2. Seeing a dust cloud or general haze in the sky not associated with a dust storm. 3. Feeling particles striking the nose or forehead or collecting on the hands and arms or in the eyes or ~ between the teeth. 4, In the rain, after turning on the windshield wiper of your car, seeing fallout particles in raindrops slide downward on the glass and pile up at the edge of the wiper stroke, like dust or snow. The particles generally move readily like sand, rather than tending to smear and stick to the glass Like fine dust." It is reasonable to assume that life-threatening radiation exposures will be evident in such ways, as illustrated by this calculation: A K-factor of 2000 is equivalent to 4 x 10733 (R/hr)/(f¥ssions/sq ft). Typical specific activities of fallout particles are 5 x 10 fissions/ gram of fallout; thus for each R/hr at 1 hour exposure rate produced, 5 milligrams of particles would be deposited per sq ft of area. This amount of fallout would be clearly visible. According to DCPA's Nuclear Emergency Operations Plan (NEOP), the threshold of short-term radiobiological injury (defined as no medical care required) is an exposure of 150R in one week or less. For an * = effective fallout-arrival time of one hour after detonation, such an exposure would occur in an open-field location where the fallout contour would be about 50 R/hr at 1 hr. If the fallout-arrival time were 4 hours after detonation, the corresponding fallout contour would be about 75 R/hr at l hour. The total weight deposited would, according to the above data, be about 1/4 gram per square foot for the l-hour arrival time and about 3/8 gram per square foot for the 4-hour arrival time. Such amounts of fallout particles, depositing on a clean surface over a period of an hour should be readily visible. Much smaller amounts of volcanic fallout were yigually detected on streets, roofs, and macadam roads in Costa Rica.~? Use of such advice is necessarily a calculated risk. The Subcommittee is quite willing to agree that if a person can detect fallout, he should go to shelter. The reverse statement, that a person is safe if he cannot see or feel fallout, has loopholes the importance of which the Subcommittee has not evaluated, but which enter into the calculation of that risk. First, the advice, even when it is sound and ig followed, exposes the individual to some increment of exposure beyond that which he would get if he goes to shelter as soon as he learns of an attack. Second, the advice may not be fully understood or trusted or properly followed. Third, these detection indices break down in a naturally dusty area such as the western great plains during the summer, or in the mountain states. Fourth, the fallout- detection indices are not very good when it is raining. 20 Rainout brings