Table 1. Per Cent Abundance and Relative Maximum Permissible Concentration of Fallout Radioisotopes of Biological Interest Fission Per cent abundance products week One One gr89 §r90 y90 yy! 2.1 ----2.4 --- Half life?) 6.7 ----7.6 2.7 1.8 1.8 3.9 --21.8 21.8 --- 50 28 64 58 4.1 15.0 -=- 35 days 6.3 3.7 --- --- --- Ru 106 Rh106 ----- i131 Bal3?m --- 8.2 ------- Ba1l40 Lal40 8.8 9.4 10.8 12.5 prl44 Pm 14? ----- 2.0 --- Cel44 Ten years 2.5 Csl37 One Relative year zr95 Nb95 month at:)) ~-- 2.0 7.300 2.4 2.4 1.5 1.5 ----- 26.5 26.5 5.7 --- days years hours days 65 days 100 1 200 300 600 1, 000 ----- 365 days 2 hours 18.2 27 years 200 ~---- 13 days 40 hours 300 200 17 mins. 950 days * 2,000 --- 18.2 --- --15.8 Non-fission products Mn°4 Fed Feo9 Co®? C08 C060 zn65 8 days 3 mins. 285 days 290 days 100 * 20 * 100 1, 000 950 days 8, 000 270 days 71 days 5, 000 1, 000 245 days 1,000 45 days 1900 days 1) Hunter and Ballou (1951) 2) Strominger, Hollander and Seaborg (1958) 3) MPC values relative to Sr99; based upon values from * MPC values9) Handbook 69 for which MPC for Sr90 ig 1076 pe/ce A short-lived daughter for which hazard is negligible in comparison to hazard for parent 600 500