13 slightly atrophic. Treatment of the skin lesions con- sisted of daily cleansing and symptomatic therapy with the exception of locally applied antibiotic ointments for infected lesions and in one case parenterally given peni- cillin. The possibility that cancer might develop at the site of some of these lesions must be considered. Favoring such development are the long life expectancy of the numerous children in the exposed group, constant ex- posure to tropical sunlight, and the possible influence of additional sublethal whole-body exposure. Against such development are the superficial nature of the lesions, rapid healing with little in the way of residual gross defects, and only minimal evidence of histological damage by six months. Pigmentation of the semilunar area of the fingernails and toenails was observed about the 23rd day in most of the Marshallese in the higher exposure groups and in the five American Negroes but in none of the white Americans. The pigmentation was beneath the nail and progressed distally with growth of the nail. A similar phenomenon has been observed in a Negro womanafter local therapeutic irradiation.® INTERNAL RADIATION HAZARD Radiochemical analysis of numerous urine samples of exposed personnel showed that the degree of internal absorption of radioactive materials was roughly propor- tional to the calculated external dose and, therefore, to the concentrations of air-borne fission products. The degree of internal radiation hazard was too low to have contributed significantly to the acute radiation syndrome observed. The concentration and type of internal radioactive contaminants minimize the probability of any significant long-term effects from the internal radiation. SUMMARY AND CONCLUSIONS After detonation of a thermonuclear device in the Marshall Islands in the spring of 1954, radioactive fallout occurred over an area of thousands of square miles 6. Sutton, R. L., Jr.: Transverse Band Pigmentation of Fingernails After X-Ray Therapy, J. A. M. A. 150: 210 (Sept. 20) 1952. JU12Z 101