Deposition and retention of plutonium in human populations

Since 1959, the Los Alamos Scientific Laboratory (LASL) has analyzed over 5000 human tissues from 1100 individuals of the non-occupationally exposed general population for fallout plutonium. These data have been useful in determining the tissue distributions and the current baseline levels of environmental plutonium in the U.S. population. The effects of age, sex, date of death, cause of death and geographic location of residence on the observed plutonium deposition have been evaluated. Because of the difference in biological turnover times in the various organs of the body and the changing concentrations of plutonium in the atmosphere, the plutonium concentration ratios between tissues have changed as a function of time. However, our date indicate that over the past 10 years, the highest concentrations in the general population are found in the tracheobroncheal lymph nodes and the liver and the lowest concentrations are in the spleen, gonads and kidney. Total body burdens in the U.S. population are estimated to have reached 12 pCi during the 1960's and have declined to about 2 pCi in 1977. The relative distribution of plutonium in the U.S. population, determined from the above data, is 5.4 +- 2.4% residing in the lung, 28.4 +- 9.1% in the liver and 64.7 +- 9.1% in the skeleton. We are currently evaluating our data to obtain estimates of the biological turnover times of fallout plutonium in humans. Deposition of Pu in the tissues of occupationally exposed workers has been measured. The observed variation in the whole body distribution suggests that each exposure incident is unique and must be evaluated on the basis of the chemical form, solubility, particle size, mode of entry and duration of exposure. Several of the highest deposition cases are presented to illustrate the variations observed. (author)