Recently, renewed attention has been drawn to 12' 1, a radionuclide which, because of its long half-life (1.6 x lo7 yr), has a potential for long-term accumulation in the environment from low level chronic releases at nuclear facilities. The transfer of 1291 through the biosphere and the resultant radiation doses to man are discussed. Metabolic parameters are tabulated for four ages; 1, 4, 14 and adult. These parameters include fractional uptake via inhalation and ingestion, breathing rate, mass, radius and iodine content of the thyroid, and the energy absorbed per disintegration of l2'I vs thyroid size. Factors are presented for calculation of doses from intake or concentration of ' ' '

The inadvertent release of 60 c of 1311 from a Hanford Separations plant stack occurred in September 1963. Plant Operations were shut down as soon as the abnormal release was detected and a comprehensive program of 'environmental surveillance was undertaken. Sampling efforts were guided by rapid calculation of the probable region of maximum 1311 deposition made by plant meteorologists. The initial data obtained allowed a more precise definition of the area of maximum deposition and location of the individual who probably received the maximum thyroid radiation dose resulting from the release. This individual, a small child residing at the farm where the maximum 1311 concentrations in milk were measured, received an estimated maximum total thyroid dose of 0.03 rem. For comparison, the Radiation Protection Guide published by the Federal Radiation Council for individuals is 1.5 remlyear to the thyroid.

Thyroidal burdens of "'1 were calculated for 1-, 4-and 14-yr-olds, and adults, using available dietary data. Milk and milk products contributed 63, 57, 54 and 33% of the total thyroidal '"1 burden of the four respective age groups. As the contribution from dairy products decreased, that from meat increased from about 12% for 1-yr-olds to 35% for adults, while that from leafy vegetables remained relatively stable, from 17 to 21%. From ingested foods produced in air assumed to contain 1 pCi "' I per m3, daily dietary ' ' ' 1 intakes of 1.3, 1.2, 1.7 and 1.5 nCi were computed for the 1-, 4-, and 14-yr-old child and adult, respectively. For each nCi ingested daily, thyroidal dose rates for the respective age groups were calculated to be 4.9, 2.1, 1.7 and 2.6rem/yr, with the altered dose rates reflecting age-related differences in thyroid gland size and iodine kinetics.

Studies of some parameters affecting radiation doses received from consumption of water derived from the Columbia River downstream of the Hanford production reactors were performed. Included were measurement of radionuclides in (1) water entering and leaving the water treatment plants at Richland and Pasco, Washington; (2) sanitary (municipal) water at a number of points in Richland; and (3) coffee brewed from sanitary water.The removal efficiencies for the alum-floc water treatment plants studied ranged from 80 % for rare-earth nuclides to 10 % for Cr-5 1.The relative concentration of radionuclides (principally Na-24, As-76, Sb-122, Np-239) found within the Richland distribution system was used to estimate the average dose to residents consuming the water. Average GI tract doses calculated for persons residing at each of six locations within the city were 1/3-1/2 of those calculated for consumption of water leaving the treatment plant.The average dose received, calculated by weighing these six individual doses by the population distribution, yielded 45% of that calculated for consumption of water leaving the treatment plant.Since coffee represents a major liquid intake mode for adults, the volume of coffee consumed and the potential removal of radionuclides during coffee brewing was studied. The average drinkable volume of coffee per cup was 200 ml. The concentrations of radionuclides in the water and coffee brewed from it were not significantly different for those radionuclides and hence those doses were not significantly contributing the most to the GI tract dose, reduced.