Volume 87, Number + heavily exposed to radiation from the atom bombs.*2: 53, 5+ In another study of Japanese atomic bomb survivors, a higher incidence of cancer of all types (excluding leukemia and lymphoma) among those exposed within 1,500 M. was reported™; the increased frequency was not related to age or sex. This finding, however, has not been substantiated.** %° The development of bone tumors following irradiation with doses in excess of 3,000 r is well documented.*’? An increase in frequency of osteochondromas over the expected number of cases has also been observed’ in children treated with several hundred r for thymic enlargement. Bone tumors have also been observed in watch dial painters from internal deposition of radium. Radiogenic bone neoplasms from Sr®° deposition have been experimentally produced in animals and presumablycould occur in man.*’ Malignant tumors of the lung and the skin are also known to be related to radiation exposure. Cancer of the lung has been associated with high atmospheric content of radium and particularly of radon. The risk of radiuminduced cancer of the skin is generally con- sidered to be less than that of many other types of tumors.°*7 Growth and development. Several analyses of the growth data on Hiroshima and Nagasaki children subjected to atomic bombirradiation have suggested a retardation of growth among the exposed group.*® 56° This deleterious effect seemed more promi- nent among boys than girls and among those exposed at younger ages.*® ® Interpretation of the results is complicated since the children suffered psychic and physical trauma as well as nutritional disturbances and diseases. A similar trend in retardation of growth and development has been noted in a study of 38 Marshall Island native children who were exposed to whole body irradiation of 69 to 175 r from radioactive fallout.61 Highly suggestive differences were noted, particularly between male children exposed at 12 to 18 months of age and the unexposed comparison group. Clinical experience has long emphasized Effects of ionizing radiation 661 the occurrence of developmental abnormalities among children receiving irradiation in utero.'? Of the offspring of 11 pregnant women who were exposed during the first trimester of pregnancy to the atomic bomb in Hiroshima at distances less than 1,200 M. from the hypocenter, seven had microcephaly and mental retardation.®? In Nagasaki, the over-all morbidity and mortality were high among babies born to 30 mothers who were exposed during pregnancy and who manifested major radiation symptoms as compared to those among babies born to 68 mothers exposed within 2,000 M. but without histories of major symptoms and to infants born to 113 “control” mothers. Four of the 16 surviving children of mothers with major symptoms were mentally defective.® Experimentally, many types of malformations have been produced in the animal fetus by irradiation.'® 65 Life shortening. Shortening of the life span and premature senescence have been established in mammals receiving acute or chronic irradiation.’& 67 68 Jt has not been conclusively demonstrated that a similar life shortening effect occurs in human beings exposed to radiation,’’ although mortality statistics from retrospective surveys have been interpreted to show decreased longevity of American radiologists in comparison with other physicians and with the general male population.’® *7° The Atomic Bomb Casualty Commission—National Institute of Health (Japan) Study of Life Span of A- Bomb Survivors has under surveillance a sample of approximately 100,000 persons.** Analyses of these data may provide some firm answers in reference to the relative life span of those exposed to radiation during childhood and infancy, although results thus far have not revealed any positive correlation. Chromosome changes. Persistent chromosomal aberrations have been noted in the leukocytes of human beings who received whole or partial body irradiation."1-"* Diagnostic radiation ranges in levels of 12 to 35 r, and even in levels as low as 1 to 12 r, have been associated with postradiation aberra- tions.”> The clinical significance, however, of