Le ro organ burdengy;£ heavy smokers, the effects may be correnpondingly greater because the total population is exposed, and a the inhalation exposures begin at birth. If the health risks attributable to fallout plutonium exceed 10 percent of the risks of heavy smoking, thea inhalation exposure at ~20 tines " Fallout (the surface soil concentration of plutonium which corresponds to the interin soil standard adopted by the Coloradc Board of Health in 1973) would give rise to organ burdens more than twice that of heavy smokers. Exposing children to such levels would be tantamount to their smoking four packs of cigarettes per day, beginning at birth. This estimate assumes, as I believe to be the case, thet the inhaled, insoluble radioactive smoke ° perticles give rise to the serious health effects of smoking. For the estimation of organ burdens which may result from the inhalation of soil contaminancs, it is common practice to attempt to determine the ° average surface soil concentrations, the epplicable resu spension factors, inhalation exposure patterns, particle size distributions, lung retention, elearance and translocation patterns and rates, ete. The large cumulative wae PDE - errors and uncertainties in the prediction of the ultimate organ burdens OM, from long-term exposure to contaminated surface soils and urban dusts by ¥ 7 such a long sequence of complex processes serve to make this procedure an oe almost useless exercise. There is a more direct approach which sould give more reliable estimates. Lewis et ai?) show that the adult lung burden of nitric acid-insolwble particles increases almost linearly with age, with a about 1.5 grams per kilogram of lung tissue at age 60. It seems reasonable | to assume that individuals chronicaily exposed to soil dust and urban dusf. 4 . ¢ will acquire just such burdens cf the insoluble constituents in the res.’ ¥ size fraction of dust particles (1.e., particles less than ~3 pn diar” p It should be noted that PuO, particles are highly insoluble and friab. ° eR apse ™ - — : - ee a : es re a Fy / ar aN ee Lo ee‘oT. 2h ol re. Ng of aeera LE I OG OE SE ET ae are: Y rere 3 arp aNSe* ‘ 4 eee oh a 4, é,a ALT aor aaa rae ee