ae ao . oat ‘ . . not hee ke te ee . . Maa. “4 T." Tf, "4% 45 1 . . oo Ae nee ivtiebis, tahPeas is ed a Bae te a ‘ sey Pee: eS CGS Table 3. - Surface Doses Required To Produce Recognizable Epidermal Injury Investigator Animal Henshaw, et al. (22) Raper and Barnes Raper and Barnes Snider and Raper Raper and Barnes Lushbaugh (25) (23) (23) (24) (23) Moritz and Henriques (26) " " " " " " " " " " Isotope rats p>? sheep sr®° rats mice mice rabbits pigs pigs pigs pigs pigs pigs Eneray Mev) 0.5 p?? p>? p??. p*? 0.5 0.5 0.5 0.5 35 0.05 Co®® cs'*? sr°° y*! y*? 0.3 0.01 0.2 0.3 0.5 0.7 Deantee) 1, 500-4, 000 4,000 2, 500 2,500 §, 000 2,500-5, 000 20 , 000-30 , 000 4, 000-5, 000 2, 000-3, 000 1, 500-2, 000 1,500~2, 000 1,500-2, 000 The outlook for the development of,malignancies at the site of healed lesions is uncertain. Certain factors tend to make the outlook more favorable. (a) The majority of the lesions vere superficial. (b) Visible signs of chronic radiation dermatitis were absent in the vast majority of cases. Such changes have been generally observed prior to the development of radiation cancer. (c) The lack of any marked histological damage six months after exposure. (d) The fact that low energy radiation was chiefly responsible for the skin lesions. It has been reported (27) that none of 1,100 individuals exposed to low voltage X-ray for dermatological conditions developed epidermoid carcinoma five to twenty-three years after treatment. (e) The fact that epitheliomata rarely develop after a single dose of radiation to the skin (12), (f) The incidence of skin cancer in Negroes is one-sixth to one-ninth the incidence in Caucasians (28) in the United States. Other factors tend to make the outlook less favorable. (a) Deeper lesions of the feet and neck continued to show pigment aberrations and slight atrophy at 1 year, and one severe ear lesion showed marked atrophy and scarring at this time. (b) It is not known whether or not radiation of the epidermis per se can predispose to malignant change. Since the epidermis was heavily irradiated in these cases, compared with the dermis, this becomes an important cmsideration. (c) Since many children and young adults were involved, the life expectancy of a large number of the individuals will exceed the long induction period for the development of radiation cancer observed in radiologists. (d) Exposure to tropical sunlight, potentially carcinogenic in itself, may increase the probability of neoplastic change. (e) The influence of the sublethal whole-body exposure received by these people on skin cancer induction is not known. The occurrence of epilation 2 to 3 weeks after exposure corresponds roughly to the time of appearance of epilation in the Japanese exposed to gamm radiation at Hiroshima and Nagasaki (29, 30). Since the greater amount of epilation occurred over a period of a week to ten days there was apparently no phasic response dependent on the growth cycle of the follicles (inactive, or telogen and active, or anagen follicles ) as has been reported (31, 32). The regrowth of hair, beginning about 9 weeks after exposure in the Marshallese, was about the same time as noted in the Japanese fisherman (11), and slightly later than the time of regrowth (6 to 8 weeks) noted in the Japmese bomb casualties. In contrast to the marked pigmentation changes noted in the irradiated skin of the Marshallese, there were no pigment aberrations in the new hair which was observed to be of normal texture and abundance at six months. Increased graying has been reported in animals (33-36) but has not been seen in human beings. Neither was there any appearance of dark hair in aged individuals who already had 437