cnsc guest speaker series in cooperation with · pdf filecnsc guest speaker series . in...

CNSC Guest Speaker Series in cooperation with CNS

CNSC, Ottawa, Canada

2016 May 25

Christopher Clement ICRP Scientific Secretary

[email protected]

INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION

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IARC

ICRU

NEA/OECD

EAN

EURADOS

ISOE WHO

ILO

ISO

IEC

FAO

PAHO

UNEP WENRA

HERCA

NCRP

ISR


1928: Founded as the International X-ray and Radium Protection Committee (IXRPC)

1950: Renamed International Commission on Radiological Protection (ICRP)

1988: Registered as a Charity in the UK

Provides independent recommendations on radiological protection for the public benefit

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ICRP is a registered Charity Work in the public good Transparency, particularly in finances

Members are experts recruited from around the world and in different areas of radiological protection

Members are unpaid*

Voluntarily giving their time and effort to ICRP Many with very busy full-time jobs

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239 members from 36 countries as of 2015 Aug 31, including liaison organization primary contacts

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3

2

50

9

16

8

1

6

26

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1

20

24

16

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Main Commission

Committee 1 Effects

Committee 2 Doses

Committee 3 Medicine

Committee 4 Application

Committee 5 Environment

Scientific Secretariat

TASK GROUPS TASK GROUPS TASK GROUPS TASK GROUPS TASK GROUPS TASK GROUPS


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INWUN


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Advance for the public benefit the science of

radiological protection, in particular by providing

recommendations and guidance on all aspects

of protection against ionising radiation


The System of Radiological Protection is the basis of:

Standards Regulations Guidance Programmes Practice …

worldwide, and has been for nearly 90 years

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UNSCEAR

ICRP

IAEA

Science (doses and

effects)

Philosophy and Policy

Regulatory Practicalities

Sci

ence

P

arad

igm

S

tand

ards

http://www.unscear.org/unscear/en/publications/2006_1.html


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Regional Standards (e.g. PAHO, EC, NEA)

Topical Standards (e.g. ILO, WHO, FAO)

Industry Standards (e.g. ISO, IEC)

National Standards (e.g. CSA, ANSI, JSA)

National Regulations

Radiation Protection Programs


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Regional Standards (e.g. PAHO, EC, NEA)

Topical Standards (e.g. ILO, WHO, FAO)

Industry Standards (e.g. ISO, IEC)

National Standards (e.g. CSA, ANSI, JSA)

National Regulations

Radiation Protection Programs


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http://www.xray.hmc.psu.edu/rci/


Wilhelm Röntgen discovers x rays, winning the first Nobel Prize in Physics in 1901

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Wolfram Fuchs first to publish radiological protection advice:

make the exposure as short as

possible

do not stand within 12 inches (30 cm) of the x-ray tube

coat the skin with Vaseline and leave an extra layer on the area most exposed

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Rapid adoption of radiation in medicine

1898: Curie discovers radium

c. 1900: First radiotherapy

1902: Mobile x-ray for war use

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Increasing concerns about skin effects seen in radiologists

X-ray dermatitis of the hands was observed in the U.S. by Grubbe

Drury described radiation damage to the skin of hands and fingers of experimental investigators in the UK

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1925: First International Congress of Radiology, London Predecessor of International Commission on Radiation Units and Measurement (ICRU) formed

1928: Second International Congress of Radiology, Stockholm Predecessor of International Commission on Radiological Protection (ICRP) formed

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Protection of medical practitioners

Known effects: “injuries to superficial tissues, derangements of internal organs, and changes in the blood”

It was thought that effects only occurred at high doses (above a threshold)

Protection: avoid unnecessary exposure to x rays, and stay as far as practicable from the x-ray tube

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Characterised by a threshold

Severity increases with dose

21 Increasing Dose

Incr

easi

ng S

ever

ity

Threshold


Concern expands to all occupational exposures

Focus continues to be on effects with thresholds

Dose limits introduced based on thresholds

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Protection of the public is now considered

New evidence of effects including leukaemia, cancer, cataracts, and genetic effects

Emerging evidence that some effects may not have thresholds

“In view of the incomplete evidence ... it is strongly recommended that every effort be made to reduce exposure … to the lowest possible level”

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No threshold is assumed

Probability increases with dose

“LNT” model

24 Increasing Dose

Incr

easi

ng P

roba

bilit

y

Linear no-threshold (LNT) model


It is now clear that some effects are stochastic

Assume LNT which “may be incorrect, but ... unlikely to lead to the underestimation of risks”

“any exposure may involve some degree of risk”

“any unnecessary exposure be avoided and that all doses be kept as low as is readily achievable, economic and social consequences being taken into account”

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ICRP Publication 26 (1977) introduced the ‘modern’ system of radiological protection

Built on experience and scientific knowledge gained since 1895

Built on ethical considerations of utilitarianism (seeking the best results for society) and deontology (the duty to treat all individuals justly)

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Protection philosophy: “protection of individuals, their progeny and mankind as a whole, while still allowing necessary activities from which radiation exposure might result”

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People Control the risk from stochastic effects, and avoid deterministic effects

Environment “if man is adequately protected then other living things are also likely to be sufficiently protected”


Fundamental Principles of Protection

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Justification “no practice shall be adopted unless its introduction produces a positive net benefit”

Optimisation “all exposures shall be kept as low as reasonably achievable, economic and social factors being taken into account” (ALARA)

Limitation “doses to individuals shall not exceed the limits”


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SCIENCE EXPERIENCE ETHICAL VALUES

PRIMARY AIM

PROTECTION GOALS

FUNDAMENTAL PRINCIPLES

CONCEPTS / TOOLS / REQUISITES

(INTERNATIONAL) STANDARDS

REGULATIONS

OPERATIONAL RP

SYST

EM O

F R

ADIO

LOG

ICA

L PR

OTE

CTI

ON

G

OO

D

PRAC

TIC

E


Aim

Protection Goals

“Fundamental” Principles

Concepts / Tools / Requisites

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Justification Optimisation Dose Limitation

Human Health Environment

ETHICAL VALUES

SCIENCE

EXPERIENCE


Aim

Protection Goals



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ETHICAL VALUES

SCIENCE

EXPERIENCE


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Contribute to an appropriate level of protection

for people and the environment against the

detrimental effects of radiation exposure without

unduly limiting the desirable human actions that

may be associated with such exposure

Aim

Protection Goals



http://www.google.ca/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=1JDF0tSfsZp1RM&tbnid=rqmiYeefu8RRkM:&ved=0CAUQjRw&url=http://people-who.tumblr.com/&ei=JXoeUdfvEOPz2QW8kIHABw&bvm=bv.42553238,d.b2I&psig=AFQjCNFPKnNN_buXoYcMgZ_LV6xPaHVbug&ust=1361038237191554

http://www.google.ca/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=KUAE1D46BZcXOM&tbnid=wGkrnJuBmrLrxM:&ved=0CAUQjRw&url=http://www.123rf.com/photo_12761136_earth-globe-cloud-map-side-of-the-asia-and-australia.html&ei=CXseUeOhNoWQ2AXcqIHQAQ&bvm=bv.42553238,d.b2I&psig=AFQjCNFmorOvy2HfcBReUplUluJFIJJJ2g&ust=1361038467350584


Aim

Protection Goals



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ETHICAL VALUES

SCIENCE

EXPERIENCE


Manage and control exposures so that:

Harmful tissue reactions (deterministic effects) are prevented

The risks of stochastic effects (cancer or heritable effects) are reduced to the extent reasonably achievable

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Aim

Protection Goals



http://www.google.ca/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=1JDF0tSfsZp1RM&tbnid=rqmiYeefu8RRkM:&ved=0CAUQjRw&url=http://people-who.tumblr.com/&ei=JXoeUdfvEOPz2QW8kIHABw&bvm=bv.42553238,d.b2I&psig=AFQjCNFPKnNN_buXoYcMgZ_LV6xPaHVbug&ust=1361038237191554


Prevent or reduce the frequency of deleterious radiation effects to have a negligible impact on:

the maintenance of biological diversity the conservation of species the health and status of natural habitats, communities and

ecosystems

No universal definition of environmental protection Radiation is one factor to consider, often likely to be a minor one

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Aim

Protection Goals



http://www.google.ca/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=KUAE1D46BZcXOM&tbnid=wGkrnJuBmrLrxM:&ved=0CAUQjRw&url=http://www.123rf.com/photo_12761136_earth-globe-cloud-map-side-of-the-asia-and-australia.html&ei=CXseUeOhNoWQ2AXcqIHQAQ&bvm=bv.42553238,d.b2I&psig=AFQjCNFmorOvy2HfcBReUplUluJFIJJJ2g&ust=1361038467350584


Aim

Protection Goals



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ETHICAL VALUES

SCIENCE

EXPERIENCE


Justification Do more good than harm

Optimisation Keep likelihood of exposures, number of people exposed, and magnitude of individual doses As Low As Reasonably Achievable (ALARA), taking into account economic and societal factors

Dose Limitation Doses to individuals should not exceed limits (for regulated sources in planned exposure situations)

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Aim

Protection Goals




In all circumstances: Optimise protection to maximise benefit and avoid/minimise harm

Manage doses to individuals to avoid an unfair distribution of risk

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Aim

Protection Goals




Aim

Protection Goals



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ETHICAL VALUES

SCIENCE

EXPERIENCE


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Fundamental Principles

Justification Optimisation

Limitation

Categories of exposure

Medical Occupational

Public

Exposure situations

Existing Planned

Emergency

Dose criteria

Reference levels Constraints

Limits etc.

Requisites

Information Training

Monitoring etc.

Aim

Protection Goals



Key Concepts

Dose (D, HT, E) Types of Effects

Reference Individual RAPs etc.


Absorbed Dose D A measureable, physical quantity Energy imparted to a mass

Equivalent Dose HT

Accounts for ‘effectiveness’ of radiation types Absorbed dose x radiation weighting factor

Effective Dose E Also accounts for ‘sensitivity’ of organs Equivalent dose x tissue weighting factor

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Physics (Gy)

Protection (Sv)


Stochastic Effects e.g. cancer and heritable effects Mis-repair and mutation of cells ASSUMPTION: no threshold, probability increases with dose

Tissue Reactions (aka Deterministic Effects) e.g. skin effects, cataracts, circulatory disease Injury to populations of cells ASSUPTION: threshold below which there are no effects

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Stochastic Effects

e.g. cancer and heritable effects

Misrepair and mutation of cells

MODEL: no threshold, probability increases with dose

Tissue Reactions (aka Deterministic Effects)

e.g. skin effects, cataracts,

circulatory disease Injury to populations of cells

MODEL: threshold below which there are no effects

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Courtesy of J. Boice, from his Sievert Lecture, May 2016


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Studies of the Mortality of Atomic Bomb Survivors, Report 14, 1950–2003: An Overview of Cancer and Noncancer Diseases Ozasa et. al.

RADIATION RESEARCH 177, 229–243 (2012)

Clear evidence at medium & high levels

But we are most interested in what’s going on at low levels


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Linear no-threshold

Super-linear

Threshold

Hormesis

ASSUMED for protection purposes


There is no reliable evidence that risk estimates for low-level exposures* have seriously underestimated risk Epidemiological studies have found statistically significant evidence

of risk above ~100 mSv but not below

There is some evidence for some risk of some cancers, but interpretation is difficult E.g. from studies of antenatal radiography, CT scans, background

radiation, and radiation workers Low dose and low dose-rate studies need to be refined; the results may provide persuasive evidence of some risk for some cancers

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From a presentation by R Wakeford, Seoul, October 2015

* For low LET radiation, brief dose <100 mGy, or < 0.1 mGy/min averaged over ~1h (UNSCEAR)


Clear evidence of increased cancer above ~ 100 mSv Some evidence at low exposures No direct evidence of heritable effects in humans

Model for protection: probability of effect increases with dose,

without threshold Protection optimisation, keep doses ALARA

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Model for protection: characterised by a threshold

Threshold: dose below which there is no effect, and above which the severity increases with dose

Protection keep doses below threshold

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Aim

Protection Goals



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ETHICAL VALUES

SCIENCE

EXPERIENCE


Aim

Protection Goals



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SCIENCE

EXPERIENCE

ETHICAL VALUES


ICRP Task Group 94 Ethics of Radiological Protection Consolidate the ethical basis of the system improve understanding basis for communication on radiation risk and perception

Supported by a series of international workshops Publication in ~2017 http://tinyurl.com/RPethics

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SCIENCE

EXPERIENCE

ETHICAL VALUES


Beneficence / Non-maleficence Do good and avoid doing harm

Prudence Recognize and follow the most sensible course of action, especially

in the face of uncertainty, avoiding unwarranted risk

Justice Fair sharing of benefits and risks

Dignity Treatment of individuals with unconditional respect, and having the

capacity to deliberate, decide and act without constraint

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SCIENCE

EXPERIENCE

ETHICAL VALUES


These are values:

Already found in the system of radiological protection

Similar to widely accepted principles of biomedical ethics

Draw from western and eastern schools of ethical thought

Part of the ‘common morality’ of cross-cultural ethics

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SCIENCE

EXPERIENCE

ETHICAL VALUES


Beneficence / Non-maleficence Justification to ensure more good than harm Equivalent dose limits to avoid harm (tissue reactions)

Prudence Assume small risks even at small doses (LNT), and therefore

optimise protection to keep doses ALARA

Justice Effective dose limits, and constraints & reference levels in

optimisation, to avoid unfair distribution of dose (≈risk)

Dignity Stakeholder involvement, informed consent, self-help protection

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SCIENCE

EXPERIENCE

ETHICAL VALUES


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Uses the best available science Is founded in sound ethical values Draws on more than a century of experience

It aims to: Prevent effects that are reasonably preventable Manage the risk of unpreventable effects to a reasonable level Protect the environment

ICRP continues to: Review and assess science, values, and experience Respond to emerging needs Promote awareness of radiological protection

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Paris, France

October 10-12, 2017

In conjunction with the 2nd European

Radiological Protection Research Week

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www.icrp.org

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