Technical Report No. 1-77

Life Span Study Report 8. Mortality experience of atomic bomb survivors, 1950-74

Kato H, Schull WJ

 

Editor’s note:

The following journal articles, based on this ABCC technical report, were published in the scientific literature:
Beebe GW, Kato H, Land CE: Studies of the mortality of A-bomb survivors. 6. Mortality and radiation dose, 1950-1974. Radiat Res 75:138-201, 1978
Beebe GW, Kato H, Land CE: Studies of mortality of A-bomb survivors. 6. Mortality and radiation dose, 1950-74 (Part 1). Hiroshima Igaku [J Hiroshima Med Assoc] 32:745-61, 1979 (in Japanese)
Beebe GW, Kato H, Land CE: Studies of mortality of A-bomb survivors. 6. Mortality and radiation dose, 1950-74 (Part 2). Hiroshima Igaku [J Hiroshima Med Assoc] 32:842-61, 1979 (in Japanese)

 

Summary

Since the last report, covering the experience of the 82,000 A-bomb survivors for the period 1950-1972, there have been 1,704 deaths (by 30 September 1974) and total deaths now stand at 20,230 since 1 October 1950. For cancer the increase was 390 and the new total 3,957. The entire 1950-1974 mortality experience, supplemented by tumor registry information for Hiroshima (1957-1970) and Nagasaki (1958-1970), has been re-analyzed with particular attention to these questions: 1) Is radiation carcinogenesis the only important late effect from the standpoint of mortality? 2) Is the carcinogenic effect a general one, affecting all tissues and histologic types? 3) Are there reliable city differences from which relative biological effectiveness estimates could be made? 4) Are Nagasaki data numerous enough to permit any close examination of the functional form of the gamma dose-response curve for specific cancers? and 5) Can further insight be gained into the role of age in 1945 at the time of the bomb (ATB) upon the carcinogenic effect of ionizing radiation?

With the possible exception of deaths from diseases of blood and blood-forming organs (anemias), for which certification is always suspect because of the possibilities for confusion with leukemia and because of failure to find hidden tumors causing anemia, mortality from diseases other than cancer is thus far unrelated to ionizing radiation. Although there were 14,405 deaths from natural causes other than cancer, analysis of the whole material and its major components provided no support for the belief that diseases other than cancer are involved in the late mortality effect. To the extent that the hypothesis of accelerated aging requires that ionizing radiation increase mortality from disease generally, these findings cast doubt upon that hypothesis.

Analysis of the updated death certificate data suggests that, to the effects identified in previous reports in this series, cancer of the stomach, esophagus, and urinary organs, and the lymphomas, should now be added. Perhaps the most interesting of these is stomach cancer since it is the most common cancer in Japan.

The effect on stomach cancer seems to be of the same order of magnitude as those on cancer of other organs, and is quite small in relation to the natural incidence of stomach cancer in Japan.

Carcinogenic effects seen in this experience generally are not proportional to spontaneous incidence. Further, it seems probable that one or more digestive organs other than esophagus and stomach are involved in the carcinogenic effect, and that one or more yet unidentified sites in other organ systems may also be involved. The tumor registry data point to the possible involvement of the large bowel, the liver, and perhaps other organs as well.

Evidence of radiation carcinogenesis is much stronger in Hiroshima than in Nagasaki, and for many sites the Nagasaki data alone would not suffice to show a radiation effect. It seems clear also that absolute risks per rad are higher in Hiroshima where neutrons contribute substantially to the total dose, than in Nagasaki where they make almost no contribution.

The leukemogenic effect seems still to be present in the 1970-1974 period, especially in those aged 20-34 ATB, and the average absolute risk for all malignant neoplasms other than leukemia continues to increase, reaching 4.2 deaths per million person-year-rad (PYR) in 1970-1974. In retrospect it appears that, for most sites of cancer for which an effect now seems established, the minimal latent period prior to the appearance of statistical evidence of excess mortality varies by type of cancer and by age ATB. Most of the effects thus far identified appeared within 15 years after the bombing for at least some ages ATB.

Age ATB plays an important role in the carcinogenic effect, one that cannot be fully understood until the youngest members of the cohort are old enough to have experienced the full force of the major forms of cancer. In general the absolute risk, averaged over the entire period, increases with age ATB, but leukemia and breast cancer are notable exceptions, and much of the apparent increase may be no more than a reflection of the fact that for some sites radiogenic tumors have the same general age distribution as naturally occurring tumors. Thus, for lung cancer, which is rare below age 35, no effect is seen in A-bomb survivors under age 35 ATB (under 70 in 1974), and this may mean, not that the younger subjects will escape the effect, but only that they are not old enough to express it perceptibly.

For none of the specific types of cancer except leukemia in Hiroshima are the data numerous enough to permit confident statements to be made about the shape of the dose-response curve in the low-dose region, which is so critical in the formulation of public policy designed to minimize the hazards of ionizing radiation. The Hiroshima curve for leukemia is quite acceptably linear. The Nagasaki data are unfortunately too weak in the sampling sense to be of great value in evaluating the effect of linear energy transfer on the dose-response function for leukemia. For other major sites the Hiroshima data provide less certain guidance: without more data the functional form of the dose-response curve cannot be specified.

The leukemogenic effect that dominated any consideration of late mortality effects until recently has now been exceeded by the effect of radiation on forms of cancer other than leukemia. At the end of 1974 excess deaths numbered about 85 for leukemia and 100 for other forms of cancer among the 82,000 A-bomb survivors under study. Sites of cancer that seemed especially involved in the continued increase in absolute risk estimates for all forms of cancer except leukemia were the respiratory organs, and the digestive organs. Incidence data suggest that breast cancer is also on the rise, but this does not show in the mortality analysis.

Under the linear hypothesis, which is far from proved for any form of cancer, except perhaps leukemia in Hiroshima, the estimated absolute risk for all forms of cancer, including leukemia, would suggest that the A-bomb survivor population of 285,000 registrants at the time of the 1950 census may have experienced 400 or 500 deaths from cancer induced by radiation in addition to perhaps 69,000 naturally occurring deaths in the interval 1950-1974.

 

Editor’s note:

The following components of this report contain data on communicable disease frequencies, allergies, malignancies, and many other symptoms that may be of interest from a public health standpoint.

 

List of Tables

1. Comparison of Tumor Registry & death certificate series by city, 1959-1970
2. Deaths from cancer of selected sites among A-bomb survivors, 1960 A-bomb survivors survey & 1965 mail survey
3. Observed & expected deaths from leukemia at all Japan death rates, in those exposed to 100+ rad, by age ATB, & calendar period
4. Comparison of Tumor Registry and death certificate information as to evidence of dose response relationship for stomach cancer, by city
5. Observed and expected deaths from stomach cancer by occupation of head of household, both cities, both sexes, 1960-1974
6. Malignant neoplasms of rectum & rectosigmoid junction, 1967-1970
7. Breast cancer cases, Tumor Registry series, 1959-1970
8. Deaths from malignant neoplasms of lymphatic & hematopoietic tissue except leukemia, with diagnostic distribution based on pathology examination & hematologic examination for leukemia registry
9. Thyroid cancer cases by T65 dose, Tumor Registry, 1959-1970
10. Summary test probabilities, deaths from all diseases except neoplasms
11. Summary of regression estimates of absolute risk for both cities & all ages combined, 1950-1974
12. Comparison of Hiroshima & Nagasaki as to strength of main effects

 

List of Figures

1. Leukemia deaths per 100,000 persons per year by T65 dose & city
2. Measures of leukemogenic effect by age ATB, 1950-1974, average of both cities
3. Deaths from leukemia per 1000 persons alive 1 October 1950, by age ATB & T65 dose, cumulative 1950-1974
4. Absolute risk estimates for leukemia vs other forms of cancer, by age ATB, over time regression estimates of excess deaths per million PYR
5. Comparison of leukemia, all cancer, & all cancer except leukemia, as to relative & absolute risk, by age ATB
6. Stomach cancer deaths per 1000 persons alive 1 October 1950, by age ATB & T65 dose, cumulative 1950-1974, Hiroshima
7. Lung cancer deaths per 1000 persons alive 1 October 1950, by age ATB & T65 dose, cumulative 1950-1974
8. Deaths per 10,000 per year from all diseases except neoplasms, by age ATB, 1950-1974, 100+ rad vs 0-9 rad
9. Dose response plots for main effects, relative risk ratios for 100+ rad vs 0-9 rad as base, by city, 1950-1974
10. Deaths per 100,000 per year by cause of death and calendar time, 100+ rad vs 0-9 rad, 1950-1974
11. Absolute risk estimates over time for all cancer except leukemia, by city, with 90% confidence intervals
12. Absolute risk estimates for main effects, by age ATB, 1950-1974
13. Dose response for leukemia, LSS death certificates & leukemia registry, by city
14. Dose response for all cancer except leukemia, by city
15. Dose response for stomach cancer, by city
16. Dose response for lung cancer, by city
17. Dose response for breast cancer, by city