| - i ° : | | .!~ | . _ Ld 1 | ji a ty os ae fou ' ~ 71 be see tl La se OT | . fn a = SPLLBY BRSseg Be e.fe oS 3 3 ge @é SE Ses e gps ESS gf ES E 3 3 ~ ze 23 <£3i35 ese of 0.2 rep (March to May 1956). sion March 1956 was an accumulated exposure Fg 3% 8 During this period the maximum activ- SgRe Sak Ss 2 day. The average radiation to all range-fed : . soe 2 SAS sad d Ze g s g< S36 2é é garithmic scale as a The dashed horizontal line, A~B, i um and other long-lived radioact: § g <2 <* 3 g3 .& cattle is close to 0.01 repep P per day . ad for this entire . period, Thus the maximum exposure of bovine thyroid was (June 6, 1956 to October 11, 1956) s > 2 5 = a ° 38 Siig 33 :. & i gyi BBRE Tp : we _ bee Fane “" ee | | ‘| bh aresots evs vis scdomnm . ae 3 gx B.&s east = & Be 2: 3 = pESE ce $.2 Bs 33 g ose 3 32 5 = sisex 2? > & E g z3 & 2s S Zz oo S8 1 | | day mucigm 6235 267 BBR aneigtt aamapte BT 4em lehiole thyroid OT am 43 emo... concentration}. Median lowof thyroid 15 content in range-fed animals 182 -.. . -.. 1181 6.409 4.3 —¢m 27 em Average tremensela “ATage pale Median JeveLof thyraid 1!) content in feed lot-fed animals 52 2... 2... 289 0,008 43 em 27 gm "nianificant) Number 68 initial count .. . 68 recount --. ait 6.214083 4.3 em 5. 18:40. 76 _ 103 Lig taitt (O81 16 em Hrerence no t half-lives of radioiodine (lapse of at least 28 days). Even though any one of the human thyroids contained too little 1! to be detected, it was possible to make a finer estimate of the TI content in human thyroids, by combining Samples were counted an average of 3.8 days after death, therefore if human thyroids had 1.03 counts of 1 per sample the average IM burden of human thyroids would be 0.0006 millimicrocuries per gram. Radiciodine levels in human thyroids either individually or as a group-measure were not significantly established in the same time period whencattle [ content in thyroid tissue ranged up to 2.7 millimicrocuries per gram thyroid. time periods: One of low cattle I" content (January 1956 to March 4, 1956) and the other of the period (June to October) when range cattle thyroids were measurable as having 2to3 thousand counts per minute per total countable thyroid had appreciable [' content comparable with beef thyroid. It measured 0.025 millimicrocuries per gram, which is about 1/20th of the bovine I™ concentration, during this time period. This man, upon investigalion thyroids and establishes that the average human thyroid concentration of !is probably half-lives of I! earlier. Thus the observed Jevel is entirely within the expected value for all the human measurements according to 2 gos 2 gs . &8 ae es 5 Res 3 = Me Bs 3 3 s .2 g&s y BSis counts somple per beef or human contained similar levels of Humanand beef thyroid were measured for radioactivity both initially and after 4 or more 3s Nuraber 1 (highest measured . Humanthyroids— natural radioactivity. Additional beef thyroid radioactivity was identified as ]™ byfollowing the decay of radioactivity which uniformly gave an 8-day half-life to the radioactivity above the natural background. = June to October 1956 . ue — Bovine thyroids * | 7 7 ge . Thyroids -having more than 1 myge/gm: Acerage Average mera approximately 1.9 7. Human thyroids at all times of collection were in the range of 1/1000ththe level of range- fed beef thyroid I content. During times when Icontent was not detectable in either humansor cattle, the thyroid gland tissue from 163 . Be An integral dose for the Bikini tests is estimated as including e time from May 5 to October 1956. s ; Ef 2% &e ities corresponded to 0.010 to 0.028 rep per s ‘ 1 lapse of time between last range feeding and . . Thus, much of the variance in : ye . range-fed animals may be iodine decay during . t " the pre-slaughter holding in stockyards. The cattle thyroid irradiation for the Kussian exploslaughter. = S28 remem BE 38 2 8 3 & 3 ose ae ss = 3 g& g ges 2 & I we 'y include the radioactivity of the glass vial ‘ground has been subtracted. on en rere i . UPTAKE OF IODINE-131 IN HUMAN AND BOVINE THYROIDS THE SHORTER-TERM BIOLOGICAL HAZARDS OF A FALLOUT FIELD Thus all radioactivity in cattle thyrotds above line 162 sample. By counting the human thyroid specimens initially and after decay, the following comparison fails to detect Iin human less than 1/1000th the maximum level observed in thyroids from range-fed cattle. It is interesting to note that one human through the attending physician, was found to have boen given a tracer dose (2.5 ye I) 67 days preceding death, or approximately 8 this length of decay of I". Tt is possible that human thyroids do not