THIRTY-SIX YEARS after atomic bombs were dropped on Hiroshima and Nagasaki, the grim business of cataloging the effects of radiation on the survivors goes on. Thanks to the extraordinary cooperation of these individuals and their offspring, some good is coming from the horror. Scientists are able, for the first time, to study the effects of radiation, not on a mice or monkeys, but on human beings. According to a newly published summary of work that has been under way since 1946, the good news is that humankind appears to be considerably less susceptible to genetic damage from radiation than had been thought and than existing radiation safety standards allow for.
The setting of safe levels for human exposure to nuclear radiation, chemicals or similar hazards must of necessity rely on extrapolation from animal studies or on the results of prior "accidental" human exposures. Cases where statistically large enough numbers of people have been exposed to the same risk, where the group can all be found, and where confounding factors are not overwhelming, are extremely rare. In these respects, the atomic bomb survivors are unique.
The latest results, published this week in Science magazine, only concern one of the possible kinds of damage from radiation--genetic damage that affects the offspring of those who are exposed. Effects on the exposed individual-- such as induction of cancer--are not involved. The evidence from Hiroshima-Nagasaki comes from such things as birth defects and stillbirths, death during childhood and other indicators of genetic mutation. The data show an astonishingly low level of genetic damage. In this one respect, humanity appears to be about four times as resistant to radiation as mice--the experimental animal on which current standards for human exposure are based.
No other common hazard has proved as difficult to pin down as radiation. Despite dozens of studies and research projects, the question of what is a "safe" level of exposure remains mired in conflict. In an editorial accompanying the report, one of its authors, Prof. James Neel, is putting it mildly when he notes that the new results will "elicit discussion." Despite the lack of other exposed human groups as potentially informative as the Japanese survivors, Prof. Neel argues that because public concern is so great every possible source of human data should be studied. He proposes that a "blue-ribbon committee" be appointed to study the matter.
Whether--given the current level of understanding of biological mechanisms--additional studies would clarify or confuse, seems an open question. Nevertheless, considering the great value of resolving this anxiety-producing issue, the suggestion deserves consideration.