- 14 - In obtaining the derived values in Tables I and Iti, MPLB and MPCa for Pu-239, a QF=10 was employed. This OF implies, as mentioned above, that the particles of Pu-239, which emit alpha particle radiation, in inducing cancer than X-rays. are 10 times more effective Although the irradiation of tissue by insoluble plutonium particles is highly nonuniform, no DF value has been assigned to these particles and hence, a DF=1 was employed 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 radicnuclide; for example: Number of cancers DF ~ 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, Ina subsequent section, we shall present the biological evidence that strongly suggests that a DF=1 grossly underestimates the DE for insoluble particulates of Pu-239 and, consequently, that the derived standards, MPLB and MPC, for this radionuclide, are greatly in error?°, | In fact, it will be shown that the biological data strongly suggests that for such particles one should use a Dr=].15,0092. 20/ This app 1 ies ™~ me - + in insoluble a — as well to cther alpha-emitting actniccs particulate pa form.