Tne alfaifa sampies ranged from 4.3 to 21 Sunshine Units. Unit (S.U.) is defined_ss one micro-microcurle (10°~~ Unit(S.U.)isdef: ium~ am icium. strontium-90pergramof ecalci 12 A Sunsnine curie) of The topPp inch of the soil sampl ples averaged 12 S.U., and the 1" - 6" depth of soil averaged 4.0 8.U. There was no correlation between the strontium-90 and calcium uptake and the plant concentration for strontium-90 was much higher than anticipated from the soil analyses. It vas concluded that the strontium-90 content of alfalfa was largely due to direct fall-out on the plant rather than absorption of strontium-90 from the soil by the roots. “he Lamont Laboratory analyzed corn leaves and obtained 0.5 S.U. from a 50% HCl leachate and less than 0.05 S.U. from the plant after leaching, demonstrating that most of the activity was on the surface of the plant and had not been taken up by root absorption from the soil. These findings make it impossible to project current soil and bone deposition data because the non-recurring initial fall-out contamination is obscuring the biological uptake phenomena. The problem of the fraction of strontium-90 still unaccounted for also becomes more important because of these findings. If the strontium-90 still unac- counted for should be made available by descending to the earth's surface over a long period of time, there exists a mechanism for short circuiting the early parts of the biospheric chain and thereby increasing the final deposition of strontium-90 in bone over that expected from soil analyses. In other words, the root's preferential selectivity of celcium over strontium, as indicated previously, will not be operative for that fraction of the strontium-90 which falls out on the plants and is mechanically transported to the next step of the chain leading ultimately to the bones of humans. From the point of view of human hazard, the major animal pathway of significance is that which deposits strontium-90 in milk and milk products. In certain areas of the world where, for example, small animals such as fish are eaten whole, this would be a modifying factor. In this report it will be considered that the cow and cow's milk con- 105