“a ei ££ he anne TA 2 NC 3 restricted ae The COG Le OLS 2 Atomic Ensigy ACKO €-iinec she i +b , Sane mL , le ve oe . * a” i. y ee oe a) ACA LLby H. 0. Waipple, M. Do» Health Division QUERMNT RADIATION LEVELS af WWETOK 5). ee h ee meen oiiecting the dervaoet oem os LCS. eam ee ciscles cre of ics contents in Repent cee ieee COT 48 prohibited ms Laeaseoacebdewt reaper penaitées ander —" . s eral [BWR Measurements of activity at Bniwstek Atoll during the early part of : February, 1949, agree in the main with the findings of Br. ghlaer, | dn Octobder, 1945. Levels of activity at the present tine are between 1/2 and 2/3 ef the values feunt by hia. For exemple, on Ingedi the Cte Leas OOD CS? LZa7. date) (Signature of pergon making the changa and presen¥-activity at Sero is 30-00 ar/hr (Gemma), and the maxizum (Person authorizing change in c oy Dp a RIS_H, DUNNING s Ce Clacsification changed to by authority of the U.S. ERDA lassification and date) 8-00 Ft, he we a - z activity fount by us in the *hot® sone about 300 yards out was 75 ar/hr (Senna). The corresponding values reported by Dr. Shiaer are 60 ar/hr and 100-150 ar/hr, respectively. The general > the area of int und activity over the entire island, exclusive of rp eontemination, which is believed to be due to fall-out from the Yoke shot, has however decreased to a value of from 0.1 to 0.2 ar/hr, as compared with the October level of 0.4% to 0.6. Film studies shoved the activity to be due to a fairly dense distri- bation of particulate radioactive material on the ground mrface. Bunit alone is presumably free, in the main, of such a gm eral ised particnlate hasard. Further film studies will clarify this point in the near future, The ground surface at the present time is wind-stabilised; that is, all the finest material has been blown out of the superficial layer of soil, and as a result the islands are singularly free of dust. Although we did not have facilities for collecting and counting dust samples, the group concurred in the opinion that mao respiratory hasard eurrently existed. It wae also almost painfully obvious that any aisturbaace of the ground surface immediately resolted in producing voluses of dust and an undoubtedly serious respiratory hasard, The levele of activity are such that little if any restriction ss | working time in the Shet® areas will be necessary, as far as remaining within permissible linits of external radiation exposure is soneerned. Past, Rovever, reproseste an entirely different probdlen, ead it is net pessible te specify a permissible level af aetivity in the respired air when Shis activity is in the form of finely @ivided insoluble parti cies. . A fraction ef och saterial will Be retained in the lung and pulmonary G_Svnph nodes for leng periods of time; the dosage level in body celis sijecent to such particles are extremely high even though the total activity of the particles is relatively low; and it isc believed that QO ou iw a UNGLASS to conduct operations in such a seiF FOLDER wa these circumstances are markedly increased. BOY No o Ee the statistical chances of eventual development of lung cancer under COLLECTION > aa é 4,20 aren 11, vol SS os se fig LZ LASSIFIED | Alvin Graves, d-Division Leader >° } Je ras It therefore behooves us . he respiratory exposure of mid