20 Years Of Research Yield Hope For A-Bomb Survivors

Reprinted from News Report, National Academy of Sciences, Vol. XVII, No. 1, January 1967.


Hiroshima and Nagasaki, as all the world knows, were devastated by atomic bombs in the summer of 1945. In Hiroshima, the bomb exploded on August 6, directly over the center of the city. Its effects were felt over the entire populated area. In Nagasaki, three days later, the bomb fell short of its target, bursting about halfway up the northern sector, its destructive force limited somewhat by the confining hills.

Few who were in the open, under 1,000 meters (about 0.6 mile) from the center of the explosion, lived. Of those who did, most developed severe radiation sickness and died within a few weeks. For the survivors, about 300,000 who received in a single exposure doses varying from negligible to near lethal, the ordeal had just begun. For them it remained to piece together the torn fabric of their lives and to face, as the understanding of what had happened to them grew, the appalling prospect that radiation-induced genetic damage would irrevocably alter the lives of their children and of numberless future generations.

What has become of the survivors of the holocaust? How have their lives been affected? What diseases afflict them? How firm a relationship can be established between their ills and the effects of radiation? What of their children? Their children's children?

The picture that is emerging from the records of the Atomic Bomb Casualty Commission, patiently and painstakingly compiled over the past two decades, is grim beyond doubt, yet not as grim as many had feared. Much that is hopeful for the survivors is to be found here, for by separating the real horror from the imagined, the ABCC has both identified and reduced the tragedy.

That such a record exists is a monument to the labor of American and Japanese physicians, to the spirit of cooperation of the survivors themselves, and to the foresight of government officials in both countries.

The ABCC was formed in November 1946, following a request from President Truman that the National Academy of Sciences undertake a continuing study of the delayed effects of radiation on the survivors of Hiroshima and Nagasaki. The project officially got under way in the two cities late the following year.

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From the beginning, it has been a joint Japanese-American venture. Although support for the work of ABCC is, in large part, provided by the U. S. Government, the National Institute of Health of Japan has, increasingly over the years, provided not only modest funds and access to valuable records, but also scientific manpower of high competence. The present staff numbers 824, of whom 788 are Japanese.

Largest Group Under Study

The studies are based upon a population of 100,000 persons, the largest defined population ever studied in such detail over a long period of time. It comprises the majority of survivors who were within 2,000 meters (1.3 miles) of the hypo-centers of both cities, together with two comparison groups, matched by number, age, and sex. One of the groups is composed of those who were in the cities but farther from the hypocenters at the time of the bombings, and, therefore, although they did not receive significant radiation, were subject to the physical and psychological stresses of the event. The second comparison group is selected from those who were not in the cities at the time of the bombings but were residents in 1950. This group was exposed to none of the hazards of the disaster.

The reports of the ABCC now number over 600. The following is a summary of some of the findings of major significance:

• The incidence of leukemia among survivors exposed to the bomb's radiation within 2,000 meters of the hypocenter was about 10 to 13 times higher than that of a normal population during the period between 1950 and 1960. However, it has now declined considerably, and no increase has been detected in the incidence of leukemia among the children of parents exposed within that distance.

• Investigators have observed in survivors a definite increase in cataracts and other abnormalities of the lens of the eye, directly related to distance from the hypo-center. One study showed that of 165 subjects who had experienced hair loss, an indicator of heavy exposure, 135 had also developed abnormalities of the lens of the eye. Another study reported lens abnormalities in 54.7 per cent of 159 survivors exposed within 2,000 meters of the hypocenter but in only 10.8 per cent of 277 survivors exposed beyond that distance. However, the great majority of these changes were detectable only upon examination; the number who suffered noticeable loss of vision was small.

• Cancer of the thyroid, especially in females, has occurred strikingly more often in the exposed than in the non-exposed. In one study, 355 patients were found in Hiroshima and Nagasaki who had enlarged thyroid glands. Biopsies, performed on 70 subjects without knowledge of their exposure status, revealed 17 with cancer of the thyroid. Of these, 12 occurred in patients who were close to the hypo-center at the time of the explosion.

This incidence of thyroid cancer in 25 per cent of the Japanese patients with seemingly benign nodules may be compared with the incidence in the United States, which, according to recently published studies, is in the range of 2 to 3 per cent.

• A number of studies involving a small group of subjects who were exposed in utero have confirmed an unusually high incidence of microcephaly and mental retardation. Of 183 children in this group who were examined, 33 (24 of whom were exposed early in fetal life) had head circumferences considerably below the mean for their age and sex. Of these, 15 were mentally retarded. Again, distance from the hypocenter was a telling factor. Fourteen of the retarded individuals were within the proximal zone (2,000 meters or 1.3 miles) at the time of the bomb. Seven of the total group of 191 subjects have died; of these, six were within 1,500 meters of the hypocenter. The survivors were not of marrying age at the time of the last study (1965), but will be studied in the future to determine the effect of irradiation upon their reproductive performance.

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Survivors who were within 1,400 meters have shown higher mortality than those at greater distances. The Life Span Study, one of the basic components of the ABCC program, reported that during 1950 to 1960, in a sample population of 100,000, there were 11 to 12 more deaths per year in the most heavily exposed group than would be expected in a normal population. About half of these were due to leukemia. This higher ratio applied for all causes of death, including leukemia, other malignant diseases, and (for Hiroshima males only) tuberculosis. For the heavily exposed, mortality ratios from all causes of death were especially high during 1950-52, but showed a decline thereafter. Young men under twenty were the most vulnerable sub-group.

The study also showed that non-exposed individuals had lower mortality ratios than did the survivors, no matter what their distance from the hypocenter at the time of the bombings. However, it is doubtful that this can be attributed either wholly or in part to effects of the bomb. Thus, the evidence mounts that while heavy exposure to radiation produces no new kinds of disease, it is an added burden to the victim, one which may hasten the development of disease and thereby shorten his life.

Children Show No Malformations

There is irony in the term "negative" results, for it is these, produced in abundance by the ABCC studies, which, though less provocative, offer infinitely more hope for the survivors. A few are mentioned below:

• No increase in the prevalence of diseases other than those mentioned earlier has been observed.

• Perhaps the most encouraging negative result has been the failure to demonstrate any increase in congenital malformation in children conceived by exposed parents.

A landmark study in 1956 reported that of 319 major congenital abnormalities detected among 27,000 infants examined both at birth and at age nine months, there was no excess in the group with heavily irradiated parents. Similarly, stillbirths were not significantly increased in the offspring of exposed parents.

• Results of preliminary studies of residual chromosomal aberrations in survivors have also been encouraging. Although chromosomal abnormalities were found in about one third of the heavily exposed survivors examined, and less than one per cent of the controls, no relationship could be found between this damage and the health of the subjects studied.

The success of the ABCC program rests in large measure upon the high rate of participation by Hiroshima and Nagasaki citizens, both those who were exposed to the bombs and those who were not. Their cooperation makes possible a greater understanding not only of radiation effects but also of the genesis of disease in a defined population which has been observed over a long time span. As a prominent Japanese radiobiologist said recently, "The subjects of these studies have turned their misfortune into a blessing for all men."

The director of the ABCC is Dr. George Darling, and the chairman of the NRC Advisory Committee to the ABCC is Lee Edward Farr, Professor of Nuclear and Environmental Medicine, University of Texas.

Technical summaries of some of the more significant findings of the Atomic Bomb Casualty Commission can be found in the following reports;

Hollingsworth, J.W, Delayed Radiation Effects in Survivors of the Atomic Bombings: Review of the Findings of the Atomic Bomb Casualty Commission, 1947-1959. New England Journal of Medicine 263: 481-487, 1960.

Jablon, S., Ishida, M., and Yamasaki, M. Studies of the Mortality of A-Bomb Survivors. 3. Description of the Sample and Mortality, 1950-1960. Radiation Research 25: 25-52, 1965.

Schull, W.J., and Neel, J.V. The Effect of Exposure to the Atomic Bombs on Pregnancy Termination in Nagasaki and Hiroshima. Atomic Bomb Casualty Commission, 1956. NAS-NRC Pub. 461, 241 pp.