BRAVO test. These data, together with appropriate conversion factors and living pattern models, provided an estimate of external dose equivalent. METHODS Exponentially declining activity concentrations have been observed in surface soil for 1376.) 129, and 905, from 1954 to the present on Rongelap and Utirik Atolls. Declining activity concentrations have also been observed in vegetation at a rate greater than that predicted by radioactive decay. Thus exponential decline in dietary activity was assumed and the following general equations were derived. uu/f, -¢ AP? = f ly X;K; > ’ (hi Kiki ec C+ ~ t K, t AtKi ty) (@7 Or +Ke)t _ oe ’ (1) i or L AP° = f, UZ ? “(4K gq-a° (irie t i) E) (e7AtKet _ e OR Xi ; (2) i Ki-K and D= £,AP° £ po E + Cagney Re E R m e ) 4K (0 ke ic (A Xi (K,*) (Kj *N) ERK + q° = 1 where Xi A+K, (ine CAFRA E (3)