34 EFFECTS OF IONIZING RADIATION ointment, with apparent success. When the epithelium was desquamating, all lesions were treated by daily washing with soap and water followed by the applcation of a water soluble vanishing type ointment which kept the injured skin soft and pliable. Rawareas, which became secondarily infected, were cleansed with soap and aureomycin ointment was applied. Bullous lesions of the feet were left intact as long as no symptoms were present. If painful, the fluid was aspirated with sterile technique and a pressure dressing applied. A single aspiration was adequatesince the bullae did not refill. In one instance, an extensive, raw, weeping ulcer developed for which penicillin was given for two days. During this time the lesion developed healthy granulation tissue. Some of the lesions of the skin of the foot remained thickened and less pliable after desquamation. This was relieved by the use of vaseline or cocoa butter to soften the tissues. The one persistent ear lesion did not heal after desquamation. This was treated daily with warm boric acid compresses and washing with surgical soap to remove the eschar. Slowly, regenerating epithelium grew in from the edges of the ulcer. Upon reexamination, 6 months after exposure, healing was complete with a depigmented scar remaining as evidence of the previous ulceration. The latter would penetrate well into the dermis 3.5 kvp X-ray (3). From this a rough idea of surface dose may be made. A dose to the hair follicles comparable to 400-700 r of Xradiation must have been due almost entirely to the more penetrating beta component (average energy, 600 kev). Therefore, the minimal surface dose in rep from this component alone was probably four to five times the dose at the 3.51 Factors Influencing Severity of the Lesions Character of the Fallout Material This material was composed mainly of calcium oxide from the incinerated coral, with adherentfission products. Fifty to eighty percent of the beta rays emanating from this material during the exposure period had an average energy of about 100 kev. Since 80 microns of tissue produces 50 percent attenuation of such radiation (1), a greater portion of energy was dissipated in the epidermis which is roughly 40 to 70 microns in thickness. The remaining 20 to 50 percent of the beta rays had an average energy of approximately 600 kev. spa 11i4 since it takes 800 microns of tissue to produce 50 percent attenuation of this energy radiation (1,2). In addition, a wide spectrum of gamma energies irradiated the skin. The gamma contribution to the skin was small compared to the beta dose and is discussed in Chapter I. 3.52 Dose to the Skin The skin lesions observed resulted primarily from beta radiation from fallout material deposited on the skin. The gammadose to the skin was small compared to the beta dose, and thus relatively unimportant in producing the lesions. The summation of gamma and beta contributions to the skin is considered in Section 1.3. In general it is evident that skin in- jury was largely produced by material in contact with the skin. The total surface dose cannot be calculated with accuracy but minimal and maximal values at various depths in the skin can be estimated biologically. Hair follicles in the areas in which epilation occurred must have received a dose in excess of the known minimal epilating dose of about 400 r for 200 kvp X-ray. Since regrowthof hair occurred, the upper limit of dose at the depth of the hairfollicle must not have exceeded the per- manent epilating dose of around 700 r of 2006 hair follicle, i. e., roughly 1,600-3,500 rep. The soft component (average energy, 100 kev) contributed a considerably larger share to the surface dose but with only slight penetration. 3.53 Protective Factors The following factors provided some protection: