7 RADIOSTRONTIUM IN HUMAN BONES
A list of human bone specimensto the end of 1956 analyzed at Woolwich is given in Ap-
pendix 3, and the radiostrontium results* on 34 femora and 3 tibiae among them are shownin
Fig. 7. The specimens come mostly from South East England and the Midlands, but there were
a few from the West and Northwest, and these included the two showing the highest radiostrontium activity, namely, 1.55 S.U. in a two-year-old Plymouth child and 1.3 S.U. in a three-monthold child from Carlisle.t There is a considerable scatter in the results on bones from infants
under 1 year, but thereafter there is a fall off in the Sr*’/Ca ratio with age.
a
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AGE, YEARS
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40
60
Fig. 7—Sr™ in human bone in 1956.
The average Sr°? activity of femora in various age groups is given in Table 8 at the end of
this paper.
As the minimum weight of bone for a reasonably accurate Sr°? estimation is 50 g, it was
not possible to make a detailed study of distribution within the bone, but two femora from older
children were each divided into four portions which were analyzed separately as shown in
Table 6. The pattern is the same in both specimens, with a maximum in the new sub-epiphyseal
bone and a minimum in the old bone in the centre of the shaft.
Stable Sr measurements have been made on a number of human bones, and the results are
given in Appendix 3. The average at all ages in the present series is 290 ug of Sr per gram of
Ca, which is not significantly different from the average of 270 ug of Sr per gram of Ca found
in milk. Since, however, the stable Sr content of foods not derived from milk is about 10 times
greater than this, it is by no means certain that milk is the main source of stable Sr in human
bone.
*As stated in the paragraph on methods, the practice with human bones has been to measurethetotal
radiostrontium activity and attribute it to sr®®, On specimens for which y*" has been measured independ-
ently, the Sr*® activity deduced has been within 15 per cent of that estimated by the total strontium method.
+ Provisional results of 2.3 S.U. in a one-year-old Cumberland child and 2.4 S.U. in a six-month-old
Liverpool child have been obtained in 1957.
220