-~ 14 In obtaining the derived values in Tables I and Il, MPLB and MPC, for Pu~239, a QF=10 was employed. implies, as menticrcd above, This QF that the particles cf Pu-239, which emit alpha particle radiation, are 10 times more effective in inducing cancer than X-rays. Although the irradiation of tissue by insoluble plutonium particles is highly nonuniform, no DF value has beer assigned to these particies and hence, a DF=l1 was empleycd in determining the derived values in Tables I and II. Ideally, the DF should be determined by the ratio of the observed effects in an organ following uniform and nonuniform radiation of the tissue with the same radionuclide; for example: « DF = Number of cancers Number of cancers (nonuniform irradiation) (uniform irradiation) Since direct experimental data are not available, it is necessary to derive the DF for insoluble Pu-239 particles from collateral data. In a subsequent section, we shall present the biologics: cVicencle that strongly suggests that a DF=1 grossly underestimates the DE for insoluble particulates of “ r Pu-239 and, consequently, that the derived standards, MPLB and MPC, for this radionuclide, In fact, are greatly in error. *? it will be shown that the biological data strongly suggests that for such particles one should use a DF=115,000. 20/ This applies as well to other alpha-emitting actinides in insoluble particulate form. . . ee _- . =) te, a . rt ® 4 ; ToaPad gl te: : 7 _7 erae od panes mee Ter . fr. 2 te Nees ow Fy “ie a: . . . . . ooh at r aye ; NL Sy Brees Se ea ey saebaie Uy Beet tye aod Be ” 7 ae eM es Fee 7