Urinary excretion of radionuclides @ P. S. Harris ET AL.
Dunninget al. (1979, 1981) after making an adjustment
for ingrowth of '°'l. In the work of Simon etal. (2010b),
the best estimates of the excretion fraction for the
Marshallese were about 1.70 X 104, 1.65 X 10“, and
1.43 x 104 for days 16, 17, and 19, respectively (see
Table Al, Simon et al. 2010b). The estimates in that
work were based on a biokinetic model that simulates a
relatively high daily water loss through the skin. Decaycorrecting the estimate of the iodine excretion fraction of
0.001 originally used by Harris in 1954** for the elapsed
time between intake and sampling gives an excretion
223
whose urine was sampled (or others for whom the data
are a suitable surrogate) can be estimated:
CRXKXV
Q(T) = EF) X ec
(1)
where
Q=acute intake of ''I intake (Bq, group
average);
fraction of 3.0 X 104, a value very close to those used
CR =background adjusted count rate (c s ') of
''T per mL of urine;
K =correction factor corresponding to the ra-
Harris in 1954** and others to follow, here we only focus
V = 24-h urine volume (mL) averaged over the
referred to Simonet al. (2010b) for a comparison of the
EF(t) = urinary excretion fraction for '*'I on day of
dioactive decay of ''I between time of
in the other assessments discussed.
While estimates of thyroid dose were presented by
sampling and time of counting;
sampled population;
on the data necessary for estimating intake. The readeris
sampling, ¢ being the time elapsed between
intake and sampling; and
Ec = gammadetector counting efficiency (count
per decay).
dose estimates made over the 55 years since the acute
exposures from Bravo fallout took place.
Estimating radioiodine intake
The earliest thyroid dose estimates** used simple
estimates of '*'I intake derived directly from gamma
spectrometric measurements of the count-rate of '°'I in
each of the LASL pooled urine samples.******’> The
intake (Bq) of '*'I can be estimated as shown in eqn (1)
from the gamma-ray counting results and other parameter values provided in Table 3. Using the available
counting data, only the average intake, Q, among adults
If the estimated excretion fraction is derived from
data from stable isotope experiments or is based on
short-term observations, the decay correction may need
to accountfor the total time between intake and counting
to properly assess the intake of the radioactive isotope.
This was the method used by Harris in 1954.** If the
excretion fraction pertains specifically to '*'I and is
derived from reliable measurements or a_ validated
Table 3. Bioassay data from Harris (*******S) used in 1954 assessment of ''l intake.
Group ID
LA316R
LA317R
LA318A
Group sampled and
date of sampling in
1954
Rongelap adults,
16 March
Rongelap adults,
17 March
Rongerik
(American
military weather
observers), 18
March
LA319S
Rongelap adults
exposed on Sifo,
Ailinginae, 19
March
LA328J and Japanese fishermen
LA419J
(Lucky Dragon),
28 March and
April 19
Number of
days from
intake to
sampling
Estimate of
Number of ''I counting
Assumed urinary
average
days from
results
Counting excretion on day daily urine
sampling to
(cs! per
Decay
efficiency’
of collection
volume
counting"
500 mL)
correction?
(%)
(%)*
(mL)
15
14
70
13.5
35
0.1
500
16
13
76
13.5
35
0.1
500
17
12
20
13.5
35
0.1
500°
18
11
33
13.5
35
0.1
500
27 and 49
Unknown
0 (not
detected
above
bkend)
~13.5
35
0.1
“Counting date was 30 March 1954.
> Based on elapsed time from intake to counting of approximately 30 d and a half-life of 8 d.
‘ Original estimate estimate was 39% (**), later corrected to 35%".
‘Excretion fraction estimate from J. Hamilton (see text) based on data from short-term observations.
* Actual mean 24-h urine volume was 1,072 mL (Table 2).
1L
(assumed)