- 7 Co 1. Introduction: CR / . The adequacy cf the biomedical basis of stan ards for occupational and public exposure to plutonium and other internal alpha emitters have been widely discussed (155) ‘and seriously questioned (6-8) The serious uncertainties in the cancer risks attrioutable to internal aipha emitters must be resolved before we are irretrievably committed to a nuclear energy program. This is a matter of immediate concern in the western suburbs of Denver due to plutonium and americium contamination of surface soils in public areas around the Rocky Flats Plutonium Plant (9) | Many other localities are similarly affected by. tranuranium element contamination and its attendant cancer risks. - Recent controversy regarding the adequacy of plutonium standards hae centered on several aspects of the problem of the cancer risks attributable to inhaled plutonium oxide particles, including such questions as which organ and how smali a tissue volume constitutes the "critical" organ (i.e., that experiencing the highest cancer risk), and whether the average alpha radiation dose to the critical organ or the tumor risk attributed to a given number of individual hot plutonium oxide particles provides the best guidance for the assessment of risks and standards for plutonium. . Geesaman (6) has discussed possible mechanisms of cancer » induction by hot particles and concludes that the tunorigenic risk may be as high as 1/2000 per particle for submicron particles of plutenium oxide. A recent examination of hot particle risks by Tamplin and Cochran (8) > based largely on the Geesaman study, led these authors to recommend that the occupational MPLB (maximum permissible lung burden) be reduced by a factor of 125,000, to a value of 0.14 pCi. A recent study ‘2° was carried out by Bair, Richmond and Wachholz at the request of the U.S. Atomic Erergy Commission with the specific objective of providing an updated review of the evidence bearing on the: problem of uniform vs ANNES | GB Ng ry a ee fags Rn > x 3