~13- transport from deep Jung and lymph node burdens resulting from previous inhalation ‘exposure. However, the magnitude should be similar to that pre- viously estimated for New York and would therefore lead to total annual urine levels of approximately 0.015 pCi. lead to an annual quantity of 3.65 pCi. The reported urine concentrations< If we accept the reported urine concentrations for Bikini then it would: seem that the transfer coefficient of Pu across the gut for Pu incorporated in food products must be much higher than 3 x 107°. However, the New York data indicate that the major contribution to the Pu urine concentrations is via the inhalation pathway. If the Pu concentrations reported for uriné samples from New York are accepted, the data suggest that the parameters for transfer of Pu to blood must be considerably higher than -those presently used. An increase, however , in both the amount transferred from the upper respiratory tract to the blood and the amount transferred from the blood to the urine, which are reasonable for physiological function and chemicat transport, stil] cannot account for 20% of the total annual intake appearing in the urine. Because of this seemingly large fraction of the total intake appearing in the urine, it is difficult to evaluate whether this human data indicates that transfer to urine is greater for human popula- tions than previously assumed based upon animal studies. . SUMMARY Bikini Atoll may be the only global source of data on humans where intake via ingestion is thought to contribute the major fraction of plutonium body burden. It is possibly the best available source of data ' for evaluating the transfer of Pu across the gut wall after being incorporated into biological systems. If the plutonium urine data for.