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)