Nacca-13TH Annual Convention 1959: Workmen's Compensation Section Seminar (Partial)

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rate, or the time over which the radiation was delivered. In what follows, the effects to be expected will be described under broad categories of conditions of exposure. Q 2.94 High doses of radiation, total body irradiation, acute effects By "acute effects" is meant manifestations within the k t several weeks to months following exposure. With a single exposure to radiation, no mnnlfeetatlan IHdlscernihle nt doses below 50 roentgens, From 50 to about 150 roentgens, no signs or symptoms will result, but it is possible to determine by laboratory means that such an exposure has occurred. In particular, there will be depressions of some peripheral blood elements, namely the lymphocytes, neutrophils, and platelets. Above 150 r to 200 r, severe signs and symptoms result in most individuals exposed. Death results within six weeks in a few individuals exposed of the order of 250 roentgens, and at doses of the order of 500 to 600 roentgens essentially no one so exposed will survive in the absence of treatment. Q2.95-Experience with large exposures, bombings and accidents Experience with large exposures of man to radiation has been o b tained from a variety of sources. In the Hiroshima, Nagasaki bomb ings, approximately 15%of casualties have been ascribed to radiation alone. Following the detonation of a thermonuclear device at the Pacific testing grounds in 1954, a large number of native Marshallese and some Japanese fishermen were showered with the fallout. None of these individuals is believed to have died acutely from the effects of the exposure; however they did show some symptoms, and profound changes in the peripheral blood elements were observed. There have been a variety of industrial and reactor accidents in this country and abroad. Three serious, critical assembly accidents have occurred at-Los Alamos, resulting in the death of three individuals. Other a&- dents have occurred at the Argonne National Laboratory and the Oak Ridge National Laboratory. All such accidents in the United States have resulted in a total of three deaths and 24 hospitalizations. Two. individuals were heavily exposed in a reactor accident in Russia. Seven individuals were heavily exposed in a Yugoslav reactor accident, and one died as a result of the exposure. The effects of wholebody exposure has also been observed in patients with serious diseases that are given large doses of whole-body radiation as a therapeutic

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WORKMEN'S COMPENSATION SECTION SEMINAR 0 2.97121 8 2.96---Damage to central nervous system, gastrointestinal tract, With this experience, the effects of a large single exposure are well documented and are as follows: At very high doses, perhaps in excess of ten thousand rocntgeiis or above, the effects may be essentially instnntaneous and death limy result wttlrin hours or,at best, days. The effects have been associated with damage to the central nervous system, and the individuals die in a state of profound collapse. At lower doses, of the order of a thousand to five thousand roentgens, the clinical picture seen is associated with damage primarily to the gastrointestinal tract. Almost immediate nausea, vomiting and diarrhea are therule, with continuation of these signs and symptoms until death. Death iisually occiirs within the first week. Extreme fluid loss occws, and these individuals too die in a state of shock. Data from animals indicate that it is possible to keep these individuals alive by truly heroic fluid replacement measures, however even if the fluid imbalance is corrected, the individuals are certain to die later from damage to the bone marrow. and bone followed by death 0 2.97-Bone marrow damage, antibiotics and transfusions prevent At lower doscs, of the order of 200 to 500 or 800 roentgeiis, the signs andsymptoms seen are related primarily to bone marrow damage and its sequelae. There may or may not be an initial period of nausea and vomiting, lasting for hours to a few days, and followed bv a latent period of some days'diiration in which no symptoms are apparent, In the third or fourth week, depending upon the dose, the neutrophils and platelets in the peripheral blood reach dangerously low levels. When the neutrophils reach levels of approximately 500 or less/mm3, infection is the rule. When the platelets have reached low levels rhage if the dose has been high enongh. In individuals that die as a result of exposure, the pathology is associated primarily with hemorrhage and infection. It is possible to treat individuals, with resultant survival where otherwise death would be certain, by the judicious iise of large doses of antibiotics and by massive transfusions of fresh platelets. There is m e evidence to indicate that bone marrow transfusions m a y be of value under some conditions in treating such heavily exposed indiyidd. 3.I1.It...I.

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Q 9.98 High dose, partial body irradiation, acute effects The symptomatology and signs seen following exposure of portions of the body to high doses of radiation depend upon the body region irradiated, as well as the magnitude of the dose received. With high doses, of the order of several hundred roentgens or larger, some skin damage is inevitable. The initial erythema is followed by a frank breakdown or sloughing of tissues. Large doses of radiation to the hairy areas of the body result in loss of hair, either temporary or permanent. Large doses to the gonadal region result in sterility, and large doses to growing bones result in a retardation of growth. If the doses are high enough, sloughing of all tissue so irradiated will result. Irradiation of the eye will result in opacities. With partial body irradiation, a relatively large portion of the body must be included in the beam before death will result in the acute period. In general, the doses to produce serious injury or death with partial body irradiation are several times larger than the lethal dose of whole body Q 2.99-Danger in use of certain equipment Partial body exposures are encountered of course in the therapeutic use of X-rays for a variety of malignant and other conditions. It has been seen frequently in physicians and veterinarians who unnecessarily exposed their hands or feet to large doses of radiation while doing radiological examinations of animals or human patients. Severe damage to the feet has been seen as a result of the use of fluoroscopic shoe fitting apparatus, Also, damage to the hands, eyes and other portions of the body has been seen in accidental exposures of persons working with accelerators or radioactive material. (At this point in the lecture, colored slides were shown indicating the types of lesions, and the pathology encountered following large doses of either whole or partial body radiation.) Q 2.100 Establishing cause and effect, difficult, when What has been discussed so far, the acute effects of large doses of radiation, presents no particular problem in terms of establishing cause and effect..Here, almost always, the exposure is known to have occurred, and it is beyond reasonable doubt that the effects seen were the direct result of the exposure known to have occurred. In the discussion of late effects of radiation that follows, the cause and effect relationship becomes more and more obscure, because (1) there are no lesions, or signs or symptoms that are pathognomonic for irradia-

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tion damage, since many of tlie late effects that can result from exp u r e to radiation are also known to occur with a natural incidence in the absence of known exposure, and (2) in a large group of individuals exposed, only a fraction, and frequently only an extremely small per cent, will show any manifestation of the exposure. Thus it becomes more and more difficult to conclude thnt o given pathological condition was caused by an exposure to radiation. $2.101 High dose, late effects, single or multiple exposure, total or Once an individual has been exposed to even near lethal doses of whole-body or partial body radiation, and has recovered, the recovery usually appears to be essentially complete, and to all intents and purposes tlie individual will appear to be entirely normal. Thus the Japanese who survived the acute effects of radiation from the bomb were, within a matter of weeks or months, either dead, or essentially normal and quite capable of carrying on their usual occupations. Also, . with individuals exposed to high doses of radiation in reactor or other accidents, a similar result has obtained. These people recover and leturn to their jobs. Also, with individuals receiving low doses of radiation continuously there has been no apparent effects for long pcriods of time. The radium dial painters who ingested large amounts of radiltm or mesothorium whtle pointing their brushes with their lips, slmwed no symptomatology for years, and in some cases as long as tllirty years. Thus one may recover from a large dose of radiation, or be continuously irradiated at low dose rates, and show absolutely no effects.However in some percentage of individuals so exposed, the other types of cancer, aplastic anaemia (rarely), cataracts, perhaps some reduction in life span, and, with partial body irradiation only, perhaps local effects such as skin damage or loss of hair. Also, in this general category must be included genetic damage which does not affectthe individual actually irradiated, but may affecthis offsprings. Most characteristic of late effects is the prolonged latent period. Usually the latent period lasts for at least 4 to 5 years or more, and may extend to as long as 30 years. 0 LlOZ-Leukemia and other cancers Some specific examples of late effectsare known. In Hiroshima and Nagasaki, of the individuals exposed who were closer to the hypocenter than 1500meters, SSI had developed leukemia by 1957, where only !?8 in a population of this s b would have been expected to partial body irradiations

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individuals who in the course of their occupation receive low doses of radiation chronically. The total dose received over the entirc lifetime may amount to no more than 100 roentgens or less. We are mwcmed, of Course, only with possible late effects, since no acute w e have men above tlmt with high doses of radlntlon, lata effects an occur; however they occur in only a very small per cent of those -sed, and one can never say with certainty that radiation was the a l s e of any given case exhibiting a potential late effect. This is bemuse some of the individuals in the population would come down with the disease without exposure to radiation. There is nothing pathognomonic about radiation injury, with the possible exception of r3diation-induced eye opacities which are distinguishable. But suppose, however, that an individual received 50 roentgens of total body radiation with no acute effects, or 25 roentgens to the hands, or 6 rem per year over several years when the s&alled "maximum permissible dose," allows him to receive only 5 rem. Suppose further that p r e responsible for the leukemia that he developed? It is in this situation that real disagreement among scientists occurs. Unfortunately, at present we have absolutely no data to settle the disagreement. Some scientists feel that there definitely is a "threshold" dose for late effects, and that no effects will appear in any exposed individual until this threshold is reached. Others feel that there is no threshold, and that any dose of radiation, however small, will produce late effectsto some small percentage of the population exposed. T h e analogy can be drawn that some feel that it is necessary for an adult to ingest perhaps 50 tablets of aspirin before there are any serious toxic effects. Others claim, in analogy, that if a large enough population is given much smaller doses of aspirin, that some small percentage of that population will be seriously harmed by even one aspirin, or perhaps even a small fraction of one aspirin. It is thus apparent that there is no agreement as to whether or not any harm results from low doses of radiation, let alone the degree of ham, It is impossible to determine cause when a patient has leukemia and states that he believes he may have been exposed to some kind of radiation in some degree Similar difficulties arise when an individual develops leukemia and feels that his disease may have resulted from exposure to f 3 h t radiation. There is considerable disagreement as to the number of leukemias, if any, that might appear in a population of millions of individuals exposed to low-level radiation. When it ComeS down to the individual, it is impassible to establish cause and eff& betwee0 individual later Comes down with leukemia. Was this small ex- .

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a given case of leukemia or other cancer, and a known or reported earlier low-level exposure to radiation. As indicated above, only a small fraction of individuals exposed acutely to even high doses of radiation later appear with diseases such as leukemia. Thus one can only attempt to state what is likely to happen in a population and not to the individual. This fact'poses difficulties when legal considerations are geared to the individual. One can only attempt to state the probability of an irradiated individual coming down with a late manifestation. Lewis'has estimated, on the basis of the Hiroshima and Nagasaki data, and on the basis of other data, that the probability of persons developing leukemia fol= lowing radiation exposure is of the order of .2 per million per rad p e r year. As Lewis states, these figures apply directly only to the situations from which they were derived (high dose, single exposure, large region of body exposed, etc.), and a number of unproved and very tenuous assumptions are involved in attempting to apply these data to any other situation (i.e., low-dose, chronic exposure, localized irradiation, possible late effects other than leukemia, etc.). Brue$ has stated the case against assuming any harm from low-level exposure. However, Lewis' figures are frequently used to provide some, perhaps the most pessimistic estimate of what might result from radiation exposure. One might use these figures to calculate the probability that a given case of leukemia has resulted from a known or alleged exposure.' As an example, one can take a case of leukemia in a 30 year old man exposed previously to 10 r. The natural incidence of leukemia at this age is about 25 cases per million per year. Applying Lewis' figures literally, 10 r may result in 20 leukemias per million per year, or this man's chances of getting leukemia in any one year from his 10 rad are approximately 20 in a million for the first few ' years following exposure. His total chances are 20 + 25, or approximately 45 per million per year, and the chances that the 10 rad are responsible for his leukemia are approximately 20 out of 45.Because of increasing natural incidence of leukemia with age, the chances of the 10 rad being responsible are approximately 20 out of 54 if he develops leukemia at age 40,ZO out of 169 at age 80,and 20 out of Wruer. A. M: Critique d the linear theory of Carcinogenais. Science 128: W9.1958. "he ruthor Is indebted …