Strontium-90 Dose Equivalent
intake beginning as adults always exceeds that
calculated for intake beginning at any other age.
To determine the consequence of equal
Strontium-90 is primarily deposited in the
boneafter ingestion, and the two major organs
receiving exposure are the bone marrow and the
bone surface cells. The annual dose equivalent
from the ingestion of 9°Sr beginning at different
ages is shownin Fig. 4. The maximum annual
dose equivalent to the bone marrow is about
intake of 137Cs_ for each age, the dose equivalent
for an initial intake of 1000 pCi/d was
calculated for each age group. Theresults are
listed in Table 8. Even for the extreme case of
equal, continuous intake for each age group
(which does not occur under real dietary
conditions) with the annual intake declining at
a rate determined by the radiological half-life
2mrem/y, and this occurs when 99Sr intake
begins at ages 12 and 18.
of 137Cs, the integral 30-, 50- or 70-y dose
The integral 30-, 50-, and 70-y dose
equivalent to bone marrow and bonesurface are
listed in Table 9. The integral dose equivalent
equivalents are very similar regardless of when
‘the age intake begins.
The results for the
integral 50-y dose equivalent for intake
beginning at each age rangeare birth, 688 mrem;
is very similar for all ages.
4 months, 690 mrem; 9 months, 619 mrem; 1.5 y,
619 mrem; 4 y, 622 mrem; 12 y, 633 mrem; and
18 y, 640 mrem.
Recent changes in the modeling and
dosimetry for 13’Cs used by the United Kingdom
show that the effective committed dose
equivalent per single unit intake of 137Cs is the
same regardless of the age of intake (Kendall
et al., 1986).
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intake begins at age 12.
The integral 30-, 50-, and 70-y effective
dose equivalent due to the intake of Sris also
listed in Table 9 and ranges from 8.6 to 10 mrem
for 30 y, 12.9 to 14.4 mrem for 50 y, ard 15.7 to
17.3 mrem for70 y.
Table 8. The integral 30-, 50-, and 70-y
effective dose equivalent for equal (1000 pCi/d)
initial and continuous intake of 137Cs starting
at various ages.
Total
(mrem)
50 y
70 y
513
688
794
4 months
515
690
801
9 months
444
619
729
Birth
30y
15y
444
619
729
4y
447
622
732
i2y
458
633
743
18 y
465
640
750
9000173
Effective
(137Cs + 90Sr)
)
Dose
Equivalent
The total integral 30-, 50-, and 70-y
effective doses from the ingestion of 137Cs and
90Sr at Rongelap Island are listed in Table 10.
The integral 30-y effective dose ranges from
about 370 mrem to about 510 mrem,the integral
50-y effective dose ranges from about 560 mrem
to about 700 mrem, and the integral 70-y
effective dose ranges from about 630 mrem to
about 830 mrem. Of the total estimated dose
equivalent due to the ingestion of 90Sr and 137Cs,
the 90Sr contributes only 2 or 3%, while !37Cs
contnbutes 97 to 98%.
Integral dose equivalent,
Age intake begins
For example, the
50-y integral dose equivalent ranges from 60 to
70 mrem for bone marrow and from 150 to
200 mrem for bone surface depending on when the
age intake begins. The highest dose comes when
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