_-4 SOURCES OF RADIATION FROM FALLOUT. Fig. 1 is a rough diagramatic sketch showing the relatively uniform dis- tribution of fallout on the ground, buildings, trees and personnel. The pene- trating gamma radiation which is represented by the wavy, shaded areas penetrates many yards in air before it 1s attemiated appreciably, while the beta radiation represented by the stippling is completely attermated in several feet. Damage to tha skin results largely from the beta component of the fallout in view of the fact that all of the beta radiation entering the skin 1s absorbed in the skin and because of the high beta to gamma ratio. Estimates of this rationvary widely up to 1/150, depending on the exposure conditions, The skin does receive some radiation from penetrating and soft gamma radiation, but hy far the greater part of the dose is contributed by the bata radiation. Alpha emitters are usually not present in fallout to any great extent and due to their very weak penetrating ability, they are not likely to add significantly to the akin damage. The skin dose results from two sources of beta radiations the fallout material in direat contact with the skin (contact hazard) contributes by fer the largeat part of the dose to the skin, and the material on the ground (beta bath hazard) contributes a mich smaller amount. The fallout in contact with the skin will usually be spotty in distribution and due to the particulate nature will result in miltiple point sources of radiation on the skin, Trough radiation from these sources is largely from the skin surface, it is possible that some deeper radiation may result from percutaneous absorption as well as penetration inte the dermal region via hair shafts, sebaceous and sweat glands. Some of the fission products are water soluble, and it is possible that some are lipid soluble, which would enhance this effect. ‘iitten et al. have shown