DISCUSSION 



Dr. Loutit: Alfalfa is, as far as I know the same as lucerne, and therefore one would 

 expect that caesium which gets into the vascular system, would be translocated 

 down from the aerial parts to the deep roots 24 inches down or however far they go. 

 Your first question was related to rice which is a special Oriental problem. Diet in 

 the Orient is mainly of vegetable origin and the main source of calcium is the plant 

 not the animal. For most vegetation in the East the general metabolism is probably 

 not very different from that which we have investigated in the United Kingdom. 

 But rice is peculiar. It grows in paddy fields. We predict that here the situation may 

 be similar to the conditions in, shall we say, the Welsh hills or the Scottish Highlands 

 which in our country have been the object of popular concern, and which Russell 

 has investigated. If one looks at the sheep which have grazed the Welsh hills, the 

 activity in their bones over 1954 to 1957 has gone up linearly apparently in relation 

 to the cumulative fall-out. This is in contrast to the milk figures, and therefore, 

 presumably, the bones of cows on lowland pastures. Now our prediction is that these 

 sheep bones will similarly level off. As Welsh and Highland pasture is of extremely 

 poor growth on extremely unfertile ground, the material deposited on the aerial parts 

 is washed down into the crown of the grass, and is taken up again into the new leaves 

 as they spring up, so that there is a recycling of the fall-out above ground. Also the 

 surface level and the true soil are separated by a mat of varying degrees of thickness; 

 it may be 2 inches on fairly good ground, or it may be 6 inches on extremely poor 

 ground, and this mat ultimately forms peat and, I presume, coal. It is a product of 

 the decayed unploughed permanent vegetation. It represents the accumulation of 

 centuries. In this mat are all the surface roots of the grass plant. The mat is extremely 

 deficient in all the essential elements, so that we have an enormous reservoir in which 

 the fall-out is accumulating. On good pasture the layer of mat is only a fraction of an 

 inch thick. Until this mat reservoir is saturated with ^"Sr and comes into equilibrium 

 with the soil below, one would predict that the bone level of sheep feeding on this 

 ground, would rise linearly with the cumulative fall-out. It appears to take only about 

 a year to fill this reservoir in lowland pasture; it might take 4, 5 or 6 years to fill this 

 reservoir in the heavily matted areas, and there is an indication from the 1958 results 

 that this levelling off is, in fact, now occurring in the Welsh hills. If that is so, then 

 in the Welsh hills, instead of there being a rise by a factor of five for cumulative fall-out 

 in 1967, there may, in fact, only be a rise by another factor of two over the present 

 values. That is — sheep in the Welsh hills have already got much nearer their peak 

 than animals in lowland conditions. Similar conditions may apply with rice. But 

 here, instead of a layer of mat, there is a layer of mud on the bottom of the flooded 

 paddy field, and this mud layer may be acting as a reservoir, and giving artificially 

 high figures at the present time for rice. This is only a hypothesis; until it is tested 

 one does not know what the right answer is. 



Dr. George: May I ask you, from the very interesting results you have been 

 recounting this morning, could I tempt you to hazard a guess as to the order of 

 magnitude of the radiation dosage to bone marrow in man received from fall-out, 

 the relative contributions from the y radiation of the material on the ground and 

 from '"Sr ? 



Dr. Loutit: I have not done the calculation, and I would not like to put it into any 

 quantitative form — but there is an appreciation of the problem in a little work from 

 Sweden recently, by Nelson and others, and I think one could derive from that book 

 the dose to bone marrow from various concentrations of ^"Sr in the bone. From the 

 present levels of ^°Sr in the bone, from predicted levels of *°Sr in the bone, and the 

 calculations there, I think you could get the answer, but I would not like to do it 

 out of my head. 



Mr. Jackson : The figures you gave for Britain point to a pretty pessimistic view for 

 Australia, I would say, just knowing the two factors which are really important. It 



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