infants through about 3 monthsis either breast
milk or formula. Formulas are imported and
diluted coconut milk to supplement or replace
the milk from breast- or bottle-feeding. For a
concentrations.
milk and 5% is a mixture of equal parts coconut
contain very low concentrations of 99Sr
representative of worldwide background
daily total intake of 1.3 L/d, we assumethat, on
the average, 95% of the daily intake is breast
The concentration of Sr in breast milk ma
milk and water. Consequently, the daily intake
of %Sr from 4 to 8 months would be
be determined from the OR. The ORTmule
has been reported to be 0.10 (Loughet al., 1960;
Comar, 1967), indicating a discrimination across
0.043 pCi/L(0.95) 13L/d
+ 0.016 pci/mi 2) 1300 mL/d
= 0.053 pCi/d + 0.52 pCi/d
the mammary barrier similar to that across the
placental barrier. The OR is based uponthe Sr
per g of calcium and consequently is not directly
of use in dose calculations. Thetotal g of calcium
in the reference and target must be known so that
= 0.57 pCi/d,
the total amount of 99Sr transferred from a
where the concentration of Sr in coconut milk
at Rongelap Island is 0.016 pCi/mL and in breast
specific source to a specific target can be
determined.
A more convenient form for the data for dose
calculationsto infants using current models is the
90Sr concentration per kg of mothers’ milk based
on the mothers’ dietary intake. The average
percentage of 99Sr ingested that is secreted per
kg of milk was determined to be 0.31% for
4 women (Lough et al., 1960).
milk is 0.043 pCi/L.
Infant/Child (9 months to 1.4 y). At about
age 9 months to 1.5 y, small quantities. of local
foods are given to the infants to supplement
breast-feeding. The estimated 9°Sr intake from
consumptionof local foods is assumed to be 20%
of the adult intake and is 2.8 pCi/d. Thus, the
Using this
average value for the percentage of 90Sr
daily intake of 9°Sr is assumed to go from the 4- to 8-month-old value of 0.57 pCi/d to about
average 99Sr daily intake of 14 pCi/d at
3.4 pCi/d.
ingested that is secreted in milk and the
Child (1.5 y to 3 y).
Rongelap Atoll for women, the concentration of
90Sr per kg (~1 L) of milk would be 0.043 pCi/kg.
Thus, assuming that an infant's diet is about
1.3 L/d of milk, the daily intake of 99Sr from
Child (4 y to 11 y).
birth through 3 months would be 0.056 pCi/d.
The ORZt in the first few months after
available is 8.2 pCi/d (Appendix A, Table A-3).
Loutit, 1964; Lough et al., 1963; Comar, 1967);
Teenage (12 y to 17 y). The average daily
that is, the infant nearly equilibrates with his
diet. The oR" changes to about 0.5 by 1 y
and
Loutit,
1964;
Comar,
intake of Sr for teenagers from our diet model
when imported foods are available is 11 pCi/d
(Appendix A, Table A-4).
1967;
Kawamuraet al., 1986) and levels out at about
the adult value of 0.25 by age 3 to 5 y (Lough
Adult (2 18 y). The average daily intake of
90Sr for adults from our diet model when
et al., 1960, 1963; Comar et al., 1965; Comar,
1967; Burton and Mercer, 1962).
imported foods are available is 14 pCi/d
This type of
information has been incorporated in the
retention model discussed later in the paper.
Infant (4 to 8 months). We assumethat
infants from 4 to 8 months occasionally receive
I0001b4
The average daily
intake of 29Sr for children 4-y to 11-y old from
our diet model when imported foods are
birth is about 0.9 (Comar et al., 1965; Bryant and
(Bryant
The average daily
intake of 99Sr for the 1-y to 3-y age group from
our diet model is 9.2 pCi/d (Appendix A,
Table A-2).
(Appendix A, Table A-1).
The daily intakes of 9Sr for the various
age groups, based on the data and assumptions
described above, are summarized in Table 4.
10