30-, 50-, and 70-y dose equivalents are less when
intake begins as an infant or child than when
intake begins as an adult.
Even if the ?9Sr intake for infants and
children were significantly higher than what
we have estimated, the total integral 30-, 50-,
and 70-y effective dose equivalent from both
initial intake is the same regardless of age, the
integral 30-, 50-, and 70-y dose equivalents are
slightly greater when intake begins as an adult
than for intake beginning at any other age. This
results from the combination of changing body
weights, fractional deposits, and biological
half-life for 137Cs with age and the reduced
concentration of !37Cs in food with time. For
example, when intake begins as an infant, the
137Cs concentration in food has declined by
about 35% by the time the infant reaches 18 y of
age, when the dietary intake is greater and the
biological half-life of 137Cs
longer.
Consequently, if the intake of 137Cs for an infant
or child were equal to that for the adult (which
it is not based on available dietary information
137Cs and 9Sr would be greater for adults than
for infants and children because !37Cs accounts
for about 97% of the total estimated effective
dose equivalent at the atolls via the ingestion
pathway and %Sr for less than 3%.
Doses from 137Cs and Srare insignificant
through the inhalation pathway as compared
to that via ingestion (Robison et al., 1987; ICRP,
1979; Cristy et al., 1984; Kendall, 1986).
Consequently, the relative magnitude of the
from the Marshall Islands), the estimated
integral
integral 30-, 50-, and 70-y dose equivalent would
children, and adults can be determined by
dose equivalent
among
infants,
still be similar to that estimated for adults.
In the case of 99Sr, the dose commitmentper
unit intake is greater by about a factor of 5 for
intake beginning at ages 0 to 5 y than for intake
beginning as an adult. However, when agedependent differences in intake of 29Sr via the
diet are accounted for, the estimated integral
evaluating the ingestion pathway; that
analysis indicates that the estimated effective
integral dose equivalents for adults due to
ingestion of 137Cs and 99Sr is a conservative
estimate for intake beginning in infancy and.
childhood.
References
Aarkrog, A. (1963), “Caesium-37 from Fall-out in Human Milk," Nature 197, 667-668.
Abraham, S., M.D. Carroll, C.L. Johnson, and C.M.. Villa Dresser (1979), Caloric and Selected Nutrient
Values for Persons 1-74 years of Age: First Health and Nutrition Examination Survey, United
States 1971-1974, U.S. Department of Health, Education and Welfare, DHEW Publication No.
(DHS) 79-1657,-Series 11, No. 209.
Adams, N. (1981), "Dependence on Ageat Intake of Committed Dose Equivalents from Radionuclides,”
Phys. Med. Biol. 26, 1019-1034.
Bengtsson, L.G., Y. Naversten, and K.G. Svensson (1964), "Maternal and Infantile Metabolism of
Caesium,” Assessment of Radioactivity in Man, Vol. H, International Atomic Energy Agency,
Vienna, Austria, pp. 21-32.
I0001 1b
22
steaeee
radiological half-life of 137Cs and where the