International Commission on Radiological Protection

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The International Commission on Radiological Protection (ICRP) is an independent, international non-governmental organisation providing recommendations and guidance on radiation protection.

It was founded in 1928 by at the second International Congress of Radiology in Stockholm, Sweden (later these were organized by the International Society of Radiology (ISR)) and was then called the International X-ray and Radium Protection Committee (IXRPC).[1]

In 1950 it was restructured to better take account of uses of radiation outside the medical area, and given its present name.

The ICRP is a sister organisation to the International Commission on Radiation Units and Measurements (ICRU). In general terms ICRU defines the units, and ICRP recommends, develops and maintains the International System of Radiological Protection which uses these units.

Operation[edit]

International policy relationships in radiological protection

The ICRP is a not-for-profit organisation registered as a charity in the United Kingdom and currently has its scientific secretariat in Ottawa, Canada.

It is an independent, international organisation with more than two hundred volunteer members from approximately thirty countries across six continents, who represent the world's leading scientists and policy makers in the field of radiological protection.

The International System of Radiological Protection has been developed by ICRP based on (i) the current understanding of the science of radiation exposures and effects and (ii) value judgements. These value judgements take into account societal expectations, ethics, and experience gained in application of the system.

The work of the Commission centres on the operation of five main committees:

Committee 1 Radiation effects Committee - - the risk of induction of cancer and heritable disease (stochastic effects) together with the underlying mechanisms of radiation action; also, the risks,severity, and mechanisms of induction of tissue/organ damage and developmental defects (deterministic effects).

Committee 2 Doses from radiation exposure - development of dose coefficients for the assessment of internal and external radiation exposure, development of reference biokinetic and dosimetric models, and reference data for workers and members of the public.

Committee 3 Protection in medicine - concerned with protection of persons and unborn children when ionising radiation is used for medical diagnosis, therapy, or for biomedical research; also, assessment of the medical consequences of accidental exposures.

Committee 4 Application of the Commission’s recommendations - concerned with providing advice on the application of the recommended system of protection in all its facets for occupational and public exposure. It also acts as the major point of contact with other international organisations and professional societies concerned with protection against ionising radiation.

Committee 5 Protection of the environment - concerned with radiological protection of the environment. It aims to ensure that the development and application of approaches to environmental protection are compatible with those for radiological protection of man, and with those for protection of the environment from other potential hazards.[2]

Supporting these committees are task groups and working parties.

The ICRP's key output is the production of regular publications disseminating information and recommendations through the "Annals of the ICRP". A full list of the publications can be seen here [1]

History[edit]

Organisational[edit]

Taking an X-ray image with early Crookes tube apparatus in 1896. The Crookes tube is visible in the centre. The standing man is viewing his hand with a fluoroscope screen. No precautions against radiation exposure are being taken; its hazards were not known at the time.

Only a year after Rontgen’s discovery of X-rays, the American engineer Wolfram Fuchs (1896) gave what is probably the first protection advice, but many early users of X-rays were initially unaware of the hazards and protection was rudimentary or non-existent. It was not until 1925 that the establishment of international protection standards was discussed at the first International Congress of Radiology (ICR).

The second ICR was held in Stockholm in 1928 and ICRU proposed the adoption of the rontgen unit; and the ‘International X-ray and Radium Protection Committee’ (IXRPC) was formed. Rolf Sievert was named Chairman, but a driving force was George Kaye of the British National Physical Laboratory.

Rolf Maximilian Sievert

The committee met for just a day at each of the ICR meetings in Paris in 1931, Zurich in 1934, and Chicago in 1937. At the 1934 meeting in Zurich, the Commission was faced with undue membership interference. The hosts insisted on having four Swiss participants (out of a total of 11 members), and the German authorities replaced the Jewish German member with another of their choice. In response to this, the Commission decided on new rules in order to establish full control over its future membership.

The first post-war ICR convened in London in 1950, and only two IXRPC members had survived the war; Lauriston Taylor and Rolf Sievert. Taylor was invited to revive and revise the Commission, and the Commission was now given its present name: the International Commission on Radiological Protection (ICRP). Sievert remained an active member, Sir Ernest Rock Carling (UK) was appointed as Chairman, and Walter Binks (UK) took over as Scientific Secretary because of Taylor’s concurrent involvement with the sister organisation, ICRU.

At that meeting, six sub-committees were established on:

  • permissible dose for external radiation
  • permissible dose for internal radiation
  • protection against X rays generated at potentials up to 2 million volts
  • protection against X rays above 2 million volts, and beta rays and gamma rays
  • protection against heavy particles, including neutrons and protons
  • disposal of radioactive wastes and handling of radioisotopes

The next meeting was in 1956 in Geneva. This was the first time that a formal meeting of the Commission took place independently of the ICR. At this meeting, ICRP became formally affiliated with the World Health Organization (WHO) as a ‘participating non-governmental organisation’.

In 1959, a formal relationship was established with the International Atomic Energy Agency (IAEA), and subsequently with UNSCEAR, the International Labour Office (ILO), the Food and Agriculture Organization (FAO), the International Organization for Standardization (ISO), and UNESCO.

At the meeting in Stockholm in May 1962, the Commission also decided to reorganise the committee system in order to improve productivity and four committees were created:

  • C1: Radiation effects;
  • C2: Internal exposure;
  • C3: External exposure;
  • C4: Application of recommendations

After many assessments of committee roles within an environment of increasing workloads and changes in societal emphasis, by 2008 the committee structure had become:

  • Committee 1 - Radiation effects Committee
  • Committee 2 - Doses from radiation exposure
  • Committee 3 - Protection in medicine
  • Committee 4 - Application of the Commission’s recommendations
  • Committee 5 - Protection of the environment [2]

Evolution of Recommendations[edit]

The key output of the ICRP and its historic predecessor has been the issuing of recommendations in the form of reports and publications. The contents are made available for adoption by national regulatory bodies to the extent that they wish.

Early recommendations were general guides on exposure and thereby dose limits, and it was not until the nuclear era that a greater degree of sophistication was required.

In the "1951 Recommendations" the Commission recommended a maximum permissible dose of 0.5 rontgen in any 1 week in the case of whole-body exposure to X and gamma radiation at the surface, and 1.5 rontgen in any 1 week in the case of exposure of hands and forearms. Maximum permissible body burdens were given for 11 nuclides. At this time it was first stated that the purpose of radiological protection was that of avoiding deterministic effects from occupational exposures, and the principle of radiological protection was to keep individuals below the relevant thresholds.

A first recommendation on restrictions of exposures of members of the general public appeared in the Commission’s part of the 1954 Recommendations. It was also stated that ‘since no radiation level higher than the natural background can be regarded as absolutely ‘‘safe’’, the problem is to choose a practical level that, in the light of present knowledge, involves a negligible risk’. However, the Commission had not rejected the possibility of a threshold for stochastic effects. At this time the rad and rem were introduced for absorbed dose and RBE-weighted dose respectively.

At its 1956 meeting the concept of a controlled area and radiation safety officer were introduced, and the first specific advice was given for pregnant women.

In 1957, there was pressure on ICRP from both the World Health Organisation and UNSCEAR to reveal all of the decisions from its 1956 meeting in Geneva. The final document, the Commission’s 1958 Recommendations was the first ICRP report published by Pergamon Press. The 1958 Recommendations are usually referred to as ‘Publication 1’.

The significance of stochastic effects began to influence the Commission’s policy and a new set of recommendations was published as Publication 9 in 1966. However, during development its editors became concerned about the many different opinions on the risk of stochastic effects. The Commission therefore asked a working group to consider these, and their report, Publication 8 (1966), for the first time for the ICRP summarised the current knowledge about radiation risks, both somatic and genetic. Publication 9 then followed, and substantially changed radiation protection emphasis by moving from deterministic to stochastic effects.

In 1977 Publication 26 set out the new system of dose limitation and introduced the three principles of protection:

(a) no practice shall be adopted unless its introduction produces a positive net benefit

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

(c) the doses to individuals shall not exceed the limits recommended for the appropriate circumstances by the Commission

These principles have since become known as justification, optimisation (as low as reasonably achievable), and the application of dose limits. The optimisation principle was introduced because of the need to find some way of balancing costs and benefits of the introduction of a radiation source involving ionising radiation or radionuclides.

The 1977 Recommendations were very concerned with the ethical basis of how to decide what is reasonably achievable in dose reduction. The principle of justification aims to do more good than harm, and that of optimisation aims to maximise the margin of good over harm for society as a whole. They therefore satisfy the Utilitarian ethical principle proposed primarily by Jeremy Bentham and John Stuart Mill. Utilitarians judge actions by their overall consequences, usually by comparing, in monetary terms, the relevant benefits obtained by a particular protective measure with the net cost of introducing that measure.

On the other hand, the principle of applying dose limits aims to protect the rights of the individual not to be exposed to an excessive level of harm, even if this could cause great problems for society at large. This principle therefore satisfies the Deontological principle of ethics, proposed primarily by Immanuel Kant.

Consequently the concept of the "collective dose" was introduced to facilitate Cost–benefit analysis and to restrict the uncontrolled build-up of exposure to long-lived radio nuclides in the environment. With the global expansion of nuclear reactors and reprocessing it was feared global doses could again reach the levels seen from atmospheric testing of nuclear weapons. So, by 1977, the establishment of dose limits was secondary to the establishment of cost–benefit analysis and use of collective dose.

During the 1980s, there were re-evaluations of the survivors of the atomic bombing at Hiroshima and Nagasaki, partly due to revisions in the dosimetry. The risks of exposure were claimed to be higher than those used by ICRP, and pressures began to appear for a reduction in dose limits.

By 1989, the Commission had itself revised upwards its estimates of the risks of carcinogenesis from exposure to ionising radiation. The following year, it adopted its 1990 Recommendations (ICRP, 1991) for a ‘system of radiological protection’. The principles of protection recommended by the Commission were still based on the general principles given in Publication 26. However there were important additions which weakened the link to cost benefit analysis and collective dose, and strengthened the protection of the individual, which reflected changes in societal values:

(a) No practice involving exposures to radiation should be adopted unless it produces sufficient benefit to the exposed individuals or to society to offset the radiation detriment it causes. (The justification of a practice)

(b) In relation to any particular source within a practice, the magnitude of individual doses, the number of people exposed, and the likelihood of incurring exposures where these are not certain to be received should all be kept as low as reasonably achievable, economic and social factors being taken into account. This procedure should be constrained by restrictions on the doses to individuals (dose constraints), or on the risks to individuals in the case of potential exposures (risk constraints) so as to limit the inequity likely to result from the inherent economic and social judgements. (The optimisation of protection)

(c) The exposure of individuals resulting from the combination of all the relevant practices should be subject to dose limits, or to some control of risk in the case of potential exposures. These are aimed at ensuring that no individual is exposed to radiation risks that are judged to be unacceptable from these practices in any normal circumstances.

In the 21st Century, the latest overall recommendations on an international system of radiological protection appeared. ICRP Publication 103(2007), after two phases of international public consultation, has resulted in more continuity than change. Some recommendations remain because they work and are clear, others have been updated because understanding has evolved, some items have been added because there has been a void, and some concepts are better explained because more guidance is needed.[3]

Radiation quantities[edit]

External dose quantities used in radiation protection and dosimetry based on ICRU 57, jointly developed with the ICRP

In collaboration with the ICRU, the commission has assisted in defining the use of many of the dose quantities in the accompanying diagram.

The table below shows the number of different units for various quantities and is indicative of changes of thinking in world metrology, especially the movement from cgs to SI units.[4]

Quantity Name Symbol Unit Year System
Exposure (X) röntgen R esu / 0.001293 g of air 1928 non-SI
Absorbed dose (D) erg•g−1 1950 non-SI
rad rad 100 erg•g−1 1953 non-SI
gray Gy J•kg−1 1974 SI
Activity (A) curie Ci 3.7 × 1010 s−1 1953 non-SI
becquerel Bq s−1 1974 SI
Dose equivalent (H) röntgen equivalent man rem 100 erg•g−1 1971 non-SI
sievert Sv J•kg−1 1977 SI
Fluence (Φ) (reciprocal area) cm−2 or m−2 1962 SI (m−2)

Although the United States Nuclear Regulatory Commission permits the use of the units curie, rad, and rem alongside SI units,[5] the European Union European units of measurement directives required that their use for "public health ... purposes" be phased out by 31 December 1985.[6]

See also[edit]

External links[edit]

References[edit]

  1. ^ Clarke, R.H.; J. Valentin (2009). "The History of ICRP and the Evolution of its Policies". Annals of the ICRP. ICRP Publication 109 39 (1): pp. 75–110. doi:10.1016/j.icrp.2009.07.009. Retrieved 12 May 2012. 
  2. ^ a b Abridged from Clarke, R.H.; J. Valentin (2009). "The History of ICRP and the Evolution of its Policies". Annals of the ICRP. ICRP Publication 109 39 (1): pp. 75–110. doi:10.1016/j.icrp.2009.07.009. Retrieved 12 May 2012. 
  3. ^ Abridged from: Clarke, R.H.; J. Valentin (2009). "The History of ICRP and the Evolution of its Policies". Annals of the ICRP. ICRP Publication 109 39 (1): pp. 75–110. doi:10.1016/j.icrp.2009.07.009. Retrieved 12 May 2012. 
  4. ^ "International Commission on Radiation Units and Measurements". International Commission on Radiation Units and Measurements. 14 March 2012. Retrieved 1 June 2012. 
  5. ^ 10 CFR 20.1004. US Nuclear Regulatory Commission. 2009. 
  6. ^ The Council of the European Communities (1979-12-21). "Council Directive 80/181/EEC of 20 December 1979 on the approximation of the laws of the Member States relating to Unit of measurement and on the repeal of Directive 71/354/EEC". Retrieved 19 May 2012.