on Radiation Protection and Measurements) becomes about 10 million roentgens per million population. This particular recommendation applying to radiation per million of population was selected be- cause of genetic considerations, that is radiation doses to rela- tively large populations, The average exposure to ‘those conmunities around the Nevada Test Site that experienced the greatest amount of fallout (.2 roentgens or more) is 6, roentgens for the six years ‘ since the nuclear tests started, The actual round numbers for their exposure are 58 thousand roentgens per 100 thousand people. This is, of course, of less genetic significance than a .6 roentgen average exposure to one million people, Even if it had the same significance, .6 roentgens for six years is at the rate of 3 roentgens per 30 years, or only about 1/3 of the value called for by the National Committee on Radiation Protection and Measurement. In an area around the Nevada Test Site which includes the nearest one million people, the average exposure has been only about one-tenth of a roentgen for the six years, or at a rate of about 1/2 roentgen per 30 years. This is 1/20 of the NCRP value, Outside the Test Site regién, the total dose since the beginning of nuclear testing generally has been a very small fraction of a roentgen - considerably less than the average exposure to natural "background" radioactivity which persons have received over the same time period. Roughly speaking, the additional exposure resulting from test fallout outside the Test Site region has been about equivalent to the additional exposure to background radiation which a person would receive by moving from sea level to a locality a few hundred feet higher in altitude, (Background radiation levels increase with altitude because of an increase in cosmic ray frequency.) Fallout radioactivity noted in other countries has been even less, Except for some of the Pacific islands, the cumulative gamma dose at foreign monitoring stations from October 1951 to September 1955 ranged from four to 23 thousandths of one roentgen. Many measurements of the strontium-90 content of soil, food and feed crops, milk, meat and human bones have been made, since strontium-90 is considered to be potentially the most hazardous fallout material when taken into the body. None of these measurements has disclosed a dangerous concentration of strontium-90 from Nevada test outside of the controlled areas of the Test Site. Radiological Monitoring The Test Organization's monitoring program is concentrated largely in the region up to 200 miles from the Test Site. Outside of this area, other monitoring networks provide information on levels of radioactivity in the United States and in other parts of the world. The U. S. Public Health Service, the U. S. Weather Bureau, and 11 Commission installations cooperate in this monitoring activity. Monitoring programs have been expanded in several respects to provide more detailed information on the distribution of fallout and the exposures resulting from it. The monitoring stations detect whatever radioactivity is present in their localities, whether it \v