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Representative HOSMER. Aside from that factor, however, there are instances such as standardization that are a nationwide matter and simply cannot be controlled by an individual State.

Mr. ABRAHAMS. That is correct.

Representative HOLIFIELD. Thank you very much, sir.

Tomorrow at 10 a.m., in this room, we will take up topic III-A, "Biological Concepts Underlying Radiation Protection Standards." The committee will stand adjourned until tomorrow morning at

10 a.m.

(Thereupon at 4:35 p.m., a recess was taken until 10 a.m., Thursday, May 26, 1960.)

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RADIATION PROTECTION CRITERIA AND
STANDARDS: THEIR BASIS AND USE

THURSDAY, MAY 26, 1960

CONGRESS OF THE UNITED STATES, SPECIAL SUBCOMMITTEE ON RADIATION, JOINT COMMITTEE ON ATOMIC ENERGY, Washington, D.C. The subcommittee met, pursuant to recess, at10 a.m., in room P-63, the Capitol, Hon. Chet Holifield (chairman of the subcommittee) presiding.

Present: Representatives Holifield and Hosmer.

Also present: James T. Ramey, executive director; Carey Brewer, and George F. Murphy, professional staff members; Hal Hollister, James E. Turner, and Richard T. Lunger, technical consultants, Joint Committee on Atomic Energy

Representative HOLIFIELD. The committee will come to order.

The committee will continue its hearings this morning on the subject of standards and our first witness will be Dr. G. Failla, director, Radiological Research Laboratory, Columbia University.

Our topic today is biological concepts underlying radiation protection standards.

Doctor, you will please take the witness stand there. We are glad to have you before us, sir. You may proceed.

STATEMENT OF DR. G. FAILLA, DIRECTOR, RADIOLOGICAL RESEARCH LABORATORY, COLUMBIA UNIVERSITY, NEW YORK, N.Y.

Dr. FAILLA. Mr. Chairman, I have a prepared statement here that I had intended to read. Since arriving here last night, I have heard some comments about NCRP and the Federal Radiation Council, and I think it will be profitable if I talk extemporaneously, and discuss these matters that have been mentioned in the last 2 days, because I think they are rather important.

Representative HOLIFIELD. That is fine. We will accept your statement, and any part you do not cover will be printed in the record.

1 Director of Radiological Research Laboratory and professor of radiology (physics), College of Physicians and Surgeons, Columbia University; Vice Chairman Emeritus of International Commission on Radiological Protection; vice president emeritus VII, VIII, and IX International Congresses of Radiology; honorary member, British Institute of Radiology; honorary member, James Ewing Society.

Awards: Pulitzer scholarship, 1911-15 Leonard prize, American Roentgen Ray Society, 1923, 1925; Janeway Medal, American Radium Society, 1939; Caldwell Medal, American Roentgen Ray Society, 1945; Gold Medal, Radiological Society of North America, 1947; American Cancer Society annual national award, 1956.

Scientific contributions: Many papers and book chapters on radiological physics, radiation protection, and radiobiology.

We will question you on the points in the statement at the proper time.

Dr. FAILLA. As stated in the press release of May 5, 1960, one of the purposes of these hearings is to "clarify some of the confusion and misunderstanding by the public and the scientific community concerning the basis and use of radiation standards." My prehearing statement has already appeared in the advance committee print. Now I should like to emphasize a few points.

There is public fear of ionizing radiation chiefly for the following reasons: (1) The vivid description and pictorial illustrations of the atomic bomb casualties at Hiroshima and Nagasaki; (2) exaggerated statements about the consequences of radioactive fallout made by scientists and others under emotional strain; (3) the intangible nature of ionizing radiation, which cannot be detected by our senses and produces effects long after the exposure has occurred; (4) unfamiliarity with the terminology of the subject; (5) the impression that nobody seems to know much about the consequences of exposure to radiation. The horrible effects of overwhelming exposure to radiation in a nuclear war must be disassociated from the possible effects of controlled exposure in peacetime. I think most people do so now. The average citizen can get a good idea of the present situation by observing people who have been occupationally exposed to radiation for a long time. Among these are radiologists, physicians, and dentists who use radiation for the diagnosis or treatment of disease. At one time or another most people come in contact with one or more of these specialists. It is a matter of simple observation that these individuals cannot be distinguished from other doctors who have not been exposed to radiation. Some of the very old radiologists or dentists may show skin damage in the hands or face, but no other signs.

Of course, casual observation of this sort is not proof that there has been no radiation effect. The point I wish to make is that the effect-if it exists can be determined only by statistical studies of large numbers of exposed and nonexposed individuals. One such study has shown, for instance, that the incidence of leukemia in radiologists (of the old school) is significantly higher than in other medical specialists. Since this disease occurs also in nonexposed persons, no one can say for sure that the leukemia occurring in a particular radiologist has been caused by exposure to radiation. At the present time there is no clinical or laboratory test by which the effects of occupational exposure can be detected in an individual exposed at the permissible level. With the exception of leukemia no other effect has been found to be significantly more prevalent in radiologists than in nonradiologists. However, further studies of possible differences should be carried out while some of the old radiologists are still alive.

Now, if it is difficult to detect radiation effects in radiologists, it is to be expected a fortiori that the effects produced in other personsthe public exposed to much lower levels of radiation, would be practically undetectable. These statements apply to somatic effects and are based on actual observations of fairly large groups of exposed individuals over a long period of time. They are not guesses.

As to genetic damage, the situation is much more difficult and speculation plays a larger part. I should like to make only a few remarks on this subject. In the future it may be expected that im

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pediments and diseases of genetic origin will assume greater and greater importance in our society. Therefore it is imperative to prevent a substantial increase in the pool of deleterious mutations in the population. With the discovery of a dose rate effect in the production of gene mutations in spermatogonia of mice by W. L. Russell and coworkers, I think it is now felt by geneticists that the recommended limit of 10 roentgens per generation for the genetic dose is satisfactory, since a large fraction of the dose would be received by the population at low dose rates. There is also another factor that may overshadow the effect of exposure to radiation at this level.

In a population in genetic equilibrium deleterious mutations are eliminated at the same rate at which they are produced. The pool of undesirable genes may be increased by increasing the rate at which they are produced (for instance by exposure to radiation) or by decreasing the rate at which they are eliminated. Elimination takes place by the death of individuals carrying deleterious genes before they reproduce. Modern medicine makes it possible for a much higher percentage of babies to reach maturity and have children. It is very likely that this will tend to increase the pool of undesirable genes in the population and that the effect ultimately may be much greater than that due to peacetime exposure to radiation. In that event, society will be forced to take suitable countermeasures irrespective of any exposure to radiation. Personally I believe that education of the public in this respect should start now.

I should like to discuss next the matter of threshold and linearity of the dose-effect curves in the case of somatic effects. Everybody agrees that at present there is insufficient information to settle these points. I have attempted to explore the situation by formulating theories of the aging process and cancerogenesis. The problem of chief concern is what happens when humans are exposed at very low dose rates throughout life or for a considerable portion of the life span. Since the dose rate is very low, the effect must result from some initial damage to an essential and very sensitive part of the cell. The cell nucleus is such a part. For the sake of quantitative study I have postulated that the primary damage is gene mutation in any body cell, although other possibilities exist. It is then assumed that on the whole cells with one or more mutated genes do not function properly and this malfunction eventually shows up as general aging and the diseases of old age. According to this theory exposure to radiation should accelerate the aging process and there should be no threshold for this effect. Calculations based on chronic exposure of mice and extrapolation to man indicate that the life-shortening in man from occupational exposure should be approximately 1 day per roentgen of highly penetrating radiation received over the whole body.

As to cancerogenesis, I have suggested that gene mutations in two. specific loci are needed before a normal cell turns into a cancer cell. However, this is not at all sufficient to establish a tumor. For the cancer cell to divide and multiply it must find itself or lodge in a region of tissue that is not functioning properly for a multitude of reasons. This forms the precancerous state emphasized by pathologists. In this terrain the cancer cell can divide and eventually produce a tumor. On this basis there should not be true threshold in the induction of cancer by radiation. However, a practical threshold

may well be expected. In the first place the dose or chronic dose rate-effect curve will rise slowly near the origin and very steeply later. Therefore, it will be difficult to establish an increase in the incidence of cancer at low doses. Then it is well known that the latent period for the manifestation of a cancer is longer the smaller the dose, and it may well be that for very small doses the latent period is longer than the lifespan. There are also other factors that may operate to give the appearance of a threshold in the dose-effect curve for cancer induction by radiation.

It is my opinion at the present time that in the case of leukemia produced by chronic exposure at low levels, there is no threshold but that the dose-effect curve is curvilinear, rising rapidly at the higher accumulated doses. As for bone tumors I feel that there is surely a practical threshold when the exposure is from external sources. There is good clinical evidence for this. There is also some "impressional" evidence. Radium dial wrist watches have been worn for a long time by very large numbers of people. The dose delivered to the bones of the wrist directly under the watch in a period of 25 years or so is of the order of 100 roentgens. Inquiry among bone tumor specialists reveals that the incidence of osteogenic sarcoma in the bones of the wrist is extremely low, especially in older persons and it is not higher in the left wrist (where most people wear watches) than in the right wrist. Of course, this is not a statistical study and the numbers in any one surgeon's experience are entirely too small. I mention it only as being suggestive. Similar "impressional" evidence may be derived from the fact that dentists used to hold films in the mouth of the patient during radiography. Some must have received rather large doses in their fingers. Many have developed cancer of the skin, but cancer of the bone in the hands of dentists is extremely rare. This is also true in the case of the pioneer radiologists. It might be worthwhile to make statistical studies along these lines.

As to bone tumors produced by such internal emitters as strontium 90, it is difficult to see in what way the effect of the beta radiation may be different from that of the secondary electrons produced in the bone by external X- or gamma rays. Yet there may be a difference and I prefer not to express an opinion on the matter of a threshold in this case. On the other hand, I feel quite sure that in the case of chronic exposure (by external or internal radiation) the dose-effect curve for bone tumors is curvilinear, rising rapidly at the higher accumulated doses.

May I make another request to insert two publications in the record? One is on the "Aging Process and Cancerogenesis," and the other one is "The Shortening of Life by Chronic Whole Body Irradiation.” There are items in these papers that are pertinent to the present discussion.

Representative HOLIFIELD. I understand they have been scrutinized by our consultants and they tell me they are pertinent, and they should be in the record, so they will be accepted. they will be accepted. (The material referred appears on p. 194.)

Dr. FAILLA. I have heard that some statement was made here vesterday, or the day before, about the operation of NCRP or ICRP, that their discussions are conducted in an "ivory tower," irrespective

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