18 



At0777'ic Radiation a?7d Oceanography and Fisheries 



tration factors of the organisms for each ele- 

 ment, and the rates of excretion, and in addition 

 will depend on the decay rates of the radioactive 

 isotopes) . 



The most important radio isotopes from the 

 standpoint of accumulation in organisms are, 

 therefore, those which are concentrated in large 

 degree by organisms, are retained by them for 

 relatively long periods of time, and have slow 

 decay rates. An additional consideration from 

 the standpoint of human hazards is the uptake 

 and biological half-life of the elements in hu- 

 mans who may consume the marine organisms 

 as food. 



The most important fission product from all 

 these considerations is strontium 90 and its 

 daughter yttrium 90. This isotope has a large 

 fission yield and a long physical half-life, is 

 concentrated by organisms, and can be tolerated 

 in human food only in very low amounts. 



Ce 144 is another isotope with a large fission 

 yield, which is concentrated by organisms (Har- 

 ley, 1956), and has a moderately slow decay 

 rate. Due to its small uptake and low retention 

 by humans, it can, however, be tolerated in 

 human food in much greater concentrations than 

 Sr90. 



Zn 65 and Co 60, although not fission prod- 

 ucts, are sometimes produced in relatively large 

 quantities in weapons tests. They are concen- 

 trated by very large factors in fish and mollusks 

 used for human food, but fortunately they 

 possess a relatively high tolerance level in 

 humans. 



Because of its biological role both in marine 

 organisms and in humans, strontium 90 dom- 

 inates consideration of depositing mixed fission 

 products in the sea. For other radioactive 

 wastes, and for mixed fission products from 

 which Sr 90 has been removed, other elements 

 will be the critical determinants, but in most 

 cases, prior removal of Sr 90 will permit the 

 safe disposal in the sea of larger quantities than 

 would otherwise be possible. 



The safe quantity of fission products depends 

 on the concentrations that reach man's food or- 

 ganisms. The quantity will be greater if sites 

 of introduction are chosen to give either long 

 periods of isolation of the wastes or high dis- 

 persion (and thus low concentration) of the 

 fractions that come into the environment (both 

 physical and biological) of human food organ- 



isms. 



Somatic and genetic effects on marine organisms 



It is sometimes suggested that sufficient quan- 

 tities of radioactive elements may be accumu- 

 lated by marine organisms to endanger their 

 populations, either by direct somatic effects or 

 through genetic changes. Some aspects of this 

 problem are discussed by Donaldson and Foster 

 in Chapter 10 of this report. 



So far as somatic eflFects are concerned, ex- 

 perimental data indicate that primitive forms 

 are more resistant to ionizing radiation than the 

 more complex vertebrates. It has not been possi- 

 ble to demonstrate any large-scale radiation 

 damage to marine populations in the vicinity of 

 large weapons tests. Levels of radiation safe 

 from the standpoint of human hazards are also 

 probably safe for the populations of marine 

 organisms that are used as human food. 



By analogy with results from genetic studies 

 on laboratory animals, it may be inferred that 

 significant genetic population effects will occur 

 in marine organisms at much lower levels of 

 radiation than will produce somatic effects. 

 These genetic effects might be related to the in- 

 crease in amount of total body radiation above 

 the natural background. As shown by Folsom 

 and Harley (Chapter 2), the normal radiation 

 background of organisms in the deep sea is very 

 low, so that appreciable quantities of radioactive 

 wastes would significantly increase the radiation 

 received by them. Craig (Chapter 3) has shown 

 that the deposition of 1,000 tons per year of 

 fission products in the deep sea would, at secular 

 equilibrium, almost triple the average radiation 

 level in the deep water. This could, conceivably, 

 result in genetic effects in the marine popula- 

 tions in these waters, which might seriously up- 

 set the ecological system of the oceans. At the 

 present state of knowledge, however, this is 

 pure speculation. The matter does require, 

 nevertheless, serious investigation. 



VII. Predicted Effects of Introduced 

 Radioactive Materials 



Prediction of the effects of the introduction 

 of radioactive materials into the different do- 

 mains of the oceans must take into account the 

 various physical, chemical, and biological proc- 

 esses discussed above. While our knowledge of 

 these processes is very imperfect, we can make 

 rough evaluations of the effects of disposal of 

 fission products in different parts of the sea. 

 Because of the limitation of knowledge, these 



