a 3) The reason for the serious discrepancy between AEC conclusions and our own conclusions regarding the safety of the Nevada test program is the following: Nearly all monitoring data reported by the AEC represent radioactivity measurements of either the gamma-ray intensity emanating from the ground, the total beta-radioactivity deposited on a gummed film placed on or near the ground, or of total beta activity in the eir. There are established safety stan- Gards regarding exposure to the body fron a given level of radioactivity which has its source outside the body. These standards for externa] exposure have been used, by the AE, to evaluate environmental radioactivity measurements during nuclear tests. a In most cases, the measurements in the regions neighboring the test site did not exceed this safety linit, The AEC therefore concluded that there was no hazard to the nearby populations. In the few instances where the gamma and beta measurements indicated that this safety level for exter- mal exposure would be exceeded, protective measures (remaining indoors, or evacuation) were recommended. The foregoing AEC interpretation of gamma and beta rediae tion measurements is, however, valid onlyifthefalloutwhiod gives rise to this redioactivity does not enter into the food ghein. If fallout radioisotopes do enter the food chain and find their way into the body, certain isotopes become highly eoncentrated in a particular part of the body and expose it to very intense rediation. Safety standards for externa) exposure are then no longer applicable. Iodine 131 is a par-