Strontium-90 Dose Equivalent
intake beginning as adults always exceeds that
calculated for intake beginning at any otherage.
To determine the consequence of equal
intake of 197Cs for each age, the dose equivalent
for an initial intake of 1000 pCi/d
Strontium-90 is primarily deposited in the
bone after 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 90Gr beginning at different
ages is shown in Fig. 4. The maximum annual
dose equivalent to the bone marrow is about
was
calculated for each age group. The results 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
2mrem/y, and this occurs when 90Sr intake
a rate determined by the radiological half-life
of '37Cs, the integral 30-, 50- or 70-y dose
begins at ages 12 and 18.
The integral 30-, 50-, and 70-y dose
equivalent to bone marrow and bonesurface are
listed in Table 9. The integral dose equivalent
is very similar for all ages. 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
intake begins at age 12.
The integral 30-, 50-, and 70-y effective
dose equivalent due to the intake of 9°Sr is also
listed in Table 9 and ranges from 8.6 to 10 mrem
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 range are birth, 688 mrem;
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 137Cs 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).
Table 8.
for 30 y, 12.9 to 14.4 mrem for 50 y, and 15.7 to
17.3 mrem for 70 y.
The integral 30-, 50-, and 70-y
Total
effective dose equivalent for equal (1000 pCi/d)
(137Cs + 90Sr)
initial and continuous intake of 137Cs starting
at various ages.
Dose
Equivalent
The total integral 30-, 50-, and 70-y
effective doses from the ingestion of 157Cs and
Integral dose equivalent,
Age intake begins
Effective
30y
(mrem)
50 y
70 y
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
Birth
513
688
794
4 months
515
690
801
9 months
444
619
729
to about 700 mrem, and the integral 70-y
effective dose ranges from about 680 mrem to
1.5 y
444
619
729
about 830 mrem.
4y
447
622
732
458
633
743
12 y
1B y
465
640
Ofthe total estimated dose
equivalent dueto the ingestion ofSr and 137Cs,
the 2Sr contributes only 2 or 3%, while 137Cs
750
contributes 97 to 98%.
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