be minuscule compared to natural background levels or even to normal variations of background radiation. G. WATER AND AIR Background Information Water Contamination of water supplies does not constitute a major source of intake of radioactive fallout debris. In the case of surface water supplies there is a very large dilution factor. In the case of underground nuclear detonations the fission products are restricted largely to the immediate vicinity of the detonation due principally to two factors. Firstly, for underground shots to date approximately 90 percent of the fission products have been fixed in a glassy type of material formed by the detonation. Secondly, ion exchange between such key fission products as strontium 90 and cesium 137, and the soil resulted in almost all of the remaining activity being adsorbed within a matter of perhaps tens to hundreds of feet away from the source.”° In addition to fission prod- ucts, tritium may be formed in varying amounts. This radio- isotope probably is not greatly influenced by the two factors mentioned and must depend upon the dilution factor for re- duction of the concentration in the water—at least for underground detonations. For above ground or cratering shots, the tritium largely escapes into the atmosphere where very large dilutions occur. Theoretical calculations suggest it may be possible for relatively high concentrations of tritium to be present in the amount of water immediately surrounding ground zero of some underground nuclear detonations.”! Essential to predicting potential contamination of ground water is the determination of the water movement. The most satisfactory method of obtaining the necessary data for this prediction is by drilling operations. Although these are expensive operations they are carried on extensively at the testing sites. Air As long as the fallout material from atmospheric tests remains in the air some maybe inhaled and irradiate the lungs. This radiation dose to the lungs normallyis less than external whole body exposure occurring after the fallout has been de- eo ca 3 wen co cri Cm posited on the ground. Also in general, inhalation is only a minor contributor to the intake of fallout debris into the body — ingestion is the much more important route. The whole body will also receive some exposure from the penetrating “amma rays while the fallout material is in the 18