Short-term Retention of Strontium-85 and Estimation of Initial Strontium-90 Burdens in Humans

Data on the short-term retention of strontium-85 in twenty-three human subjects are presented. Following a single intravenous injection, body burdens were measured in a total body counter facility at frequent intervals over periods ranging up to several months. Eleven subjects were on metabolic balance regimens in the hospital so that urines and stools were collected and assayed for 85Sr and Ca. This group includes examples of the extremes of skeletal calcium metabolism including those with avid retention of Ca, normal or balanced cases, and those with large daily loss of endogenous Ca. The amounts of 85Sr excreted soon after administration varied widely among individuals and reflected the state of Ca metabolism for each person. Retention could be expressed as a power function of time R = atb, with values of the slope b ranging from −0.83 in cases of negative Ca balance to −0.12 in a case with large positive balance. Normals ranged −0.27 to −0.29. Repetitive monitoring of knee and tibia areas divulged no reliable correlation with total body retention. Methods for estimating human body burdens of 90Sr from bioassay data were reviewed briefly. Applicable data on 85Sr urinary excretion vs. retention were collected, combined with the present series and evaluated for utility in estimating 90Sr burdens from single urine measurements. They suggest that the initial body burden of 90Sr following an acute contamination can be estimated with a standard deviation of about +/− 38 per cent by multiplying the number of μc of 90Sr found in all the urine collected during the seventh full day by 47.