At the outset I commented on the need to consider the relative validity of standards set for other aspects of our environment in com­parison to radiation standards. There are formidable difficulties in doing this but I shall attempt it nevertheless. Chauncey Starr (1969) has ana­lyzed social benefit versus technological risk in terms of individual or soci­etal benefits versus the cost. Looking at risk of a fatal event per hour of ex­posure it is interesting to note that we voluntarily accept fourth-order risks (i. e., one chance in 104), in general sixth-order risks in hunting, skiing, smoking, or being in the Vietnam war. Note these are risks of fatality per hour. To compare these with the risks discussed above, the figures must be multiplied by the number of hours of exposure and corrected in various ways. The benefits are placed on a cost basis or, for some items, on an arbitrary scale of “benefits awareness.” This latter is determined by considering the percentage of the population involved in the activity and its relative usefulness or importance to the individual. The automobile is at the top of the list with 104 risk of a fatality per hour of exposure and a benefit awareness of about 50 (with 100 as the maximum). Nuclear power is at the bottom with a risk factor of 109 (i. e., one chance of a fatality per billion hours of exposure) with a benefit awareness of about 0.0005 — five orders of magnitude below the automobile! These exact numbers have little quantitative significance, but the implication is clear. Such analyses must be considered in any comprehensive evaluation of our technology.

I shall turn now to an area more comparable to the radiation field and one with which I am more directly familiar — namely, toxicology. On the order of one in twenty hospital admissions may be related to an unrecognized or undiagnosed untoward side effect of a drug taken for therapy. The risk of an untoward drug reaction while in the hospital is correspondingly large. This is a major public health problem and bespeaks the need for far more sophistication in toxicology than we now have. In an editorial in Clinical Pharmacology and Therapeutics Gerhard Zbin — den (1964) wrote: “Drug-induced side effects have been called diseases of medical progress. They are part of the price we may have to pay for more effective and better medicaments. Since there are no active drugs without undesired side actions, no toxicological experiment will ever be able to assure complete safety for their use in humans. It should, however, enable the therapist to better judge the risk involved in any kind of phar­macotherapy, so that he may weigh the expected benefit of a drug against possible injuries.” (Italics mine.) Does this not sound somewhat familiar? And it is from a man directing research for a major pharmaceutical company.

Current practices in toxicological testing can be seen in this outline of animal toxicological tests (abbreviated from Loomis, 1968):

Single dose acute tests using two species and two routes of adminis­tration (24-hour test and survivors followed for 7 days)

Prolonged tests (daily doses) — 3 months, two species, three dose levels

Chronic tests (daily doses) — 1-2 years, two dose levels

Special tests — potentiation, effects on fertility, teratogenicity, car­cinogenicity.

Note that the “special tests” are done only in unusual cases — or were until recently. These last include some of the long-term effects of greatest importance to radiobiology. As a part-time toxicologist I can testify that carrying a test beyond 30 days was indeed unusual until recently. And who says 6 months should usually be enough unless carcinogenicity is suspected. The story is different in radiobiology, partly because society has been willing to give the needed support for long-term studies largely through the federal government and partly because dedicated scientists have been willing to wait patiently for long latent periods to pass in order to see these experiments through.

Why is the situation so different in toxicology? There are many rea­sons, of which financial support is only one. Familiarity with chemicals as toxic agents is an important one. We have had drugs and chemicals in our daily lives for generations. Perhaps even more important is the fact that there has been little evidence of long-term effects of the type character­istic of radiation exposure. This may be partly because we did not look. Also, the existence of an irreversible component has not been demonstrat­ed in those few cases where really long-term toxicological studies have been undertaken. Indeed, as stated earlier, it may be that radiation effects differ in this fundamental way from chemical effects, but this is by no means proved. Long-term toxicological studies comparable to those done with radiation are hardly available at all. Only very recently under the stimulus of the thalidomide and similar unfortunate incidents has the possible long-term effect of drugs been considered and tested seriously before some use is permitted. The now familiar story of the reckless use of insecticides and pesticides and the irresponsible dumping of chemical wastes points further to the issue before us.

Many chemical mutagens are known to exist. Many more probably exist. Toxicologists are far behind the radiation field in examining quan­titatively the potential effects of chemical mutagens, and routine screening is just being considered. And one seldom hears even speculation that there may be anything but a threshold dose-response relationship since its presence is a basic tenet of classical toxicology.

Obviously, the fact that things are worse in chemical toxicology is no reason to relax vigilance toward radiation hazards. But there seems to be or was until very recently, an unfortunate tendency of large segments of the public to accept familiar hazards while reacting violently to the possible presence of a radiation source. Science — indeed logical reason­ing itself — seems to play a minor role in these reactions. The way in which the nuclear age was bom and the relatively mysterious nature of radiation, of course, have played their roles. Perspective wifi not come to our evalu­ations until these two major types of potential environmental modifiers can be and are reduced to the same terms and examined on comparable bases. A very large effort in toxicology will be required to permit this.

There appears to be no doubt that in general we are willing to accept risks in other spheres of activity which we will not accept from exposure to radiation. The acceptability of exposure even depends to some degree on the source of radiation. The largest single source of radiation exposure to the population except for natural background, about which we can do nothing, is found in the medical uses of radiation, particularly diagnostic X rays. This is true because of the large segment of the population in Western cultures which may receive an X-ray exposure for medical or den­tal reasons, and reflects an assumption that the benefit is clearly worth the risk involved. The benefit is to the individual exposed, the risk is largely to the race. I must admit to being, to a degree, mystified that a rad de­livered to the population by a nuclear power program is of so much more concern than a rad delivered by such more familiar routes. Perhaps it is again the matter of its voluntary nature as well as its familiarity. Perhaps it is the lack of clear benefit and the fact that alternative routes to the same end are not clear or do not exist. Remember, too, that medical uses of ra­diation are specifically excepted in promulgation of any standard because they rest on the individual professional judgment made by the physician.

These are not biological factors and I prefer not to digress further in­to them. Instead, I shall present my conclusions from this rather rudimen­tary comparison.

The biological risk associated with primary radiation standards is, in general, lower than in most of the more familiar activities of man. I speak of the risk of a delivered dose, not of the secondary standards such as those for air and water.

Present standards incorporate safety factors — large ones in the case of occupational exposures, smaller ones for exposure of adults as a popu­lation, still smaller ones for exposure of the fetus.

The information on long-term effects of radiation far outweighs simi­lar knowledge for drugs, chemical toxic agents in the environment, and so forth. A major effort is needed to put these on a comparable basis.

Although there may be some unique ways in which radiation affects living cells and tissue, only further work can establish whether or not these are truly unique.

Most radiation standards have been set largely on the assumption of linearity of the dose-effect relationship and the assumption that any in­crease above background may be harmful. Toxicological standards have been based largely on the concept of a threshold. Only a major scientific effort can establish whether or not there is a real difference. In fact, for radiation probably only major exposure incidents with thousands or mil­lions exposed would provide the needed data — and we do not countenance these.

Meanwhile I see no reason to reduce primary radiation standards without new and compelling evidence.* Some derived standards may need much adjustment to account for the events between release of a potential dose and its actual delivery to living tissue, and for the possible multipli­cation of sources impinging on the same population. But these are matters requiring new information and careful dispassionate study. Let us proceed about this as responsible citizens and scientists interested only in the truth.

*This paper was prepared and presented before the Joint Committee on Atomic Energy hearings and other current writings which state that there is compelling evidence even though it is not new data. Comment on this would not be appropriate here since these matters require careful study, as emphasized above.

REFERENCES

International Commission on Radiological Protection. The evaluation of risks from radiation, icrp Publication 8. London: Pergamon Press, 1966.

Loomis, Ted A. Essentials of toxicology, Table 12-1, p. 142. Philadelphia: Lea & Febiger, 1968

Starr, Chauncey. Social benefit versus technological risk. Science, 1969, 165, 1232— 1238.

Zbinden, Gerhard. The problem of the toxicologic examination of drugs in animals and their safety in man. Clinical Pharmacology and Therapeutics, 1964, 5, 537­545.