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H O W A R D J. C U R T I S , Oak Ridge, T e n n .
HEN it first became apparent that a chain-reacting pile was a definite pos sibility, it also became apparent that if large chain-reacting piles were to be used for producing plutonium and this pluto nium separated for use in a bomb, some tremendous protection problems would have to be solved. In the enthusiastic language of W. L. Laurence, "The energy emitted in the form of radiation is many thousands of times greater than that generated by all the radium isolated in the entire world to the outbreak of the war. Such a gigantic quantity of radiation would kill any living thing in its vicinity within a fraction of a second. T h e atomic pile therefore created t h e biggest problem of protecting human life that mankind ever faced." In order to cope with these very dif ficult health problems, it was necessary to recruit qualified personnel trained in the fields of biology, chemistry, physics, and medicine and organize a health divi sion for the purpose of carrying on funda mental investigations to determine safe working conditions, for t h e thousands of scientists who would be exposed to the many health hazards. A great deal of the biological research was devoted to the development of meth ods of working with the various radioactive agents and of isolating them s o that the effect of a single agent at a time could be studied. N o t only were there tremendous quantities and intensities of radiations to cope w i t h but there were radioactive gases, for example, liberated in the plutonium process many millions of times more lethal than mustard gas or Lewisite, and solids to be handled in large quan tities which are many millions of times more lethal, gram for gram, than arsenic or cyanide. Broadly speaking, the research problems were divided into two parts. T h e first was t h e problem of the ingestion or inhala tion of radioactive substances which would be deposited in some organ of the body and emit destructive radiations which would gradually destroy that organ over a period of months or years. T h e fate suffered b y the radium dial painters is an excellent example of this type of hazard. T h e second was the problem of the biological effects of radiations pro V O L U M E
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duced by the pile or by radioactive ma terials outside the body. The fate suf fered by the early x-ray workers illustrates this type of hazard. Both classes of hazards arc particularly insidious because small exposures go unnoticed at the time but may produce profound effects years later, and for this same reason they are difficult t o study in animals. Considering first the ingestion problem, the fission process itself forms radioactive isotopes of some thirty elements in the center of the periodic table—the fission products—as well as plutonium and nep tunium which are also radioactive. There fore after a lump of uranium has been in a chain-reacting pile for some time it contains, as a small impurity in t h e metal, these radioactive elements. Therefore the lumps cannot b e handled directly because of the radiations from these ele ments, but t h e plutonium must be sepa rated from the uranium by remote control
AboEdt tHe As DIRECTOR of biological research a t Clinton Laboratories, Oak Ridge, Tenn., since 1943, Dr. Curtis has been responsible for planning, organizing, and supervising a n extensive biological research program involving the use of several thousands of animals. His wide experience has been most helpful in directing the details of the investiga tions which yielded practical solutions to the many complex problems with which we had to cope. His interpreta tions of t h e biological effects produced by various kinds of radiations have played an important role in making it possible t o provide safe working condi tions for the many thousands of em ployees who took an active part in the development of atomic energy. Born i n Lansing, Mich., Dec. 11, 1906, Dr. Curtis attended public schools in Washington, D - C. His un dergraduate years were spent at the University of Michigan, where he graduated with a B.S. degree in 1928. He received an M.S. degree from Swarthmore College in 1929, and a Ph.D. in physics from Yale University in 1932.
APRIL
10,
1946
methods from t h e fission products behind several feet of concrete shielding. T h e dusts and sprays from this operation had to be carefully avoided and were not even allowed to go up the stack; and the waste solutions had to be stored indefinitely in special underground tanks and holding ponds. In order to specify the amount of these materials which could be tolerated in the river water, or as dust in the air, it was necessary t o study the way in which each element in question is handled by the body and what destructive effects it would cause. A certain amount of physiological information was previously known about each element, a n d knowing the physical properties one could predict the toxicity effects of the element. However, in order to check these guesses and to be able t o specify the toxicity quantitatively, it was necessary to administer various quantities of these elements, in several different forms, and by several different routes of
Author From 1932-35, a s a biophysicist with the Biological Laboratories, Cold Spring Harbor, Ν . Υ., Dr. Curtis did research on electrical properties of biological systems, properties of cell membranes, and permeability. Dur ing the years from 1935 to 1938, he was associate in physiology, College of Physicians and Surgeons, Columbia University, where he did research on electrical properties of biological sys tems, especially nerve and muscle. From 1938-40 he was a fellow of the Rockefeller Foundation in residence a t Johns Hopkins University School of Medicine. Here he did research on central nervous system using electrical techniques. In 1940-41, he was in structor in physiology a t Johns H o p kins; and from 1941 t o 1943, assist ant professor of physiology, College of Physicians and Surgeons, Columbia University, teaching physiology and continuing research on shock. Dr. Curtis is co-author of a textbook on "Physiology in Modern Medicine", and he has contributed over thirty technical papers t o various scientific publications.
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administration, to experimental animals. Rats and mice were used almost exclusively i n this work. The problem of t h e external radiations was, in a sense, somewhat easier because of the fairly close analogy between the effects expected here and those which have been found for x-rays. T h e radiations t o be dealt with included gamma-rays, betarays, fast noutrons, and slow neutrons. This originated as an invariable accompaniment of the fission process as well as from the radioactive decay of the unstable fission products. T h e problem was a p proached b y arranging experimental equipment which would give relatively pure and intense beams o f these different radiations. Animals were then exposed to various amounts and in various ways and the animals carefully observed. Some experimental work was done with radioactive gases, which had to do with the combination of external and internal radiation problems This work was seriously handicapped by the difficulties of obtaining the gases and working with them ; and largely for these reasons their effects wero n o t thoroughly investigated. Unknown
Hasards
The unknown nature of some of the hazards and the urgency of attaining rapid progress made it imperative to proceed before the hazards were completely understood. Preliminary investigations were made b y placing animals around the grounds and inside the buildings of the first experimental production pile. These animals were very carefully observed and frequently examined for radiation effects. Fortunately, no detrimental effects were ever found. As a result of this research program we now have what w e believe t o be a rather clear understanding of the hazards involved i n the operation of chain-reacting units. I t has been possible t o show that, if certain definite rules are followed, work in this field can proceed with perfect safety. When animals are given large doses of radiation death occurs in from 10 t o 30 days as a result of the combined effects of a number of physiological changes caused by the radiation- However, it has not yst been possible to single out any one of these changes as being the cause of death. When animals are subjected to large single sublethal doses o f radiation, or t o very small doses repeated rather frequently over a long period of time, one of two effects will be produced: Either the animals Mil die of "old age"—that is, sooner than normal animals—or they Vill develop cancer i n later life and die. Fortunately, it h a s been found that sterility is produced only by relatively large doses and, when produced, is only temporary unless the dose is very large. From a practical point of view it has been found possible to keep the exposures to all persons working o n the plutonium project
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well below that which would cause any of these effects, and it should be much easier to do s o in the future. Efforts have been concentrated on developing methods of working with the individual hazards and performing experiments which might be classed as physical toxicology. Therefore, it is not surprising that very few new and fundamental ideas in the fields of biology and medicine have emerged from all this activity. One might almost say that the benefits of atomic power, from the biological and medical points of view, have not y e t been explored. Therefore, I cannot say, as some enthusiastic newspapermen have said that we are about to witness tremendous advances in biology and medicine as a direct result of this new age. I would say, JEeSitoiritsB 1
HAVE had t h e opportunity of o b -
serving the biological effects produced by exposing animals t o various kinds of radiation. Some of t h e results were almost unbelievable. What appeared to be, in one instance, a mild erythema on a rat's head gradually developed into a vicious cancer which finally reached the stage where half the animal's head had vanished. T o some people, no doubt, it m a y seem cruel and inhuman to subject poor helpless creatures to such fatal tests; however, by so doing, we gained information which enabled us t o avoid having similar things happen t o the personnel who took an active part in the development of atomic energy. . Many interesting biological studies have been carried out, the results of which, for security reasons, have not been released for publication. Investigations have been conducted for the purpose of determining the biological effects of slow neutrons, fast neutrons, gamma-rays, and beta particles of different dosages applied continuously and intermittently, a n d various combinations of these radiations t o deterr mine if the effects produced were additive. The results obtained were extremely informative, interesting, and in some instances, startling. There is also t h e constructive side to the· application of t h e by-products of atomic energy i n the field of biology. The advancements i n this field, like that of medicine, will surely reflect the impacts of nucleonics, even though the rate of progress m a y be slow in t h e immediate future. However, there' is every reason to believe that the investigations will rapidly gain momentum and much information having t o do with biological processes will be gained through the use of various radioactive isotopes used as tracers. As pointed o u t in D r . Curtis' article, we have observed t h e effects of radia-
CHEMICAL
rather, that history has shown that a d vances in biology and medicine usually follow advances in physics and chemistry only after biologists h a v e p u t in much hard work on the subject—and that hard work still lies ahead. The most promising field at the present time is that of tracer techniques. A chain-reacting pile has been described as a nuclear boiler in which many new elements are formed, most of which are radioactive. In addition to these radioactive elements formed as a direct result of fissions, it i s possible t o place various elements inside a chain-reacting pile and perform various nuclear reactions which will yield other very important radioactive isotopes. Among these could b e listed radioactive carbon, hydrogen, phosphorus, calcium, €k*mmews& tions o n animals which appear to be the same, physiologically speaking, as those produced by the natural process of "growing old". I t m a y be possible to find ways and means of using correct dosages and proper applications of radiations to accomplish the opposite— that is, extend the period of youth and effectively delay t h e inevitable symptoms and characteristics of "old age". Our ability t o march forward in this field of science will be determined to a great extent by t h e number of scientists w h o are encouraged to carry on investigations, and b y the quantity and variety of radioactive tracers made available for this purpose. The dividends derived therefrom m a y very well justify the investment. In m y opinion, this is one of the most important of the life sciences, in view of the fact that all forms of life are directly affected, and should be among the first to receive strong support and encouragement i n t h e immediate future. This is particularly true since s o many of the investigations must necessarily extend over an appreciable length of time, i n order to obtain t h e desired results. Active warfare results in the annihilation of the most virile and healthy human specimens of the combatant nations and thereby causes a shortening of t h e average life span of the i n habitants. This situation i s horrible, deplorable, and inexcusable. However, it m a y be true t h a t our knowledge of new scientific facts, improved techniques, and more effective means o f utilizing our natural resources, gained as t h e result of waging a war, m a y lead to better things in t h e future, such a s the creation of a more wholesome e n vironment in which t o live, thereby d e laying the inevitable effects of old a g e and increasing t h e human life span. E D G A R J. M U R P H Y , EditoricU
Consultant for
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Nucleonics
ENGINEERING
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iron, copper, cobalt, iodine, to mention only a few. Therefore, it should be possible in the future—and I should like to emphasize the woi-d future—to supply relatively large quantities of these radioactive isotopes so that, within limits, a person will be able to choose the ones which lie would like to use rather than, as in the past, using very small quantities of isotopes a cyclotron could best manufacture. It is not necessary to stress the tremendous strides in biology and medicine that have taken place as a result of the use of these isotopes which were produced before the war. When relatively large quantities of these substances become available for use by any laboratory in the country, it is difficult to see how large-scale advances could fail to be made as a direct result of this technique. But the advances due to these tracers need not be confined to research. It is quite possible that, with large quantities available, in a few years, routine hospital tests for such things as intestinal absorption, or liver and kidney functions, will be commonplace. In addition, these materials will undoubtedly prove to be very useful in the field of radiation therapy. I t will be possible, for example, to make gamma ray sources of almost any desired strength and one can think of a variety of different uses to which such large sources might bo applied. Before the war, interesting experiments were being performed on the treatment of thyroid disease by moans of radioactive iodine. Furthermore, ouo can imagine making special radioactive compounds which will localize in cancers, thereby retarding or stopping their growth. Or one can think of injecting certain substances directly into a tumor which would radiate the tumor continuously over any specified length of time. Other diagnostic and therapeutic uses of radioactive materials will probably occur to most research-minded clinicians. Furthermore, the research and therapeutic uses of the radiations themselves should not be overlooked. I n tho field of cancer research, it is highly probable that some of the radiations used hero will be extremely valuable. For example, betarays produce skin tumors in a way which has not previously been observed. The problem of aging, which is just beginning to be attacked, undoubtedly will be advanced with the aid of these radiations, since we have found that many of our animals, under the Influence of these radiations, die of "old age" at a relatively "young age". One of the most promising fields of future research is that of radiation biochemistry. It has long been known that radiations produce destructive chemical reactions such as the decomposition of proteins, but it is also known that certain organic compounds can be synthesized with the -aid of radiations. With very high intensities of a wide variety of difV O L U M E
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