Further Studies on the Gastrointestinal Absorption of Plutonium

chronically fed plutonium was determined as 0.0026 =0.0004 %. This value was obtained in experiments with rats, employing plutonium solutions ranging in concentration from 10-6 to 3 X 10-5 ig/ml. We have now extended these studies to cover the concentration range from 10-4 to 1 ;g/ml. Because of the uncertainties involved in extrapolating from rat to man, data were sought from a larger animal more closely akin to the human. Results are reported comparing the gastrointestinal absorption of acutely administered plutonium in pigs and rats. Data are also presented comparing the gastrointestinal absorption of plutonium fed to rats as solutions of different pH and valence state, and with nitrate or citrate present as the anion in solution. Based on these results, a re-evaluation of the maximum permissible concentration of plutonium in water for human consumption has led to an increase in this limit from the previous value of 1.5 X 10-6 ~c/ml (2) to a less restrictive value of 6 X 10-6 Mc/ml (3).