we wee Ne eetMT em ee we oe teem 2 Ae om in + es oh wr mm: oe tee ee 2.6 - about 50 per cini .: that on the southern end of the island and wa. approximately the same as the fall-out 5: Japtan. It became evident that ‘ 2.6.1 the major portion of the fall-out occurred on the ~ Assuming that the decay continued according FALL-OUT Introduction effect on the population (Sec. 2.6.4). It was not immediately apparent whether inhalation of the - fall-out material was a serious health hazard. The answer depended primarily on the particle size distribution of the fall-out material. If the active material was carried mainly on particles considerably less than 10 microns in diameter, much of the material might reach the alveoli of the lungs, from which it would not be eliminated readily, and the possibility of serious consequences could be envisioned. If, on the other hand, mostof the activity was carried by particles much larger than 10 microns, the situation, although undesirable from a numberof studies revealed them to be approximately the same size as those that fell during the Dog shot. Results of island surveys following Item shot appear in Appendix D, and results of atoll surveys are given in Table 2.4. TABLE 2.4 Ww oe This section deals with investigations that were started a few hours after Dog shot when fall-out of radioactive material occurred on Parry, neighboring islands, and vessels. The fall-out was sufficient to give a gamma ray dosage rate of about 60 mr/hr on Parry. It was soon apparent that the total gamma ray exposure from this source would have no serious western part of the Atoll, decreasing at Eniwetok and Parry and decreasing further on Japtan. toat''? law, it was possible to predict that if an individual had remained in the open for a period of 15 days the total dose received would have been 7,370 mr; at the end of 30 daysit would have amounted to 9,520 mr. (Note: These. predictions were not borne out by measure. ments made after the departureof the task force from the Atoll. Heavy rains set in at the end of May and apparently washed away most of the radioactive material from the inhabited islands.) The particles collected in a cascade impactor on Parry Island were all captured in the first stage of the instrument. Microscopic ~ 5 ATOLL SURVEYS, ITEM Intensity (mr/hr) 1030 25 May I-day Eniwetok Parry Aniyaanii Runit Piiraai Biijiri Bogon Teiteir Bogombogo Bogallua Rigili Giriinien Pokon Igurin 45 6 0.5 1.2 0 0.02 420 550 10,000 9,000 7,000 2,800 1,600 1,400 100026 May +1 40 30 15 5 090027 May I+2 28 May 1+3 28 18 8 2.4 30 10 5.5 1.6 1,2 2.2 55 60 850 900 1,4 25 33 700 800 1.2 14 18 400 300 650 410 270 155 450 250 160 90 280 140 60 50 eeem s ¢ omarON = ERRE S 29 May 1+4 3.1 1.5 0.9 270 170 110 30