The Relationship of Intra-Uterine Radiation to Subseqtjent Mortality and Development of Leukemia in Children

Diamond, E. L., H. Schmerler and A. M. Lilienfeld (Johns Hopkins Univ. School of Hygiene and Public Health, Baltimore, Md. 21205). The relationship of intra-uterine radiation to subsequent mortality and development of leukemia in children: A prospective study. Am J Epidemiol 97: 283–313, 1973.—Approximately 10,000 white and 10,000 black children who were exposed to intra-uterine x-rays from 1947 to 1959 in Baltimore were traced during 1961 to 1967 to determine their mortality experience. For comparison, about 19,000 white and 16,000 black children not exposed and matched by selected characteristics were traced in a similar manner; about 95% of both groups were successfully traced. The total mortality experience of the white exposed group during the first 10 years of life was almost twice that of the white control children, for all causes of death except malignant neoplasms (exclusive of leukemia), congenital malformations among males and diseases of the nervous system among females. The death rate from leukemia was about 3 times higher for the exposed than for the controls, a finding consistent with previous studies. In contrast, the mortality experience of the black exposed children was not greater than their controls. The absence of a difference in mortality from malignant neoplasins (exclusive of leukemia) in the exposed and control groups differs from several previous reports. The findings may be biased in that white mothers selected for prenatal x-ray had characteristics which predisposed to increased mortal ity in their offspring; this method of selection was not present among blacks. The possibility of a bias was analyzed by dividing the study groups into subgroups with characteristics that might have produced the observed mortality difference, including such characteristics as obstetrical factors and socioeconomic distribution. The socioeconomic adjustment did decrease the mortality differential from a 2-fold to approximately a 1.4 to 1.8-fold difference. The persistence of the mortality differential among whites suggests a real biological effect of radiation and its absence among blacks suggests differential susceptibility of the effect of radiation.