RADI0-AC:TI\T. FISSIOX-PRODUCT.S I\ Till- HTMAN FOOD f:iIAIX 



So that with an Observed Ratio (9"Sr/Ca, l)one: ""Sr/Ca, diet) of 0-25 one 

 would expect bone to l)e about 10 S.U. The present work of the joint survey 

 beint; carried out by the Agricultinal Research Council, Medical Research 

 Coiuicil Joint Connnittee, with help from the Atomic Energy Authority 

 and others, is designed to affirm the preliminary survey of Bryant et al., to 

 identify conditions in special areas of high rainfall and low productivity, and 

 especially to validate the predictions. 



REFERENCES 



I Stewart, N. G., Crooks, R. N. and Fisher, E. M. R. A.E.R.E. HP/R 2017(1957) 

 ^Stewart, N. G., Osmond, R. G. D., Crooks, R. N. and Fisher, E. M. R. A.E.R.E. 



HP/R 2354 (1957) 

 'Bryant, F. J., Chamberlain, A. C, Morgan, A. and Spicer, G. S. /. Nuclear 



Energy 6 (1957) 22 

 ''Bryant, F. J., Chamberlain, A. C, Morgan, A. and Spicer, G. S. A.E.R.E. 



HP/R 2353 (1957) 

 * Bryant, F. J., Chamberlain, A. C, Spicer, G. S. and Webb, M. S. W. Brit. 



med.J. i (1958) 1371 

 «Bryant. F. J., Morgan, A. and Spicer, G. S. A.E.R.E. HP/R 2730 (1958) 

 'Bryant, F. J., Henderson, E. H., Spicer, G. S. and Webb, M. S. W. A.E.R.E. 



C/R 2553(1958) 



sBooker, D. V. A.E.R.E. HP/R 2183 (1958) 

 'Rundo, J. Second Conference on the Peaceful Uses of Atomic Energy Paper P/1467 



Geneva, 1958 

 i" Russell, R. S., Schofield, R. K. and Newbould, P. Second International Con- 

 ference on the Peaceful Uses of Atomic Energy Paper P/287 Geneva, 1958 



II Squire, H. and Russell, R. S. /. exp.^Bot. 9 (1958) 262 



i^Middleton, L. J. and Sq,uire, H. Communication to the Food Chain Conference, 



Harwell, 1958 

 I'MiDDLETON, L.J. Nature, Land. 181 (1958) 1300 

 I'lMiLBOURN, G. M., Ellis, F. B. and Russell, R. S. Communication to the Food 



Chain Conference, Harwell, 1958 

 15 Russell, R. S. Nature, Lond. 182 (1958) 834 



DISCUSSION 



Dr. Davis: You mentioned in passing the use of ^®Sr to give a measure of the age of 

 strontium activity. Could you tell us a little more about the use of the ratio in 

 practice and give us some idea of the absolute levels of '^''Sr normally encountered in 

 biological materials? 



Dr. Loutit : Let us assume that one looks at the assays of grass or milk for a representa- 

 tive year in England. The '*''Sr/^"Sr ratio starts low in January: the cattle are on 

 stored feed, collected the previous summer. In the spring the ratio rises as the cattle 

 are put out to gra.ss onto which perhaps there is a fresh deposit of fission-products 

 from a recent series of tests in Nevada (tropospheric fall-out). The ratio falls off as 

 the summer and time proceeds. In the autumn perhaps there is a megaton test by 

 the U.S.S.R. and the ratio rises again (stratospheric and tropospheric fall-out). When 

 the cattle go indoors for winter quarters the levels fall again. In the local circumstance 

 at Windscale, the levels of "^Sr in milk rose in some cases some 30-fold compared with 

 '"Sr — evidence of recent fission. 



Dr. Green: Could you elaborate the fission-product situation in relation to crops 

 such as rice and alfalfa grass ? 



218 



