136 THE SHORTER-TEERM sufficiently concentrated. BIOLOGICAL HAZARDS OF A FALLOUT FIRLD It seems likely that the occurrence of fallout would haveto be visible to result in such damage. | For example, in the Marshall Island experience, the extent and severity of the skin lesions were directly related to the amount of visible fallout and on Utirtk, the least contaminated island of the inhabited croup no fallout was visible and no beta lesions of the skin developed. The particulate nature of the material produces spotty distribution on the body. The Marshilleso clatmed that the material adhered closely to the skin and was difficult to brush off. This was borne out by the difficulties of complete decontiumination. Arenas of the body where perspimlion is grenter such as the neck folds, axilfnge, antecubitnl fossac ete. caused the materia} to stick and lesions were more predominant in these areas. The hair tended to collect the material also, particularly in view of the coconnut oil hair dressing used by these people, which made decontamination extremely difeult. Clothing, even a single lnyer of cotton material, afforded almost complete protection as evidenced by the fact that. almost all of the skin lesions developed on exposed parts of the body. The loose clothing worn would not have xecounted for more than about & 25 percent attenuation of the radiation so that the protection must have been due in part to the facet that the loosely fitted clothing tended to hold the radionetive material away from the skin. Tt is also possible that) the material did not stick to the clothing as well ag to the skin, . There are certain bfological factors known to influence the sensitivity of (he skin to radiation. Tn addition to species differences, it is known that the skin of certain parts of the body is moresensitive than that of others. Tn general the thinner-skinned flexor surfaces of the body are more sensitive than the thicker-skinned extensor surfaces [16]. This was found to be true in the Marshallese since lesions were more prevalent on the front and sides of the neck, axilla and antecubital fossae. Another factor is associated with pigmentation of the skin. J0ESi 13 Darker-skinned pcople, brunettes, are known to be less sensitive to radiation than blonds or people with ruddy complexions [17]. A factor which was pointed out earlicr is that arcas of the body where perspiration is more profuse cause the fallout to collect resulting in greater skin effects. Sources of radiation to the skin.—Damage to the skin results largely from the beta component of the fallout in view of the fact that the beta-gammnratio is quite high. All of the energy of the beta particles entering the skin is absorbed in the skin. Soft gamma rays accounts for some of the radiation dose to the skin, and the harder gamma rays contribute least. since they are more penctrating. The skin dose results from two sourecs of beta radiation, the fallout material in direct contact with the skin and the material on the ground. 1. Contact source.—The spotty distribution and particulate nature of the fallout in contact with skin results in multiple point sources on the skin. By far the grontest part of the skin dose comes from this source. Radiation is largely from the skin surface. However, tho possibility must be considered that a certain umount of percutaneous absorption may take place and some penctration into the dermal region via the hair shafts, sebaceous and sweat glands may ocenr. Tho Castle fallout: contained about 10 percent water soluble fission products, some of which might conceivably have been absorbed pereutancously. Whitten et al. [18] have shown that thorium-x applied to the | skin results in some percutancous whsorption and entry into the hair shafts and glands. We intend to investigate this problem with fission products on the skin by means of autoradiography. 2. Ground source.—A certain amount of the skin dose mayresult from. beta radiation from the fallout material on the ground. This contribution is likely to be far less than that from the cuntact source. The lower parts of the body will receive the greater part of this radiation since the beta particles are completely stopped in 2 meters of air.