little protection to the populace, there would be a saving in radiation exposure to them. On the other hand, people better sheltered, as illus- trated in Column V, would receive less total exposure if they stayed in the protected areas until the out-of-doors activity had decreased, and : at the same time a delay of entry into the contaminated area would re- | i sult in less radiation exposure to the rescue crews who might then be used again for other missions. DISTANT FALLOUT PATTERNS FROM HIGH YIELD WEAPONS The discussion above suggests the wide variability possible in distant fallout patterns from high yield weapons and the great variation in radiation dose that one may receive due to shielding and weathering effects. Therefore, the following analysis is intended to be only a generalized one to illustrate the parameters and how they may operate in determining the radiation doses. Consider the case of fallout from a high yield weapon where people continue to live in an area without any special measures to protect themselves. Assume (a) for the first week following the fallout, the measured gamma activity decays according to (time)71-2, for the sec- ond week (time)71+3 and for the third week and thereafter (time)7l°4, and (b) the shielding factor afforded by normal housing will reduce the out-of-doors daily dose by 25%, and (c) the half-time of repair of biological injury is four weeks. Probably all of these assumptions are conservative, i.e., they overestimate the hazard. Based on these assumptions, Figure 6, shows the dose rates at time of fallout or entry e -13~-