4.4 Infant Dosage
The doses that have been under consideration are for adults. In the
case of children and infants, the doses might be different owing to
variations in (1) physical and physiological processes and (2) dust and
diet.
Physical and physiological factors.
conversion factors in Tables 4.2 #1A & #1B.
These variables affect the
For example, the smaller
size of children can diminish the fraction of gamma ray energy absorbed
in the body; the residence time of the radionuclide in the body may be
less than in adults; the fraction aWsorbed from the gut might be puch
more. Furthermore, a long-lived radionuclide deposited in the body at
age 6 months will be diluted by growth so that its “picocuries per gran
of tissue", on which a dose depends, will fall significantly with time.
Table 4.4 #1, based on the United Kingdom NRPB report (1987b), and
consistent with the recommendations of the ICRP (International Commission
on Radiological Protection), shows that the corrections for children are
well on their way to disappearing by age 10 y, but are important in the
first year or so
of not more than
transuranics, it
for ingestion it
that year.
of life. The correction for cesium-137 is an increase
20%, but that for strontium is about 3.6-fold. For the
is 2.4-fold for inhalation during the first year, but
is 22-fold for months 0-6, and 2.1-fold thereafter in
These factors are for committed doses which in the case of children
aged 10 and less are calculated to age 70 years rather than for the
standardized period of 50 years in adults. For radionuclides with short
physiological half-lives such as cesium-137 (less than 110 days), this is
of no consequence. But for the transuranics with half-lives in liver and
bone marrow of 20 and 50 years, respectively, the extra residence time
adds to the 50-year committed dose.
In general it would be expected that the smaller intake of children
and infants will compensate for the increased size of their dose-factors
compared to the adult ones in Tables 4.2 #1A & #18.
Since there are almost no directly pertinent Rongelap data on such
inputs, we have approached the problem in two ways.
First, we have made
some calculations aized at setting upper bounds. Second, we have
attempted to obtain inforpation fron the Marshall Islands on infant and
small child diets.
3000b42