There has been great concern for a number of years about observations of an increased incidence of childhood leukaemia around nuclear sites and the possibility that this might be linked to operations at the sites. In this issue of Journal of Radiological Protection (p 361) Rommens, Laurier and Sugier report on a study to consider this possibility for the Nord-Cotentin region of France. The nuclear fuel reprocessing plant at La Hague is located in this region together with other nuclear installations. The aim of the study was to estimate the exposures from all sources of ionising radiation and the corresponding risks of radiation induced leukaemia for young people aged 0 to 24 yrs living in the region. This study was an essential part of an on-going investigation into an observed trend towards an excess of childhood leukaemia in this area [1] and whether these findings might be due to radiation exposure. When looking at the paper it is important to recognise that it represents `the tip of an iceberg' in terms of the effort involved and the results obtained in the complete study. The full report comes in five volumes, including a summary, and there is also a CD-ROM containing a compilation of measurements of radionuclides in environmental materials. This type of study is more complex than many other radiological assessments. This is because of the need to estimate cumulative radiation exposures over long periods of time. Allowance has to be made for exposure of individuals starting in utero and going through childhood to age 24 yrs. For internal exposures you have to be able to estimate doses from intakes by inhalation and ingestion both in the year of intake and for all subsequent years, taking into account changes in size and metabolism of the growing child. You can not simply use the dose coefficients published by ICRP, but have to use the underlying models to estimate this cumulative dose. Estimating risks then entails combining the dose estimates with a time dependent risk model, again keeping track of cumulative risks to the population group of interest. The study reported by Rommens et al involved detailed work at each stage of the study, from establishing the source term for routine and accidental releases for each nuclear establishment to estimating the risks. Particularly impressive was the compilation of all of the available data for measurements of radionuclides in the environment. These data were used directly in the dose assessment and also to ensure that the models used were an adequate representation of reality. In carrying out the Nord-Cotentin study it was felt important to involve as many interested parties as possible to ensure that the methods and data were subject to scrutiny throughout. This was done through establishing the Nord-Cotentin Radioecology Group headed by Mme A Sugier, Director of Protection at IPSN (Institute for Protection and Nuclear Safety). The group involved 50 experts from a range of organisations including regulators, government experts, the site operators, experts fr...
International Commission on Radiological Protection (ICRP) Publication 103 provided a detailed explanation of the purpose and use of effective dose and equivalent dose to individual organs and tissues. Effective dose has proven to be a valuable and robust quantity for use in the implementation of protection principles. However, questions have arisen regarding practical applications, and a Task Group has been set up to consider issues of concern. This paper focusses on two key proposals developed by the Task Group that are under consideration by ICRP: (1) confusion will be avoided if equivalent dose is no longer used as a protection quantity, but regarded as an intermediate step in the calculation of effective dose. It would be more appropriate for limits for the avoidance of deterministic effects to the hands and feet, lens of the eye, and skin, to be set in terms of the quantity, absorbed dose (Gy) rather than equivalent dose (Sv). (2) Effective dose is in widespread use in medical practice as a measure of risk, thereby going beyond its intended purpose. While doses incurred at low levels of exposure may be measured or assessed with reasonable reliability, health effects have not been demonstrated reliably at such levels but are inferred. However, bearing in mind the uncertainties associated with risk projection to low doses or low dose rates, it may be considered reasonable to use effective dose as a rough indicator of possible risk, with the additional consideration of variation in risk with age, sex and population group.
In 1990, the Ministry of Agriculture, Fisheries and Food (MAFF) Working Party on Radionuclides in Food agreed that a standard set of UK food consumption data was needed for the estimation of radiation doses from ingestion. It was decided that MAFF and the National Radiological Protection Board (NRPB) as two of the main users of such figures would work together to produce a set of revised food consumption data. Tn the past MAFF and NRPB have used food consumption data which have differed slightly in detail. The aim of the work described is to provide an agreed set of data for general use in the two organisations and elsewhere, for example by local authorities and nuclear operators. The availability of survey data on dietary habits, collected within the past 12 years, for adults, schoolchildren and infants offered the opportunity for revising the previous estimates of food consumption and producing a new and comprehensive set of data.
The International Commission on Radiological Protection has published a report (Publication 147) on the use of dose quantities in radiological protection, under the same authorship as this Memorandum. Here, we present a brief and partial summary of the report. ICRP Publication 147 consolidates and clarifies the explanations provided in the 2007 ICRP Recommendations (Publication 103) but reaches conclusions that go beyond those presented in Publication 103. Further guidance is provided on the scientific basis for the control of radiation risks using dose quantities in occupational, public and medical applications. It is emphasised that best estimates of risk to individuals will use organ / tissue absorbed doses and specific dose-risk models. However, bearing in mind the uncertainties associated with risk projection to low doses or low dose rates, it is concluded that effective dose may be considered as an approximate indicator of possible risk, recognising also that lifetime cancer risks vary with age at exposure, sex and population group. A further conclusion is that equivalent dose is not required as a protection quantity. It will be more appropriate for limits for the avoidance of tissue reactions for the skin, hands and feet, and lens of the eye to be set in terms of absorbed dose rather than equivalent dose.
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