Strontium-calcium movement from soil to man.

The calcium reservoirs of the biosphere are becoming labeled to varying degrees with strontium-90 from nuclear weapons. These reservoirs include the human and animal skeleton, the milk, the vegetation, the upper layers of soil, and the waters. The degree of labeling is governed by the dilution that occurs, or the differential behavior of calcium and strontium in various steps of the food chain. This differential behavior normally provides a factor of protection against strontium-90 in the soil and vegetation that may be as high as 25 for the newborn and is most likely not less than 6 for adults, depending on food habits. The physiological steps that are important in the movement of the two elements in the biosphere are described to provide a basis for an approach toward increase of the discrimination against strontium in favor of calcium. Some aspects of agricultural practices are discussed from this standpoint. The matter of hazard from levels now existing and the present need to undertake remedial measures are not discussed, in major part because of lack of experimental data on which to base such considerations.