- 34 - As seen from Table IV, using Geesaman's lung model, a particle with an alpha activity between 0.02 pCi and 0.14 pCi is required to give a dose of 1000 rem/yr to irradiated lung tissue. For purposes of establishing a maximum permissible ’ lung particle burden we will use 0.07 pCi from long halflived (greater than one year) isotopes as the limiting alpha activity to qualify as a hot particle. Thus, throughout the remainder of this report, hot particle will imply a particle with at least this limiting alpha activity which is insoluble in lung tissue. A, . , Exposures at Rocky Flats The AEC has a plutonium facility associated with its nuclear weapons program at Rocky Flats, Colorado. This facility is operated under contract to the AEC by the Dow Chemical Company. The employees, the environment and undoubtedly the surrounding population have been contaminated with plutonium particles as a result of the operation of this plant. 60-62 It is, therefore, pertinent here to examine the information —— 60/ Mann, J.R. and A.R. Kirchnev, Op. cit. 61/ Poet, S.E. and E.A. Martell, "Plutonium-239 and Americium-241 in the Denver Area," Health Physics, Vol. 23, 1972, po. 537-549, 62/ Richmond, Chet, Transcript of Plutonium Information Meeting cf the Advisory Committce on Reactor Safeguards, Los Alamos, N. Mex., 5 January 1974, pp. 319-320.