fe particle problem. ¢ ate The question is: docs such a particic have an enhanced potential for cancer ? No one knows. evolve from dead cells, carcinozenic. . One can argue that cancer cannot hence a depleted cell population must be legs This is believeable, and must be true on occasion. The facts are, though, that intense , local doses of radiation are extremely eficcui.c carcinogens, mucn more so than if the energy weie averaged _over a larger tissue mass (Geesaman,D.P., 1968b) Furthermore, this can take place at high doses of radiation where only one cell in ten thousand has retained its capacity to divide. The cancer susceptibility of lung tis- sue to radiation has been demonstrated in many species; one can say in Some very careful skin experiments of Dr. Albert have indicated that tissue disrup- tion is a very likely pathway'of radioactive induction of cancer after intense _ exposure (Albert, R.E., et al., 1967a, 1967b, 1867c, 1969). The experiments showthat the most severe tissueinjury is not necessary, nor even optimal, for the induction of cancer. When these notions are applied toa t . . . hot particle in the lung, the possibility of one cancer from 10, 000 disruptive particles is realistic. This is disturbing because an appreciable portion of the total radioactivity in a plutonium aerosol is usually in the large particle component. Let me dernonstrate what I mean. ° Suppose a man received a hota permissible ung burden fer plutonium, and suppose roughty pee" . : . . . recr the anass of the burdest was associated with the most active class ee wk weet tte particles and implants than it is to diffuse uniform radiation. eo —— Slee lees a eA RTD ee! Eel elas betas om eeteSeek Bh Fbde IMR 9 Red Ial aOECEs eb beenele wet Cwm ae Fades UrearbiARIathena general that the lung is more eusceptible to inhomogeneous exposures from