- Email: [email protected]
ICRP 60: The next step
Clinical Oncology (1993) 5:131-132 © 1993 The Royal College of Radiologists
Clinical Oncology
Editorial ICRP 60: The Next Step* L. K. Harding and W. H. Thomson Birmingham Regional Radioisotope Centre, Dudley Road Hospital, Birmingham B18 7QH, U K
Since the International Commission on Radiological Protection (ICRP) published its latest recommendations [1] there has been considerable discussion as to how these recommendations will be incorporated into the legislation of European countries, once they have been issued in the form of a European Community (EC) Directive. Some of the key points have already been highlighted in Nuclear Medicine Communications. Editorials on the draft ICRP document [2] and the final version [3] have already been published. In the UK, the National Radiological Protection Board (NRPB) advises government departments and other statutory bodies on implementation of the ICRP recommendations so that they can be incorporated into UK law. Recently they have issued four consultation documents [4-7] giving their views, and professional bodies have been given the opportunity to respond. Initial impressions are that these are sensible documents, and while there is no guarantee that these proposals will be made into law, it is difficult to believe that there will be material changes. A fifth document on irradiation in pregnancy will be the subject of another editorial. Most people will be aware that with some provisos the dose limit for workers is to be reduced from 50 to 20 mSv per year, and for the general public from 5 to 1 mSv. In nuclear medicine, occupational whole body doses do not create a problem, but a reduction in the limit for the general public could. There are situations where a friend or relative might well decide that exposure above this level is reasonable, for example, in visiting radiotherapy patients, or even living at home with a patient who has had treatment in a nuclear medicine department. ICRP has suggested that a member of the general public can be exposed to radiation 'knowingly and willingly in the support and comfort of a patient'. The NRPB now recommends that this exposure should not normally exceed 5 mSv. It is difficult to envisage circumstances where this figure is too low, but it may be exceeded with therapy patients and the justification for choosing this level rather than a higher one is not clear. Partners of patients treated with more than 400 MBq 1311 would have to be advised to use a separate * This Editorial was initially prepared for publication in Nuclear Medicine Communications 1993;14:157-9, but it was felt that the discussion of the recent ICRP recommendations was of considerable importance to clinical oncologists, and so, with the approval of the authors and the publishers, the text is reprinted here.
bedroom [8]. Because 'knowingly and willingly' implies consent which is not appropriate for a child, NRPB have suggested that such exposure, for example, from a mother who is breastfeeding and has had a nuclear medicine test, should not exceed 1 mSv. This figure has already been chosen by Mountford [9] on the very reasonable basis that it was the ICRP limit for the general public. In ICRP 60 one of the areas which is far from clear is related to constraints. It was apparent that a constraint was not a dose limit, but an investigation level which could be set nationally or locally. On the recommendation of the NRPB, the Health and Safety Executive (HSE) has already set a national constraint at 15 mSv for workers and a 1 mSv for the general public [10]. For medical exposures NRPB has proposed that the term used is 'reference dose level' (RDL). If these levels are exceeded an investigation is required. An RDL will not refer to a measurement on a single patient, but an average figure for patients of standard size. Higher doses can be given to individual patients where this is indicated by sound clinical judgment. However, if average figures exceed the reference dose level, then an internal investigation will be required. The maximum usual activities (MUA) recommended by the Administration of Radioactive Substances Advisory Committee (ARSAC) [11] represent a similar concept, and can also be exceeded in an individual patient for defined clinical circumstances (for example, a patient who is markedly overweight, or in severe pain). Reference dose level refers to an average radiation dose, and MUA to maximum administered activity, but it is difficult to see that day to day these will be any different from the point of view of nuclear medicine. For the general public a dose constraint of 0.3 mSv is proposed. This relates to the radiation dose from a single source, for example, the nuclear medicine department, or from a patient who has had a nuclear medicine test. Patients travelling home after nuclear medicine procedures, particularly after 131I treatment will present a problem since the dose rate is 1320 ~tSvh-~at 0.5 m after 200 MBq 131I [12]. We must try to resist anything which prevents such patients being sent home. Estimates of doses to individuals in a nuclear medicine department waiting room [13] suggest that this will not be an area of concern. A welcome feature is a return to the concept of occupancy. The guidance notes [14] relating to the Ionizing Radiation Regulations 1985 [15] based their
132
advice for dose rates on the assumption of a continuous exposure through the working day. In the case of contact between children and their parents where the latter have had a nuclear medicine test, Shields [16], on behalf of the British Institute of Radiology Radiation Protection Committee, has argued strongly that the time of exposure is an important factor and that the current parameters are too restrictive. Parents do not sit with the children all day. With a constraint of 0.3 mSv for the general public, supervised areas could become large, and thus impractical to enforce, if they were designated without taking occupancy into account. Definition of controlled areas will no longer be decided on the grounds of being likely to exceed 3/10 of the dose limit for workers, but on operational grounds. Category A classified workers will be those working in controlled areas likely to exceed 6 mSv a year (3/10 of 20 mSv), and their exposure will have to be monitored. Category B is a second type of classified worker who will mainly be working in supervised areas, defined above the 1 mSv level for the general public. They will not necessarily need individual monitoring as long at it can be shown that they do not fall into category A. Presumably those working in nuclear medicine will be included in category B although they do not fulfil the precise definition as they often work in a controlled rather than a supervised area. Regular routine medical examinations are no longer required, except for pre-employment examinations as in the case of other hospital employees. The very limited value of routine blood tests is recognized, and using chromosomal abnormalities in the blood when there is reason to question whole body radiation exposure should be supported. Evaluating radiation risks is difficult, and explaining them to the general public even more difficult. Radiation pie charts, or quoting figures of 1:20000 mSv -1 seem to have little impact, and in the latter case they are not understood by most people. The NRPB recommend moving to days of life lost, and the quality adjusted life year (QALY). The concept and application of cost-benefit analysis is also expanded. Different values are proposed for children, adults and the elderly, and this would seem entirely reasonable. The European Association of Nuclear Medicine (EANM) Task Group Explaining Risks, in a poster presentation to the 1992 EANM meeting have also chosen days of life lost to explain radiation effects. Based on the work of Cohen [17] they quote a loss of life expectancy of 31 days fi'om
L. K. Harding and W. H. Thomson
being 1 lb (0.45 kg) overweight, compared with only 1.5 days from a single exposure of 10 mSv. Attaching quality of life to these figures may be difficult and requires further thought. Finally, NRPB highlight the point that management commitment to radiation protection is essential, together with the resources to achieve improvements. We have an important task in bringing these recommendations to our management.
References 1. ICRP Publication 60. 1990 Recommendations of the International Commission on Radiological Protection. Ann ICRP 1991;211-3. 2. Harding LK. ICRP 60 and future legislation [editorial]. Nucl Med Commun 1991;12:753-5. 3. Harding LK, Thomson WH. International Commission on Radiological Protection. Nucl Med Commun 1990;11:585-7. 4. NRPB Consultative Document. Advice on the 1990 recommendations of ICRP concerning occupational exposure. August 1992. 5. NRPB Consultative Document. Advice on the 1990 recommendations of ICRP concerning medical exposure. August 1992. 6. NRPB Consultative Document. Board response to ICRP 60 on public exposure. August 1992. 7. NRPB Consultative Document. Dose quantities for protection from external irradiation. August 1992. 8. Thomson WH, Mills AP, Mostafa AB, et al. Measurement of the radiation doses to the relatives of nuclear medicine outpatients. Radioactive Isotopes Clin Med Res. Published. 9. Mountford PJ. Estimation of close contact doses to young infants from surface dose rate on radioactive adults. Nucl Meal Commun 1987;8:85%63. 10. Health and Safety Commission 1991. Dose limitation: Restriction of exposure. Approved Code of Practice, Part 4. ll. DHSS. Notes for guidance on the administration of radioactive substances to persons for the purposes of diagnosis, treatment or research. London: HMSO, 1988. 12. Harding LK, Mostafa AB, Roden L, et al. Dose rates from patients having nuclear medicine investigations. Nucl Med Commun 1985 ;6:191-4. 13. Harding LK, Harding NJ, Warren H, et al. Radiation dose to accompanying nurses, relatives and other patients in a nuclear medicine department waiting room. Nucl Med Commun 1990;11:1%22. 14. National Radiological Protection Board. Guidance notes for the protection of persons against ionising radiations arising from medical and dental use. London: HMSO, 1988. 15. Health and Safety Executive. The ionising radiations regulations. London: HMSO, 1985. 16. Shields RA. The guidance notes revisited: Advice to patients leaving hospital after diagnostic nuclear medicine (editorial). Brit J Radiol 1991;64:567-8. 17. Cohen BL. Catalog of the risks extended and updated. Health Phys 1991;61:317-35.
Clinical Oncology
Editorial ICRP 60: The Next Step* L. K. Harding and W. H. Thomson Birmingham Regional Radioisotope Centre, Dudley Road Hospital, Birmingham B18 7QH, U K
Since the International Commission on Radiological Protection (ICRP) published its latest recommendations [1] there has been considerable discussion as to how these recommendations will be incorporated into the legislation of European countries, once they have been issued in the form of a European Community (EC) Directive. Some of the key points have already been highlighted in Nuclear Medicine Communications. Editorials on the draft ICRP document [2] and the final version [3] have already been published. In the UK, the National Radiological Protection Board (NRPB) advises government departments and other statutory bodies on implementation of the ICRP recommendations so that they can be incorporated into UK law. Recently they have issued four consultation documents [4-7] giving their views, and professional bodies have been given the opportunity to respond. Initial impressions are that these are sensible documents, and while there is no guarantee that these proposals will be made into law, it is difficult to believe that there will be material changes. A fifth document on irradiation in pregnancy will be the subject of another editorial. Most people will be aware that with some provisos the dose limit for workers is to be reduced from 50 to 20 mSv per year, and for the general public from 5 to 1 mSv. In nuclear medicine, occupational whole body doses do not create a problem, but a reduction in the limit for the general public could. There are situations where a friend or relative might well decide that exposure above this level is reasonable, for example, in visiting radiotherapy patients, or even living at home with a patient who has had treatment in a nuclear medicine department. ICRP has suggested that a member of the general public can be exposed to radiation 'knowingly and willingly in the support and comfort of a patient'. The NRPB now recommends that this exposure should not normally exceed 5 mSv. It is difficult to envisage circumstances where this figure is too low, but it may be exceeded with therapy patients and the justification for choosing this level rather than a higher one is not clear. Partners of patients treated with more than 400 MBq 1311 would have to be advised to use a separate * This Editorial was initially prepared for publication in Nuclear Medicine Communications 1993;14:157-9, but it was felt that the discussion of the recent ICRP recommendations was of considerable importance to clinical oncologists, and so, with the approval of the authors and the publishers, the text is reprinted here.
bedroom [8]. Because 'knowingly and willingly' implies consent which is not appropriate for a child, NRPB have suggested that such exposure, for example, from a mother who is breastfeeding and has had a nuclear medicine test, should not exceed 1 mSv. This figure has already been chosen by Mountford [9] on the very reasonable basis that it was the ICRP limit for the general public. In ICRP 60 one of the areas which is far from clear is related to constraints. It was apparent that a constraint was not a dose limit, but an investigation level which could be set nationally or locally. On the recommendation of the NRPB, the Health and Safety Executive (HSE) has already set a national constraint at 15 mSv for workers and a 1 mSv for the general public [10]. For medical exposures NRPB has proposed that the term used is 'reference dose level' (RDL). If these levels are exceeded an investigation is required. An RDL will not refer to a measurement on a single patient, but an average figure for patients of standard size. Higher doses can be given to individual patients where this is indicated by sound clinical judgment. However, if average figures exceed the reference dose level, then an internal investigation will be required. The maximum usual activities (MUA) recommended by the Administration of Radioactive Substances Advisory Committee (ARSAC) [11] represent a similar concept, and can also be exceeded in an individual patient for defined clinical circumstances (for example, a patient who is markedly overweight, or in severe pain). Reference dose level refers to an average radiation dose, and MUA to maximum administered activity, but it is difficult to see that day to day these will be any different from the point of view of nuclear medicine. For the general public a dose constraint of 0.3 mSv is proposed. This relates to the radiation dose from a single source, for example, the nuclear medicine department, or from a patient who has had a nuclear medicine test. Patients travelling home after nuclear medicine procedures, particularly after 131I treatment will present a problem since the dose rate is 1320 ~tSvh-~at 0.5 m after 200 MBq 131I [12]. We must try to resist anything which prevents such patients being sent home. Estimates of doses to individuals in a nuclear medicine department waiting room [13] suggest that this will not be an area of concern. A welcome feature is a return to the concept of occupancy. The guidance notes [14] relating to the Ionizing Radiation Regulations 1985 [15] based their
132
advice for dose rates on the assumption of a continuous exposure through the working day. In the case of contact between children and their parents where the latter have had a nuclear medicine test, Shields [16], on behalf of the British Institute of Radiology Radiation Protection Committee, has argued strongly that the time of exposure is an important factor and that the current parameters are too restrictive. Parents do not sit with the children all day. With a constraint of 0.3 mSv for the general public, supervised areas could become large, and thus impractical to enforce, if they were designated without taking occupancy into account. Definition of controlled areas will no longer be decided on the grounds of being likely to exceed 3/10 of the dose limit for workers, but on operational grounds. Category A classified workers will be those working in controlled areas likely to exceed 6 mSv a year (3/10 of 20 mSv), and their exposure will have to be monitored. Category B is a second type of classified worker who will mainly be working in supervised areas, defined above the 1 mSv level for the general public. They will not necessarily need individual monitoring as long at it can be shown that they do not fall into category A. Presumably those working in nuclear medicine will be included in category B although they do not fulfil the precise definition as they often work in a controlled rather than a supervised area. Regular routine medical examinations are no longer required, except for pre-employment examinations as in the case of other hospital employees. The very limited value of routine blood tests is recognized, and using chromosomal abnormalities in the blood when there is reason to question whole body radiation exposure should be supported. Evaluating radiation risks is difficult, and explaining them to the general public even more difficult. Radiation pie charts, or quoting figures of 1:20000 mSv -1 seem to have little impact, and in the latter case they are not understood by most people. The NRPB recommend moving to days of life lost, and the quality adjusted life year (QALY). The concept and application of cost-benefit analysis is also expanded. Different values are proposed for children, adults and the elderly, and this would seem entirely reasonable. The European Association of Nuclear Medicine (EANM) Task Group Explaining Risks, in a poster presentation to the 1992 EANM meeting have also chosen days of life lost to explain radiation effects. Based on the work of Cohen [17] they quote a loss of life expectancy of 31 days fi'om
L. K. Harding and W. H. Thomson
being 1 lb (0.45 kg) overweight, compared with only 1.5 days from a single exposure of 10 mSv. Attaching quality of life to these figures may be difficult and requires further thought. Finally, NRPB highlight the point that management commitment to radiation protection is essential, together with the resources to achieve improvements. We have an important task in bringing these recommendations to our management.
References 1. ICRP Publication 60. 1990 Recommendations of the International Commission on Radiological Protection. Ann ICRP 1991;211-3. 2. Harding LK. ICRP 60 and future legislation [editorial]. Nucl Med Commun 1991;12:753-5. 3. Harding LK, Thomson WH. International Commission on Radiological Protection. Nucl Med Commun 1990;11:585-7. 4. NRPB Consultative Document. Advice on the 1990 recommendations of ICRP concerning occupational exposure. August 1992. 5. NRPB Consultative Document. Advice on the 1990 recommendations of ICRP concerning medical exposure. August 1992. 6. NRPB Consultative Document. Board response to ICRP 60 on public exposure. August 1992. 7. NRPB Consultative Document. Dose quantities for protection from external irradiation. August 1992. 8. Thomson WH, Mills AP, Mostafa AB, et al. Measurement of the radiation doses to the relatives of nuclear medicine outpatients. Radioactive Isotopes Clin Med Res. Published. 9. Mountford PJ. Estimation of close contact doses to young infants from surface dose rate on radioactive adults. Nucl Meal Commun 1987;8:85%63. 10. Health and Safety Commission 1991. Dose limitation: Restriction of exposure. Approved Code of Practice, Part 4. ll. DHSS. Notes for guidance on the administration of radioactive substances to persons for the purposes of diagnosis, treatment or research. London: HMSO, 1988. 12. Harding LK, Mostafa AB, Roden L, et al. Dose rates from patients having nuclear medicine investigations. Nucl Med Commun 1985 ;6:191-4. 13. Harding LK, Harding NJ, Warren H, et al. Radiation dose to accompanying nurses, relatives and other patients in a nuclear medicine department waiting room. Nucl Med Commun 1990;11:1%22. 14. National Radiological Protection Board. Guidance notes for the protection of persons against ionising radiations arising from medical and dental use. London: HMSO, 1988. 15. Health and Safety Executive. The ionising radiations regulations. London: HMSO, 1985. 16. Shields RA. The guidance notes revisited: Advice to patients leaving hospital after diagnostic nuclear medicine (editorial). Brit J Radiol 1991;64:567-8. 17. Cohen BL. Catalog of the risks extended and updated. Health Phys 1991;61:317-35.