RADIATION AND MAN External Exposure - a While mankind has lived for probably millions of years in a naturally radioactive environment, it has only been since the creation of artificial sources of radioactivity such as - bombs that X-raymachines, atomic reactors, and nuclear man-made radioactivity has presented an increased danger individually As discussed in this report, r 4m or on a mass basis to man, external exposure from nuclear devices or fallout from their explosion will be mainly considered, although the effects are the same whether from bombs, reactor accidents, or medical overexposures, As mentioned before, one peculiar quality of radiation is its ability to “ionize,” that is, the ability of a particle to pass through material and disrupt the atom arrangements, Particularly dangerous in the area of external exposure are neutrons and gamma rays, since they are very penetrating and can actually pass through the human body, leaving in their path ionized atoms. In effect, the thousands of these particles which pass through the human body may disrupt hundreds or thousands of atoms comprising the molecules of the body's cells--its basic building blocks, In regard to low exposure to whole-body a Most data about such exposure is limited to that of from 50 rads up to thousands of rads. ~—_—— is known, (total body) radiation, little 30 days, although at the upper end it approaches the LD-50 range, From 50 to about 300 rads would he considered a sublethal dose within dependent upon available treatment. This is also This means that it is not likely for death to occur; however, within this range a number of "acute" or severe effects, 13