population estimated exposure. Las Vegas, Nevada, had the second highest. population estimated exposure but the estimated exposure was quite low at 0.21 R. Most of this estimated exposure, 0.17 R, was due to event BEE. Only a few events accounted for most of the population estimated exposure. _Jhe data in Table 6 show that event HARRY resulted in 30,000 person-R; this is 35% of the total cumulative population estimated exposure. The-three events, HARRY, BEE, and SMOKY, accounted for 57% of the total: cumulative population estimated exposure. The IMCEFD(SHS9) also attempted to estimate the uncertainties associated with theircalculations. They considered these sources of uncertainty: 1) Fission-product decay rate, 2) Instrument response to the mixed fission-product-Field as compared to calibration source, 3) Inaccuracy of instrument readings at lower exposure rates, 4) The use of film badge data in the calculations as opposed to exposure-rate measurements, 5) Analysis or interpolation to derive results for communities where no exposure-rate measurements were made, and 6) Uneven deposition of fallout. Their estimates of the cumulative + 80% for <0.1R, i+ 60% for 0.1 to 1.0 R, and + uncertainty factors were ~ 40% for > 1.0R. Recently, Krey and Beck (Kr81) have measured the total areal deposition of 1376, and 239,2405 for soils in Utah, and Wave also determined the ratio 2405 y /23 9p, Because this ratio is different 213