CARBON-14 AND SOCIETY

By Linus Pauling

Talk given to the Alumni of the California Institute of Technology on Alumni Day, 11 April 1959.

Carbon-14 is a radioactive isotope of carbon (ordinary carbon, which is stable, is carbon-12). There is a small amount of carbon-14 in the atmosphere, as carbon dioxide, and in all living organisms on earth. This carbon-14, which amounts to one atom per seven million million atoms of ordinary carbon, is manufactured in the upper atmosphere by cosmic rays. The cosmic rays contain neutrons, and liberate neutrons, and these neutrons react with the nuclei of nitrogen atoms, converting them into carbon-14. The carbon-14 decomposes at such rate that only half of it remains at the end of 5,600 years, but in the meantime an equal amount has been manufactured by the cosmic rays, so that the concentration in the atmosphere and in living organisms has in the past, for many thousands of years, remained constant. The total amount of carbon-14 on earth is about 160,000 pounds.

Dr. Willard F. Libby made a very valuable discovery a few years ago, when he showed that it is possible to determine the age of objects containing carbon by measuring their radioactivity. A tree that is growing at the present time contains a certain amount of carbon-14, corresponding to the fraction of carbon-14 in the atmospheric carbon dioxide. After 5,600 years, the piece of wood from the tree will contain only half as much carbon-14, because the other half will have decomposed. After 11,200 years there will be only a quarter as much carbon-14 in the wood. Dr. Libby showed that by determining the radioactivity of the carbon, and hence the amount of carbon-14 in it, it is possible to determine how old the sample of wood is. This method has been applied very effectively. For example, it has been shown that the explosion of Mt. Mazama in Oregon, producing the crater that is now called Crater Lake, occurred 5,500 years ago, and that early men were living in the Lascaux Caves, where they painted pictures of mammoths and other animals on the walls and ceiling, 15,000 years ago.

Carbon-14 does some harm to human beings. It is estimated by geneticists that about ten percent of the defective children who are born with hereditary defects have these defects because of mutations caused by high-energy radiation. About one percent of the natural background radiation is due to carbon-14, and accordingly approximately one tenth of one percent of the children who are born with hereditary defects are the result of the presence of carbon-14 in the world. For example, each year about 6,000 children are born with the genetic disease that causes them to be dwarfs (the disease achondroplasia). About six of these children can be said to be defective because of carbon-14. There are hundreds of other hereditary defects caused by high-energy radiation, including that from carbon-14.

In addition, it is known that high-energy radiation can cause cancer, and many scientists believe that about ten percent of the cases of cancer are caused by high-energy radiation. If we accept this estimate, we can conclude that one tenth of one percent of the cases of cancer are to be attributed to carbon-14.

There is nothing that we can do to protect ourselves against the carbon-14 that is formed by cosmic rays in the upper atmosphere. We know that this carbon-14 contributes to human suffering, but we do not know how to get rid of it.

However, something can be done about the carbon-14 that is produced by the explosion of nuclear bombs. During the last five years the amount of carbon-14 in the atmosphere has increased at the rate of two percent per year. It is now ten percent greater than it was five years ago. This increase is the result of the production of carbon-14 from nitrogen atoms by the action of neutrons liberated in the explosion of the nuclear bombs that have been tested.

Last year I made an estimate of the damage to the human race that will be done by the bomb tests that have been carried out so far. My estimate is that the tests carried out so far, estimated to be a total of 150 megatons of fission and fusion together, will in the course of time, provided that there is no catastrophe that destroys the human race, cause about 275,000 children to be born with gross physical or mental defect, 850,000 stillbirths and childhood deaths, and 2,125,000 embryonic and neonatal deaths. There is a certain amount of overlap in these categories. At the same time that I was making my calculations, similar calculations were made by Drs. John R. Totter, M. R. Zelle, and H. Hollister, of the Division of Biology and Medicine of the United States Atomic Energy Commission. The estimate made by these scientists of the A.E.C. is that the carbon-14 from the bomb tests carried out so far will produce 100,000 children with gross physical or mental defect, 380,000 stillbirths and childhood deaths, and 900,000 embryonic and neonatal deaths; there is some overlap between the second and third categories. Thus the official estimate of the A.E.C. is that approximately a million damaged human beings will be produced by the carbon-14 from the bomb tests carried out so far, whereas my estimate is about two million.

There is nothing that we can do about the bomb-test carbon-14 that has already been liberated into the atmosphere, but we can feel thankful that no additional bomb tests are now being carried out. Since early November of 1958 the United States, the U.S.S.R., and Great Britain have refrained from carrying out any further explosions of nuclear weapons, and France, now manufacturing atomic weapons, has also not tested any. We may be hopeful that no more damage will be done to the human race through the explosion of these great bombs. Our hope can rest confidently on Ambassador James J. Wadsworth, who is our chief negotiator, with representatives of Great Britain and the U.S.S.R., in the Geneva Conference on the Testing of Nuclear Bombs, now going on. A few weeks ago I wrote to Ambassador Wadsworth, saying "My own opinion is that there is no activity in the world today that exceeds in importance the effort toward the formulation and execution of an international agreement about nuclear weapons on which you are now working. The making of a significant agreement, as the first in a series of great agreements about control of nuclear weapons and of other methods of waging war and the replacement of force by international law as the means of solving disputes between nations, may well in the future be considered to be one of the most important events in the history of the world. I believe that it is most important that the agreement on which you are working be formulated with extreme care, so that it cannot be subjected to just attack and that it will remain operative forever. I am not discouraged that four months of negotiation has not yet led to a final agreement. A very long period of careful study and negotiation might well be required before the agreement has been satisfactorily formulated."

In his answer to me, Ambassador Wadsworth said: "It is certainly the hope of our delegation here that an agreement can be reached that will mean the discontinuance of the nuclear weapon tests."

So long as the negotiations in Geneva continue, we may have nope that we and our children and all our fellow Americans will not be killed by nuclear blast and fire and radioactivity in a nuclear war, and also that, even if there is no war, there will not be further damage to the human race by the carbon-14 liberated in further bomb tests. Ambassador Wadsworth and his associates in Geneva deserve the support of all of us. I believe that the work that they are doing is the most important activity in the world today.