Table 1. Per Cent Abundance and Relative Maximum Permissible Concentration of Fallout Radioisotopes of Biological Interest Per cent abundanceat: 1) Fission One One products week month 589 2.1 590 “oe 90 wee y?l 2.4 zr95 | One year 6.7 Relative Ten years | MPC Half lite?) values?) 2.7 --- 50 days “++ 1.8 21.8 28 years 1 wee 1.8 21.8 64 hours 200 7.6 3.9 --- 58 days 300 2.5 8.2 7.3 --- 65 days 600 Nb?5 --- 4.1 15.0 --- 35 days 1, 000 Ru106 --- oee 2.4 --- 365 days 100 Rh 106 -7- --- 2.4 <--- 2 hours yi3l 6.3 <--- --- 8 days 20 3.7 100 * cal8t e+e - 1.5 18.2 27 years 200 Bal3im --- 1.5 18.2 3 mins. * --. 1) Hunter and Ballou. (195)) 2) Strominger, Hollander and Seaborg(1958) 3) MPC values relative to 5r99: based upon values from 69 for which MPC for Sr99 ig 1078 pelec * A short-lived daughter for which hazard is negligible in comparison to hazard for parent Handbook