The evolution of the international system of radiological protection: food for thought from the Nuclear Energy Agency Committee on Radiation Protection and Public Health.

From its inception, the Nuclear Energy Agency (NEA), which is part of the broader Organisation for Economic Co-operation and Development, has contributed to the development of international radiological protection norms and standards. This continues today, in the form of studies and workshops to assist radiological protection policy makers, regulators and practitioners to develop concepts and approaches to help the international system of radiological protection, as recommended by the International Commission on Radiological Protection (ICRP), to evolve to better serve societal needs. The NEA's Committee on Radiation Protection and Public Health (CRPPH), in providing this support, has collaborated closely with the ICRP and strongly supports the current ICRP recommendation development process. In particular, active dialogue with a broad range of stakeholders is contributing to the evolution of concepts towards consensus on new ICRP recommendations. The CRPPH, as a body of ICRP recommendation practitioners, feels that the public, workers and the environment are well protected by the current radiological protection system, but agrees that a new consolidation and clarification of ICRP recommendations would be of value. The intent of the CRPPH in collaborating with ICRP is to develop a system of radiological protection that is simplified, more coherent, firmly based upon science and more clearly presented than the current system. This paper summarises the more detailed views of the CRPPH on the evolution of the system of radiological protection.     

Changes in international radiation protection standards

The International Commission on Radiological Protection, ICRP, is the only organization that has ever effectively set standards at the international level for protection from exposure to ionizing radiation. Thus, this paper deals primarily with the ICRP, its shortcomings, and changes that should be made in ICRP and its operation. © 1994 Wiley-Liss, Inc.     

The recommendations of the ICRP vis-à-vis the Fukushima Dai-ichi NPP accident aftermath

The International Commission on Radiological Protection (ICRP) created a Task Group (ICRP TG84) on the initial lessons learned from the nuclear accident at the Fukushima Dai-ichi NPPs vis-à-vis the ICRP system of radiological protection. The ICRP TG84 is expected to compile lessons learned related to the efforts carried out to protect people against radiation exposure during and after the emergency exposure situation caused by the accident and, in light of these lessons, to consider ad hoc recommendations to strengthen the ICRP system of radiological protection for dealing with this type of emergency exposure. The Chairman of ICRP TG84 presents in this paper his personal views on the main issues being considered by the group at the time of the Fukushima Expert Symposium. ICRP TG84 expects to finalize its work by the end of 2012.     

Control of low-level radiation exposure: what is the problem and how can it be solved?

The carcinogenic risks of exposure to low-level ionizing radiation used by ICRP have been challenged as being, at the same time, both too high and too low. This paper explains that the epidemiological evidence will always be limited at low doses, so that understanding the cellular mechanisms of carcinogenesis is increasingly important to assess the biological risks. An analysis is then given of the reasons why the challenges to ICRP, especially about the linear nonthreshold response model, have arisen. As a result of considering the issues, the Main Commission of ICRP is now consulting on a revised, simpler approach based on an individual oriented philosophy. This represents a potential shift by the Commission from the past emphasis on societal-oriented criteria. These proposals have been promulgated through IRPA, and an open literature publication was published in the Journal of Radiological Protection in June 1999. On the basis of comments received and the observations presented at the IRPA 10 Conference, the Commission will begin to develop the outline of the next recommendations. It is now more than 10 y since ICRP distributed, for comment, a draft of what was to become the publication of the 1990 recommendations. The Commission plans to develop its new recommendations on a time scale of the next 4 or 5 y. In this paper, many of the issues that will need to be addressed in the development of the recommendations will be identified. These issues will cover biological effects, dosimetric quantities, and the establishment of those levels of dose at which different protection requirements will be put into place. Concepts of exclusion and exemption will need to be clarified as well as the meaning of how to achieve what the proposal identifies as "as low as reasonably practicable." Finally, the Commission has decided to develop an environmental radiation protection philosophy that will need to be developed as part of the new recommendations.     

Regulatory perceptions of the future: a view from the United States

Herbert Parker, in his keynote address at the 1971 Health Physics Society Topical Symposium in Richland, WA, made an interesting comment which questioned whether the increasing number of radiation protection handbooks really contributed to solving the basic problems of radiation safety. He estimated that by the year 1991 there should be at least 1897 radiation protection handbooks. The U.S. regulator, charged with the responsibility of assuring the protection of the worker, the public and the environment, must face this myriad of expert reports and derive from them radiation protection norms for implementation. Like his European counterpart, the regulator derives requirements based on standards and recommendations of national and international scientific authorities, such as the International Commission on Radiological Protection (ICRP) and the National Council on Radiation Protection and Measurements (NCRP). In recent years, the reports from these scientific authorities recommend changes ranging from simple to complex. The fundamental philosophy of the standards has slowly evolved from a consideration of the risk to individual organs to the consideration of the "total" risk to the whole body. This philosophy now appears to be evolving from one that considers the risk associated with radiation in comparison with other safe industries to one that balances the risk from radiation with other occupational sources of risk. Nonetheless, if the recommendations of scientific authorities were the only driving force behind the U.S. regulations, the life of the regulator would be relatively easy. Recommendations must be balanced with legal-social-political issues and the resources needed to implement the recommendations. Consideration must also be given to the technical ability to implement changes; for example, the adequacy of measurement technology. This paper will present a summary point of view on possible issues confronting the U.S. regulator's plans for the future.     

Suggested reference values for regional blood volumes in humans

Estimates of regional blood volumes (BVs) in man are needed for the dosimetry of radionuclides that decay in the circulation to a significant extent. The tabulation of regional BVs in Publication No. 23 of the International Commission on Radiological Protection (ICRP Reference Man document) may be the best available for dosimetric applications but is not consistent with current information for some organs and does not address some important blood pools. The purpose of this paper is to suggest an improved set of reference values for regional BVs in adult humans. The total blood volume (TBV) is viewed as comprising 22 separate pools, including several pools not addressed in the ICRP Reference Man document. Values suggested here for brain, liver, skin, active marrow, inactive marrow, and bone differ by at least a factor of two from those given for ICRP Reference Man.     

Current activities of the international commission on radiological protection

The advice of the International Commission on Radiological Protection (ICRP) is aimed principally at the regulators and operators that have responsibility for establishing protection standards. ICRP's present recommendations were published in 1991. Since then, the Commission has published additional recommendations, and the system of protection has become increasingly complex. The Commission has decided to simplify its system and make it more coherent. In 2005, the Commission plans to adopt a new set of recommendations that should be seen as a consolidation of earlier recommendations. In the review of the current system of protection, many topics are being looked at and all committees are currently addressing issues of relevance for the revision. A proposal for the new recommendations on radiological protection will be discussed at the 11th International Radiation Protection Association conference in Madrid in 2004. When the Commission adopts the new recommendations in 2005, 15 y will have passed since the 1990 recommendations were adopted.     

Forty years on: how radiological protection has evolved internationally.

In the 40 years since the Society for Radiological Protection (SRP) was founded, the international scene has changed considerably. The United Nations bodies primarily involved, the United Nations Scientific Committee on the Effects of Atomic Radiation and the International Atomic Energy Agency, have evolved from fledgling organisations to indispensable major resources. A similar development characterises regional entities such as Euratom and the OECD Nuclear Energy Agency. The International Commission on Radiological Protection (ICRP), once interested in occupational health in the practice of medicine only, has shifted its emphasis towards protection of members of the public and of patients exposed to ionising radiations and is currently looking at protection of non-human species. The International Radiation Protection Association, the federation that is now the 'mother society' of the SRP, had not even been launched formally when the SRP started. At that time, non-ionising radiation was on nobody's mind, and the forerunner of today's International Commission on Non-Ionizing Radiation Protection (ICNIRP) was not formed until 1977. Basically, the developments during this period must be described as a great success story. Average occupational exposures to ionising radiation have decreased markedly, the number of accidents is small, almost all countries now regulate exposures roughly in line with ICRP and ICNIRP recommendations, and quite a large number of countries also have reasonable regulatory infrastructures. An area where problems appear to be on the increase, perhaps in part because of increasing awareness, concerns 'orphan sources' and lack of source security. This may indicate a need for closer attention to security outside the nuclear fuel cycle, e.g. in hospitals and non-nuclear industry.     

Contents of cesium, iodine, strontium, thorium, and uranium in selected human organs of adult asian population

Contents of cesium, iodine, strontium, thorium, and uranium in some selected human organs were estimated for adult Asian population using data obtained in four Asian countries: China, India, Philippines, and Republic of Korea, as part of a Coordinated Research Program of the International Atomic Energy Agency on "Ingestion and Organ contents of elements of importance in radiation protection." These countries together represent more than 40% of the world population. Highly sensitive analytical techniques were employed to measure cesium in skeletal muscle, iodine in thyroid, strontium in skeleton, thorium and uranium in skeleton, liver, kidneys, and lungs where, in comparison to other organs, these elements are present in higher concentrations. The organ contents for adult Asian population, when compared with the corresponding data proposed for Reference Man by International Commission on Radiological Protection (ICRP), showed about 40 times lower kidneys content and about 10 times lower skeleton content of uranium. The content of thorium in skeleton for Asian population was also half of the ICRP Reference Man value. Interestingly, organ contents for the other elements such as iodine in thyroid, cesium in skeletal muscle, and strontium in skeleton were comparable for Asian and the Caucasian population (represented by ICRP Reference Man). Organ contents for these elements were also calculated by applying the new ICRP models of these elements to their daily intakes. The comparison of the calculated and measured organ contents showed that despite uncertainties in the organ content values arising due to the inter-country variations in daily dietary intakes, the contents were within a factor of two to three. This observation is significant since human data both on organ contents and ingestion were obtained at environmental level of intakes. The study suggests that currently available ICRP models for these elements are quite realistic.     

A view from Europe: stability, consistency or pragmatism

The last few years of this decade look like a period of reappraisal of radiation protection standards. The revised risk estimates from Japan will be available, and the United Nations Scientific Committee on the Effects of Atomic Radiation will be publishing new reports on biological topics. The International Commission on Radiological Protection (ICRP) has started a review of its basic recommendations, and the new specification for dose equivalent in radiation fields of the International Commission on Radiation Units and Measurements (ICRU) will be coming into use. All this is occurring at a time when some countries are still trying to catch up with committed dose equivalent and the recently recommended change in the value of the quality factor for neutrons. In Europe, the problems of adapting to new ICRP recommendations are considerable. The European Community, including 12 states and nine languages, takes ICRP recommendations as a basis and develops council directives that are binding on member states, which have then to arrange for their own regulatory changes. Any substantial adjustments could take 5 y or more to work through the system. Clearly, the regulatory preference is for stability. Equally clearly, trade unions and public interest groups favor a rapid response to scientific developments (provided that the change is downward). Organizations such as the ICRP have to balance their desire for internal consistency and intellectual purity against the practical problems of their clients in adjusting to change. This paper indicates some of the changes that might be necessary over the next few years and how, given a pragmatic approach, they might be accommodated in Europe without too much regulatory confusion.     

Radiation protection--a look to the future: ICRP perceptions

The author was invited to talk about ICRP perceptions of a look to the future. Many questions will be addressed when the International Commission on Radiological Protection (ICRP) initiates a revision of its basic recommendations from 1977, which were published in ICRP Publication 26. This process will take several years, and in the meantime the author does not expect any major changes in the present policy of the commission. It is still too early to predict the commission's future policy but, to some extent, present trends might be extrapolated, as indicated in this discussion.     

Calculation of the estimated collective effective dose equivalent (SE) due to x-ray diagnostic examinations--estimate of the SE in Finland

The collective effective dose equivalent caused by diagnostic x-ray examinations in Finland has been estimated. The influence of how the remaining organs are selected, as specified by the International Commission on Radiological Protection (ICRP), on the effective dose equivalent, HE, has been studied. The doses to 23 different organs, including the six primary organs and 17 relevant remaining organs, were calculated. The HE was assessed by first choosing the five most exposed remaining organs according to the ICRP, and subsequently the 12 remaining organs. Depending on the type of examination, the difference in the respective effective dose equivalents was typically 20-40%. The estimated dose equivalent per capita is 0.7 mSv.     

Impact of the revision of 10CFR835 with regard to neutron field surveys

The compliance requirements for Department of Energy facilities are codified in Title 10 Code of Federal Regulations Part 835. The regulation was recently revised to adopt the 1990 Recommendations of the International Commission on Radiological Protection (ICRP). Although the impacts of this change include areas other than neutron dosimetry, the intent of this text is to outline the new regulation's effect on neutron instrument calibrations and field surveys. A significant change as a result of the adoption of the ICRP 60 recommendations is the change in the quality factor applied to operational quantities including the quantity used for area monitoring and instrument calibrations, notably the ambient dose equivalent, H*(d). Since the definitions of the operational quantities were not changed, the absorbed dose values for these quantities remain consistent with previous recommendations so the only adjustment necessary is to account for the revised quality factors. For this work, commonly encountered neutron spectra were folded with energy dependent conversion coefficients, h*(10)(E), determined using the old and new quality factors to compute conversion coefficients for the various sources. Additionally, the effect on a single point calibration for the widely used "Rem ball" is discussed. In general, the change in conversion coefficients under the newer guidelines results in a 5 to 15% increase in H*(10), which will require modifications to instrument calibrations.     

Dose coefficients for the embryo and foetus following intakes of radionuclides by the mother.

Committee 2 of the International Commission on Radiological Protection (ICRP) has the responsibility for calculating radiation doses from intakes of radionuclides for all age groups in the population. Publication 88 of the ICRP, which has recently been published, describes the development of models used for calculating radiation doses to the embryo and foetus following intakes of radionuclides by the mother. It also gives radiation doses to the offspring for intakes of radionuclides by the mother either before or during pregnancy. The approaches used in the development of the biokinetic and dosimetric models are summarised here together with a comparison of the doses to the offspring with those to the reference adult.     

New ICRP recommendations

This paper provides a review of the 2007 recommendations of the International Commission on Radiological Protection (ICRP). These new recommendations take account of the latest biological and physical information and consolidate the additional guidance provided by ICRP since 1990. The changes to the scientific data are not substantial. ICRP has retained its fundamental hypothesis for the induction of stochastic effects of linearity of dose and effect without threshold and a dose and dose-rate effectiveness factor (DDREF) of 2 to derive nominal risk coefficients for low doses and low dose rates. While the overall detriment from low radiation doses has remained unchanged, ICRP has made adjustments to the values of the radiation and tissue weighting factors. In particular, the tissue weighting factor for breast has increased while that for gonads has decreased. There are some presentational changes to the system of protection. While ICRP has maintained the three fundamental principles--justification, optimisation of protection, and dose limitation-it has attempted to develop a more holistic approach to radiological protection covering all exposure situations--planned, existing and emergency--and all radiation sources, whether of natural or artificial origin. This approach should ensure that attention is focused on those exposures that can reasonably be controlled. It has also strengthened the principle of optimisation of protection with a particular emphasis on the use of constraints for planned exposure situations and reference levels for existing and emergency exposure situations. Dose constraints and reference levels are categorised into three bands which should assist in rationalising the many values of dose restrictions given in earlier ICRP publications. There are no changes to the dose limits. ICRP also indicates its intentions with respect to the development of further guidance on the protection of the environment. The fact that these new recommendations are more a matter of consolidation of previous ICRP recommendations and guidance should provide confidence that the system of protection established by and large in its present form several decades ago has reached a certain level of maturity. As such, no major changes to radiological protection regulations based on the 1990 recommendations should be necessary.     

Future development of biological understanding of radiation protection: implications of nonstochastic effects

Radiation-protection standards are based on minimizing or preventing biological effects in exposed populations. Radiation-induced biological effects can be classified as stochastic--malignant and hereditary diseases for which the probability of an effect occurring is a function of dose without threshold--and nonstochastic--inflammatory and degenerative diseases for which the severity and frequency of the effect varies with the dose and for which a threshold is present. The current International Commission on Radiation Protection (ICRP) approach for setting limits for intakes of radionuclides by workers, which accounts for doses to significantly exposed organs of the body, is based on limitation of stochastic effects in most situations. When setting exposure limits, nonstochastic effects are generally considered to be unlikely at the limits for stochastic effects. In some situations, limits based on prevention of nonstochastic effects are lower than for stochastic effects. This review considers the threshold radiation doses for thyroid, bone, liver and lung and their relationship to the limits recommended by the ICRP and the cancer risks at the limits. This review indicates that the threshold dose for nonstochastic effects in thyroid and lung is much above the dose limit as advocated by ICRP. The threshold dose for nonstochastic effects in bone and liver is much closer to the dose limit, but protection from nonstochastic effects should still be afforded by the dose limits.     

A history of the international commission on radiological protection

Within twelve months of the discovery of x rays, papers appeared in the literature reporting adverse effects from high exposure. By the time of the First World War, several countries were proposing restrictions for the exposure of radiation workers. In 1925, the first International Congress of Radiology, held in London, considered the need for a protection committee, which it established at its second Congress in Stockholm in 1928. This paper traces the history of the development, by ICRP, of its policies and the personalities involved in their development from its inception up to the modern era. The paper follows the progress from the early controls on worker doses to avoid deterministic effects, through the identification of stochastic effects to the concerns about increasing public exposure. The key features of the Recommendations made by ICRP from 1928 up to the current 1990 version are identified.     

A history of the international commission on radiological protection

Within twelve months of the discovery of x rays, papers appeared in the literature reporting adverse effects from high exposure. By the time of the First World War, several countries were proposing restrictions for the exposure of radiation workers. In 1925, the first International Congress of Radiology, held in London, considered the need for a protection committee, which it established at its second Congress in Stockholm in 1928. This paper traces the history of the development, by ICRP, of its policies and the personalities involved in their development from its inception up to the modern era. The paper follows the progress from the early controls on worker doses to avoid deterministic effects, through the identification of stochastic effects to the concerns about increasing public exposure. The key features of the Recommendations made by ICRP from 1928 up to the current 1990 version are identified.     

Estimation of electron absorbed fractions in the extrathoracic airways

Dose calculations using the respiratory tract model presented in Publication 66 of the International Commission on Radiological Protection (ICRP) frequently predict that the basal cells of the anterior portion of the nose, the extrathoracic region ET1 of the model, are the most highly irradiated tissue of the body. The dose to the basal cells is averaged over a layer of tissue 10 microm thick located at a depth of 40 microm into the airway. Reported here are the results of a series of absorbed fraction calculations undertaken to compare with values tabulated in ICRP Publication 66. The Monte Carlo code MCNP4B and the geometric model of the ET1 region specified in Publication 66 were used in the calculations. Although some calculated differences are evident between the two sets of absorbed fractions, typically less than 20%, the calculations confirm that the electron absorbed fractions tabulated in Publication 66 are not responsible for the high estimates of the ET1 dose.