The icrp and ncrp standards for permissible human exposure to radioactive substances are based on the assumption that the permissible amount of radioactive substances accumulated within the body or in the critical organ should not cause the permissible annual dose to be exceeded. These figures are then translated into maximum permissible concentra­tions (mpc) of each radionuclide in air or water using a set of physio­logical parameters that describe the movement of each element to the critical organ, and the daily rate at which the contaminants are inhaled or ingested. In the case of ingestion, the aec regulations give only the mpc’s in drinking water. This is a defect, since ingestion may be by way of food or water. The Federal Radiation Council’s approach is different —and more logical, since their recommendations, called radiation protection guides, focus on the permissible daily intake of a given nuclide, regardless of the source.

Where several nuclides are present, the aec regulations provide a method for weighing the effects of each in relation to the others in such a way that the maximum permissible radioactivity of the mixture of nu­clides takes into consideration the contribution of the individual nuclides. In this case, the method errs on the side of safety. For example, if 131I and 90Sr are present in drinking water, the mpc of the mixture might allow 50 per cent of the 131I permissible concentration and 50 per cent of the 90Sr permissible concentration — despite the fact that one nuclide irradiates the thyroid, the other the skeleton, and the effects are not thought to be additive.

Another safety factor exists where long-lived radionuclides are con­cerned, because the mpc is taken as that concentration which will result in accumulation of the lifetime permissible body burden in 50 years. It can be shown from the mathematics of 80Sr accretion in the skeleton that this provides a significant additional safety factor.

Since the aec regulations are stated in terms of the mpc’s of radio­nuclides in air and water, the regulations implied for many years that if the mpc is not exceeded at the point of discharge to the environment, the dose to humans will not be exceeded anywhere beyond the site boundaries. The point of release in the case of a radioactive liquid effluent is the point at which the waste is discharged to the receiving body of water. In most cases, this is an enormously conservative assumption, since dilution up to several orders of magnitude can take place beyond the point of release. However, it is also possible for physical or biological concentration to take place, and when this occurs, the risk can be correspondingly increased.

Within the past few years, the aec standards have been modified to

allow for biological concentration. In the case of 181I, the mpc in air has been reduced by a factor of 700 to allow for the fact that exposure to man is increased by the tendency of iodine to deposit on forage and eventually pass to cow’s milk. Additionally, the regulations have been modified to require the licensee to demonstrate that accumulations in the food chain are not taking place. The discharges to the environment are considered to be excessive if the radionuclides ingested by a sample of the population by any route of exposure exceed one-third of the annual intake permitted for water and air.

The Commission has always had the right to place upon the prospec­tive licensee the responsibility for demonstrating that such concentration did not take place, and although the aec regulations were formerly silent on this point, no one who has followed the course of reactor licensing pro­cedures over the years ever doubted that the aec has meticulously probed into questions of biological concentration beyond the point of discharge.

Under the aec regulations, a licensee can discharge radioactive waste to the environment in concentrations greater than those permissible for immediate inhalation or ingestion if he can demonstrate the extent to which dilution does take place. Many utilities undertake micrometeoro­logical studies of a proposed site, and on the basis of data generated in this way the licensees are frequently permitted to take advantage of the natural dilution that takes place between the top of the stack and the site boundary. To my knowledge, however, reactor operators have not taken advantage of this approach in regard to liquid discharges. This is due to tha fact that the art of forecasting dispersion in the aquatic environment is not developed to the same degree as forecasting dispersion in the atmos­phere.

The aec requires the licensee to conduct monitoring programs in the vicinity of the reactor. This provides information about the concen­tration of radioactive substances in air and water and also in whatever food products may be grown in the vicinity. Thus, the question of human safety is not left to conjecture but is based on actual measurement of sam­ples collected from the environment. Some of the aec facilities, such as Oak Ridge and Hanford, have been collecting data for more than a quarter of a century; experience at these places has produced valuable information that in many cases is directly applicable to civilian power reactors.

For years, many of us in the field of public health and environmental protection have argued that, on balance, electrical generating stations powered by nuclear fuels make better neighbors than do stations using coal or oil. It is true that the current generation of nuclear plants discharge 40 per cent more heat to the environment and this places more stringent limitations on the use of water for condenser cooling, but regulations deal­ing with this problem are being promulgated in the various states for application to both nuclear and fossil fuel stations.

Much has been said about the ecological effects of radioactivity dis­charged to the environment, but there is no evidence that this occurs at levels of radioactivity permitted by the aec. Putting it more strongly, there is a considerable body of scientific data that demonstrates that such effects do not take place. In contrast, we do know that certain vegetation is adversely affected by traces of sulfur dioxide and possibly by other com­ponents of the combustion products of coal and oil (Stem, 1968). There have been millions of dollars spent investigating the ecological effects of low levels of ionizing radiation exposure — but there have been compara­tively few studies of the ecological effects of the chemicals in fossil fuel effluents, despite the fact that we know these effects take place and can be observed.

In most parts of the country, fossil fuels are the only practical alter­native to nuclear fuels. We know, beyond any doubt, that sulfur dioxide discharged to the environment by plants burning fossil fuels has been responsible for many deaths in the general population, particularly during periods of meteorological stagnation. Even the innocent gas carbon diox­ide, produced by combustion of fossil fuels, is accumulating in the earth’s atmosphere and is regarded as a long-range threat to the world’s heat balance, with the possibility of eventual climatic changes on a disastrous scale (Conservative Foundation, 1963). Finally, it is a curious fact that because radium and other radioactive substances are normally present in fossil fuels, the radioactive atmospheric emissions from fossil fuel plants are not insignificant compared with those from many nuclear plants. (Eisenbud & Petrow, 1964; Fish, 1969). These are among the reasons that some of us are convinced that nuclear reactors make good neighbors.

Additional reasons are to be found in the actual operating experience of the civilian power producing reactors. The atmospheric and liquid effluents are in most cases less than 1 per cent of the amounts permitted by aec standards, and the public health risks, though finite, are so small as to be more than offset by even the most modest of the benefits of in­creasing man’s available electrical resources.

Conclusions

From the foregoing, together with various additional information that has been presented by other contributors to this volume, it is possible to draw certain conclusions which constitute the thesis of this presentation and which argue that although the record of the aec has been a good one from the point of view of the public health official, changes in the present regulatory system are needed to reconcile differences between public attitudes and the aec that have not been resolved after 15 years of almost continuous debate.

There are obvious advantages to having radiation protection stand­ards that are applicable on a national scale, there being no reasons why the standards applicable in one state should be more or less stringent than in another.

The aec regulations are substantially compatible with the recom­mendations of icrp and ncrp. Moreover, they are both scientifically and philosophically compatible with evaluations of the state of our knowledge of radiation effects that have been undertaken from time to time by other national and international bodies, including the United Nations Scientific Committee on the Effects of Atomic Radiation, the National Academy of Sciences (Reports of the Committee on the Biological Effects of Atomic Radiation, 1956), and the British Medical Research Council (1956).

The aec regulations have resulted in a safety record that is probably unsurpassed for any new industry. In the 27 years that have passed since the first reactor went critical in December 1942, there has been time to evaluate the basic adequacy of the systems of control that have been derived.

Although there are ambiguities, inconsistencies, and perhaps even deficiencies in the aec regulations, they are sufficient to protect the public’s health. The standards contain enormous built-in conservatism.

There are mechanisms by which local government and individual citizens can bring to the attention of aec the need for changes in its regu­lations. The aec techniques of publishing new rules or proposed changes in rules and the public hearing associated with the licensing procedure are examples of how the thinking of local government or individual groups can be incorporated into the aec regulatory procedure.

The present system of aec regulation, which puts major emphasis on the maximum permissible concentrations of radionuclides in air and drink­ing water, should be changed in favor of specifying the maximum permis­sible daily intake from all sources. This is the method used by the Federal Radiation Council and is preferable because it automatically considers such factors as multiple sources of exposure and the ecology.

Neither ncrp nor aec is sacrosanct, but considerable weight must be given to the fact that the ponderous procedures of these organizations have produced a set of regulations that are workable, and that have suc­cessfully protected the public’s health for more than a quarter of a century.

An examination of 27 years of experience would seem to indicate that the aec has been fully prudent in discharging the responsibilities which the Congress bestowed on it in the health and safety field. However, this judgment is not shared by everyone. For reasons which are probably related to factors other than the excellent safety record it has achieved in the nuclear power field, the aec does not have the high degree of public confidence that is necessary for smooth development of the electrical gen­erating industry. There remains a credibility gap which has not been closed after more than 15 years of debate.

A significant factor in the credibility gap is the unusual dual respon­sibility of the aec for both development of civilian nuclear power and protection of the public’s health. I myself believe that the aec has an ex­cellent record of accomplishment in both areas, and has retained a high degree of objectivity in facing its responsibilities for health and safety, but the public is not fully convinced that this is so. For this reason I believe it would be in the public interest to begin active consideration of the means by which the regulatory responsibilities of the aec can be transferred to or shared with some other governmental agency. Only in this way can the public be assured that the present apparent conflict of missions is not operating to its detriment. However, a transfer of regulatory responsibility cannot be accomplished easily. The aec has well-developed regulatory machinery of a type that does not exist in any other branch of government. Although in theory it would be possible to transfer this entire organization to another agency, this would not be wise because interagency transfers are always disruptive of morale and working efficiency.

As a compromise, the Public Health Service should be given a more prominent role in the regulatory program. The Public Health Service rather than aec should promulgate the numerical standards of permissible exposure. The aec, with its highly developed capability to evaluate reactor designs, should continue to consider applications for new reactors and should continue to monitor construction and operation to assure com­pliance with the terms of the licensee. However, the Public Health Service, in its traditional collaborative relations with the states, should undertake the responsibility of effluent monitoring and ecological surveillance. By sharing its present statutory regulatory authority with the Public Health Service in this way, one may hope for the closing of the credibility gap that now exists between aec and many segments of the public.

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Ehrenberg, Lars, Gunter von Ehrenstein, & Abne Hedgran. Gonad temperature and spontaneous mutation-rate in man. Nature, 1957, 180, 1433-1434.

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——- . Committee I. The evaluation of risks from radiation. Health Physics,

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——- . Report. General Assembly Official Records: 21st Sess., Suppl. No. 14

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