f Fe aes pee MS ot ART OUR Tee CORR ot apeingep nee caer ” (3 [ Reprinted by the — : —~, U.S. DEPARTMENT OF HEALTH, EDUCATION, AND LFARE Public Health Service From RADIOLOGICAL HEALTH DATA, Vol. 6, No. 12, December 1965 D1) Kaa AL onl, CONFIRMED TO BE UNCLASSIFI AUTHORITY: DOE/SA-20 akt. HALF-TIME OF CESIUM-137 IN MAN? HrR; BY h.@ Cllsop ©. MeCrau* / *. part of participation in the Federal © Available data Kaha:..n Council Working Group and Ad Hoe F.. ©, un Strontium and Cesium Radionuclides 4: -:~-«veloped Report No.7, the available matevial ond dat:. pn the half-time of cesium-137 :. att were reviewed. The purpose of this .” :zt was to collect data on measured values ©. ve .am~187 half-time that could be employed, _sfodac. witn other material, to support the . « of an assumed value of biological half-life :: whole body and bone marrow dose calculatigas. This report represents (1) collected data on aaeasured values of cesium-187 half-time in Table 1 lists data from the literature. The symbol T, will be used to represent the biological half-time of cesium-187 in man. Where possible, the range of observed values for each group of individuals studied is included. Discussion of data ' Rather than present individual measurements of T, for each subject, many investigators have reported an average value with an indication of the range of observed man, (2) a suggested model for expressing “values, Considering the lower limits of the ce’ ar -137 half-time as a function of age, and ‘; ust.aates of doses and body burdens for a . * : salake of cesium-137 and for intake of 437 in milk, using an assumed pattern -* -}% consumption by various ages.. ~"..@ Anportant consideration in determining 11. body and bone marrow radiation dose w an exposed population from internal cesium237 is the effective half-time of this radionu- clide in man. Should there be a different bio- logic .«] half-time for cesium—137 in various age ucoups within a population and an effective ‘half-time* which varies as a function of age, it will be necessary to consider this factor in determining doses to the population and in ,ie:ermining which age group in the population will receive the highest exposure from a conwaninating event. + AG.upted from HASL-164:281-300, Clearinghouse for Federal Sciextifie and Technical Information, 5285 Port Royal Rosd, Springfield, Virginia 22151 (October 1, 1965). Price $7.00. -?Mr, McCraw is a Health Physicist with the Division of Operational Safety, Atomic Energy Commission, Germantown, Maryland. * For cesium. 137 in man, the radiological half-time is so tong (about-11,000 days) and the biological halfaime is a0 short ‘of the order of 100 days or less) that for purposes of this report, the effective half-time ean be considered equal to the biological half-time. range of values for “adults” (unweighted for numberof subjects) for all investigators where ‘ a range was given, the average value for the -lower limits is about 78 days. The average value for the upper limits is about 122 days, and the overall average is about 98 days for these data. The unweighted mean of the “Body Radioactivity Measurements and Excretion or Dietary Analysis” data from Rundo’s summary is 110 days. The “Body Radioactivity Measurements” give an unweighted mean of 108 day:. The “Excretion or Dietary Analysis” data give an unweighted mean of 114 days. Thus, the two techniques appear to give results which are in close agreement. The data collected on T, for groups of sut- jects are presented graphically in figure 1. Aix: plotted are individua] values for 6- and 8-year-. old girls and for two infants (Rundo), and values for three young women and twoinfants (Bengtsson et al.). In order to display the data for “adults”, it has been assumed that this age - group consists of those about 20 to 26 years of ‘age and older, and the elderly are assumed to be over 60 years of age. Le maceen December 7965 1 Pod