234 THE SHORTER-TERM BIOLOGICAL HAZARDS OF A FALLOUT FIELD DISCUSSION It appears that this is a very very strong assumptions that injury processes plied by Col. Brennan. Dr. Bond exhaustively demonstrated the facets that determined depth-dose patterns in proved wrong,it is quite evident their theories will predict inaccurately. What appears more importantis that as further analyses are made, by movement, by clothing, by a foxhole. If one were prone or supine, immobile and nude, suspended 5 centimeters from the ground, the effect would be great indeed at a beta-gamma ratio of 50 to 1. For situations that I can see with dose rates that are probable, one would have to be precisely prone, immobile, and nude and probably dead. Not meaning to introduce levity, but this is a difference of opinion, and certainly more study is needed to resolve these differ- feasibility. important area in which further analyses are necessary. phantoms. From the data of Chamber, Imirie and Sharp, he conclusively demonstrated that the patterns observed in the fallout field and with initial radiation are approximately what theory indicates they should be when the source is treated as multiple separate discrete sources, and using the appropriate buildup versus distance considerations. The inadequacies of air dose to express biological effect was proved, and the dependence of the logical effect on depth-dose pattern evident. It can only be hoped that approaches and conclusions of Drs. Borg biowas the and Bond will be used by the hazard-evaluation people, and by those people performing further empirical field studies. In addition the apparent acute hazard of neutrons to man was dealt a rather severe blow when depth-dose considerations were dropped by use of what one might call the engineering RBE from a maximum of two to a mouse to less than 0.1 for a large animal, such asman. This is in respect to the acute effect.* In the section on biological repair, Dr. Hen- are linear. If these basic assumptions are one realizes the death function both acutely and chronically is exceedingly complex. Repair processes proceed at different rates in different tissues. Death can be reached by a multiplicity of mechanism and causes, and it appears that much more experimentation with all the permutations and combinations of radi- ation techniques, of varying dose rate, area of body irradiated, fractionation, etec., will be necessary to finally resolve the relationship between total dose, dose rate, fractionation and life shortening. The areas of agreement seem to have broadened considerably. Although Dr. Blair doubts half times for the recovery of injury processes can be correlated with any measureable physi- ologic parameter, it appears that this would be a desirable area to investigate. From the practical standpoint, a correlation of recovery in peripheral blood with half time seems desirable for here is a point to use in extrapolation to man, since long term hema- tologic data is becoming available in the shaw has courageously proposed a work capacity Marshallese. It is quite evident that this is one area in which the direct clinical research accepted gratefully by those who haveto esti- It was of interest that Dr. Trum’s date on versus dose and time graph. This will be mate hazards. However, it can only be hoped that they will use it in the manner that was proposed, and with all the reservations that Dr. Henshaw presented. I can’t help but feel that the rather flat depth-dose effect response that Dr. Henshaw presented for man might be much more steep if all of the air doses that went into it were appropriately converted to tissue dose. Dr. Storer, Sacher, Blair and Jones were fortunately assembled all in the same room at the same time. The result was certainly from my standpoint most educational and interesting. As a basis for all approaches are some “Subsequent work has shownthattherelative effectiveness factor may Ue in the vicinity of 0.5. is not acceptable. the hematologic recovery in burros looked very muchlike the Marshallese data to date. In the section on beta burns, Col. Brennan, making certain assumptions on energy and uniform distribution of fission products, calculated the contributions of dose at a point in a planarfield as a function of radius and height above surface. This approach coupled with the Spencer-Fano equation could describe the dose at this point from polyenergetic fission field more adequately. This dose should repre- sent the maximum hazard sincedrift, directionality and shielding wouldall effectively diminish the effect as previously considered by Drs. Bond and Borg. I personally do not share the feeling that beta bath is a real hazard as im- The contact beta burn is areality. The beta bath effect is diminished ences. In respect to the biological effect of beta irradiation, the obvious question is, do animal studies apply to man? In part, I think the answer is yes. However, J have been assured by manyveterinarians that the skin of cattle and of swine is particularly more reactive and prone to produce hyperkeratosis and acan- thotic lesions as observed. There can be no question about a qualitative similarity, but I somewhat question whether one can say there will be quantitative similarity between the animal studies and man. I personally think that the cosmetic future of the Marshallese is rather good. Certainly Dr. Conard in his continuing studies of the Marshallese through- out their lifetime or his will find out the answers. Particular importance in assessing the beta hazard, I believe, are the attentuation curves that Dr. Conard presented. In Dr. Morgan’s presentation it was certainly welcome news to know that the National Bureau of Standards Handbook 52 will be revised and have a broader base and include new nuclides and both single and chronic hazard estimates. I do not see how he and his group can possibly do all this work that is involved in these revisions and we certainly owe themall a debtof gratitude. Dr. Jones’ studies on iodine-13! uptake in the thyroids of cattle and of man certainly were most encouraging and show quite con- clusively that the dose is small. The observations of Trum concurred with this indeed. OF TOPIC Vv 235 I was most interested in the studies of Dr. Durbin on the kinetics of strontium-90 uptake, retention and excretion. It goes without saying that much more studies of this type, as has been so ably demonstrated by Dr. Langham a few moments ago, are urgently needed in a wide spectrum of animals and over the wide entire spectrum of the radio nuclides. Dr. Placak’s observation on plutonium-239 and its distribution in the Nevada test site and areas remote from there quite conclusively demonstrated that though there is apparently no hazard here again is another subject that must be closely watched and a continuing study is essential. Dr. Stannard listed the physical and physiological parameters necessary to evaluate the pulmonary hazard from particle inhalation. However, the problem was not putto rest. It looks as thougha start has only been made, and a tremendous amount of work yet is to be done to try to evaluate a single nuclide, let alone the sphere of size and substances from fission products. In Major Woodward’s absence, Dr. Schrodt presented the problems that were closcly allied to the previous observations of Dr. Jones and Col. Trum onurinary excretion of iodine-131. It seems that there is one minor or possibly importantdifference here. It seems inconceivable that man could be taking the iodine in other than by inhalation. The cattle intake was from feed, predominantlygrass. The studies of Dr. Lindberg and Dr. Larson brought out what struck me as two rather im- portant considerations. First, the fractiona- tion of fission products by the size of the particles between plants on which animals graze, and the underlying ground, and the fractionation of iodine-131 and strontium-90 with dis- tance from the site of detonation. It appears that all of these factors must have to be fed into the ultimate models for assessing both acute and long term fallout hazards. I was quite impressed with the mass of data that Drs. Weiss and Cohn presented. However, as a physician, I find myself completely unable to interpret the importance. Tt appears