Answer to Question #1452 Submitted to "Ask the Experts"
Category: Alpha Emitters — Polonium
The following question was answered by an expert in the appropriate field:
What is a total activity of 210Po and 210Pb in the standard 70-kg person? What would the range of values in the United States be (Bq or pCi)?
According to the UNSCEAR 1982 Report "Ionizing Radiation: Sources and Biological Effects," 70 percent of the body content of 210Pb is in the skeleton. UNSCEAR estimates the typical 210Pb concentration in the skeleton to be 3 Bq/kg. This equates to a total skeletal activity of 15 Bq. The other 30 percent of the 210Pb in the body, 6.4 Bq, would be distributed more or less uniformly throughout the soft tissues. The grand total of 210Pb in the body is thus 21.4 Bq. In the skeleton, UNSCEAR 1982 assumes the 210Po concentration to be 80 percent that of the 210Pb concentration. As such, UNSCEAR estimates that the soft tissue concentration of 210Po is 2.4 Bq/kg. This, in turn, translates to a total skeleton 210Po activity of 12 Bq. In the soft tissues, UNSCEAR 1982 assumes a 1:1 ratio between 210Po and 210Pb. Hence the 210Po activity in the soft tissues would be 6.4 Bq. The grand total of 210Po in the body would be 18.4 Bq.
UNSCEAR, by the way, stands for United Nations Scientific Committee on the Effects of Atomic Radiation. The more recent UNSCEAR reports don't seem to contain as specific information about the body's 210Pb and 210Po content as the 1982 report.
The levels can be expected to be lower for women than men and lower for children than adults. Smokers have higher concentrations than nonsmokers.
An idea as to the variability of these activities in the U.S. population can be obtained from R.B. Holtzman's "Measurement of the
Natural Contents of RaD (210Pb) and RaF (210Po) in Human Bone—Estimates of Whole-Body Burdens" (Health Physics 9(4):385; 1963). The 210Pb
concentrations measured by Holtzman in samples of bone ash ranged from 0.037 to 0.454 pCi/g. The average value was 0.146 pCi/g. The
concentration in bone ash is approximately twice that in the skeleton (wet weight).
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