The early and later effects of the nuclear bombs detonated at Hiroshima and Nagasaki in 1945 are the most extensive and reliable measures of the long-term effects of ionizing radiation on humans. These findings have been incorporated into radiation protection standards adopted internationally.

The authors, who are Japanese and highly qualified, have surveyed the extensively detailed data and present a careful analysis, comparing their findings with research in other populations who had similar exposures, as recorded in the world literature. Consequently, the findings are dispassionate and reliable.

The initial chapter, entitled "Overview," briefly summarizes the major findings from 1945 through 1991. Each exposure to the bombings was a single, acute, external exposure that involved either the entire body or a portion of the body, depending on the location of the person and the extent to which he or she was shielded.

Blast and heat from the atomic bombing had the most lethal effect on humans. Survivors who were closest to the hypocenter had long painful convalescences and longstanding psychological effects. Those farther away are still concerned about the possible increased likelihood of cancer and other radiation-associated diseases. These factors are discussed throughout this text to examine their relative effects.

With regard to late effects, the text describes increased incidences of leukemia; thyroid, breast, lung, gastric, and colon cancer; and multiple myeloma. In addition, detailed summaries of major categories of diseases of all organ systems are included with clear statements of the effect of radiation, or lack thereof, on the frequency of diseases. Recent developments, including chromosome abnormalities, possible mutations, effects on immune function, and biochemical changes, determined using newer analytic techniques, are also presented.

Observations of congenital and genetic effects have led to speculation about the future significance of these effects. This report summarizes approximately five decades of human radiation history. According to many epidemiologists, continued follow-up of this population would be of inestimable value for a continuing re-evaluation of human exposure standards, especially with regard to latent effects on genetics. This report analyzes the slow progress of the examination of these possible changes to date.

Radiation dosimetry is, of course, vital to the evaluation of late effects. An early estimate of dose, called T6SD, was revised as described by a second determination, called DS86. This method of calculating estimated dose effectively lowered an individual person's estimated radiation dose, resulting in an increase in radiation-induced cancer risk (cases per 100 persons exposed per sievert). Consequently, the number that results from dividing the cases of cancer observed by the dose from rays is increased. As a result, radiation standards have become much more rigorous both internationally and in the United States.

Recent analyses, discussed briefly in this report, present evidence to show that the increase in the radiation effect has been overestimated and that the estimates should be decreased. The arguments in this debate are not currently conclusive, but they may eventually be resolved. Because a decrease in the estimation of radiation effects per dose would change the cost–benefit ratio of radiation protection, radiation standards, and nuclear waste storage, among other crucial issues, this debate requires further elucidation. Presently, the recommendations in this text, and as reflected in the 1991 report of the International Commission on Radiation Protection, are conservative.

This work is an excellent summary of the Japanese experience for cancer and non-malignant disease and will be valuable both for the expert and for those who wish to become familiar with the many complex factors discussed in these chapters.