disease and other cerdiovascular effects and to a lesser extent of cancer and pulmonary emphysema ‘*”? , Based on evidence reviewed above it appears that atherosclerosis is a cancer of the artery wall and thus that coronary heart disease and other diseases of the cardiovascular and renal system are expected effects of inhaled plutonium and of other insoluble alpha " emitting particles. An adequate assessment of the magnitude of these risks can only be obtained by a comprehensive medical, follow-up of all past and present plutonium workers. Until the age distribution of these effects among plutonium workers is fully assessed, any claim by the proponents of nuclear energy that there is little risk associated with the MPLB (maximum permissible lung burden), 16 nCi of plutonium, or fractions thereof, is totally unjustified. The growing evidence suggests that as little as-: ferry cicocuries of alpha activity in the lung, in arterial tissue, and in other organs gives rise to a significant cancer risk. 5. Discussion: The published evidence, reviewed above, clearly indicates that a linear extrapolation to lower doses and dose rates is not conservative for internal alpha emitters. The initial effects of alpha inter- actions with cell chromosomes are irreversible and thus will vary linearly with alpha dose xate. However the cumulative effects of internal alpha emitters gives rise to an increase in the populations of mutated cells: (cells with viable structural changes in their chromosomes) and in the health consequences of such changes. Therefore the tumor incidence per alpha disintegration must increase with decreasing dose rate. For this reason a given cancer risk is equated with smaller cumulative alpha doses and with much smaller internal alpha emitter burdens as the period of exposure increases.