The rapidly expanding interest in the utilization of nuclear energy as a power source has started to focus public attention on the benefits and risks associated with the peaceful uses of the atom. The context of the current concern differs markedly from the last period of major public interest in atomic matters, which occurred during the period of weapon testing with its associated worldwide radioactive fallout. The current phase happens to be concomitant with a more general concern about environmental quality and with the impact of technology on the environment. Thus, today the nuclear reactor, in terms of its potential as a cheap energy source, repre­sents a very important element among the several alternative technologies available to provide needed electrical energy. Each of these alternative technologies has a potential impact on the local environment. Each, there­fore, must be considered in terms of its long-term costs versus short — and long-term benefits. Nuclear power stations represent one of several alter­native possibilities. Any judgment of the risks and benefits associated with a nuclear power station must include, as part of the complex of facts and variables that enter into the formulation of such a judgment, the risks and benefits associated with fossil fuel power stations because fossil fuel is presently the first alternative.

Each kind of power station has risk associated with it that is more or less unique. For nuclear power stations, this risk is generally recognized as that associated with radioactivity. However, there is evidence that fossil note: The research in this paper was sponsored by the U. S. Atomic Energy Com­mission under contract with the Union Carbide Corporation.

fuel power stations also may release radioactivity from their stacks (Eisenbud & Petrow, 1964;Fish, 1969),so that differences between pow­er stations in terms of their impact on the environment may, in part, be quantitative, as in the case of radioactivity, or distinctly qualitative, as in the case of S02. The radioecological impact of power stations must be evaluated in the light of these considerations.

The public concerned about environmental radioactivity has wit­nessed a gradually increasing growth in the atomic energy program. Dur­ing the earliest years environmental studies and related surveillance were primarily centered on the major government-owned nuclear facilities, such as the Hanford works and the Oak Ridge National Laboratory, where radionuclides were being produced and released to the environment in accordance wtih prevailing standards. The Hanford works was of particu­lar concern because radioactive waste resulting from irradiation of the cooling water used in the large production reactors was discharged rou­tinely to the Columbia River, which had important fisheries. An ecologi­cal analysis and surveillance program was established and now has docu­mentation extending over twenty years on the behavior and effects of the quantities of radionuclides released to the Columbia River.

By the mid-1950’s, the potential of nuclear energy with its associated problems of radioactive wastes and the concern over weapons fallout resulted in an intensification and broadening of effort in radioecology. The problems of movement of radionuclides through food chains and the effects of radiation on the environment were quickly perceived as being the two major facets of the radiation problem. Likewise, the effect of chronic, low-level ionizing radiation was early recognized as one of the most difficult, if not intractable challenges facing radiation ecologists — much as it has been for radiation biologists concerned with the effects of low-level ionizing radiation upon man. In this paper, I shall examine some of the evidence which bears on the long-term, low-level effects of chronic ionizing radiation upon organisms within the natural environment. Movement and trophic level or food chain transfers and accumulation of radionuclides is the subject of another paper in this volume.

To evaluate the facts and related information on the environmental impact of radioactivity properly, some perspective on the known effects of ionizing radiation is necessary. Likewise, it is necessary to judge these data in the context of the quantities of radiation likely to be encountered in the vicinity of a nuclear power station. The quantity of artificial radionuclides which can be released to the environment is legally limited on the basis of hazard to man. The maximum permissible doses of radiation to man and the permissible levels of radionuclides derived from these doses are eval­uated continuously by regulating agencies and certain scientific bodies which were established for the express purpose of establishing standards of permissible radiation exposure for human beings. These scientific bodies include the U. S. National Committee on Radiation Protection and Meas­urements (ncrp); the Committees on the Biological Effects of Atomic Radiation, under auspices of the National Academy of Sciences, National Research Council; the United Nations Scientific Committee on the Effects of Atomic Radiation; and the Federal (U. S.) Radiation Council (frc), which was established to provide protection policy on exposures of radia­tion workers and members of the public.

Other nations also have governmental agencies with functions similar to the frc and the ncrp. All of these groups and agencies were established because of the concern with ionizing radiation and the need to protect human beings from overexposure to radiation. The problems in determin­ing what quantity of radiation constitutes overexposure are manifold and complex. Nevertheless, it is to the credit of these agencies, and to the hundreds of scientists who have conducted the many kinds of radio­biological research which provided the necessary data, that a body of acceptable standards has been developed. Although the standards them­selves are complex in both interpretation and application, they reflect an effort in research and standards development that is unique and out­standing.

We have no comparable standards for the environment. Research in radioecology during the past fifteen years or so has been directed toward ascertaining the effects of radiation on natural populations as a function of dose. As this research matures, a body of doctrine will emerge to pro­vide the basis for development of any further standards that are shown to be necessary. Meanwhile, the present standards provide both guide­lines and a set of baseline levels which are useful now in comparing the known effects of chronic, low doses of radiation on organisms against the legally permissible levels of radionuclide release.

My concern here is with the potential effects of ionizing radiation resulting from releases of radionuclides that are in accordance with cur­rent standards. The extant data on low-level effects should be evaluated in terms of the doses that are likely to be received by organisms in the environment as a result of releases at or below the maximum permissible concentration (mpc). The maximum permissible concentrations and doses established by the International Commission on Radiological Pro­tection (icrp) and the ncrp form the basis for the regulations set forth in 10CFR20 (Code of Federal Regulations, Title 10, Pt. 20) pertaining to the discharge of radioactive wastes by nuclear establishments. The stand­ards of radiation exposure and therefore the mpc’s differ for the popula­tion groups exposed, icrp Publication No. 9 has established two cate­gories of individuals for which the Commission now gives recommenda­tions: first, adults exposed in the course of their work (radiation workers), and second, members of the public. Under current practice, members of the public (including populations in the vicinity of nuclear power stations) are limited to an exposure no greater than 170 mrem/yr, excluding back­ground and medical exposures. The 170 mrem/yr refers to the somatic dose to the gonads, total body, and red bone marrow. No official guid­ance is presently available on how this 170 mrem/yr should be appor­tioned among exposures from nuclear power stations, Plowshare applica­tions, and industrial products producing ionizing radiation. Although Table 2 of Appendix В in 10CFR20 lists occupational mcp’s x 1/10, it is implied elsewhere (Regulation 20.106(e) of 10CFR20) that these 1/10 x (mpc) occ values should be multiplied by an additional factor of 1/3. Thus, continuous exposure at 1/3 X 1/10 X (mpc) (K.(. would result in a maximum dose rate of 170 mrem/yr to an average man.

It is important to bear in mind that the criteria for assessing exposures of the public are the radiation protection standards of 5 rems/30 years for genetically significant dose and 170 mrem/yr somatic dose. The mpc’s are only secondary standards derived from these primary standards.

A certain amount of experience already has been gained in operating nuclear power stations below the limits specified in 10CFR20. Blomeke and Harrington (1969) recently have reviewed the waste management experience obtained with six operational power reactors (Dresden-1; Big Rock Point, Humboldt Bay, Elk River, Indian Point-1; Yankee). For liquid wastes, the activity discharged per year as a percentage of limit (limit based on a continuous discharge [averaged over 12 consecutive months] of 10_e /лСі/сс [1 pCi/cc] of unidentified isotopes of plant origin) ranged from a low of 0.0002 per cent to a high of 9.9 per cent. The aver­age annual release rates of gaseous radioactive wastes ranged from .00013 to 28 per cent of the specified aec license limits.

Since all of the mpc’s are derived for internal exposure of man, an obvious question relating to exposure of biota arises. What is the dose to organisms of natural populations submerged in water maintained at the (mpc)w or some fraction of the (mpc)w for individual radionuclides? Would these dose rates be expected to result in detectable biological effects to aquatic organisms over a period of time? The accompanying tabulation shows the results of calculating the yearly dose rates at the surface of an organism submerged continuously in water containing va­rious radionuclides maintained at the (mpc)w for the general human population. This is an unrealistic exposure condition which results in incomplete dose estimates because, first, the (mpc)w ~ 30 relates to the critical organ dose to man for each nuclide and includes the important requirement that there is no other exposure to that critical organ, and second, the internal dose to the biota has not been computed for the radio­nuclides that might be present in the digestive tract or tissues of the “biota” organisms.

When a mixture of radionuclides is present, a weighted total mpc is computed so that the maximum permissible dose (mpd) to any organ is not exceeded. Consequently, the limit used in current nuclear power sta­tions of 10~6 р-СЇ/cc (1 pCi/cc) is one to several orders of magnitude lower than the mpc’s for the individual radionuclides used to derive this table.

Radionuclide	rem/yr	Radionuclide	rem/yr
“Co……………….	……… 0.797	13TCs………………	…….. 0.0117
“Mn……………….	……… 0.525	131J	…….. 0.00620
51Cr……………….	………. 0.377	“*Ce………………	…….. 0.00420
“Zn……………….	……… 0.341	M6Ru……………….	…….. 0.00370
“°Ba……………….	……… 0.0658	“Sr………………..	…….. 0.00060
“Sr………………..	……… 0.0173

How do these annual dose rates (and doses) compare with our current factual knowledge of the effects of ionizing radiation? The rest of my paper wifi be concerned with this question.

It is not my intention to review the developing literature on the ef­fects of large doses of radiation delivered in an acute or chronic mode. The interested reader can refer to several symposia on radioecology (Aberg & Hungate, 1967; Hungate, 1965; Nelson & Evans, 1969; Schultz & Klement, 1963) for facts and details. In the area of radiobiology the lit­erature on such things as effects, dose response, and survivorship is vast, and it would be presumptuous of me to attempt a review. There are, nevertheless, some generalizations which can be derived from this body of fact. An acute dose of 100 rad is the general lower limit that can be expected to produce mortality in a number of organisms, but not in all. Depending upon the biological endpoint, acute doses greater than 100 rad will produce an effect proportional to the dose. On the other hand, under conditions of chronic doses, generally speaking, the effect is much less marked than for an acute dose. Moreover, the lower the dose rate and the less the total dose, the more difficult it is to detect an effect. That is, more sophisticated means of detection must be used and more sensitive biological endpoints must be the basis for detection. When dose rates are lowered to 1 rad/day, the number of factors affecting the organism are sufficient to mask any effects that might be present. Such commonly used endpoints as survivorship, fecundity, growth, development, and suscep­tibility to infection have not as yet been shown to be unequivocally affected by such low dose rates.

This volume is concerned in part with the chronic effects of radiation on biota at levels lower than mpc levels. Therefore, for the remainder of this paper I shall review some of the findings made by a number of the workers in this difficult and at times frustrating field. Very few studies have been made on natural populations exposed to chronic radiation higher than background. The salivary chromosomes of the larvae of Chironomus tentans which inhabit the radioactively contaminated bottom sediments of the White Oak Creek and White Oak Lake at Oak Ridge National Laboratory were analyzed for 5 years for chromosomal aberra­tions (Blaylock, 1965, 1966a, 1966b). Calculations and measurements of the absorbed dose for the larvae living in the sediments gave values of

	Irradiated	Nonirradiated
	Populations	Populations
Larvae analyzed……………… Different inversions found	692	714
in both populations…………… Different inversions unique	6	6
to one population……………. Deletions unique to one	10	0
population………………………	1	0

230-240 rad/yr or approximately twenty-five hundred times background for the area. Over 130 generations had been exposed to this or greater dose rates during the previous 22 years. The accompanying tabulation (from Blaylock, 1966a) summarizes the number of different chromosome aberrations observed in irradiated and nonirradiated populations; the data include the White Oak Creek (irradiated), the Ten Mile Creek (non­irradiated), and other populations. Column one shows a total of seven­teen different aberrations which were observed in the irradiated popula­tion. The second column shows that only six different inversions were ob­served in the nonirradiated populations and that all six of these inversions were also found in the irradiated population. These inversions were found in each population more than once, and three occurred at relatively high frequency. Eleven aberrations — ten inversions and one deletion — were observed only once, except for one inversion which was found five times in two collections from one site and was probably the result of one event (Blaylock, 1965). The frequencies of these unique aberrations, found only in the irradiated population, were very low when compared with the frequencies of the endemic inversions. Blaylock concluded that the occur­

rence of new aberrations in the contaminated area was increased by the high background radiation and that these new aberrations were rapidly eliminated by selection or genetic drift.

The presence of endemic inversions at high frequencies in both popu­lations provided Blaylock an opportunity to test the effect of ionizing radiation on the chromosomal polymorphism of these populations. Gen­eticists believe that polymorphic populations are superior in fitness to monomorphic populations. Therefore, a decrease in chromosomal poly­morphism could indicate a decrease in fitness of the population. Blaylock found there was no difference between the irradiated and control popula­tions with respect to their chromosomal polymorphism as evidenced in the endemic inversions. Therefore, he concluded that the chronic environ­mental radiation which was capable of producing a detectable increase of new chromosomal aberrations was not affecting the frequencies of the endemic inversions in the populations of White Oak Creek and White Oak Lake.

This radioactive habitat was also the site for another series of investi­gations by Blaylock (1969). In this case the natural population investi­gated was the hardy, highly adaptable mosquito fish, Gambusia affinis affinis. Approximately one hundred generations of fish have lived in this area since the first release of radioactive waste effluents. In this investi­gation, another parameter of population fitness, fecundity — or the num­ber of offspring per female — was considered, since laboratory studies have shown that it can be influenced by ionizing radiation. These fish lived in a shallow portion of the lake where the sediments contained appreciable quantities of 137Cs, 106Ru, 60Co, 90Sr, and eEZn. Based on measurements and calculations, these fish were exposed to approximately 11 rads/day of external gamma radiation and 1.75 rads/yr from internal beta radiation.

To obtain fecundity data female Gambusia were collected from White Oak Lake and the control area, measured to the nearest millimeter and dissected in order to make embryo counts. In 98 fish from White Oak Lake a total of 4,625 embryos were scored. The brood size ranged from 13 embryos in a 3.0-cm fish to 105 in a 4.0-cm fish. In 98 fish from the control pond, 3,257 embryos were scored; the brood size ranged from 11 embryos in a 3.3-cm fish to 63 embryos in a 4.4-cm fish. The frequency of dead embryos and abnormalities was greater in the irradiated population than in the nonirradiated population.

The most striking finding of this study, however, was the fact that the irradiated populations had a highly significant greater fecundity than the control population. In his paper Blaylock marshals evidence which sup­ports the idea that irradiation can increase the fitness of organisms. These data support the hypothesis that radiation-induced mutations, most of which would be deleterious in the homozygous condition, produce suffi­cient cumulative effects in the heterozygous condition to more than coun­terbalance induced dominant deleterious mutations. Apparently, under certain conditions, genetic variability resulting from radiation-induced mutations can improve the fitness of organisms. Natural selection operat­ing on a population with increased genetic variability results in an in­creased rate of evolution of the population and in its adaptation to environmental factors.

The increased fecundity of the female in the Gambusia population in White Oak Lake may be an adjustment to the chronic environmental radiation. An increased mortality of embryos that could be attributed to ionizing radiation was also found in this population. In this respect radia­tion would be analogous to an environmental factor that increases mor­tality. Another effect of radiation would be the increased genetic varia­bility resulting from radiation-induced mutations. This would increase the rate of evolution and speed up the adjustment of the population to the increased mortality. However, this would not occur without some ex­pense to the population. Many genetic combinations would be selected against, and the individuals eliminated. In populations with a relatively short life cycle, such as fish and insects, where overproduction of young is the rule and selection is severe, the population level could be main­tained in spite of the elimination of many individuals.

At the University of Washington, Loren Donaldson has had under way a long-term study of the effect of chronic low-level gamma radiation on the chinook salmon (Oncorhynchus tshawytscha) (Bonham & Don­aldson, 1966; Donaldson & Bonham, 1964; Donaldson et al., 1969). In these experiments eggs and alevins were exposed to rates of 0.5, 1.0, 2.5, or 5.0 r/day beginning immediately after fertilization until the yolk is absorbed and the young fish are completely formed, a period of 80-100 days, depending on water temperature. The fish from the exposed lots and a like number from the control group were fed for a period of about 90 days before being released to migrate to the sea. In the ocean the young fish must compete in a natural environment that presents many hazards. Upon return from the sea, the adult fish and their progeny are subjected to detailed study for all possible effects.

The results of this series of long-term experiments with large num­bers of fish (ranging from 96,000 to 256,000 fingerlings released per experiment) have given no indication that these high exposure rates are injurious to the fish. Irradiations at early life stages have not caused sig­nificant mortality or retardation of growth in either smolts or returning spawners, or in fecundity of the females. In fact, Donaldson and his co­workers report that at the lowest exposure rate of 0.5 r/day — an exposure rate which is 10,000 times greater than background (0.2 mr/hr) — the irradiation stock returned in greater numbers and produced a greater total of viable eggs than the controls.

Templeton, Nakatani, and Held (1970) provide some pertinent viewpoints on the genetic effects: “The genetic consequences of radiation exposure have been and are still being studied very extensively in connec­tion with the potential hazards to man. In general, the conclusion from these studies is that any significant increase in radiation levels is detri­mental from the genetic point of view. However, for man, this acceptance rests on ethical considerations, which take note of the individual, and the fact that genetic anomalies are not reparable in an individual. When con­sidering the marine environment, however, we are not concerned with in­dividual organisms, but with populations, and at the population level, ge­netic damage is reparable by natural selection.”

A similar viewpoint has been expressed by Purdom (1966), aBritish worker in this field: “It would seem likely that the genetic response of populations is relatively unimportant and that general mortality and in­fertility would be the limiting factors in the extent to which populations may overcome radiation exposure. This certainly seems true for animals which have been studied extensively — Drosophila, the mouse, and do­mesticated farm animals. Provided that marine organisms are not more sensitive genetically than these other organisms, genetic damage will prob­ably have negligible effects, even under the maximum radiation exposures that seem possible from present day practice.”

Additional insight on the probable ecological effects resulting from radionuclide release may be obtained from laboratory investigations. The number of investigations is too large to cover in this paper; moreover, they are treated more fully by Templeton, Nakatani, and Held (1970). Some that are illustrative of many of the findings are summarized briefly here.

Phytoplankton are important because they are one of the main bases of the ecological food chains of the ocean. Phytoplankton are known to accumulate a large number of elements, including radioisotopes, in con­centrations many times greater than their concentrations in the surround­ing media. Rice and his co-workers (personal communication) tested the effect of 1S7Cs on the division rate of a marine plankton Nitzschia closte- rium. The rate of cell division controls the population size and cell divi­sion rate is an easily followed parameter. In one experiment the popula­tions were started in a median containing 14.3 /*Ci 13TCs per liter (1.43 x 104 pCi/cc). After 26 weeks at this concentration the cultures were trans­ferred to media containing 10 times the previous concentration of 137Cs (1.43 X 105 pCi/cc) and followed for 30 more weeks. Rice and his group found no evidence of injury to the cells or to the population during this period of time.

The effects of 65Zn, 51Cr, and "Sr"Y on the development of oyster larvae were examined in a series of experiments by Nelson (1968). There is an important oyster fishery in Willapa Bay which is located near the mouth of the Columbia River and thus receives radionuclides originating from the Hanford Plant (Battelle Pacific Northwest Laboratory). The concentrations of radionuclides used and the dose rates resulting there­from appear in Table 1. In addition, stable zinc and stable chromium were tested in conjunction with the nuclides for the effect of carrier upon the organisms. The biological endpoint was abnormal larvae — defined as those larvae which had incompletely developed shells 48 hours after fer­tilization. Nelson’s results are illustrated in Table 2. These results show that there were significant increases in abnormal larvae as follows: (a) in 85Zn (carrier-free), at a concentration of 108 pCi/1 and greater; (b) in 66Zn (with carrier), at a concentration of 107 pCi/1 and greater; (c) in 51Cr, at a concentration of 10s pCi/1 and greater (stable chromium had no effect at any of the levels tested); (d) in 90Sr90Y at a concentration of 109 pCi/1. On the basis of these experiments, Nelson concluded that the concentration of 90Sr"Y necessary to produce abnormal oyster larvae above control levels (10s pCi/1) is ten million times greater than the max­imum concentration of 90Sr in natural marine environments (10 pCi/1) as reported by Miyake and Sarakashi (1960). The concentration of carrier — free e5Zn necessary to produce an effect on oyster larvae in the first 48 hours after fertilization of the eggs is ten million times greater than the 65Zn concentration in Willapa Bay. Concentrations of 51Cr which caused

Table 1. Calculated Exposure Rates in Rads per Day for Solutions of “Zn^Cr, and 04Sr I — °°Y Concentration pCi/l pCi/cc “Sr + “У №Zn nCr 1010 107…….. … 430 40.0 3.0 10» 10е…….. … 43.0 4.0 0.3 10s 105…….. … 4.3 0.4 0.03 107 104…….. … 0.43 0.04 0.003 10e 103…….. … 0.04 0.004 source: Reprinted, with permission, from V. A. Nelson, “Effects of Strontium-90 + Yttrium-90, Zinc-65, and Chromium-51 on the Larvae of the Pacific Oyster, Crassostrea gigas” (M. S. thesis, Uni­versity of Washington, 1968).

Table 2. Mean Percentage of Abnormal Pacific Oyster Larvae 48 Hours after Fertilization at Various Concentrations of !K, Sr+MY, KZn (Carrier-Free), "Zn (with Carrier), and MCr

Seawater

Concentrations "Sr + "Y Carrier-Free “Zn “Zn with Carrier B1Cr

pCi/1 pCi/cc Iа 2” 1“ 2” 1» 2Ь 1[1] [2] 2b

Control……………………… (15) 8.5 ±2.5 (9) 7.7 ± 2.2 (10) 8.6 ± 4.1 (12) 6.8 ± 1.4

109 1 03…………. (6 ) 8.3 ±1.6 (4) 9.0 ± 4.2 (6) 9.3 ± 2.6 (6) 7.5 ± 3.7

107 10‘………………….. (2)…….. 5.5 ±0.7 (3) 21.7 ±15.0 (2) 43.5 ± 6.4* (5) 9.2 ± 1.8

10" 10s………………….. (7)….. 11.0 ±2.7 (5) 28.0 ± 9.9* (4) 32.7 ± 10.7* (6) 16.3 ± 6.9

109 10e………………….. (4)….. 98.0 ±0.8* (2) 100.0 ± 0* (2) 100.0 ± 0* (6) 26.3 ± 3.1

10“ 107………………….. (4)….. 95.8 ±2.1* (1) 100.0 ± 0* (3) 100.0 ± 0* (3) 56.7 ± 35.7

demonstrable effects are 800,000 or more times greater than those re­ported in water collected between the mouth of the Columbia River and Willapa Bay in 1961, when all eight Hanford production reactors were stiff in operation. Since then five of these have been shut down.

The biological effects of the effluent from Hanford production reac­tors have been monitored for over twenty years by raising salmonid fish in the diluted effluent. The three main factors in the potential pollution ef­fects of Hanford reactor effluent on fish are thermal increment, radioac­tivity, and chemical toxicity, since hexavalent chromium was used as a corrosion inhibitor (Templeton, Nakatani, & Held, 1970). Freshly ferti­lized eggs of salmonids were incubated, and the fish were raised in various concentrations of effluents until they reached migrant-sized fingerlings. Table 3 shows the mortality, growth, and radionuclide concentration in Chinook salmon as raised under various effluent conditions.

Table 3. Mortality, Growth, and Radionuclide Concentration in Chinook Salmon, Oncorhynchus tshawytscha, Raised under Various Reactor Effluent Conditions from December 1965 to April 1966 Treatment Groups" Percentage of Mortality (5 mo.) Mean Weight (g) Concentration b “Na “Cr ®Zn 0 ………… ………… 18 0.70 77 19 6.8 2 ………… ……….. 10 0.82 750 38 20 4 ………… ………… 13 1.05 1,390 53 36 6 ………… ………… 13 1.20 2,210 65 45 source: Reprinted, with permission, from William L. Templeton, R. E. Nakatani, & Edward Held, “Radioactivity in the Marine Environment” (Washington, D. C.: National Academy of Sciences, 1970). “By percentage of effluent. At least 1,000 fish in each group. bIn pCi/g, wet weight.

No significant lethality occurred in 6 per cent effluent, a concentra­tion far above the existing levels in the Columbia River. The greater growth observed in fish maintained in effluent is due to the heat in the ef­fluent, which accelerates growth. The concentration of the three gamma emitters, 21Na, 51Cr, and 66Zn, in the fish were approximately proportional to the effluent concentration. The investigators point out that the body burdens at these levels produced no demonstrable damage in Chinook sal­mon.

No review of this nature can forego mention of Russian work in this field, especially since Russians report effects at much lower concen­trations of radionuclides than do other workers. Russian emphasis has been placed on marine fish eggs. Polikarpov (1966), who pioneered the

studies in this field, has reported on extensive studies with eggs of a large number of marine and freshwater species over the concentration range of 10~2 pCi/1 to 10s pCi/1. They reported reduced hatching of the larvae and early mortality at concentrations of 105 pCi/1 and above, and the number of abnormalities were increased significantly at concentrations of 102 pCi/1 and above with remarkable consistency.

British workers (Templeton, Nakatani, & Held, 1970) did similar experiments with eggs of two fish species maintained from immediately after fertilization until hatching, in water contaminated with 0OSr9OY over a concentration range of 102 to 10s pCi/1. They did not observe any sig­nificant increase in mortality or in the production of abnormal larvae.

Templeton, Nakatani, and Held (1970) point out that the particular significance of the work from the u. s.s. r. is the unique concentration effect response reported by Polikarpov in 1967. An increase in concen­tration over six orders of magnitude (from 200 to 200 million pCi/1) no more than triples the abnormality production rate and only increases mor­tality fivefold. This result is totally inconsistent with the linear hypothesis of dose response as well as with data from many radiobiological in­vestigations.

Preliminary experiments of the effect of tritium on fish eggs are under way at Oak Ridge National Laboratory (ornl) and at the Univer­sity of Washington. At ornl, Blaylock (personal communication) has subjected fertilized carp (Cyprinus carpio) eggs to various concentrations of tritiated water. The biological endpoint was hatchability which nor­mally occurs at 72 hours when maintained at 26°C. Eggs either hatch or die. Since the embryonic stages are considered among the most sensitive stages of the life cycle to irradiation, this was considered a useful method for testing the effect of tritiated water. An additional advantage is that the eggs imbibe water and swell. Assuming no discrimination against tritium, the eggs would be exposed to both external and internal doses from trit­ium. The concentrations used ranged (Table 4) from 6.75 X 107 to 51.8 X 107 pCi/cc. These concentrations delivered a 72-hour dose to the eggs and developing embryos of from 57 to 436 rads. Although the percentage of eggs that hatched is less in three of the concentrations than in the con­trols, statistical tests showed no significant differences between any of the doses and the controls.

At the University of Washington (Held et al., 1969), hybrid trout eggs were exposed to tritiated water at concentrations ranging from 109 to 1011 pCi/1 of water. No significant differences between groups were observed. The investigators are repeating the experiments with a hundred­fold increase in the highest concentration (1018 pCi/1). These workers

Table 4. The Hatchability of Carp Eggs in Different
Concentrations of Tritiated Water

Concen — Accumulated

tration Dose (rads) Total No. Percentage

OtCi/cc) in 72 hr of Eggs of Hatch

0 ……………………………….. 0……………. 436 93.1

67.5 …………………………… 57……………. 285 85.6

127.0 ……………………….. 107……………. 293 86.6

274.0 ……………………….. 231……………. 474 85.9

375.0 ……………………….. 316……………. 408 93.4

518.0 ……………………….. 436……………. 257 92.6

source: Reprinted, with permission, from B. G. Blaylock, “Chromosomal Polymorphism in Irradiated Natural Popu­lations of Chironomus” (Genetics, 1966, 53 [No. 1], 131—

136).

also tested the effects of tritiated seawater on spore germination and sporling development of the algae Padina japoinia Yamada. Effects on germination and subsequent growth were observed only at the highest concentrations of tritium used (З x 1010 pCi/1!) Admittedly, these trit­ium experiments have not followed up on any effects which might show up after fresh eggs have hatched. Nevertheless, one should bear in mind that concentrations up to 100 million times greater than mpc levels showed no effects on fish eggs and that in algae effects showed at 10 million times greater than mpc levels.

What inferences may be drawn from these data? “Insufficient in­formation and more research is needed” is frequently the response of re­search workers in situations such as this. As a scientist I am not entirely immune to this special type of bias. To call for such research is easy; to attract first-rate scientists to devote years of their professional lives to experiments wherein the outcome may be the production of consistently negative results is not so easy. Journals are not interested in publishing such data. Moreover, one might question whether the investment required could not be put to better use in other needed research areas.

These data, as well as many others that I have not mentioned, with the possible exception of Russian work, show that the dose necessary to evoke an unequivocally detectable biological response is considerably above that resulting from mpc’s in the environment.

It is not unreasonable to infer also that low dose rates (at or around mpc levels) delivered to ecosystems under field conditions may present an intractable problem. At present, our best technologies and methods cannot demonstrate effects to these systems at these doses that are clearly and uniquely attributable to ionizing radiation. The possibility of develop­
ing sufficiently sensitive methods exists, but will undoubtedly require superbly controlled laboratory conditions. I doubt that these methods, if developed, could be used in complex field situations where manifold perturbing factors are interacting on and with organisms.

One might invoke special effects, or organisms with undefined or special roles in the ecosystem that make them uniquely sensitive (and therefore the ecosystem also) to the low dose rates that might occur in the vicinity of nuclear power stations. The possibility exists that the radio­sensitivity of organisms may be increased significantly as a result of en­vironmental interactions. Ecologists are always seeking some unusual effect, or a species with high sensitivity to ionizing radiation. So far they have not found any organisms which, within an environmental context, have a radiosensitivity at the levels of release permitted under current standards. Research is continuing to include as many different kinds of organisms as possible from a variety of environments (habitats) in order to demonstrate and differentiate the effects of radiation within an en­vironmental context.

All of the foregoing suggests essentially the same answer to a ques­tion posed at the recent Burlington, Vermont, public education meeting. Namely, if mpcw levels of radionuclides have an effect on the biota living in the vicinity of nuclear power stations, these effects will be essentially undetectable. The reason for this judgment lies in the fact that there un­doubtedly would be other factors changing in the environment, or other substances added to the aquatic environment that may, and undoubtedly will, have an effect on the constituent organisms. These substances — chemicals, nutrients, and so forth — may modify the habitat to the extent that it will be extremely difficult, using current methodologies, to demon­strate effects that might result from the low levels of radioactivity.