Quotes from Publications on the System of Radiological Protection

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Module One: The System of Radiological Protection

ICRP Publication 103 paragraph 44

The Commission’s system of radiological protection applies to all radiation exposures from any source, regardless of its size and origin. The term radiation is used to mean ionising radiation. The Commission has been using the term radiation exposure (or exposure in short) in a generic sense to mean the process of being exposed to radiation or radionuclides, the significance of exposure being determined by the resulting radiation dose ... The term ‘source’ is used to indicate the cause of an exposure, and not necessarily a physical source of radiation ...

ICRP Publication 103 paragraph 45

The Commission has aimed to make its Recommendations applicable as widely and as consistently as possible. In particular, the Commission’s Recommendations cover exposures to both natural and man-made sources. The Recommendations can apply in their entirety only to situations in which either the source of exposure or the pathways leading to the doses received by individuals can be controlled by some reasonable means ...

ICRP Publication 103 paragraph 27

... The Recommendations are based on scientific knowledge and on expert judgement. Scientific data, such as those concerning health risks attributable to radiation exposure, are a necessary prerequisite, but societal and economic aspects of protection have also to be considered. All of those concerned with radiological protection have to make value judgements about the relative importance of different kinds of risk and about the balancing of risks and benefits. In this, radiological protection is not different from other fields concerned with the control of hazards ...

Module One: Objectives of Radiological Protection

ICRP Publication 103 paragraph 29

The Commission’s system of radiological protection aims primarily to protect human health. Its health objectives are relatively straightforward: to manage and control exposures to ionising radiation so that deterministic effects are prevented, and the risks of stochastic effects are reduced to the extent reasonably achievable.

Types of effects: ICRP Publication 103 paragraph 5

Most adverse health effects of radiation exposure may be grouped in two general categories:

• deterministic effects (harmful tissue reactions) due in large part to the killing/ malfunction of cells following high doses; and
• stochastic effects, i.e., cancer and heritable effects involving either cancer development in exposed individuals owing to mutation of somatic cells or heritable disease in their offspring owing to mutation of reproductive (germ) cells.

ICRP Publication 103 paragraph 30

... The Commission’s aim is now that of preventing or reducing the frequency of deleterious radiation effects to a level where they would have a negligible impact on the maintenance of biological diversity, the conservation of species, or the health and status of natural habitats, communities and ecosystems. In achieving this aim, however, the Commission recognises that exposure to radiation is but one factor to consider, and is often likely to be a minor one ...

ICRP Publication 103 paragraphs 7 and 8

... The biological endpoints of most relevance are therefore those that could lead to changes in population size or structure. Nevertheless, radiation affects individuals, and most available data on the effects of radiation relate to individuals rather than populations.

The biological endpoints of interest to individuals that could have a consequence at a population level are those of:

• early mortality (leading to changes in age distribution, death rate, and population density);
• some forms of morbidity (that could reduce ‘fitness’ of the individuals, making it more difficult for them to survive in a natural environment);
• impairment of reproductive capacity by either reduced fertility or fecundity (affecting birth rate, age distribution, number, and density); and
• induction of chromosomal damage.

Module One: Fundamental Principles of Radiological Protection

ICRP Publication 103 paragraph 203

The principle of justification: Any decision that alters the radiation exposure situation should do more good than harm. This means that, by introducing a new radiation source, by reducing existing exposure, or by reducing the risk of potential exposure, one should achieve sufficient individual or societal benefit to offset the detriment it causes.

ICRP Publication 103 paragraph 205

The Commission recommends that, when activities involving an increased or decreased level of radiation exposure, or a risk of potential exposure, are being considered, the expected change in radiation detriment should be explicitly included in the decision-making process. The consequences to be considered are not confined to those associated with the radiation – they include other risks and the costs and benefits of the activity. Sometimes, the radiation detriment will be a small part of the total. Justification thus goes far beyond the scope of radiological protection. It is for these reasons that the Commission only recommends that justification require that the net benefit be positive. To search for the best of all the available alternatives is a task beyond the responsibility of radiological protection authorities.

ICRP Publication 103 paragraph 203

The principle of optimisation of protection: The likelihood of incurring exposures, the number of people exposed, and the magnitude of their individual doses should all be kept as low as reasonably achievable, taking into account economic and societal factors. This means that the level of protection should be the best under the prevailing circumstances, maximising the margin of benefit over harm. In order to avoid severely inequitable outcomes of this optimisation procedure, there should be restrictions on the doses or risks to individuals from a particular source (dose or risk constraints and reference levels).

ICRP Publication 103 paragraph 211

The process of optimisation of protection is intended for application to those situations that have been deemed to be justified. The principle of optimisation of protection, with restriction on the magnitude of individual dose or risk, is central to the system of protection and applies to all three exposure situations: planned exposure situations, emergency exposure situations, and existing exposure situations.

ICRP Publication 103 paragraph 212

The principle of optimisation is defined by the Commission as the source related process to keep the likelihood of incurring exposures (where these are not certain to be received), the number of people exposed, and the magnitude of individual doses as low as reasonably achievable, taking economic and societal factors into account.

ICRP Publication 103 paragraph 203

The principle of application of dose limits: The total dose to any individual from regulated sources in planned exposure situations other than medical exposure of patients should not exceed the appropriate limits recommended by the Commission.

ICRP Publication 103 paragraph 204

Regulatory dose limits are determined by the regulatory authority, taking account of international recommendations, and apply to workers and to members of the public in planned exposure situations.

ICRP Publication 103 paragraph 243

Dose limits apply only in planned exposure situations but not to medical exposures of patients ... Within a category of exposure, occupational or public, dose limits apply to the sum of exposures from sources related to practices that are already justified.

Module Two: Exposure Categories and Situations

Occupational Exposures: ICRP Publication 103 paragraph 178

Occupational exposure is defined by the Commission as all radiation exposure of workers incurred as a result of their work. The Commission has noted the conventional definition of occupational exposure to any hazardous agent as including all exposures at work, regardless of their source. However, because of the ubiquity of radiation, the direct application of this definition to radiation would mean that all workers should be subject to a regime of radiological protection. The Commission therefore limits its use of ‘occupational exposures’ to radiation exposures incurred at work as a result of situations that can reasonably be regarded as being the responsibility of the operating management...

Medical Exposures: ICRP Publication 103 paragraph 322

Medical exposures are predominantly delivered to individuals (patients) undergoing diagnostic examinations, interventional procedures, or radiation therapy. Other individuals caring for and comforting patients are also exposed to radiation. These individuals include parents and others, normally family or close friends, who hold children during diagnostic procedures or may come close to patients following the administration of radiopharmaceuticals or during brachytherapy. Exposure to members of the general public from released patients also occurs, but this exposure is almost always very small. In addition, volunteers in biomedical research often undergo medical procedures involving radiation exposure that are similar to procedures performed on patients. Medical exposure refers to all these types of exposures ...

• The exposure of individuals for diagnostic, interventional, and therapeutic purposes, including exposure of the embryo/fetus or infant during medical exposure of patients who are pregnant or breast-feeding;
• Exposures (other than occupational) incurred knowingly and willingly by individuals such as family and close friends helping either in hospital or at home in the support and comfort of patients undergoing diagnosis or treatment;
• Exposures incurred by volunteers as part of a programme of biomedical research that provides no direct benefit to the volunteers

Public Exposures: ICRP Publication 103 paragraph 180

Public exposure encompasses all exposures of the public other than occupational exposures and medical exposures ... The component of public exposure due to natural sources is by far the largest, but this provides no justification for reducing the attention paid to smaller, but more readily controllable, exposures to man-made sources. Exposures of the embryo and fetus of pregnant workers are considered and regulated as public exposures.

Planned Exposure Situations: ICRP Publication 103 paragraph 253

Planned exposure situations are where radiological protection can be planned in advance, before exposures occur, and where the magnitude and extent of the exposures can be reasonably predicted. The term encompasses sources and situations that have been appropriately managed within the Commission’s previous recommendations for practices. In introducing a planned exposure situation all aspects relevant to radiological protection should be considered. These aspects will include, as appropriate, design, construction, operation, decommissioning, waste management, and rehabilitation of previously occupied land and installations, and will take account of potential exposures as well as normal exposures. Planned exposure situations also include the medical exposure of patients, including their comforters and carers. The principles of protection for planned situations also apply to planned work in connection with existing and emergency exposure situations, once the emergency has been brought under control ...

Existing Exposure Situations: ICRP Publication 103 paragraph 284

Existing exposure situations are those that already exist when a decision on control has to be taken. There are many types of existing exposure situations that may cause exposures high enough to warrant radiological protective actions, or at least their consideration. Radon in dwellings or the workplace, and naturally occurring radioactive material (NORM) are well-known examples. It may also be necessary to take radiological protection decisions concerning existing man-made exposure situations such as residues in the environment resulting from radiological emissions from operations that were not conducted within the Commission’s system of protection, or contaminated land resulting from an accident or a radiological event. There are also existing exposure situations for which it will be obvious that action to reduce exposures is not warranted. The decision as to what components of existing exposure are not amenable to control requires a judgement by the regulatory authority that will depend on the controllability of the source or exposure, and also on the prevailing economic, societal, and cultural circumstances ...

Emergency Exposure Situations: ICRP Publication 103 paragraph 180

Even if all reasonable steps have been taken during the design stage to reduce the probability and consequences of potential exposures, such exposures may need to be considered in relation to emergency preparedness and response. Emergency exposure situations are unexpected situations that may require urgent protective actions, and perhaps also longer-term protective actions, to be implemented. Exposure of members of the public or of workers, as well as environmental contamination can occur in these situations. Exposures can be complex in the sense that they may result from several independent pathways, perhaps acting simultaneously. Furthermore, radiological hazards may be accompanied by other hazards (chemical, physical, etc.). Response actions should be planned because potential emergency exposure situations can be assessed in advance, to a greater or lesser accuracy depending upon the type of installation or situation being considered. However, because actual emergency exposure situations are inherently unpredictable, the exact nature of necessary protection measures cannot be known in advance but must flexibly evolve to meet actual circumstances ...

Module Two: Absorbed, Equivalent, and Effective Dose

ICRP Publication 103 paragraphs 107, 108, and 109

In radiation biology, clinical radiology, and radiological protection the absorbed dose, D, is the basic physical dose quantity, and it is used for all types of ionising radiation and any irradiation geometry. It is defined as ... the mean energy imparted to matter ... [divided by the mass]

The SI unit of absorbed dose is J kg^-1 and its special name is gray (Gy) ... While it is defined at any point in matter, its value is obtained as an average over a mass ... Absorbed dose is a measurable quantity and primary standards exist to determine its value.

When using the quantity absorbed dose in practical protection applications, doses are averaged over tissue volumes. It is assumed that, for low doses, the mean value of absorbed dose averaged over a specific organ or tissue can be correlated with radiation detriment for stochastic effects in that tissue with an accuracy sufficient for the purposes of radiological protection.

ICRP Publication 103 paragraph 112

The protection quantities are used to specify exposure limits to ensure that the occurrence of stochastic health effects is kept below unacceptable levels and that tissue reactions are avoided. The definition of the protection quantities is based on the average absorbed dose, D_T,R in the volume of a specified organ or tissue T (see Table 3), due to radiation of type R (see Table 2). The radiation R is given by the type and energy of radiation either incident on the body or emitted by radionuclides residing within it. The protection quantity equivalent dose in an organ or tissue, H_T, is then defined by

where wR is the radiation weighting factor for radiation R. The sum is performed over all types of radiations involved. The unit of equivalent dose is J kg^-1 and has the special name sievert (Sv).

ICRP Publication 103 Table 2

ICRP Publication 103 paragraph 101

... The development of ... effective dose has made a significant contribution to radiological protection as it has enabled doses to be summed from whole and partial body exposure from external radiation of various types and from intakes of radionuclides.

ICRP Publication 103 paragraph 125

The effective dose, E, ... is defined by a weighted sum of tissue equivalent doses as:

where w_T is the tissue weighting factor for tissue T and Σw_T = 1. The sum is performed over all organs and tissues of the human body considered to be sensitive to the induction of stochastic effects. These w_T values are chosen to represent the contributions of individual organs and tissues to overall radiation detriment from stochastic effects. The unit of effective dose is J kg^-1 with the special name sievert (Sv). The unit is the same for equivalent dose and effective dose ... Care must be taken to ensure that the quantity being used is clearly stated.

ICRP Publication 103 Table 3

Module Two: Dose limits

ICRP Publication 103 paragraph 243

Dose limits apply only in planned exposure situations but not to medical exposures of patients. ... dose limits ... recommended in Publication 60 ... continue to provide an appropriate level of protection. ... Within a category of exposure, occupational or public, dose limits apply to the sum of exposures from sources related to practices that are already justified ...

ICRP Publication 103 paragraph 247

Dose limits do not apply in emergency exposure situations where an informed, exposed individual is engaged in volunteered life-saving actions or is attempting to prevent a catastrophic situation. For informed volunteers undertaking urgent rescue operations, the normal dose restriction may be relaxed ...

ICRP Publication 103 paragraph 248

For informed individuals of the general public involved in caring and comforting patients released from a hospital following therapy with unsealed radionuclides, the normal dose restriction may be relaxed and such individuals should in general not be subject to the public dose limit ...

ICRP Publication 103 paragraph 186

... Once an employer has been notified of a pregnancy, additional protection of the embryo/fetus should be considered. The working conditions of a pregnant worker, after declaration of pregnancy, should be such as to ensure that the additional dose to the embryo/fetus would not exceed about 1 mSv during the remainder of the pregnancy ...