118 THE SHORTER-TERM BIOLOGICAL HAZARDS OF A FALLOUT FIfLD Therefore, when this is applied to the data, the dose as received in the last 10 or 20 days hefore death is given its proper weight in the contribution to the lethality. This leaves unresolved the question of whether the acute injury and the irrecoverable chronic injury combine and simply add to the death. I am quite convincedthat they do notdo so precisely. However, to think so and to know what to do about it are two entirely different things. DISCUSSION ON TOPIC III Biological Repair Factor Dr. Bertin, To start off the general dis- cussion, I would like to ask Dr. Jones if he would initiate this discussion for us. We have heard from Dr. Blair and Dr. Sacher, and T think we should hear what Dr. Jones has to say on this field. I think we are fortunate in having all three in the auditorium at the same time. Perhaps we can arrive at some syn- thesis of mutual thought with them present. Dr. Jones (University of California, Berke- ley). I think it is a remarkable thing thatall of us who have talked either here or recently elsewhere who are expressing opinions on radiationeffects and particularly radiationeffect. upon the life span have an essentially coherent viewpoint about the thing, and are in essential agreement with regard to all major factors that, I understand. Where we differ are differences in fine points of interpretation which are very important to our current work, but it is per- below the level where you get frank burn, the reparative processes will give you a lissue that looks like a tissue that was notirradiated. If you look at the problem from the standpoint of the genetic effect or the long-term effects of radiation, you have apparently another coherent viewpoint which seems to be at. the opposite end of the scale. T wonder if these two viewpoints can't be brought together by the consideration of a radiation effect on a cellular basis. In the first place, I think our concepts of threshold effects and reversible effects of radiation are Jargely the effects of radiation upon complex organisms such as mammals, where many cells are involved, and you have the potentiality of replacement. of injured cells by cells which are not so muchinjured. You can divide and veryrapidly, and take the place of together and what things perhaps do not. injured tissue. As wegetto the cellular level, I think the classical example is that cells do show a recovery effect such as Dr. Henshaw’s early papers on the subject, Evenat the same time and subsequent timesince effects of radia- thumbnail sketch. quantum effect of radiation so we have the haps as useful to us to surveyat this time some of the overall aspects of the radiation effect problem from the standpoint of what things fit Let me try to do this in about a 2-minute In the first place, histori- tion at the cellular level turn to be more cally in radiation effects, I think everyone was hit theory, and the like. Below the cellular level at the chemical level ulcer, whelming evidence for quantum interaction between radiation and matter and radiation first impressed by the gross aspects of radiation injuries. Things that had to do with burn, tissue necrosis and the like. These things have enormous threshold effects. Thera are doses of radiation below which you do not see these effects at all. Between the range of out and outtotal killing of cells from which there may be no recovery because the cells don’t exist any more to exhibit recovery and the threshold effect, you get regions where there are great reparative processes. So as Jobn Storer expressed it, if you wait long enough and structural level of tissues, one finds over- effects that are largely irreversible in nature. Now, let us look for 2 moment at the radiation effect in mammalian tissue. If we take a fairly uniform setof tissues such as the marrow, lymphatic tissue, and so on, there exists from the laboratories of quite a number of different observers, quantitative effects of radiation upon these tissues, either in terms of estimating 119