INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTIONICRP ref 4832-9526-9446

Areas of Research to Support the System of Radiological Protection
Approved 2017 June 16

One of the three priorities in the International Commission on Radiological Protection (ICRP)Strategic Plan for 2016-2020 is to “maintain and improve the system of radiological protection”. A
key action under this priority is to “identify and encourage research needed to support radiologicalprotection”. This document presents ICRP’s views, to encourage dialogue and help focus research
initiatives. In no particular order, the areas of research identified are:
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Effects of protracted exposures and low dose rates
Mechanisms of low-dose effects and dose-response models that take account of them
Organ-specific, and age and sex differences in, sensitivity to cancer induction
The role of genetic differences in determining individual sensitivity
Effects other than cancer and genetic effects and their contribution to detriment
Relating exposures, doses, and effects on population viability for non-human biota
Reliability of dose assessments
Dosimetry and protection methods in medicine
Ethical and social dimensions of the system of radiological protection
Mechanisms for interaction with stakeholders

Effects of protracted exposures and low dose rates
Studies of population groups exposed as workers, patients, or public are important to provide
information relating to protracted exposures to moderate doses and low dose rates (< 5 mGy/h)from external sources and internally deposited radionuclides.
Mechanisms of low-dose effects and dose-response models that take account of them
Health effects at low doses (defined as <100 mGy) and low dose-rates are generally not discernible
in epidemiological studies but are inferred based on biological plausibility and quantitative estimatesobtained using risk extrapolation models, the simplest of which is the LNT model used for protection
purposes. There is a need for further studies of mechanisms of low dose effects at molecular,
cellular and tissue levels and the development of dose-response models that take account of thesemechanisms. Biological samples of normal and diseased tissues taken during epidemiological andexperimental studies have the potential to link molecular changes to observed health effects.

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INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION
Organ-specific, and age and sex differences in, sensitivity to cancer induction
There is a reasonable understanding of the effects on human health of high and moderate doses ofradiation in relation to tissue reactions and stochastic effects. However, it is important that all
sources of direct information continue to be pursued, including, but not limited to, the follow-up
studies of the survivors of the atomic bombings at Hiroshima and Nagasaki, which have provided
much of the quantitative data on cancer risks that are used in the development of protection
standards. This and other epidemiological studies will yield additional information on organ/tissue
sensitivity to cancer induction and age and sex differences in sensitivity.
The role of genetic differences in determining individual sensitivity
As noted above, there are differences in the sensitivity of groups to exposure to radiation based onage and sex. Differences due to some lifestyle characteristics, such as smoking, have also beenobserved. The role of genetic differences in determining individual sensitivity also has potential tosignificantly influence radiological protection, and requires further study.
Effects other than cancer and genetic effects and their contribution to detriment
Stochastic effects are taken to include cancer, for which there is direct epidemiological evidence,and hereditary disease, for which reliance is placed on mouse data. There are concerns that somediseases thought to occur above dose thresholds, notably including circulatory diseases andopacities of the lens of the eye, might in fact exhibit dose-response relationships more like the linear
non-threshold (LNT) dose-response assumed for stochastic effects. Further work is required todetermine whether other diseases should be considered as contributors to low-dose detriment.
Relating exposures, doses, and effects on population viability for non-human biota
In general, considerations applying to effects of radiation in humans apply also to non-human faunaand flora. Thus, it is important to develop appropriate dosimetric models, understand dose-response
relationships and account for differences in sensitivity between organisms and life stages. However,the focus of protection for non-human biota is on population viability and hence on tissue reactions,
including gross impairment of reproductive capacity and effects on future generations. Further
research is needed to understand exposures, doses, and effects relevant to population viability forvarious species. This would include improving the understanding of dosimetry in the environment,
the relationships of those measurements to a measure of exposure to the organism of interest, andthe relationship of those estimated exposures to population endpoints.
Reliability of dose assessments
All studies of health effects caused by radiation require reliable assessment of dose. In general,
absorbed dose is calculated as an average for the mass of a whole organ or tissue but, in a few

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cases, account is taken of the location of target cells for the induction of stochastic effects, assumed
to be the stem cell population. Such considerations are important when calculating doses fromradionuclides with short-range emissions of, for example, alpha particles and low energy beta
particles. Also important in such cases are considerations of radiation quality and the relative
effectiveness of radiations in causing health effects. Further work is required to ensure the reliabilityof dose assessments, including considerations of localised doses within tissues in relation to target
cells, radiation quality and microdosimetry.
Dosimetry and protection methods in medicine
Improved radiological protection in medicine and other applications requires a better understandingof dosimetry and methods of protection of patients, staff and the public. Assessment of lens of theeye, skin, and extremity doses and methods of protection is necessary to improve occupational
protection in interventional and nuclear medicine procedures. Similarly, lens of the eye, skin andorgan dose evaluation must be better understood to improve protection for patients who undergo CT
and high-dose interventional procedures. Dosimetric data are needed to help in the assessment ofnon-cancer effects (such as cardiovascular and cerebrovascular) in radiotherapy and high-dose
imaging procedures. Additional methods need to be developed, on a continuing basis, to reduce
patient dose while maintaining diagnostic information.
Ethical and social dimensions of the system of radiological protection
In the consideration of the development of an integrated protection system for humans and theenvironment, further analysis and case studies will be required to evaluate suitable approaches andmethodology. It is also important that ethical and social values are appropriately applied incircumstances of occupational, public, environmental, and medical exposures, to achieve
acceptable and sustainable decisions. Tolerability and acceptability of radiation exposures dependsupon the situation and circumstances of exposure. Further work is required to elaborate andincrease the practical utility of guidance provided to support these judgements, particularly inrelation to existing and emergency situations, developing approaches to the determination of what
may be reasonable levels of exposure, balancing potential benefits and inferred risks.
Mechanisms for interaction with stakeholders
Practical implementation of decision making following the principles of justification and optimisationof protection relies on the development of mechanisms for involving stakeholders. Further research,based on the analysis of successful experience, is needed to identify approaches to engage those
directly impacted more effectively. This is particularly relevant for existing and emergency exposure
situations.

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