Sweeter: TS es wad. RADIATION STANDARDS, INCLUDING FALLOUT 317 INDUSTRIAL EXPOSURE EXPERIENCE Although the employment of workers by industry engaged in the handling of large sources of radiation has expanded rapidly during the past 20 years, the present work force of some 200,000 (7) is still very smali in comparison with that of the major industries. Nevertheless, a substantial experience record has been accumulated which attests to the exemplary success of the operators in minimizing radiation exposure through prudent engineering design and strict control. Quantitative assessment of the performance of the larger atomic energy sites is practical in four broad areas, viz: (1) The magnitude of the exposure from external sources received by employees during the normal course of their work assignments. (2) The small burden of radioactive materials which may be deposited in the bodies of the workers. (3) The magnitude of the exposure received by persons who live in the vicinity of the plant. (4) The frequency and severity of accidents which result from loss of control, The first three classes of exposure can be compared with pertinent limits, and the accident experience can be followed as a trend. Compilations of exposure records for recent years (table I) indicate that the vast majority of workers employed by AEC contractors receive a radiation dose of less than 1 rem per year. Only in very few cases (about 1 worker in 10,000} has the NCRP short-term control limit of 3 rems in 18 weeks been exceeded and invariably this has resulted from some sort of an accident rather than imprudent work assignments. We were unable to make a comprehensive survey of the radiation experience of the whole of industry. While our information from industrial users is incomplete, in replies from representative major users covering about 30,000 people, the average annual radiation exposure in 1960 and 1961 was about 0.3 rem per person. There is a widely used formula for the control of accumulated dose for an individual over the years, which is written (10) MPD—5 (N—i8) rems where MPD = maximum permissible accumulated dose, and NV is a number equal to the present age of the individual in years; (the formula begins to apply after age 18, the employment of minors below this age being avoided). Among the group replying to our survey, including ourselves, only two eases showing accumulated doses exceeding the formula values appeared. Including all the radiation accident cases known to us, the total is less than 15; if our resources had been complete, the total would probably remain below 30. It is important to reiterate that many of these do not represent real injury to the recipients and some will be self-correcting as the respective values of N increase. To the best of our knowledge these cases are principally due to single large accidental exposures. We were not able to uneover any specific case in which an employee was in excess of this limit due to radiation received chronically in the course of his work. There is very little public data available on the radiation control experience of the small users. Examination of the most recent data on licensee experience reported by the Atomic Energy Commission for about a 144-year period ending November 30, 1961, gives some indication of the degree of control experienced by the small user. In this 17-month period during which about 10,000 licenses were in force, the great majority of the 40 radiation incidents reported were minor in nature. None of the incidents reported resulted in a serious level of radiation exposure. Nationwide experience on internal deposition of radionuclides in industrial workers is not readily available in published reports but in our limited survey, there was a nearly complete absence of significant deposition cases. In our own experience at Hanford in 6,600 man-years of direct werk with one of the most dangerous elements, plutonium, only three employees have acquired body burdens of plutonium which approximate or exceed the present applicable standards. The quantities involved are not expected to produce clinically observable symptoms and none have appeared? Additionally, in about 75,000 man-years 8 There is growing evidence that the present standard for plutonium, which is based on analogy with radium depositions, may have a yery considerable safety margin. bey Paley yee a geet ad el tite cated Sys tiated, Wlnlspe alee Liat arte stan tale ca SUH SAPAYS8 SERRE OSTGEREE OES