ef . . we For these (Tisons, the insoluble alpha emitcing suoke particle, — uranium exide, thorium oxide. and other alpha emitting particles of moderate to low specific activity may be expected to give rise to a higher tumer risk per cipha disintegration or for a given cumulative dose. Similarly plutonium-239 in mixed fallout particles may be expected to produce more tumors per disinteczration than is the case for pure * 7 rud,- 2386. ~~, "and **°pud, + However although larger burdens of hot particles wiil be required for a given tumor risk, such risks can be expected to increase with both alpha specific activity and with particle surface area, and the effects should occur earlier tor a given burden of smaller particles of higher | specific activity. The above considerations make it obvious that the present practice of - averaging the alpha dose over the whole lung or sone arbitrary fraction thereog 19-13) is a highly questionable and grossly misleading procedure at best. It also should be noted thac americium-24) is present in association with plutoniun contanination in the Rocky Flats area and in nuclear test areas. In addition, curium isotopes as well as americium-241 will be present in high concentratien in che nuclear fuel mixture from fission and breeder reactors which use plutonium fuel. The chemical beliavior of emerjicium and curium in the environment will give rise to their substantial uptake in the biosphere and the food chain. Thus the ingestion of americium and curium, their uptake from the gastrointestinal tract, and their accumulation in the liver and skeletal tissue of mammals and man will give rise to additional serious health risks. These contaminants will be relatively more serious than plutonium inhalation in some environments, particularly in vegetated arcas of moderate to high rainfall, where soil resuspension processes are not cffective, EEREem) ge HE Seen ITFTT Bip tive Maherte : Treeey —_— Paneeert a ¥: Bt pe .Ve Sng ae: ae, ¥ -* fo ett hi 1. . °