SKIN LESIONS AND EPILATION The early symptoms of itching and burning of the skin and eyes were probably due mainly to skin irradiation from the fallout material. Ifowever, the chemical nature of this material may have contributed to the irritation. It has Leen noted (12) that irritating chemicals applied during or shortly after irradiation enhance the effects of radiation. The lack of prominence of an erythema was notable. particularly in view of the severity of some of the lesions that developed. Wilhelmy (13) states that erythema only occurs when the dose reaching the papillary layer exceedsa certain level. Perhaps due to the low energy of the beta radiation the dose to the dermis wasinsufficient to evoke the response. On the other hand. the darkness of the skin and the development of hyperpigmentation may have masked an erythema. Microscopically, a superficial hyperemia was not prominent. Wirth and Raper (10) point out that they were impressed in their studies on P * radiation of the humanskin with the difficulty of distinguishing between true erythema and tanning, particularly in the skin of brunette individuals. It was unfortunate that color filters were not available to aid in distinguishing an erythema as suggested by Harris et a/. (14). In general, the length of the latent period before development oflesions of the skin is considered to be roughly inversely proportional to the dose of radiation (15, 16). In the present series of cases the relatively long latent period is suggestive of a low dose of radiation. Dueto the wide spectrum of beta energies and particulate distribution of radioactive material, strict comparisons cannot be made with previous experience. However, the later develop- ment ofless severe lesions in the Ailinginae and Rongerik groups as contrasted with earlier development of moreseriouslesions in the Rongelap group is in keeping with a lower skin dose in the former, and a higher skin dose in the latter. It is of interest, however, that the latent period was dependent to some extent on anatomical location. The foot lesions, which were generally the most severe lesions encountered, had a longer latent period than did 37 the less severe lesions occurring elsewhere on the body. It is logical to assume that the feet received a higher dose of radiation because of proximity to the ground and this may explain the severity of these lesions. The longer laten: period (desipte higher dose of radiation) may be related to thickness of the epidermis, differences in length of mitotic cycles or other inherent characteristics of skin in different areas of the body. The histopathological changes noted, such as destructive and atrophic changes of the epi- dermis, disturbances in keratinization, and atrophy of hair follicles, when taken together are consistent with radiation injury to the skin (9, 12, 17, 18, 19, and 20). Severe injury to the dermis and blood vessels was not observed. The minimal dermal injury with severe epiderma]injuryis in keeping with the large component of low energy beta material present, resulting in absorption of the greater portion of the energy in the epidermis. Hyperpigmentation of injured areas was a consistent finding in the Marshallese and the American Negroes. Pigmented lesions were also observed to a lesser extent in the white Americans. Such pronounced pigmentation is not characteristic of the usual lesions as described following exposure to beta or penetrating radiation, but may be more typical of the response to ultra soft roentgen or “Grenz rays” (21). There is no satisfactory explanation for the darker dusky-gray color that appeared in some of the skin lesions as healing progressed. Vascular changes or pigment aberrations might have been responsible. The return to nearnormal in this pigmentation by 6 months showed the transient nature of this change. The continued absence of pigmentation at the site of the deeper foot lesions at 6 months and 1 year later suggests that the pigment-producingelements in these areas were permanently damaged. The unique features of the lesions such as the marked pigmentation, the absence of obvious multiphasic response, the long latent period,