International Commission on Radiological Protection

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INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION

The International Commission on Radiological Protection (ICRP) is a non-governmental organization that issues recommendations for radiation protection from ionizing radiation. With Wilhelm Roentgen's 1895 discovery of x-rays that, unlike the rays of visible light or of radio transmissions, tend to break down or ionize atomic structures, a new phenomenon was added to human experience. As this phenomenon became increasingly utilized especially in medical work, its dangers were likewise progressively recognized. The recommendations issued by the ICRP are used by many national and international radiation protection agencies to deal with such dangers and have a profound influence on radiation protection all over the world.

History and Activities

The ICRP was established in 1928 by the Second International Congress of Radiology, in order to address health and safety issues concerning radiation used for medical purposes. Until 1950 it was called the International X-ray and Radium Protection Committee. The new name reflected a widened scope to include all aspects of protection against ionizing radiation.

The ICRP functions as an advisory body to national and international agencies in the field of radiation protection. According to its constitution, the ICRP shall provide recommendations and guidance on all aspects of radiation protection and consider the fundamental principles and quantitative bases for radiation protection, while leaving to national bodies the responsibility of formulating specific advice, codes of practice, or regulations best suited for each country. No country or international organization is obliged to follow the recommendations of the ICRP. International organizations that use the ICRP recommendations include the International Atomic Energy Agency (IAEA), the World Health Organization (WHO), the International Labor Organization (ILO), and the Nuclear Energy Agency of the Organization for Economic Cooperation and Development (OECD).

The ICRP is registered as an independent charity in the United Kingdom and is mainly financed by voluntary contributions from international and national bodies with an interest in radiation protection. The organization consists of the Main Commission and five standing committees. The Main Commission has twelve members and a chair. The Main Commission elects itself, and three to five members of the Main Commission are replaced after each four-year period. According to the constitution of the ICRP, members shall be chosen on the basis of their recognized activity within professional fields of relevance to radiation protection. The standing committees are chaired by members of the Main Commission and consist of fifteen to twenty experts (mostly biologists, physicians, and physicists) appointed by the Main Commission. The committees are Committee 1 (radiation effects), Committee 2 (doses from radiation exposure), Committee 3 (protection in medicine), Committee 4 (application of ICRP recommendations), and Committee 5 (protection of non-human organisms). In addition to these committees, the ICRP also appoints task groups comprised of radiation protection experts outside the ICRP. At any given time, about 100 scientists are involved in ICRP work.

The ICRP publishes reports containing guidelines on a variety of topics related to radiation protection. Examples of such reports include: "Radiological Protection in Biomedical Research" ICRP Publication 62, 1993), "Radiological Protection Policy for the Disposal of Radioactive Waste" (ICRP Publication 77, 1998) and "Principles for Intervention for the Protection of the Public in a Radiological Emergency" (ICRP Publication 63, 1993). The ICRP Recommendations are special reports containing fundamental principles for radiation protection advocated by the ICRP. The main objective of these recommendations is "to provide an appropriate standard of protection for man without unduly limiting the beneficial practices giving rise to radiation exposure" (ICRP 1991, p. 3). The ICRP recognizes that this objective cannot be achieved solely on the basis of scientific data, but must also include value judgments and ethical considerations.

ICRP Recommendations

The basic principles of the ICRP recommendations for radiation protection have evolved considerably over time. In 1928 the first ICRP report on health effects concerned primarily damage to the skin and the destruction of blood forming tissues, that is, injuries caused by massive cell death following exposure to high levels of ionizing radiation. There is a threshold dose for these effects, which means that they occur only when sufficient numbers of cells are destroyed. The first ICRP report aimed to prevent these kinds of effects by providing recommendations on working practices and guidelines for use, but due to problems of defining a relevant dose measure, a dose limit was not included. In a subsequent 1934 report, however, the ICRP did recommend a dose limit, called a tolerable dose, which added a margin of safety to the threshold dose.

The system of tolerable doses was retained into the 1950s when a new appreciation of the risks from ionizing radiation altered the foundation for radiation protection. Previously it had been assumed that in the absence of no immediate negative health effects below a threshold level, there were also no long-term effects. But evidence had accumulated that ionizing radiation could also cause cancer and hereditary defects. Such longer-term results are called stochastic effects and are caused by modification, rather than the destruction, of cells, and occur with a certain probability, which was taken to be proportional to the dose. It was argued likely that no threshold existed for these kinds of effects. This meant that every dose implied a risk—that there was no completely safe level for ionizing radiation. Ever since, radiation protection has had to deal with the implications.

In 1950 the ICRP recognized the potential for cancer and hereditary effects from ionizing radiation, and recommended new, lower dose limits, called maximum permissible doses. But if there is no wholly safe dose, the concept of permissible dose becomes problematic. What is permissible or not? The ICRP based its judgments on a comparison with other hazards in life. The ICRP also recommended that exposure to ionizing radiation should be reduced to the lowest possible level, meaning that doses should be kept as low as practicable and that any unnecessary exposure should be avoided. Eventually this evolved into the principle that doses should be kept as low as reasonably achievable (ALARA), which became known as the ALARA-principle.

The next major step was taken in 1977 when ICRP introduced a protection system consisting of three BASIC principles. No practice involving exposure to radiation should be adopted unless it produces a positive net benefit (the justification principle). All exposures should be kept as low as reasonably achievable, economic and social factors being taken into account (the optimization or ALARA-principle). Doses to individuals should not exceed specified dose-limits (the dose-limitation principle). The emphasis was no longer on permissible doses, but on the requirement that doses should be kept as low as reasonably achievable (optimization). Mere compliance with dose limits was not sufficient—exposure must also be justified and optimized. The ICRP recommended that the optimization procedure should operate on the collective dose, defined as the product of the number of exposed individuals and their average dose.

Subsequent recommendations were adopted in 1990 (ICRP 1991) retaining the overall structure from the recommendations of 1977. The emphasis was still on the optimization principle, but in order to limit inequities that could follow from application of its three principles, the ICRP introduced a restriction on the optimization process. The reason for this was to prevent situations where the optimization principle would advocate a protection alternative (that is, the lowest collective dose) where, although all individuals would be below the dose limits, a few individuals would also be exposed to much higher doses than the rest of the exposed population. This is obviously a problem if there is no threshold for the risk from exposure to ionizing radiation. To avoid this the ICRP recommended additional individual limits, usually much lower than the old dose limits, called dose constraints. The concept of dose limits was retained but the definition was changed in order to define a boundary above which individual risk was considered unacceptable. Another difference was that the dose constraints were source-related, while the dose limits included exposure from all relevant sources.

The recommendations from the ICRP have been updated at intervals of ten to fifteen years, and the ICRP plans to deliver the next general recommendations in 2005. The proposed recommendations (ICRP 2003) involve further emphasis on the concept of dose constraints. The new system is based on the idea that constraints should be applied for each individual. The starting point for selecting the level of these constraints should, according to the proposal, be the concern that can reasonably be felt about the annual dose from natural sources. After applying the dose constraints there will still be a requirement to reduce doses even further. The proposal also suggests less emphasis than previously on the application of the collective dose and that individual doses below a fraction of the average annual dose from natural sources should be excluded from the system of protection.

The proposal for the new recommendations has been publicly discussed by the ICRP since 1999. Critics claim that the 1990 recommendations work well and that no substantial change to the basic system is needed. It has also been argued that the previous application of the collective dose ought to be retained, and that the introduction of a general exclusion level for very small doses has not been satisfactory justified.

PER WIKMAN

SEE ALSO Radiation;Regulatory Toxicology.

BIBLIOGRAPHY

International Commission on Radiological Protection. (1991). 1990 Recommendations of the International Commission on Radiological Protection–ICRP Publication 60. Oxford: Pergamon Press. Contains the basic principles of the ICRP 1990 recommendations, which have had a profound influence on radiation protection internationally.

International Commission on Radiological Protection. (1998). International Commission on Radiological Protection: History, Policies, Procedures. Oxford: Elsevier Science. A comprehensive work on the history and operations of the ICRP.

International Commission on Radiological Protection. (2003). "The Evolution of the System of Radiological Protection: The Justification for the New ICRP Recommendations." Journal of Radiological Protection 23: 129–142. Describes the proposed ICRP 2005 recommendations.

Mould, Richard F. (1993). A Century of X-rays and Radioactivity in Medicine: with Emphasis on Photographic Records of the Early Years. Bristol, PA: Institute of Physics Publishing. A thorough description of the history and development of radiation protection.

Sowby, David, and Jack Valentin. (2003). "Forty Years On: How Radiological Protection Has Evolved Internationally." Journal of Radiological Protection 23: 151–157. Gives an overview of international organizations in radiation protection and describes the development of the ICRP recommendations since 1950.

Taylor, Lauriston S. (1979). Organization for Radiation Protection: The Operations of the ICRP and NCRP 1928–1974. Springfield, VA: National Technical Information Service. Provides a detailed account of the early relations between the ICRP and the U.S. organization NCRP (National Council on Radiation Protection and Measurements).

Wikman, Per. (2004). "Trivial Risks and the New Radiation Protection System." Journal of Radiological Protection 24: 3–11. Contains a review of the proposed ICRP 2005 recommendations from an ethical and philosophical perspective.