52 BIOLOGICAL EFFECTS OF ATOMIC RADIATION 



fallout from weapons tests. Looking to the future, it is likely that products escaping or re- 

 leased from nuclear power or fuel-element processing plants may present analogous problems, 

 which to a different degree may also arise from future industrial or agricultural uses of radio- 

 active materials. 



In the past three years much attention has been devoted to these matters, and many have 

 been the statements on them in the press and elsewhere — some alarmist, some reassuring, some 

 judicial, and some indefensible. The public may well be left with a feeling of dismay, because 

 of the apparent lack of unanimity of opinion among those to whom it wishes to turn as experts. 

 The difficulty confronting the scientist, however, is that many of the essential facts necessary 

 to arrive at the answers sought are not yet available and, what is worse, are unlikely to be 

 quickly available, despite his best efforts. Because he is under great pressure for an answer, 

 he is forced uneasily into extrapolation or prediction. It is here that the grey areas of apparent 

 disagreement develop. The chemist or physicist may not give sufficient weight to biological 

 factors; the biologists, with as yet only vague understanding of the mechanism of radiation 

 injury, even at levels where this is easily observed, is not ready confidently to predict or assess 

 the effects of long exposure to very low levels of radiation from isotopes incorporated in the 

 organism and perhaps continually presented in its food. Our colleagues on the Committees 

 on Genetic Effects and Pathologic Effects are wrestling earnestly with these latter issues. 



The levels that are currently present in agricultural products and food are very low; 

 they are indeed measurable only because of remarkable developments in instrumentation. In 

 most cases the measurement depends on the character and amount of radiation emitted; 

 prior chemical separation may not be necessary or possible. The analytical procedures are 

 expensive in man-hours and equipment; routine analysis or monitoring of all foods is not 

 currently feasible. There has been debate and controversy as to the "permissibility" of the 

 level of this or that isotope in food or water. Although this device may ultimately have merit 

 in regulatory procedures, it is obviously inadequate in that, in considering the welfare of 

 the consumer, it is the cumulative and retained isotope burden which must be weighed. 

 Dietary preferences and difTerences in the geographic sources of foods will result in an infi- 

 nitely complex pattern. The radioisotopes of greatest long-term concern are of course stron- 

 tium-90 and cesium- 137, which closely resemble in chemical properties the physiologically 

 vital elements, calcium and potassium respectively. The cycling of these and other radioactive 

 substances in the biosphere, through all plants, all animals, and all micro-organisms, presents 

 biologists with a multitude of challenging problems of which the sequence through the ag- 

 ricultural domain forms only a small and not independent part. State and national bound- 

 aries have no meaning in relation to these events — every living organism, man included, now 

 has a radioisotope burden higher and different from that in the pre-atomic eras. 



Substantial progress, however, has been made at the technical level in the understanding 

 of the mechanisms involved in entry and uptake of fallout elements into plants from either 

 soil or leaf deposition; their movement in crop plants, their accumulation in those parts used 

 for food by animals and man; their subsequent transfer, incorporation, retention, or excre- 

 tion; and the equilibrium level that may be established. It is now recognized that fallout 

 deposition in the northern hemisphere is quite variable, which means that the radioisotope 

 levels of similar crop or animal products from different locations may vary considerably. The 

 implications of this are of concern in view of the current inability to monitor all foods or food 

 ingredients. 



