a ~—- ~~ burns have been seen in the biopsy sections, However, the energy of the beta rays in the fall- out may have been very low, thus limiting the injury to the superficial epidermis and sparing the vascularized dermis. Accordingly, the absence of specific vascular lesions in the biopsies would not necessarily eliminate radiation as a causative factor. The dose rate from fall-out varied continuously, and the total dose was received over a period of many hours or days. This is in contrast to previous experience mentioned, in which the dose can be considered to be either essentially instantaneous or received at a constant dose rate over a period of minutes. From previous animal experimentation it might be expected that the dose received by exposed individuals in the present study, extending over two or three days, would produce less of an effect than would the same total dose given over afew _ minutes. It is not possible without further experimentation to attempt quantification of the degree to which observed effects in the population studies may have been altered by this particu- lar combination of dose rate and time during which the total dose was delivered. Hematological findings were somewhat similar to those seen following single doses of penetrating radiation in animals. However, the time course of changes in both the leucocyte and platelet counts in the Rongelap group was markedlydifferent from that seen in animals. Maximum depression of these elements occurred much later in these individuals than is seen in animals, and the trend toward normal was considerably delayed. The marked delay in return to normal leucocyte values in the present study appears to exceed that observed in the Hiroshima and Nagasaki casualties. Further evidence that the return to normalmaybe later in hur an haiegs than in animals can be s2en in the response of :! e few cases of the Argonne and Los Atanos accidents. Although the doses, types, .nd cond‘titns of ir:udiations were sufficiently different in the several series of ¢xposcd $-.man'! ¢ings to precivde strict comparisons a song them, the added evidence from the present studies would seem to validate the general conclusion that the time pattern of hematological changes following irradiation in man is significantly different from that observed in the large species of animals studied to date. 2.3.5 Program 6, Service Equipment and Techniques Program 6 included six projects concerned with the developing, testing, and analyzing of various aspects of weapons effects on service equipment and operational techniques, Project 6.1 was successful in obtaining excellent radarscope photos of the detonation and blast phenomenafor utilization in establishing Indirect Bomb Damage Assessment (IBDA) procedures for high-yield weapons, The high-yield weapons detonated in regions such as Bikini, where sharp land and water contrasts are obtainable, gave excellent results for radar-return studies and air-crew training for the 20 Strategic Air Command (SAC) air crews who participated, Projects 6.2a and 6.2b were successful in obtaining significant data concerning blast, thermal, and gust effects on B-36 and B-47 aircraft in flight, Minor blast damage was sustained by the B-36 on several shots; however, predictions on temperature rise as a function of incident thermal energy for both the B-36 and B-47 were shown to be conservative. Sume concern arose over the response of the B-36 horizontal stabilizer to gust-loading at a critical station. Additional studies will be required, including instrument calibration, before any revisions of current concepts of delivery capabilities can be expected. Project 6.4 was successful in evaluating the effectiveness of washdown systems for naval ° vessels. Also much valuable experience was gained in ship-decontamination procedures and techniques. In addition, one vessel (YAG-329) assisted in the collecting of fall-out data for Project 2.5a. Project 6.4 has demonstrated that a typical naval vessel, when adequately equipped with washdown apparatus, can operate safely in regions of heavy fall-out and still maintain operational capability without excessive exposure of the ship’s companyto residual radiation from fall-out. Project 6.5, operating in conjunction with Project 6.4, evaluated current d-eontamination to the procedures on representative walls, roofing, and paving surfaces v hich were subjected barge shots, wet contaminant of barge and land shots. The contaminant, particclarly from the ” 24 Te