34 The increase in cancer mortality resulting from the dosages of Table 4.5 #1 can be calculated as follows. Suppose that 500 persons w live continuously on Rongelap Island for the period 1978-2008. average each would accumulate a committed dose (whole-body) of 1 over that 30-year period. For simplicity, I will assume that ea receives the dose all at once. Then, taking an overall cancer m e to the 5 ren tality factor of 5 x 10-4 per rem (Shimizu et al, 1987; Preston and Pie ce, 1987), I find the increment to be: 500 x 1.25 x 5 x 10-* = .31 extra cases. The factor for first generation genetic defects is smaller for cancer mortality (National Academy of Sciences, 1972; NCRP, being approximately 1 x 10-4. han that 987a), The foregoing comments apply to the future. But what about the past? The Rongelap residents exposed to the Bravo shot received an acute dose of 190 rem in 1954 and during 1957-1978 they received a chr nic dose of 1-3 rem. My opinion is that the addition to these past doses of something like 1.25 rem during the next 30 years will not apprec ably increase detectable health and genetic risks in a way that shoul preclude return to Rongelap Island.