SESSION I 101 Now I wou. like to take a minute or two on the thyroid dose because the thyroid sitcation turned out jo be one of the most difficult problems we had to face in these people. The thyroid dose is usually calculatee on the percent uptake of the radioicdines by the thyroid gland, the half-life in the gland, the size of the gland, and the various isotopes to which the thyroid is exposed. 31, 132, 133, and 135. In the fallout we have iodine- Quite a few isotopes are involved, most of which are very short-lived — the iodine-131 having the longest halflife. The earliest dit-ect measurements were made by Payne Harris* at Los Alamas on [5-day urine. By using this indirect approach from the urine it was calcu.ated that at that time about one-tenth of one percent was still being excreted and this, extrapolated back, gave about tL, 2 microcuries in the thyroid gland originally. This represented about 160 rads of radiation to the adult gland, plus the whole-body exposure, cf course. In the children it was a different story because of the amaitler size of the glands. James at Lawrence Laboratory (Reference Iljhas cal- culated for ua that tue cuildren probably received in the range cf 700 to 1400 rads to the thyroid gland. It was decided that the beta irradia- tion of the neck which produced ‘beta burns" as shown in Figure 4 did not contribute significantly to the thyroid dose in view of the superficial nature of the beta radiation. Fiaure 4. “Beta burns" of neck (sudject No. 39, Macch 1954). The area over the thyroid was a frequen site of “burns”. From R. Conard. * rfarris, Payne— unpublished data.