Almentary tract absorpbon @ SA Tarauim er aL measurements 1s in doubt The opportumty afforded by the historical bioassay data to estimate f, for close-in fallout, particularly for '*7Cs, and Sr and ®Sr, 1s unique For this reason, the derived cesium and strontium f, values are given considerable weight in the analysis presented here LITERATURE REVIEW AND SELECTED f, VALUES 239 various organizations for both occupational and environmental exposures for all ages (ICRP 1979, 1989, 1996, Kendall et al 1988, US EPA 1988) Selected f, values for iodine. Al] literature mfor- mation support complete absorption for all commonly occurring forms of iodine An f, value of 1 0 should apply well to most fallout conditions mcludmg tests conducted at the Marshall Islands We, therefore, chose Todine 1s a Iughly fractionatmg element im fallout f, to be umity for most types of nuclear tests and atall distances from ground zero for both acute and chrome intakes of I This f, value 1s also chosen for all ages and for direct mgestion of coral particles The exception to complete alimentary tract absorption of I might be for local fallout from land tests mvolving silicate soil Fractional release of radio1odme from fallout particles 1s a function ofthe particle diam- deposit on the surface of particles rather than throughout that iodine fraction released from silicate particles re- In the following sections, we discuss mdividual elements and the available data on each from which our “best estrmate” of the f, values for radionuclides in particulate fallout were made Iodine (I) debris due to its volatility and, hence, its tendency 1s to eter, diffusion coefficient, and trme It has been proposed them (Norman 1973) Exposure to direct environmental sides within O 1 jum ofthe surface (Norman and Winch- release from fallout particles (Norman 1973) particles (Norman and Winchell 1970) and therefore conditions, mcluding sunlight, greatly accelerates 1odme After detonation, its isotopes are probably present im free form m the gaseous cloud or condensed onto the surface of small fallout particles Over time, iodine 1s expected to deposit on the ground and become attached to solid and liquid particulates Iodime isotopes are readily soluble and mobile im the environment and exhibit high accumulation ratios through the food cham, mcludmg milk (Whicker and Schultz 1982) Iodme 1s an essential nutrient and, when assimilated by mammals, tt concen- trates primarily im the thyroid gland ell 1970) For "I, about 30% may be locked msidelarge unavailable e1ther for vapor release or water solubility Basedon this mformation, 1t 1s appropriate to set a lower f, value of 07 for local fallout resultmg from ground bursts on silicaceous soil, such as at the NTS and other similar sites Tellurium (Te) ‘Te 1s an important racionuchde m fallout and 1s the precursor for “I In thefireball, tellurium 1s a volatile and moderately fractionatmg element (Freilng 1961) "I was readily detected m urmeofpeople residing Therefore, 1t 1s likely to become condensed onto fallout after their exposure to Bravo fallout debris (Harms 1954, detonation In fallout, Te 1s expected to be m the oxide at the Marshall Islands m urine samples collected 16 d Harris et al 2010) Measurable concentrations of '"I have also been reported m human and animal thyroids from the US and other countnesas a result of global fallout durmg the years of worldwide atmospheric nuclear weapons testing (Van Middlesworth 1963) In humans and ammals, absorption of I isotopes m the alimentary tract 1s almost complete when imgested in a widerange of forms mcluding aqueous solutions, milk, and mcorporated m foodstuffs Studies of mgestion of local fallout particles from land-surface detonations in- dicate that most "I 1s available for alrmentary tract absorption by humans (LeRoy et al 1966) Literature review by Hamilton (1944, 1948) also supports a complete oral absorption of 1odme m the rat Lessard (1986) reportedthat the mgestion of Bravo debris resulted m an efficient release of radiorodine trapped m fallout particles dueto the acid environment of the human stomach Anf, value of 1 O for radioiodmes has been recommended by particle surfaces as the fireball cools followmg the form (TeO, and/or TeO,), both are water soluble The metabolism and alimentary tract uptake of Te has been reported only in a few ammal species In a review by Hamulton (1948), the f, for tellurium was reported to be about 0 25 im rats Mullen and Stanley (1974) reported that 025 of tellurate fraction was absorbed from the ahmentarytract of dairy cows The ICRP (1979) adopted an f, value of 0 2 for acute takes by workers and 0 3 for chromic intakesby the general public (ICRP 1993, 1996) Selected f, value for tellurium. Due to the lack of imformation on Te absorption in humans, we suggest using the f, values adopted by ICRP for both acute and chromic mtakes (0 20 and 0 30,respectively) It 1s possible that a small fraction of Te could be trapped imlarge fallout particles, particularly if refractory silicates and oxides are mcorporated, as in the case of some ground bursts, which may reduce its solubilty and alimentary