level of intake. Under these conditions the growing body would tend to stabilize at the lower level, but the added early high intake might be a factor worthy of assessment. For example, the suggestion has been modet2/ that proper interpretation of 1 microcurie as the maximum permissible concentration in an sdult, based on the radium type of experience, would allow between 1.5 and 5.0 microcuries strontium-90 in bone one year after initial exposure, in order to be equivalent to 0.5 to 1.0 microcurie 25 years later. The 1.5 to 3.0 microcuries would be 5% or less of the initially ingested dose. This reasoning points up the meaning of the body burden as found in the human radium cases with regard to extrapolating back to initial exposure. In a uniformly con- taminated environment this problem will not require consideration. In a uniformly contaminated environment it is possible to calculate the relationship between strontium-90 in the diet and that which will deposit in bone. Animal uptake studies of daily radio- strontium intake indicate that bone retention will, within a period of weeks, reach a maximum and that the relationship between the maximum bone radio-strontium level and the radio-strontium intake may be described by A= Ae x Sr, 8 Sr£ where A, = maximum attainable bone radio-strontium level Ap = quantity of radio-strontium consumed per day Sr_= quantity of strontium in bone Sr£ quantity of strontium consumed per day The bone strontium content has been measured and found to be approximately 0.67 gms. 4a/ ‘The daily intake of strontium is epproximately Stover, C. N., Second Annual Conference on Plutonium and Mesothorium, University of Utah, Jume 1954. 108