‘found in the sgile of the nidweatern U. 8, and that perhaps 15 to 17 mc/mi* is the total to be expected for similar latitudes elsewhere in the world, the difference: being due | to our proximity to our own weapons testing site’ in. Nevada.’ These 22 mc/mi2 of Sr90 inthe soil of the U. S.' amount to about 0.040 MPC2/units inthe top two inches of soil where that the human body burden’ of Sr90 might well be! as high | +o erptmetneten aoenine wt most of the fallout is absorbed. Earlier, it seems reason, able to conclude on the basis of a plausible mechanism for . the transport of radiostrontium from the soil to! humans as 70 percent of the concentration in the top soil on which) people live; furthar avidence seems to indicate that this should be reduced to batwean 10 and 30 percent. ‘ There- fore at the moment we would expect, assuming that no fur~ ther weapons are fired, th; the body burden fon children : born now in America evantu..ly would amount to between 0.004 and 0.010 MPC units. Consideration of the rate of si |; transfer from the stratosphere tq the ground and the rate of radioactive decay indicatos that the body burden to be | | no D4 ‘anticipated 15 years from now probably will be substantially oY the same as it is today. - New evidence has van found for the effect of rainfall on fallout oy studying thrae particulanly arid regions; in aach crs. the arount of Sr7¥ in the soil was ‘very’much less than would be prodictad from geographical location alone. iagiens in which people normally live . have? enough precipitation so that differences in precipi- tation do not appsar to affsct tha fallout by more than a - 2/ As used in this spoech one MPC unit is 1 microcurie - | of radiostrontium per kilogram of calcium, or 1 micro- | curie per average adult human, the "maximum,| Permissible ~ concentration." A aay q cons i sai ew wees ne Ey ~ Le o anette, oe be . factor of 2.