RADIATION TO BONE FROM °*°Sr
739
data available it appeared that strontium/calcium discrimination increases somewhat between the ages of 2 and 10, when calcium accretion rates are low and then decreases during puberty when calcium
accretion rates increase. Bone turnover rates seem to be directly
proportional to net calcium accretion rates.
Based on these general observations of strontium/calcium discrimination factors and bone turnover rates as functions of age and on
estimates of the diet Sr/calcium ratio in New York City from 1956
to 1963 (diet levels before 1956 were assumed to be negligible), the
%Sr/calcium ratios of the skeletons of individuals from 1 year to 30
years of age in 1962 and in 1963 were calculated. The factors used
that gave the best fits to the data and the estimates based on observed
diet levels are listed in Tables 1 and 2, respectively. A comparison of
the calculated and the observed levels shown in Fig. 1 indicates the
reasonable validity of the factors chosen. There was very good agreement between calculated and observed levels in adult bone. As more
data become available, adjustments in the factors may result in better
agreement between predictions and observations. With the use of the
Table 1— METABOLIC PARAMETERS USED TO
PREDICT Sr CONCENTRATIONS IN HUMAN BONE
Bone/diet
Age
discrimination
factor (K)
Annual
bone turnover
rate (f)
Net calcium
accretion rate,
g/year
0
1
2
3
4
3
0.10*
0.35
0,25
0.19
0.18
0.17
0.75
0.25
0.10
0.05
0.04
6
7
8
9
10
0.16
0.15
0.13
0.13
0.13
0,04
0.04
0.04
0.04
0.07
20
25
33
44
390
11
12
13
14
15
0.14
0.15
0.16
0.17
0.18
0.08
0.08
0.09
0.09
0.08
67
76
85
91
91
16
17
18
19
20
21
0.19
0.20
0.21
0.23
0.25
0.25T
0.08
0.07
0.06
0.05
0.035
0.035t
88
79
62
38
3
OT
*Fetal bone/mother’s diet.
+These values are assumedto persist.
_
28
72
47
32
22
18