ATOMS AND GENES RISKS FOR POSTERITY IN THE H-BOMB TESTS

Press, Volume XCI, Issue 27632, 13 April 1955, Page 12

ATOMS AND GENES RISKS FOR POSTERITY IN THE H-BOMB TESTS

tß v a special Correspondent of the -Manchester Guardian’’] (Reprinted by Arrangement]

The United States Atomic Energy Commission says that in North America the radiation produced by bombs has been the equivalent of one chest X-ray for each person. At the same are told that such an amount of radiation is harmless, ; and Sir Winston Churchill has repeated this assurance. Yet the }ay remembers that X-ray 2c the chest are taken as infrequently a possible, and that in the early months of pregnancy a woman’s abdomen is only photographed if the need is great Now the Federation of Am ®rican Scientists has appealed for a United Nations investigation of the genetic hazards of nuclear explosions. We are bound to wonder where we stand what the dangers are, and how imminent they might be. The genetical hazard is not a risK of tangible death or injury; these are caused by heat, blast, nuclear radiation from the fireball of a nuclear bomb, and by contamination „ witn radioactivity from the “fall-out. Nor does it lead to recognisable signs and symptoms in an individual affected, these only appear in later generations. The widespread source of potential genetical damage is the radioactivity dispersed through the whole of the earth’s atmosphere by wind and weather after atomic explosions. The mechanism by which offspring inherit characteristics from their parents in normal circumstances can be described by using the concept or “gene.” In such terms it is said,, for example, that the children of a mixed colour marriage are half-caste because one parent contributes a “black gene and the other a “white gene” to their genetical make-up. Here the mixture of colour genes leads to characteristics intermediate between those of the parents. In humans the number of genes is very large—about 50,000 and their members are conveyed from parents to offspring by the reproductive cells (the spermatozoa and the ova).

Harmful Changes It has been known since the early 1920’s that X-rays and radioactivity can disturb this normal mechanism of heredity. Random changes or mutations of genes can be brought about by both agencies, so that the characteristics of a child can be different from, and not necessarily intermediate between, those of its parents. This mutation process also occurs spontaneously—indeed, spontaneous mutation is necessary to the operation of natural selection. Unfortunately, the great majority of genetic mutations, artificial or not, are necessarily harmful ones. They contribute to illhealth and reduced fertility.

Most of the genes produced by mutation have the property of being what the biologists call recessive. This means that if a harmful gene produced by mutation were paired off with an unmutated or “good” gene the individual concerned would not exhibit the harmful effects of the malignant gene. At first sight this appears to be a favourable circumstance, because It implies that unless genes of the same kind from both parents are mutated, a child will not be affected by malignant characteristics and will lead a normal life. However, there is more to be said than this. As an adult such a child will, on the average, provide half the second generation with a mutated harmful gene. And if he is one of a population whose size is constant, and if there are many other people who carry the same mutated gene, then, on the average, the number of these harmful genes will remain the same. Eventually two such genes will find themselves united in the same embryo. Then—perhaps several generations after the original mutations—there will be trouble, perhaps death. Whole Populations Concerned

It is clear that in the long run the recessive character of the harmful genes saves no lives. Moreover, in assessing the damage caused by genetic mutations, it becomes necessary to take account of entire populations, and to estimate the total number of harmful genes in those populations; it is necessary to study the demography of malignant genes. Several conclusions follow from this principle. Thus several experiments hhve shown that the number of mutations produced by X-rays or

radioactivity is proportional to the amount of the artificial radiation. (The amount of radiation that a person receives, or the dose, is commonly measured in units called Rontgens, written as r.) Therefore the damage done to a population as a whole is the same if 100 people are given a dose of lOr as if 10,000 people are given a dose of O.lr or if 1,000.000 people receive a dose of O.OOlr. It is clear that in such terms the smallest amounts of radioactivity endow the population as a whole with a proportional amount of malignancy. Further, it can be argued that while it may be safe to allow the workers in atomic factories to receive doses up to 0.3 r a week, it might well be disastrous to allow each member of the population to be exposed to doses as great as this. A Misleading Assurance Further, it can be seen that the famous statement that each inhabitant of North America has received merely the equivalent of one chest X-ray (about O.lr), and that therefore no damage has been done, is quite misleading. In the first place, chest X-rays do not affect the reproductive organs, which are in the pelvis. Second, the proportion of people who receive chest X-rays before they are 35 or so (when, on the average, people stop having children) must be small. Allowing for both these factors, it is not unfair to say that the genetical damage done by fall-out radiation in North America must be between WOO and 1,000,000 times the damage done by all the chest X-rays given there in the last generation. No-one, unfortunately, can say just how much this damage is. So much of the relevant data is unknown that it is not possible to work out the damage that is being done by current explosions or to calculate the number of hydrogen bombs necessary to bring about a major disaster. For example, it is not known what amouu< of radioactivity is necessary to make the rate of artificial mutation equal to that of spontaneous mutation. This quantity, which is crucial to all attempts to make quantitative estimates, is variously estimated between 3r and 300 r (in a person’s lifetime). There is also much uncertainty about the part played by cosmic rays in spontaneous mutation; about the member of genes concerned in human genetical make-up; about the nature and power of hydrogen bombs. Above all, we hdve no means of estimating the proportion of malignant genes that our population could tolerate, for this is not only a matter of biology, but also one of economics. Research Begins in Earnest Much is being done to remedy these deficiencies. Unfortunately much of the earlier research on the effects of radiation on insects is not of great significance for human beings. For this reason two large colonies of mice have been established, one in the United States and one at Harwell* The British experiment is being conducted by the Medical Research Council and has recently been moved to Harwell from Edinburgh, where it was started some six years ago. There are reports, too, from America of balloon flights in which fruit flies are carried to high altitudes in an attempt to discover the influence of cosmic rays on mutation. The essential difficulty of the biological work is that it is necessary to make experiments lasting several generations (and thus to take a long time) and to contend with the formidable satirical difficulties inherent in working with living creatures. Observations of the radioactivity present in our atmosphere are being carried out at many physics laboratories, almost as a matter of routine. It seems that the level of radioactivity is just as high in Britain as in North America. This radioactivity also pro* vides clues to the nature of the explosions that have taken place—no doubt the Russians are aware of this. And there is some evidence that recent explosions have produced a radioactive cloud that is not what one would expect from an unsophisticated hydrogen bomb. In spite of all this work, it will M many years before we shall know enough about these things. And in the meantime radioactivity will accumulate in the atmosphere. We know the kind of danger. We can only hope that it will not reach serious proportions.