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International commission on radiological protection
296
JOURNAL INTERNATIONAL REPORT
OF
THE
FACULTY
COMMISSION
ON
OF
RADIOLOGISTS
RADIOLOGICAL
PROTECTION
ON T H E W O R K OF T H E C O M M I S S I O N F O R P R E S E N T A T I O N TO T H E I N T E R N A T I O N A L E X E C U T I V E C O M M I T T E E
I. I n t r o d u e t i o n . - - I n the Recommendations of the International Commission on Radiological Protection (London, I95O), it was proposed to establish six Sub-committees to carry out detailed studies in specialized fields between Congresses. The Sub-committees suggested were as follows : - I. Permissible dose for external radiation. 2. Permissible dose for internal radiation. 3. Protection against X rays generated at potentials up to two million volts. 4. Protection against X rays above two million volts, and beta rays and gamma rays. 5. Protection against heavy particles, including neutrons and protons. 6. Disposal of radio-active wastes; handling of radio-isotopes. The Sub-committees appointed by the Commission have worked during the past three years in preparing detailed reports regarding protection in their respective fields. The final reports of all of the Sub-committees are not yet completed, but when these are available they will be combined into a composite report which will replace the existing Recommendations of the Commission. II. Details o f R e p o r t s o f S u b - e o m m i t t e e s . - - B r i e f l y , the essential points in the reports of the various Sub-committees are as follows : - i. Sub-committee i, on 'Permissible Dose for External Radiation' (Chairman: Professor G. Failla).-In formulating the recommendations on permissible levels of external radiation, emphasis has been placed on the deleterious effects of ionizing radiations manifestable in the lifetime of the individual. Genetic changes possibly injurious to the race as a whole in future generations have been considered but they do not constitute the limiting factor in setting up the permissible levels of occupational exposure, Under present conditions. Permissible dose is defined as that dose of ionizing radiation that, in the light of present knowledge, is not expected to cause appreciable bodily injury to a person at any time during his lifetime; Extension of occupational exposure to types of ionizing radiations other than X and gamma rays necessitates consideration of the doses actually received by different organs of the body. The following organs and potential late effects are regarded as critical from the point of view of protection : (a) Skin; (b) Blood-forming organs; (c) Gonads with respect to impairment of fertility; and (d) Eyes with respect to cataracts. Allowance has to be made for the fact that the biological effectiveness of a dose of ionizing radiation is dependent upon the specific ionization in tissue. The factor to be applied for the effect of differences in specific ionization is termed the ' relative biological effectiveness' (r.b.e.). The Subcommittee has recommended values of r.b.e, to cover all ionizing radiations and has related these both to the specific ionization and to the type of ionizing radiation and the critical biological effect. When it is necessary to add the doses of different radiations received, it may be convenient to introduce another unit, the rem. A dose in rems is equal to the dose in fads multiplied by the appropriate r.b.e. The following values of permissible weekly doses for the critical organs are thought to be well below the limits indicated by the definition of permissible dose. a. Basic permissible weekly doses in roentgens assigned to the critical organs. Whole body exposure : (i) 0-3 r per week in the blood-forming organs, the gonads and the eyes ; (ii) 0.6 r per week in the basal layer of the epidermis.
INTERNATIONAL
COMMISSION
REPORT
z97
b. Basic permissible weekly doses in rads for exposure to X rays with photon energies less than 3 MeV. : The dose in rads for each critical organ or tissue at a given depth is that produced by the respective organ dose or tissue dose in roentgens. For the purposes of this report it shall be assumed that the Organ dose or tissue dose in rads is numerically equal to the respective organ dose or tissue dose in roentgens. c. Transition to other photon energies and other types of radiation. Guiding principle : The potential risk of exposure to radiation of any type and energy should not be greater than that involved in exposure to X rays up to 25o kv. under comparable conditions. d. Basic permissible weekly doses for the critical organs. Whole body exposure to ionizing radiations of any type or types : (i) o. 3 millirems per week in blood-forming organs, the gonads, and the eyes ; (ii) o.6 millirems per week in the basal layer of the epidermis. These figures shall be regarded as maximum permissible weekly dose except when modifying factors apply. e. Partial exposure of the body : In the case of the hands and forearms, the feet and ankles, and the head and neck, the permissible level is i-5 r per week, provided that, in the case of irradiation of the head, the eyes must be protected so that the level does not exceed 0. 3 r per week. This may be extended to other types of ionizing radiation by substituting rein for r. 2. Sub-committee 2, on 'Permissible Dose for Internal Radiation' (Chairman: Dr. K. Z. Morgan).-An assessment has been made of the values of maximum body burden and maximum concentration in air and water of 96 radio-isotopes that are considered permissible for occupational exposure. The appropriate values depend upon the physical and chemical properties of the radio-active material and the method of body intake--ingestion, inhalation, through wounds, or direct absorption through the skin. In order to limit the scope of the report on internal dose, only general maximum permissible concentration values for soluble or insoluble compounds are considered; the only methods of body intake considered in preparing the extensive tables on maximum permissible levels (m.p.1.) and other data are ingestion and inhalation; calculations are made only for the conditions of equilibrium exposure. All calculations are referred to the so-called 'standard man ', in whom all characteristics are assumed to be those representative of the average man. Only in the case of radium is there an accumulation of human experience over a period of years that is suitable to serve as a basis of selection of the maximum permissible levels. The figure for the body burden of radium remains at that given in the previous Recommendations, namely, o.I /zC. In a few cases, the chemical behaviour of other elements is sufficiently similar to that of radium to permit comparisons with radium to serve as a basis of choice of the method of estimating the m.p.ls. In other cases, the m.p.1, is based on a calculation of that burden in the body which will result in an average biological dose of ionizing radiation equivalent to o. 3 rad per week to the organ in which maximum concentration of the isotope occurs. For bone-seeking isotopes (with the exception of radium), the dose so calculated is reduced by a factor of 5 to account for the uneven distribution of the isotope within the bone. This procedure does not apply to P ~ and K-capture isotopes. In spite of the limitations of the data on which the calculations are based, it is believed that the m.p.ls, should serve as a guide to indicate whether Or not sufficient measures are being taken to limit the internal dose from radio-active materials. Nevertheless, it is considered wise to avoid all unnecessary exposure to radio-isotopes. Following accepted practice in the industrial and public health field, it is recommended that, in the case of prolonged exposure of a large population, the permissible level for radio-active isotopes accepted for occupational exposures be reduced by a factor of to. 3. Sub-committee 3, on 'Protection Against X rays generated at Potentials up to 2 million Volts' (Chairman : Dr. R. G. Jaeger).--
298
JOURNAL
OF
THE
FACULTY
OF
RADIOLOGISTS
An extensive report has been prepared, based upon the Codes of Practice in operation in various countries. The recommendations put the main emphasis on the basic requirements of radiation protection, since it is the policy of the Commission that detailed technical requirements must be left to national committees. Advice is given on the following matters :--(i) Plans for X-ray installations ; (ii) Radiation surveys and monitoring of X-ray installations ; (iii) General working conditions and personnel tests ; (iv) Protection in X-ray diagnostic and therapeutic departments ; (v) Protection of patients ; (vi) Protection against X rays used for non-medical purposes ; (vii) Electrical and other hazards.
4" Sub-committee 4, on ' Protection AgainStX rays Above 2 million Volts ', and Sub-committee 5, on 'Protection Against Heavy Particles, including Neutrons and Protons' (Chairman: Professor W. V. Mayneord).-As no members of Sub-committee 5 could attend the Conference it was decided to unite this Sub-committee with No. 4. The main findings of the joint Sub-committee are : - a. For X and gamma rays of quantum energies above 3 MeV., the maximum permissible level shall be o"3 rad per week in any part of the body. b. For neutrons, the maximum permissible level for the energy range from 0"025 eV. (thermal) to Io MeV. may be expressed either in terms of the energy absorbed per week at a certain depth in tissue or in terms of neutron flux. As regards the former, the value is 3o millirad per week. As regards the fluxes, values are given for several different energy ranges. These flux values fall from 2000 neutrons/em.2/sec, for thermal neutrons to 3° neutrons/cm.2/sec, for fast neutrons in the energy range 3 to io MeV.
5. Sub-committee 6, on' Handling of Radio-isotopes, Disposal of Radio-active Waste, and Transport of Radio-active Materials ' . It has been necessary to re-constitute this Sub-committee during the Conference and to assign to it the task of preparing, as soon as possible, a report on those aspects which are regarded as being of the utmost importance. III. A m e n d m e n t o f ' Rules Governing the Selection and Work o f I.C.R.P.'.--For the past three years the Commission has operated in conformity with the rules proposed at the last Congress. It has now, however, been found necessary to make a slight amendment to the effect that the Chairman will now be elected not 6 months in advance of the Congress, but will be elected during one Congress to serve through the succeeding Congress. This change is necessary because, in view of the rapid development of the subject of radiation protection, it may be necessary for the Commission to meet between Congresses. IV. N e w International S u b - c o m m i t t e e s on Radiation Protection.--It was not known, when the proposal was made in i95o to establish Sub-committees to deal with the various aspects of radiation protection whether such an arrangement would prove to be satisfactory. It has been decided to continue this scheme for a further trial period, the only change which is being made is that Sub-committees 4 and 5 will b e re-constituted as one Sub-committee to deal with the closely allied sections of high-energy radiation and of heavy particles. V. N e w International R e c o m m e n d a t i o n s on Radiological Protection.--As soon as the final draft has been agreed by the Commission, copies will be sent to the International Executive Committee and to the Chairmen of all National Delegations who attended the Seventh International Congress of Radiology, Copenhagen, I953. It is expected that the Recommendations will be published in the Spring of x954.
Members of the International Commission on Radiological Protection presenting the above report:Sir Ernest Rock Carling (Chairman); J. C. Jacobsen (Hon. Chairman); W. Binks (Secretary); A. J. Cipriani; R. G. Jaeger; W. V. Mayneord; R. S. Stone; R. M. Sievert; L. S. Taylor; and M. Tubiana.
JOURNAL INTERNATIONAL REPORT
OF
THE
FACULTY
COMMISSION
ON
OF
RADIOLOGISTS
RADIOLOGICAL
PROTECTION
ON T H E W O R K OF T H E C O M M I S S I O N F O R P R E S E N T A T I O N TO T H E I N T E R N A T I O N A L E X E C U T I V E C O M M I T T E E
I. I n t r o d u e t i o n . - - I n the Recommendations of the International Commission on Radiological Protection (London, I95O), it was proposed to establish six Sub-committees to carry out detailed studies in specialized fields between Congresses. The Sub-committees suggested were as follows : - I. Permissible dose for external radiation. 2. Permissible dose for internal radiation. 3. Protection against X rays generated at potentials up to two million volts. 4. Protection against X rays above two million volts, and beta rays and gamma rays. 5. Protection against heavy particles, including neutrons and protons. 6. Disposal of radio-active wastes; handling of radio-isotopes. The Sub-committees appointed by the Commission have worked during the past three years in preparing detailed reports regarding protection in their respective fields. The final reports of all of the Sub-committees are not yet completed, but when these are available they will be combined into a composite report which will replace the existing Recommendations of the Commission. II. Details o f R e p o r t s o f S u b - e o m m i t t e e s . - - B r i e f l y , the essential points in the reports of the various Sub-committees are as follows : - i. Sub-committee i, on 'Permissible Dose for External Radiation' (Chairman: Professor G. Failla).-In formulating the recommendations on permissible levels of external radiation, emphasis has been placed on the deleterious effects of ionizing radiations manifestable in the lifetime of the individual. Genetic changes possibly injurious to the race as a whole in future generations have been considered but they do not constitute the limiting factor in setting up the permissible levels of occupational exposure, Under present conditions. Permissible dose is defined as that dose of ionizing radiation that, in the light of present knowledge, is not expected to cause appreciable bodily injury to a person at any time during his lifetime; Extension of occupational exposure to types of ionizing radiations other than X and gamma rays necessitates consideration of the doses actually received by different organs of the body. The following organs and potential late effects are regarded as critical from the point of view of protection : (a) Skin; (b) Blood-forming organs; (c) Gonads with respect to impairment of fertility; and (d) Eyes with respect to cataracts. Allowance has to be made for the fact that the biological effectiveness of a dose of ionizing radiation is dependent upon the specific ionization in tissue. The factor to be applied for the effect of differences in specific ionization is termed the ' relative biological effectiveness' (r.b.e.). The Subcommittee has recommended values of r.b.e, to cover all ionizing radiations and has related these both to the specific ionization and to the type of ionizing radiation and the critical biological effect. When it is necessary to add the doses of different radiations received, it may be convenient to introduce another unit, the rem. A dose in rems is equal to the dose in fads multiplied by the appropriate r.b.e. The following values of permissible weekly doses for the critical organs are thought to be well below the limits indicated by the definition of permissible dose. a. Basic permissible weekly doses in roentgens assigned to the critical organs. Whole body exposure : (i) 0-3 r per week in the blood-forming organs, the gonads and the eyes ; (ii) 0.6 r per week in the basal layer of the epidermis.
INTERNATIONAL
COMMISSION
REPORT
z97
b. Basic permissible weekly doses in rads for exposure to X rays with photon energies less than 3 MeV. : The dose in rads for each critical organ or tissue at a given depth is that produced by the respective organ dose or tissue dose in roentgens. For the purposes of this report it shall be assumed that the Organ dose or tissue dose in rads is numerically equal to the respective organ dose or tissue dose in roentgens. c. Transition to other photon energies and other types of radiation. Guiding principle : The potential risk of exposure to radiation of any type and energy should not be greater than that involved in exposure to X rays up to 25o kv. under comparable conditions. d. Basic permissible weekly doses for the critical organs. Whole body exposure to ionizing radiations of any type or types : (i) o. 3 millirems per week in blood-forming organs, the gonads, and the eyes ; (ii) o.6 millirems per week in the basal layer of the epidermis. These figures shall be regarded as maximum permissible weekly dose except when modifying factors apply. e. Partial exposure of the body : In the case of the hands and forearms, the feet and ankles, and the head and neck, the permissible level is i-5 r per week, provided that, in the case of irradiation of the head, the eyes must be protected so that the level does not exceed 0. 3 r per week. This may be extended to other types of ionizing radiation by substituting rein for r. 2. Sub-committee 2, on 'Permissible Dose for Internal Radiation' (Chairman: Dr. K. Z. Morgan).-An assessment has been made of the values of maximum body burden and maximum concentration in air and water of 96 radio-isotopes that are considered permissible for occupational exposure. The appropriate values depend upon the physical and chemical properties of the radio-active material and the method of body intake--ingestion, inhalation, through wounds, or direct absorption through the skin. In order to limit the scope of the report on internal dose, only general maximum permissible concentration values for soluble or insoluble compounds are considered; the only methods of body intake considered in preparing the extensive tables on maximum permissible levels (m.p.1.) and other data are ingestion and inhalation; calculations are made only for the conditions of equilibrium exposure. All calculations are referred to the so-called 'standard man ', in whom all characteristics are assumed to be those representative of the average man. Only in the case of radium is there an accumulation of human experience over a period of years that is suitable to serve as a basis of selection of the maximum permissible levels. The figure for the body burden of radium remains at that given in the previous Recommendations, namely, o.I /zC. In a few cases, the chemical behaviour of other elements is sufficiently similar to that of radium to permit comparisons with radium to serve as a basis of choice of the method of estimating the m.p.ls. In other cases, the m.p.1, is based on a calculation of that burden in the body which will result in an average biological dose of ionizing radiation equivalent to o. 3 rad per week to the organ in which maximum concentration of the isotope occurs. For bone-seeking isotopes (with the exception of radium), the dose so calculated is reduced by a factor of 5 to account for the uneven distribution of the isotope within the bone. This procedure does not apply to P ~ and K-capture isotopes. In spite of the limitations of the data on which the calculations are based, it is believed that the m.p.ls, should serve as a guide to indicate whether Or not sufficient measures are being taken to limit the internal dose from radio-active materials. Nevertheless, it is considered wise to avoid all unnecessary exposure to radio-isotopes. Following accepted practice in the industrial and public health field, it is recommended that, in the case of prolonged exposure of a large population, the permissible level for radio-active isotopes accepted for occupational exposures be reduced by a factor of to. 3. Sub-committee 3, on 'Protection Against X rays generated at Potentials up to 2 million Volts' (Chairman : Dr. R. G. Jaeger).--
298
JOURNAL
OF
THE
FACULTY
OF
RADIOLOGISTS
An extensive report has been prepared, based upon the Codes of Practice in operation in various countries. The recommendations put the main emphasis on the basic requirements of radiation protection, since it is the policy of the Commission that detailed technical requirements must be left to national committees. Advice is given on the following matters :--(i) Plans for X-ray installations ; (ii) Radiation surveys and monitoring of X-ray installations ; (iii) General working conditions and personnel tests ; (iv) Protection in X-ray diagnostic and therapeutic departments ; (v) Protection of patients ; (vi) Protection against X rays used for non-medical purposes ; (vii) Electrical and other hazards.
4" Sub-committee 4, on ' Protection AgainStX rays Above 2 million Volts ', and Sub-committee 5, on 'Protection Against Heavy Particles, including Neutrons and Protons' (Chairman: Professor W. V. Mayneord).-As no members of Sub-committee 5 could attend the Conference it was decided to unite this Sub-committee with No. 4. The main findings of the joint Sub-committee are : - a. For X and gamma rays of quantum energies above 3 MeV., the maximum permissible level shall be o"3 rad per week in any part of the body. b. For neutrons, the maximum permissible level for the energy range from 0"025 eV. (thermal) to Io MeV. may be expressed either in terms of the energy absorbed per week at a certain depth in tissue or in terms of neutron flux. As regards the former, the value is 3o millirad per week. As regards the fluxes, values are given for several different energy ranges. These flux values fall from 2000 neutrons/em.2/sec, for thermal neutrons to 3° neutrons/cm.2/sec, for fast neutrons in the energy range 3 to io MeV.
5. Sub-committee 6, on' Handling of Radio-isotopes, Disposal of Radio-active Waste, and Transport of Radio-active Materials ' . It has been necessary to re-constitute this Sub-committee during the Conference and to assign to it the task of preparing, as soon as possible, a report on those aspects which are regarded as being of the utmost importance. III. A m e n d m e n t o f ' Rules Governing the Selection and Work o f I.C.R.P.'.--For the past three years the Commission has operated in conformity with the rules proposed at the last Congress. It has now, however, been found necessary to make a slight amendment to the effect that the Chairman will now be elected not 6 months in advance of the Congress, but will be elected during one Congress to serve through the succeeding Congress. This change is necessary because, in view of the rapid development of the subject of radiation protection, it may be necessary for the Commission to meet between Congresses. IV. N e w International S u b - c o m m i t t e e s on Radiation Protection.--It was not known, when the proposal was made in i95o to establish Sub-committees to deal with the various aspects of radiation protection whether such an arrangement would prove to be satisfactory. It has been decided to continue this scheme for a further trial period, the only change which is being made is that Sub-committees 4 and 5 will b e re-constituted as one Sub-committee to deal with the closely allied sections of high-energy radiation and of heavy particles. V. N e w International R e c o m m e n d a t i o n s on Radiological Protection.--As soon as the final draft has been agreed by the Commission, copies will be sent to the International Executive Committee and to the Chairmen of all National Delegations who attended the Seventh International Congress of Radiology, Copenhagen, I953. It is expected that the Recommendations will be published in the Spring of x954.
Members of the International Commission on Radiological Protection presenting the above report:Sir Ernest Rock Carling (Chairman); J. C. Jacobsen (Hon. Chairman); W. Binks (Secretary); A. J. Cipriani; R. G. Jaeger; W. V. Mayneord; R. S. Stone; R. M. Sievert; L. S. Taylor; and M. Tubiana.