3.5 FACTORS INFLUENCING THE SEVERITY OF SKIN LESIONS 3.5.1 The Characteristics of the Fallout Material 2 The falleut material was composed mamly of cabetuo oxide from coral, with adherent: fis sion products, The skin lesions observed were undoubledly Che result primarily of beta radiation from fallout materiuil deposited on (he skin, with mintnw) or no cantribution from chemteal Irritation. The ywanioit doge to the skin was small compared to (he beta dose, and hus was reladively ununportant in producing the lesions. 3.5.2 Energy of Betu Particles From available data on the fallout material it has been calculated that 50 to 80 per cent of the beta rays during the exposure perieg.were soft with an average energy of about 100 kev. Since 80 microns of tissue prod portion of energy was dissipated’ 50 per cent attenuation of such radiation,' the wreater the epithelium which is roughly 40 to 70 microns in thick- ness. The remaining 20 t#€50 per cent of the beta rays were of higher energy, with an average of approximately 600 kev. The latler would penetrate|well tnto the dermasince tt takes 800 microns of tissue to produce 50 per cel attenuation.'? In addition, a wide spectrum of gamma energies irradiated the skin. Approximately 10 per cent of the total gamma spectrum was below 80 kev which would be absorbed largely in the superficial layers of the skin. The remainder of the gamma spectrum is distributed between 100 and 1600 kev with a large proportion be- tween 600 anc 800 kev. 3.5.3 Physical Doge to the Skin There is no practical way to estimate the physical dose tu the areas of skin where lesions were found. The entire surface of the body of the Rongelap group received approximately 175 r from gamma irradiation derived from fission products distributed on the ground, trees, and buildings. To this 175 r would have to be added the beta c anent. in view of the bigh beta to gammaratio in fission products, one might expect. te t large. The maximal skin doses from the planefield of a surtar rittixation are# eto thesith tebe ited ia chapter 1. To these doses must be added the contribution of the material d tedntthe skin. The latter can not be calculated, or estimated biologically with any. dep accuracy."A rough approximation of dose received at the hair follicles can be made ae follows: The hair follicles must have received a dose comparable to the known*pinifal epilaling@ dose of about 400 r for 200 kvp X-rays. Since regrowth of hagy occurred, the upper limit of dose at the depth of the hair follicle must not have exceedgtl the permanent epilating dose of around 700 r of 200 kvp X--ray.? mat 3.5.4 Protective and Aggravating Factors # ‘zt The individuals who remained indoors or under the trees showed some protéetion as compared to those who were in the open during the period of the fallout. Those who want swimming or bathed were also protected to varying degrees. Small children who went wading developed fewer foot lesions. Clothing, even a single layer of cotton material, offered almost complete protection, as was demonstrated by the fact that legions developed almost entirely on the exposed parts of the body. Since the lesions predominate in areas where perspiration is abundant such as folds of the neck. axillae, and antecubital fosgae, it seems likely that the abundant perspirati-: produced by a hot, humid climate tended to cause the material to concentrate and adhere t:: these areas. In addition, the coconut oil hair dressing used by the Marshallese acted as an effective collecting agent for the radioactive material. This was proved since the hair was the mosthighly contaminated part of the body. The concentration of radioactive material on the hair may have been responsible for the large number of scalp lesions, epilation and the large number and severity of neck lesions in women.