA has also reviewed accidental exposures in radiotherapy [57]. The IAEA
provides a reporting system called Safety in Radiation Oncology (SAFRON)
for radiotherapy and radionuclide therapy incidents and near misses, which at
the time of this publication includes over 1300 incident reports [58]. Further
accidental overexposures are also documented in Refs [59–61]. In many of theaccidents documented, the dose was sufficiently high that deterministic effects
occurred, which could be attributed to the overexposure.
4.3.2. Control of medical exposure in the safety standards
Requirements for control of medical exposure are established in
GSR Part 3 [24]. Recommendations for control of medical exposure are provided
in SSG-46 [54].
There are no dose limits for medical exposure. For medical exposure, theoptimization of protection and safety is the management of the radiation dose to
the patient (or to comforters and carers or medical volunteers, as appropriate)
commensurate with the medical purpose. The optimization of protection andsafety for medical exposure necessitates a special approach because in most cases
it is necessary to deliver a dose that is sufficient to achieve the desired clinical41

outcome. As such, too low a radiation dose is to be avoided as much as too higha radiation dose.
In X ray medical imaging, image guided interventional procedures anddiagnostic nuclear medicine, diagnostic reference levels are the main tool
used in the optimization of protection and safety. As stated in para. 1.31 of
GSR Part 3 [24]:“Periodic assessments are performed of typical doses or activity of theradiopharmaceuticals administered in a medical facility. If comparison withestablished diagnostic reference levels shows that the typical doses or activityof the radiopharmaceuticals administered are either too high or unusuallylow, a local review is to be initiated to ascertain whether protection andsafety has been optimized and whether any corrective action is required.”
Other tools used in the optimization of protection and safety applied to
medical exposure include the design of medical radiological equipment andfacilities, the use of operational protocols and programmes of quality assurance
and training of personnel. As a result of the optimization of medical exposure, theexpectation is that doses from diagnostic and interventional medical procedures
will be in the very low and low dose range, as described in Section 4.3.1. In
addition, the intention is that unintentional radiation induced health effects
associated with therapeutic medical procedures are avoided.

5. IMPLICATIONS OF THE CONCEPTS OFATTRIBUTION OF HEALTH EFFECTS AND
INFERENCE OF RISK FOR COMMUNICATION

5.1. COMMUNICATION ABOUT THE SAFETY STANDARDS
5.1.1. Purpose of the safety standards
As described in Section 2, there are distinctions between data relating tohealth effects that can be attributed either in individuals (deterministic effects) orin a population (stochastic effects) (see Section 2.1), models used for estimating
health effects (see Section 2.2.2) and models used for the regulatory purpose ofradiation protection (see Section 2.2.3). The safety standards apply the models
used for the regulatory purpose of radiation protection, and as such, they are42not intended to be used in estimating health effects, either retrospectively orprospectively.
5.1.2. Use of dose constraints and reference levels
With regard to optimization of protection and safety, the safety standards set
out a framework for source related dose constraints and reference levels, which
are presented as ranges of values (see Table 2). There are two considerations inTable 2 that could lead to misunderstandings or misapplication of the framework.
First, it might be assumed that the selection of a dose constraint or areference level at the lower end of that range would provide ‘better’ protection
than selection of a value at the upper end. However, that is not the case. Rather,
it is the process of optimization, which takes into account economic and social
factors, including other non-radiation risks present, that provides overall
protection to individuals. That is, optimization ensures that the level of protection
will be the best possible under the prevailing circumstances; it will not necessarilybe the option with the lowest risk or dose.
The recommended ranges of values for dose constraints and reference levels
all lie within the low and very low dose range. Consequently, irrespective of thevalue selected for a dose constraint or reference level within the range given in
Table 2, there will be no attributable health effects, either at an individual levelor at a population level. In many cases, it is other non-radiation-related risks that
could be considered more important in the process of optimization, particularly
when limited resources are available, to avoid inequitable outcomes in optimizing
the protection of groups that receive different levels of dose, or when theprotection measures could have significant social or environmental cost.
Second, the 1–20 mSv dose range in Table 2 is usually applied to annual
dose constraints or reference levels. If persons were to receive a dose at the upper
end of this range over many years, the total exposure could possibly reach into
the moderate range of doses. Consequently, if a large enough population were
exposed, health effects could be attributable. The most prominent example wheresuch a situation might arise (i.e. the exposure of a large population reaching
the moderate dose range) is in relation to radon in homes. As described in
Section 4.1.1, studies have indicated a significant association (at a populationlevel) between the risk of lung cancer and exposure to radon in homes. As such, it
is possible that compliance with the reference level for radon in homes might still
result in attributable health effects at a population level.

435.1.3. Use of dose limits
The safety standards set out dose limits for public exposure andoccupational exposure (see Sections 4.1.2.1 and 4.2.2.1), and these limits are in
the range of very low and low doses. As such, no radiation induced health effects
can be attributed to radiation exposure at an individual or population level.
It might be possible for some workers to repeatedly receive doses close to
the dose limit for occupational exposure. They could thereby receive a lifetime
effective dose in the moderate dose range in Table 1. However, as noted in
Section 4.2.2.2, it may still not be possible to attribute stochastic effects to such
workers owing to the small size of the exposed population.
Dose limits are sometimes assumed to demarcate the boundary between
what is ‘safe’ and ‘unsafe’. As such, a dose above 1 mSv to a member of the
public could even be assumed to lead to attributable health effects. However, as
shown in Table 1, doses up to 100 mSv are within the very low or low range ofdoses and would not lead to any health effect observable in either an individual
or an exposed group of individuals.
5.1.4. Use of generic criteria for emergency exposure situations
As described in Section 4.1.2.2, GSR Part 7 [25] provides generic criteria
for use in emergency preparedness and response. These criteria are used to help
in determining the need for taking protective actions and other response actions
and are given in terms of doses that are within the moderate and high dose
ranges in Fig. 1, as they aim to avoid severe deterministic effects and reduce therisk of stochastic effects. Thus, an effective response is expected to ensure that
doses are kept below the generic criteria, thereby also ensuring that there are
no radiation induced health effects that could be attributed at an individual or
population level.
5.1.5. Use of collective dose
The proper use of collective dose, namely its use in comparing options forpurposes of optimization of protection and safety, is described in Section 2.3. It
might be incorrectly assumed that the health effects used for such calculations
are actual health effects that can be attributable at an individual or a populationlevel, rather than notional health effects derived on the basis of the LNT model.
Particularly in the case of situations involving low and very low doses, where
health effects cannot be attributed to radiation exposure, this could lead tosignificant misunderstanding whereby unreasonable conclusions could be drawn
about the expected health effects following trivial exposures of large populations.
44

The ICRP, UNSCEAR and the IAEA have all strongly advocated against suchuse of collective dose [1, 2, 19]; for example, GSG-9 states that: “Collective dosemust not be used to predict health effects” [19].

5.2. COMMUNICATION ABOUT RISK AND HEALTH EFFECTS
Paragraph 1.1 of IAEA Safety Standards Series No. GSG-6, Communication
and Consultation with Interested Parties by the Regulatory Body [62], states:“Members of the public usually have incomplete knowledge and a great dealof uncertainty regarding any issue involving nuclear and radiation safety
because of the complexity of the topic. Such incomplete knowledge anduncertainty influence the public’s perception of the radiation risk associatedwith nuclear energy, radioactive waste and the use of radiation sources.
The public rightly expects to have access to reliable, comprehensive andeasily understandable (plain, unambiguous and jargon free) information
about safety and regulatory issues in order to form opinions and make fully
informed decisions.”
Table 7 of Ref. [63] sets out some influences on the public’s perception ofrisk in relation to a nuclear or radiological emergency.
5.2.1. Safety requirements for communication about risk and healtheffects
Regarding the responsibilities of the regulatory body and the authorized
party, para. 4.68 of GSR Part 1 (Rev. 1) [38] states:“The authorized party shall inform the public about the possible radiation
risks (arising from operational states and accidents, including events witha very low probability of occurrence) associated with the operation of a
facility or the conduct of an activity. This obligation shall be specified in theregulations promulgated by the regulatory body, in the authorization or byother legal means.”
Paragraph 4.69 of GSR Part 1 (Rev. 1) [38] states that: “Public information
activities shall reflect the radiation risks associated with facilities and activities, inaccordance with a graded approach”. Thus, more extensive public communicationis required for those facilities and activities with a higher risk.

45

GSR Part 3 [24] establishes several requirements regarding communication
about risk to the public. Requirement 50 of GSR Part 3 [24] states:“The government shall provide information on levels of radon indoors
and the associated health risks and, if appropriate, shall establish
and implement an action plan for controlling public exposure due toradon indoors.”
Regarding the provision of information to the public for emergency
preparedness and response, Requirement 10 of GSR Part 7 [25] states:“The government shall ensure that arrangements are in place toprovide the public who are affected or are potentially affected by anuclear or radiological emergency with information that is necessary
for their protection, to warn them promptly and to instruct them on
actions to be taken.”Requirement 13 of GSR Part 7 [25] states:“The government shall ensure that arrangements are in place
for communication with the public throughout a nuclear orradiological emergency.”
As part of these arrangements, para. 5.71 of GSR Part 7 [25] states that:“Arrangements shall be made so that in a nuclear or radiological emergency
information is provided to the public in plain and understandable language.”
Paragraph 5.72 of GSR Part 7 [25] states:“The government shall ensure that a system for putting radiological healthhazards in perspective in a nuclear or radiological emergency is developedand implemented with the following aim:
— To support informed decision making concerning protective actions
and other response actions to be taken;— To help in ensuring that actions taken do more good than harm;— To address public concerns regarding potential health effects.”

46

There are also requirements in the safety standards for proper communicationof radiation risks to workers. Paragraph 3.110(a) of GSR Part 3 [24] states:“Employers, in cooperation with registrants and licensees…[s]hall
provide all workers with adequate information on health risks due totheir occupational exposure in normal operation, anticipated operational
occurrences and accident conditions, adequate instruction and training andperiodic retraining in protection and safety, and adequate information on thesignificance of their actions for protection and safety”.
Information on radiation risks is also required to be communicated toemergency workers. Paragraph 4.18 of GSR Part 3 [24] states:“Response organizations and employers shall take all reasonable steps
to assess and record the doses received in an emergency by emergency
workers. Information on the doses received and information concerning theassociated health risks shall be communicated to the workers involved.”
There are also requirements for communication about radiation risks
associated with medical exposure. Requirement 36 of GSR Part 3 [24] states:“Registrants and licensees shall ensure that no person incurs a medical
exposure unless there has been an appropriate referral, responsibility
has been assumed for ensuring protection and safety, and the person
subject to exposure has been informed as appropriate of the expected
benefits and risks.”
5.2.2. Communication about risk and health effects using the concepts of
attribution and inference
IAEA Safety Standards Series No. GSG-14, Arrangements for Public
Communication in Preparedness and Response for a Nuclear or Radiological
Emergency [64], provides recommendations on putting radiological health hazards
in perspective that take into account the concepts of attribution of health effects
and the inference of risks. In particular, the appendix to GSG-14 [64] describes anexample system for putting radiological health hazards in perspective in relation
to a nuclear or radiological emergency. This system was derived on the basis of47

the findings of UNSCEAR 2012 [1] and the generic criteria described in Sections
4.1.2.2 and 5.14 of this Safety Report. The system comprises three levels:
(1)
(2)

(3)

‘Dangerous to health’: This corresponds to situations in which an individual
might develop a deterministic effect, that is, the high dose range in Fig. 1.
‘Possible health effects’: This corresponds to situations in which there
is a possibility that epidemiological studies would reveal an increase in
the frequency of occurrence of cancers in a large population, namely themoderate dose range in Fig. 1.
‘No observable health effects’: This corresponds to situations in which
there is no possibility that current epidemiological studies would reveal anincrease in the frequency of occurrence of malignant diseases in a large
population, that is, the low and very low dose range in Fig. 1.

During and following an emergency, some members of the public might
receive doses in the moderate dose or high dose ranges in Fig. 1. Such persons
will be urged to comply with instructions in protective actions and other response
actions issued by the relevant authorities. As noted in para. II.26 of GSG-2 [42],experience has shown that the public follow instructions best when they
understand how the actions provide for their protection. Paragraphs II.29–II.38
of GSG-2 [42] provide a plain language explanation of the various operational
intervention levels that are used to trigger specific protective actions andother response actions and that can be used in instructions to the public. These
plain language explanations can be enhanced with reference to the three levelsystem above, so as to explain to the public the health effects that can beprevented if the instructions are followed and emergency response actions aretaken in a timely manner (see also the Appendix to this Safety Report).
There are also existing exposure situations where members of the public
might receive doses in the moderate dose range in Fig. 1 (see Section 4.1.2.2).
GSG-15 [45] recommends that the conclusions of UNSCEAR 2012 [1] bereferred to when communicating about radiation risks to the public in remediatingareas affected by past activities or events. Paragraph 2.59(e) of GSG-15 notesthat “the importance of not creating unnecessary anxiety, while appropriately
recognizing relevant inferred risks and detriments, in order to enable people to
make their own informed decisions”.
The three level system set out above can also be used to communicate to
the public the health effects and radiation risks associated with high, moderate,
low and very low doses. As stated in Ref. [65]:“The risks of radiation exposure and the attribution of health effects toradiation need to be clearly presented to stakeholders, making it unambiguous48

that any increases in the occurrence of health effects in populations are not
attributable to exposure to radiation if levels of exposure are similar to theglobal average background levels of radiation.”
Paragraph 3.14 of IAEA Safety Standards Series No. SSG-32, Protectionof the Public against Exposure Indoors due to Radon and Other Natural Sourcesof Radiation [44], recommends that informational material be provided to the
public on “scientific evidence on the health risks arising from long term exposuredue to radon indoors”. The three level system set out above can also be used
to communicate to the public the radiation risk due to radon, especially for
individuals exposed to radon in their homes over the course of their lifetime andwho are in the moderate dose range in Fig. 1, for which there could be attributable
health effects at a population level (see Section 4.1.1 of this Safety Report).
For most workers, their lifetime occupational exposure will be within the
low and very low dose range (see Table 4). The three level system set out above
can also be used for communicating the associated health effects and radiation
risks associated with their occupational exposure. An example that uses the threelevel system in explaining health effects and radiation risks associated with
exposures of emergency workers in a nuclear or radiological emergency and theassociated medical actions is provided in table I–15 of Ref. [66].
With regard to medical exposure, Requirement 36 of GSR Part 3 [24]requires that “the person subject to exposure has been informed as
appropriate of the expected benefits and risks”. Although the dose associatedwith a single diagnostic procedure will be in the very low and low dose range in
Fig. 1, if certain procedures are undertaken repeatedly, the cumulative dose could
reach into the moderate dose range. In that range, there could be an increase in theincidence of health effects that could theoretically be attributable at a populationlevel, although — given the small sizes of the populations involved — in practicethis will not be able to be seen. This information, when presented in the context ofthe three level system above, can be used to support decision making by patientsand medical practitioners.

49

Appendix
A PLAIN LANGUAGE EXPLANATION OF THE
CONCEPTS OF ATTRIBUTION AND INFERENCE
TO SUPPORT PUBLIC COMMUNICATION

Exposure to high levels of radiation, such as were received by someworkers during the Chernobyl accident, can quickly lead to serious healtheffects, including death. For moderate exposures, such as were received by somemembers of the public after the accident, there can be a detectable increase in therates of diseases such as cancer and leukaemia in the population many years after
the exposure. However, the situation for low levels of radiation exposure, suchas are received by workers and members of the public in daily life, is much lessclear. This raises two important questions:— Is it possible to know whether a specific health effect could have beencaused by an exposure to radiation?
— Is it possible to estimate whether an exposure to radiation could lead tofuture health effects?
Both of these questions are often difficult to answer, particularly for low
levels of radiation.
Studies of radiation exposures received by large groups of people haveconcluded that radiation can cause diseases such as cancer and that the risk thatsuch effects will occur is higher if a higher exposure has been received. These
effects occur many years after the exposure and are medically the same as thosethat occur because of other causes. Because of this, it is generally not possible
to be certain whether a disease that occurs in a person was caused by exposure
to radiation or by another factor. A noticeable difference in the numbers ofpeople with cancer can only be seen in large groups of people who have received
moderate or high exposures. No difference in the numbers of people with cancer
can be seen if the levels of exposure were low.
Nevertheless, just because a difference in the number of people with cancer
cannot be seen for low levels of exposure, it is not assumed that there is no risk atall. The safety standards aim to protect people from harmful effects of radiation
and are based on a precautionary approach that is both ethical and practical. To
achieve this, it is assumed that any exposure to radiation might possibly cause
health effects (even if these are not detected) and that the risk of these effects
increases as the level of radiation increases.

51

It is important to understand that any risks associated with low levels ofradiation exposure are also low. This is especially important when decisions
are taken that might put people at risk from other dangers. For example, theevacuation of people from areas where there are low levels of radiation can
do more harm than good overall, considering the physical and psychologicalchallenges associated with evacuating people from their homes.

52

REFERENCES
[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]

[11]

[12]

UNITED NATIONS SCIENTIFIC COMMITTEE ON THE EFFECTS OF ATOMICRADIATION, Sources, Effects and Risks of Ionizing Radiation: UNSCEAR 2012
Report to the General Assembly with Scientific Annexes, United Nations,
New York (2015).
INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, The 2007
Recommendations of the International Commission on Radiological Protection,
Publication 103, Elsevier, Amsterdam (2007).
INTERNATIONAL ATOMIC ENERGY AGENCY, Methods for Estimating theProbability of Cancer from Occupational Radiation Exposure, IAEA-TECDOC-870,
IAEA, Vienna (1996).
INTERNATIONAL LABOUR OFFICE, INTERNATIONAL ATOMIC ENERGYAGENCY, WORLD HEALTH ORGANIZATION, Approaches to Attribution of
Detrimental Health Effects to Occupational Ionizing Radiation Exposure and Their
Application in Compensation Programmes for Cancer, Occupational Safety and Health
Series No. 73, ILO, Geneva (2010).
INTERNATIONAL ATOMIC ENERGY AGENCY, IAEA Nuclear Safety and Security
Glossary: Terminology Used in Nuclear Safety, Nuclear Security, Radiation Protection
and Emergency Preparedness and Response, 2022 (Interim) Edition,
IAEA, Vienna (2022).
OGINO, H., et al., Quantitative assessment of provability of radiation-related cancers
considering unavoidable existence of unadjusted risk factors, J. Radiol. Prot. 36 4(2016) 865‒884.
UNITED NATIONS SCIENTIFIC COMMITTEE ON THE EFFECTS OF ATOMICRADIATION, Sources and Effects of Ionizing Radiation: UNSCEAR 2008 Report to
the General Assembly with Scientific Annexes, United Nations, New York (2010).
INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Low-dose
Extrapolation of Radiation-related Cancer Risk, Publication 99, Elsevier,
Amsterdam (2005).
UNITED NATIONS SCIENTIFIC COMMITTEE ON THE EFFECTS OF ATOMICRADIATION, Effects of Ionizing Radiation: UNSCEAR 2006 Report to the General
Assembly with Scientific Annexes, United Nations, New York (2008).
UNITED NATIONS SCIENTIFIC COMMITTEE ON THE EFFECTS OF ATOMICRADIATION, Summary of Low-Dose Radiation Effects on Health: UNSCEAR 2010
Report to the General Assembly, United Nations, New York (2011).
NATIONAL RESEARCH COUNCIL (US), COMMITTEE ON THE BIOLOGICALEFFECTS OF IONIZING RADIATION (BEIR V), Health Effects of Exposure to Low
Levels of Ionizing Radiation: BEIR V, National Academy Press, Washington, DC (1990).
INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION,
Recommendations of the International Commission on Radiological Protection,
Publication 9, Pergamon Press, Oxford (1966).

53

[13]

[14]

[15]

[16]

[17]

[18]

[19]

[20]

[21]

[22]
[23]

[24]

54

INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Diagnostic
Reference Levels in Medical Imaging, Publication 135, Sage, Thousand
Oaks, CA (2017).
WORLD COMMISSION ON THE ETHICS OF SCIENTIFIC KNOWLEDGE ANDTECHNOLOGY (COMEST), The Precautionary Principle, UNESCO, Paris (2005),
https://unesdoc.unesco.org/ark:/48223/pf0000139578
INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, EthicalFoundations of the System of Radiological Protection, Publication 138, Sage, Thousand
Oaks, CA (2018).
INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION,
Recommendations of the International Commission on Radiological Protection,
Publication 26, Pergamon Press, Oxford (1977).
INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, 1990
Recommendations of the International Commission on Radiological Protection,
Publication 60, Pergamon Press, Oxford (1991).
INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL LABOURORGANIZATION, Occupational Radiation Protection, IAEA Safety Standards Series
No. GSG-7, IAEA, Vienna (2018).
INTERNATIONAL ATOMIC ENERGY AGENCY, UNITED NATIONSENVIRONMENT PROGRAMME, Regulatory Control of Radioactive Discharges tothe Environment, IAEA Safety Standards Series No. GSG-9, IAEA, Vienna (2018).
INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Assessing
Dose of the Representative Person for the Purpose of Radiation Protection of the Public
and the Optimisation of Radiological Protection: Broadening the Process, Publication
101, Elsevier, Amsterdam (2006).
INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION,
Radiological Protection Policy for the Disposal of Radioactive Waste, Publication 77,
Pergamon Press, Oxford (1997).
Statute of the International Atomic Energy Agency as Amended up to 28 December
1989, IAEA, Vienna (1989).
EUROPEAN ATOMIC ENERGY COMMUNITY, INTERNATIONAL ATOMICENERGY AGENCY, FOOD AND AGRICULTURE ORGANIZATION OF THE
UNITEDNATIONS,INTERNATIONALLABOURORGANIZATION,
INTERNATIONAL MARITIME ORGANIZATION, OECD NUCLEAR ENERGYAGENCY, PAN AMERICAN HEALTH ORGANIZATION, UNITED NATIONSENVIRONMENT PROGRAMME, WORLD HEALTH ORGANIZATION,
Fundamental Safety Principles, Safety Standards Series No. SF-1, IAEA, Vienna (2006).
EUROPEAN COMMISSION, FOOD AND AGRICULTURE ORGANIZATION OF
THE UNITED NATIONS, INTERNATIONAL ATOMIC ENERGY AGENCY,
INTERNATIONAL LABOUR ORGANIZATION, OECD NUCLEAR ENERGYAGENCY, PAN AMERICAN HEALTH ORGANIZATION, UNITED NATIONSENVIRONMENT PROGRAMME, WORLD HEALTH ORGANIZATION, Radiation
Protection and Safety of Radiation Sources: International Basic Safety Standards, IAEA
Safety Standards Series No. GSR Part 3, IAEA, Vienna (2014).

[25]

[26]

[27]

[28]

[29]

[30]

[31]

[32]
[33]
[34]
[35]
[36]

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS,INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL CIVIL
AVIATION ORGANIZATION, INTERNATIONAL LABOUR ORGANIZATION,
INTERNATIONAL MARITIME ORGANIZATION, INTERPOL, OECD NUCLEAR
ENERGY AGENCY, PAN AMERICAN HEALTH ORGANIZATION, PREPARATORYCOMMISSION FOR THE COMPREHENSIVE NUCLEAR-TEST-BAN TREATY
ORGANIZATION, UNITED NATIONS ENVIRONMENT PROGRAMME, UNITED
NATIONS OFFICE FOR THE COORDINATION OF HUMANITARIAN AFFAIRS,WORLDHEALTHORGANIZATION,WORLDMETEOROLOGICALORGANIZATION, Preparedness and Response for a Nuclear or Radiological
Emergency, IAEA Safety Standards Series No. GSR Part 7, IAEA, Vienna (2015).
INTERNATIONAL ATOMIC ENERGY AGENCY, UNITED NATIONSENVIRONMENT PROGRAMME, Radiation Protection of the Public and theEnvironment, IAEA Safety Standards Series No. GSG-8, IAEA, Vienna (2018).
UNITED NATIONS SCIENTIFIC COMMITTEE ON THE EFFECTS OF ATOMICRADIATION, Sources and Effects of Ionizing Radiation: UNSCEAR 2000 Report to
the General Assembly with Scientific Annexes, United Nations, New York (2000).
UNITED NATIONS SCIENTIFIC COMMITTEE ON THE EFFECTS OF ATOMICRADIATION, Sources, Effects and Risks of Ionizing Radiation: UNSCEAR 2013
Report to the General Assembly with Scientific Annexes, United Nations,
New York (2014).
UNITED NATIONS SCIENTIFIC COMMITTEE ON THE EFFECTS OF ATOMICRADIATION, Sources, Effects and Risks of Ionizing Radiation: UNSCEAR 2017
Report to the General Assembly with Scientific Annexes, United Nations,
New York (2018).
UNITED NATIONS SCIENTIFIC COMMITTEE ON THE EFFECTS OF ATOMICRADIATION, Sources, Effects and Risks of Ionizing Radiation: UNSCEAR 2019
Report to the General Assembly with Scientific Annexes, United Nations,
New York (2020).
UNITED NATIONS SCIENTIFIC COMMITTEE ON THE EFFECTS OF ATOMICRADIATION, Sources, Effects and Risks of Ionizing Radiation: UNSCEAR 2020/2021
Report to the General Assembly with Scientific Annexes, United Nations,
New York (2021).
WORLD HEALTH ORGANIZATION, WHO Handbook on Indoor Radon: A Public
Health Perspective, WHO, Geneva (2009).
INTERNATIONAL ATOMIC ENERGY AGENCY, The Radiological Accident inGoiânia, IAEA, Vienna (1988).
INTERNATIONAL ATOMIC ENERGY AGENCY, The Radiological Accident inTammiku, IAEA, Vienna (1998).
INTERNATIONAL ATOMIC ENERGY AGENCY, The Radiological Accident in
Istanbul, IAEA, Vienna (2000).
INTERNATIONAL ATOMIC ENERGY AGENCY, The Radiological Accident inYanango, IAEA, Vienna (2000).

55

[37]
[38]

[39]

[40]

[41]

[42]

[43]

[44]

[45]

56

INTERNATIONAL ATOMIC ENERGY AGENCY, The Radiological Accident in Lia,
Georgia, IAEA, Vienna (2014).
INTERNATIONAL ATOMIC ENERGY AGENCY, Governmental, Legal andRegulatory Framework for Safety, IAEA Safety Standards Series No. GSR Part 1(Rev. 1), IAEA, Vienna (2016).
INTERNATIONAL ATOMIC ENERGY AGENCY, OECD NUCLEAR ENERGYAGENCY, Radiation Safety for Consumer Products, IAEA Safety Standards Series No.
SSG-36, IAEA, Vienna (2016).
INTERNATIONAL ATOMIC ENERGY AGENCY, Justification of Practices, Including
Non-Medical Human Imaging, IAEA Safety Standards Series No. GSG-5,
IAEA, Vienna (2014).
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS,INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL LABOUR
OFFICE, PAN AMERICAN HEALTH ORGANIZATION, UNITED NATIONSOFFICE FOR THE COORDINATION OF HUMANITARIAN AFFAIRS, WORLDHEALTH ORGANIZATION, Arrangements for Preparedness for a Nuclear orRadiological Emergency, IAEA Safety Standards Series No. GS-G-2.1,
IAEA, Vienna (2007).
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS,INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL LABOUR
OFFICE, PAN AMERICAN HEALTH ORGANIZATION, WORLD HEALTHORGANIZATION, Criteria for Use in Preparedness and Response for a Nuclear orRadiological Emergency, IAEA Safety Standards Series No. GSG-2,
IAEA, Vienna (2011).
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS,INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL CIVIL
AVIATIONORGANIZATION,
INTERNATIONALLABOUROFFICE,
INTERNATIONAL MARITIME ORGANIZATION, INTERPOL, OECD NUCLEAR
ENERGY AGENCY, UNITED NATIONS OFFICE FOR THE COORDINATION OF
HUMANITARIAN AFFAIRS, WORLD HEALTH ORGANIZATION, WORLDMETEOROLOGICAL ORGANIZATION, Arrangements for the Termination of a
Nuclear or Radiological Emergency, IAEA Safety Standards Series No. GSG-11,
IAEA, Vienna (2018).
INTERNATIONAL ATOMICENERGY AGENCY,WORLD
HEALTHORGANIZATION, Protection of the Public against Exposure Indoors due to Radon andOther Natural Sources of Radiation, IAEA Safety Standards Series No. SSG-32,
IAEA, Vienna (2015).
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS,INTERNATIONAL ATOMIC ENERGY AGENCY, UNITED NATIONSDEVELOPMENT PROGRAMME, UNITED NATIONS ENVIRONMENTPROGRAMME, UNITED NATIONS OFFICE FOR THE COORDINATION OF
HUMANITARIAN AFFAIRS, Remediation Strategy and Process for Areas Affected by
Past Activities or Events, IAEA Safety Standards Series No. GSG-15,
IAEA, Vienna (2022).

[46]

[47]

[48]

[49]

[50]
[51]
[52]
[53]
[54]

[55]
[56]
[57]
[58]

[59]
[60]
[61]
[62]

INTERNATIONAL ATOMIC ENERGY AGENCY, National Strategy for Regaining
Control over Orphan Sources and Improving Control over Vulnerable Sources, IAEA
Safety Standards Series No. SSG-19, IAEA, Vienna (2011).
INTERNATIONAL ATOMIC ENERGY AGENCY, Control of Orphan Sources andOther Radioactive Material in the Metal Recycling and Production Industries, IAEA
Safety Standards Series No. SSG-17, IAEA, Vienna (2012).
INTERNATIONAL ATOMIC ENERGY AGENCY, Information System on
Occupational Exposure in Medicine, Industry and Research (ISEMIR) Database,https://nucleus.iaea.org/isemir
INTERNATIONAL ATOMIC ENERGY AGENCY, OECD NUCLEAR ENERGYAGENCY, Information System on Occupational Exposure (ISOE) Database,
http://www.isoe-network.net/
INTERNATIONAL ATOMIC ENERGY AGENCY, The Radiological Accident in Lilo,
IAEA, Vienna (2000).
INTERNATIONAL ATOMIC ENERGY AGENCY, The Radiological Accident in
Gilan, IAEA, Vienna (2002).
INTERNATIONAL ATOMIC ENERGY AGENCY, The Radiological Accident in
Chilca, IAEA, Vienna (2018).
INTERNATIONAL ATOMIC ENERGY AGENCY, The Radiological Accident in
Ventanilla, IAEA, Vienna (2019).
INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL LABOUR
OFFICE, PAN AMERICAN HEALTH ORGANIZATION AND WORLD HEALTHORGANIZATION, Radiation Protection and Safety in Medical Uses of Ionizing
Radiation, IAEA Safety Standards Series No. SSG-46, IAEA, Vienna (2018).
INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION,
Radiological Protection in Cardiology, Publication 120, Elsevier, Amsterdam (2013).
WINTERMARK, M., LEV, M.H., FDA investigates the safety of brain perfusion CT,
Am. J. Neuroradiol. 31 1 (2010) 2‒3.
INTERNATIONAL ATOMIC ENERGY AGENCY, Lessons Learned from Accidental
Exposures in Radiotherapy, Safety Reports Series No. 17, IAEA, Vienna (2000).
INTERNATIONAL ATOMIC ENERGY AGENCY, Safety in Radiation
Oncology (SAFRON),
https://www.iaea.org/resources/rpop/resources/databases-and-learning-systems/safron
INTERNATIONAL ATOMIC ENERGY AGENCY, Accidental Overexposure ofRadiotherapy Patients in Bialystok, IAEA, Vienna (2004).
INTERNATIONAL ATOMIC ENERGY AGENCY, Accidental Overexposure ofRadiotherapy Patients in San José, Costa Rica, IAEA, Vienna (1998).
INTERNATIONAL ATOMIC ENERGY AGENCY, Investigation of an Accidental
Exposure of Radiotherapy Patients in Panama, IAEA, Vienna (2001).
INTERNATIONAL ATOMIC ENERGY AGENCY, Communication and Consultation with
Interested Parties by the Regulatory Body, IAEA Safety Standards Series No. GSG-6,
IAEA, Vienna (2017).

57

[63]

[64]

[65]
[66]

58

INTERNATIONAL ATOMIC ENERGY AGENCY, Communication with the Public ina Nuclear or Radiological Emergency, EPR Public Communication,
IAEA, Vienna (2012).
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS,INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL CIVIL
AVIATION ORGANIZATION, INTERPOL, PREPARATORY COMMISSION FOR
THE COMPREHENSIVE NUCLEAR-TEST-BAN TREATY ORGANIZATION,
UNITED NATIONS OFFICE FOR OUTER SPACE AFFAIRS, Arrangements for
Public Communication in Preparedness and Response for a Nuclear or Radiological
Emergency, IAEA Safety Standards Series No. GSG-14, IAEA, Vienna (2020).
INTERNATIONAL ATOMIC ENERGY AGENCY, The Fukushima Daiichi Accident,
Report by the Director General, IAEA, Vienna (2015).
INTERNATIONAL ATOMIC ENERGY AGENCY, Considerations in the Developmentof a Protection Strategy for a Nuclear or Radiological Emergency, EPR Protection
Strategy, IAEA, Vienna (2021).

CONTRIBUTORS TO DRAFTING AND REVIEW
Ahier, B.

Health Canada, Canada

Asfaw, K.

International Atomic Energy Agency

Barraclough, I.

International Atomic Energy Agency

Bennett, D.

International Atomic Energy Agency

Berkovskyy, V.

Ukrainian Radiation Protection Institute, Ukraine

Boal, T.

Consultant, Australia

Bly, R.

Finnish Radiation and Nuclear Safety Authority,
Finland

Buglova, E.

International Atomic Energy Agency

Cabianca, T.

Public Health England, United Kingdom

Caruso, G.

International Atomic Energy Agency

Clement, C.

International Commission on Radiological Protection

Colgan, T.

International Atomic Energy Agency

De la Vega, R.

International Atomic Energy Agency

Delattre, D.

International Atomic Energy Agency

Delves, D.

Consultant, AustriaFriedl, A.

Ludwig Maximilians University Munich, Germany

Geupel, S.

International Atomic Energy Agency

Gonzalez, A.

Consultant, Argentina

Hirth, G.

Australian Radiation Protection and Nuclear Safety
Agency, Australia

Holohan, V.

Nuclear Regulatory Commission, United States ofAmerica

Homma, T.

Nuclear Regulation Authority, Japan59

Kaiser, P.

International Atomic Energy Agency

Karseka-Yanev, T.

International Atomic Energy Agency

Müller, W.-U.

Consultant, Germany

Nestoroska Madjunarova, S.

International Atomic Energy Agency

Nikolaki, M.

International Atomic Energy Agency

Pinak, M.

International Atomic Energy Agency

Scheidegger, R.

Federal Nuclear Safety Inspectorate, Switzerland

Shannoun, F.

United Nations Scientific Committee on the Effects ofAtomic Radiation

Shaw, P.

International Atomic Energy Agency

Telleria, D.

International Atomic Energy Agency

Webster, P.

Canadian Nuclear Safety Commission, Canada

Yllera, J.

International Atomic Energy Agency

60

@

No. 26ORDERING LOCALLY
IAEA priced publications may be purchased from the sources listed below or from major local booksellers.
Orders for unpriced publications should be made directly to the IAEA. The contact details are given at
the end of this list.

NORTH AMERICA
Bernan / Rowman & Littlefield
15250 NBN Way, Blue Ridge Summit, PA 17214, USA
Telephone: +1 800 462 6420 • Fax: +1 800 338 4550
Email: orders@rowman.com • Web site: www.rowman.com/bernan

REST OF WORLD
Please contact your preferred local supplier, or our lead distributor:
Eurospan Group
Gray’s Inn House
127 Clerkenwell Road
London EC1R 5DB
United Kingdom
Trade orders and enquiries:
Telephone: +44 (0)176 760 4972 • Fax: +44 (0)176 760 1640
Email: eurospan@turpin-distribution.com
Individual orders:www.eurospanbookstore.com/iaea
For further information:
Telephone: +44 (0)207 240 0856 • Fax: +44 (0)207 379 0609
Email: info@eurospangroup.com • Web site: www.eurospangroup.com

Orders for both priced and unpriced publications may be addressed directly to:Marketing and Sales Unit
International Atomic Energy Agency
Vienna International Centre, PO Box 100, 1400 Vienna, Austria
Telephone: +43 1 2600 22529 or 22530 • Fax: +43 1 26007 22529
Email: sales.publications@iaea.org • Web site: www.iaea.org/publications

23-02241E-T

Atoms for Peace

IAEA SAFETY STANDARDS AND RELATED PUBLICATIONSIAEA SAFETY STANDARDSUnder the terms of Article III of its Statute, the IAEA is authorized to establish or adopt
standards of safety for protection of health and minimization of danger to life and property, andto provide for the application of these standards.
The publications by means of which the IAEA establishes standards are issued in the
IAEA Safety Standards Series. This series covers nuclear safety, radiation safety, transport
safety and waste safety. The publication categories in the series are Safety Fundamentals,
Safety Requirements and Safety Guides.
site

Information on the IAEA’s safety standards programme is available on the IAEA Internet
https://www.iaea.org/resources/safety-standards

The site provides the texts in English of published and draft safety standards. The texts
of safety standards issued in Arabic, Chinese, French, Russian and Spanish, the IAEA Safety
Glossary and a status report for safety standards under development are also available. For
further information, please contact the IAEA at: Vienna International Centre, PO Box 100,
1400 Vienna, Austria.
All users of IAEA safety standards are invited to inform the IAEA of experience in theiruse (e.g. as a basis for national regulations, for safety reviews and for training courses) for the
purpose of ensuring that they continue to meet users’ needs. Information may be provided via
the IAEA Internet site or by post, as above, or by email to Official.Mail@iaea.org.
RELATED PUBLICATIONSThe IAEA provides for the application of the standards and, under the terms of Articles III
and VIII.C of its Statute, makes available and fosters the exchange of information relating
to peaceful nuclear activities and serves as an intermediary among its Member States for thispurpose.
Reports on safety in nuclear activities are issued as Safety Reports, which provide
practical examples and detailed methods that can be used in support of the safety standards.
Other safety related IAEA publications are issued as Emergency Preparedness andResponse publications, Radiological Assessment Reports, the International Nuclear Safety
Group’s INSAG Reports, Technical Reports and TECDOCs. The IAEA also issues reports
on radiological accidents, training manuals and practical manuals, and other special safety
related publications.
Security related publications are issued in the IAEA Nuclear Security Series.
The IAEA Nuclear Energy Series comprises informational publications to encourage
and assist research on, and the development and practical application of, nuclear energy forpeaceful purposes. It includes reports and guides on the status of and advances in technology,
and on experience, good practices and practical examples in the areas of nuclear power, thenuclear fuel cycle, radioactive waste management and decommissioning.

This Safety Report explains how thec o ncept s o f a t t ri but ion of he alth e ffects
and i nf erence o f ri sks can be t aken into
acco unt i n t he a ppl i c ation of IAEA s afetys t a nda rds, so a s t o i mple me nt them mor ee ff ect i vel y. In pa r t i cular, this publicationd emo nst ra t es expl i ci tly w hat the r ele vantprovisions of the safety standards are
fo r hi gh a nd mo dera t e le vels of ex pos ur e ,w here hea l t h eff ect s might be able to bea t t r i b u t e d t o t h e ex p o s u r e , a n d f o r l ow
and ver y l ow l evel s of ex pos ur e , w he r erisks can only be inferred. This Safety
Repo r t a l so a i ms t o su ppor t mor e e ffective
c o mmuni ca t i o n by cl a rify ing the pr ope r us eof cer t a i n co ncept s d e t aile d in the s afetys t a n d a r d s a n d p r ov i d i n g p l a i n l a n g u a g e
expl a na t i o ns o f t he concepts of attr ibutionof eff ect s a nd i nf erenc e of r is k.

Safety Repor ts Series
N o. 1 2 2Attribution ofRadiation Health
Effects and Inferenceof Radiation Risks
Considerations for Application of
the IAEA Safety Standards

INTERNATIONAL ATOMIC ENERGY AGENCY
VIENNA