622 RADIATION PROTECTION The recommendations numbered "1" through "7" contained in the above memorandum are approved for the guidance of Federal agencies, and the memorandum shall be published in the Federal Register. DWIGHT D. EISENHOWER May 13, 1960 REPORT NO. 1 background material for the development of radiation protection standards Staff Report of the FEDERAL RADIATION COUNCIL May 13, 1960 RADIATION PROTECTION 625 ! SECTION 1.-INTRODUCTION 1.1 It was recognized soon after discovery of x-rays that exposure to large amounts of ionizing radiation can produce deleterious effects on the human body so exposed. More recently, because of increased scientific knowledge and widespread use of radiation, additional attention has been directed to the possible effects of lower levels of radiation on future generations. Various scientific bodies have made recommendations to limit the irradiation of the human body. Probably the oldest of such scientific bodies are the International Commission on Radiological Protection (ICRP) and the U. S. National Committee on Radiation Protection and Measurements (NCRP). Initially, these bodies were interested primarily in the irradiation of those exposed occupationally, but recently they have been concerned with those who are nonoccupationally exposed. 1.2 The ICRP was formed in 1928 under the auspices of the International Congress of Radiology. It is now a Commission of the International Society of Radiology. This Commission has published recommendations about every three years except for the period 1938-49. 1.3 The NCRP was initially organized as the "Advisory Committee on X-ray and Radium Protection." The initial membership included representatives from the medical societies, xray equipment manufacturers, and the National Bureau of Standards. After the reorganization in 1946, the name was changed to the National Committee on Radiation Protection and Measurements, and additional representatives from other organizations having scientific interest in the field were included. The recommendations of this group have generally been published as National Bureau of Standards handbooks. Since 1947, 15 such handbooks have been made available on different aspects of the protection problem. 1.4 In 1956, the National Academy of Sciences-National Research Council published reports of its Committees on the Biological Effects of Atomic Radiation. For genetic protection this group recommended a maximum gonadal dose up to age 30 both for individual radiation workers and for the entire population. These committees published a revised report in 1960. 1.5 The recommendations of the NCRP, ICRP, and NAS-NRC are in rather close agreement. The recommendations of the NCRP have received wide acceptance in the United States. 1.6 In 1955, The United Nations established a Scientific Committee on The Effects of Atomic Radiation (UNSCEAR). The report of this group (UNSCEAR, 1958) summarized the current knowledge on effects of radiation exposure and on human exposure levels. The report also contained predictions on exposures from testing of nuclear devices under various assumptions. 1.7 The Joint Committee on Atomic Energy of the Congress held public hearings in 1957 on "The Nature of Radioactive Fallout and Its Effects on Man." The same committee held hearings in 1959 on "Industrial Radioactive Waste Disposal;" on "Employee Radiation Hazards and Workman's Compensation;" on "Fallout from Nuclear Weapons Tests;" and on "Biological and Environmental Effects of Nuclear War." In all these hearings, questions of the biological effects of radiation and of protection against excessive exposure to radiation received attention. 1.8 The Federal Radiation Council was formed in 1959 (Public Law 86-373) to provide a Federal policy on human radiation exposure. A major function of the Council is to ". . . advise the President with respect to radiation matters, directly or indirectly affecting health, including guidance for all Federal agencies in the formulation of radiation standards and in the establishment and execution of programs of cooperation with States... This staff report is a first step in carrying out this responsibility. As knowledge of the biological effects of radiation increases, and as factors making exposure to radiation desirable undergo change, modifications and amplifications of the recommendations of this staff report probably will be required. 626 RADIATION PROTECTION Scope 1.9 This staff report seeks to provide some of the required radiation protection recommendations. These recommendations are of an interim nature. Periodic review will be necessary to incorporate new information as it develops. This staff report includes recommendations for additional research which will provide a firmer basis for the formulation of radiation standards. 1.10 Only peacetime uses of radiation which might affect the exposure of the civilian population are considered at this time. The staff report also does not consider the effects on the population arising from major nuclear accidents. Only that portion of the knowledge of the biological effects of radiation that is significant for setting radiation protection standards is considered. Published information by the groups indicated above is summarized in this staff report; details may be found in the original reports. 1.11 Certain of the classes of radiation sources are now regulated by various Federal agencies. There are some which are not so regulated but which should be considered as aspects of the overall exposure of the population to radiation. Therefore, this staff report will consider exposure of the population from all sources except those excluded above. Preparation of the Staff Report 1.12 In preparation of this staff report, a series of meetings were arranged with staff members of various Federal agencies concerned with radiation protection. The objectives of this first phase in the preparation were (1) to determine the problems unique to these agencies; (2) to define problem areas not adequately covered by current radiation protection recommendations of the National Committee on Radiation Protection and Measurements or the National Academy of Sciences; and (3) to discuss the implications of the above recommendations. 1.13 A second phase in the preparation of this staff report consisted of a series of consultations with Governmental and nongovernmental scientists in the various fields involved in the development of radiation protection standards. The purposes of these consultations were (1) to discuss the bases upon which recommendations on radiation protection standards are formulated; (2) to obtain the most up-to-date information on the biological effects of radiation; and (3) to elucidate some of the physical and chemical problems involved in the establishment and implementation of radiation protection standards. 1.14 These consultations and the reports of the groups indicated above provided a basis for the present staff report. Definitions1 1.15 The activity of a radioactive source is the number of nuclear disintegrations of the source per unit of time. The unit of activity is the curie. The weight of a radionuclide corresponding to one curie is directly proportional to the half-life and to the atomic weight of the nuclide. For example, uranium-235 with a half life of 7.07 x 108 years requires about 4.65 x 105 grams to obtain an activity of one curie. The mass-activity relationship for iodine-131 with a half life of 8.0 days is about 8.05 x 10-6 grams to produce a curie. 1.16 Any biological effect produced by radiation depends on an absorption of energy from the radiation. For many years the roentgen (r)1 has been used as a measure of x- and gammaray absorption in body tissue. Conceptually, the roentgen is only a measure of the ability of x- or gamma-rays to produce ionization in air and not of the absorption of these rays in tissue. More recently (ICRU H62, 1957), the absorbed dose of any radiation has been defined as "the energy imparted to matter by ionizing particles per unit mass of irradiated material at the place of interest." The unit of absorbed dose is the rad. However, under most conditions and to the accuracy required for radiation protection purposes, the number of roentgens is numeri. cally equal to the number of rads in soft tissues.2 1For detailed definitions see ICRU, H62, 1957. For the accuracy of this approximation and the conditions for its applicability, see the International Commission Radiological Units (ICRU) Report (1957). |