Strontium 90 effective half-life is 2.7 x 10/sup 3/ days. It emits beta rays and is selectively absorbed by bone. Strontium-90 is chemically allied to calcium and it moves with this element through the food chains and the foods which supply calcium to the body also supply strontium. In fact, exposure of the population occurs primarily by the contamination of dietary calcium by strontium- 90. A study is made of the strontium-90-calcium ratio in the food chains and in the final deposition in the body. (auth)