a4 ticular problem in this regard for it becomes quickly concentrated in the thyroi:! gland when taken in with the food. Thus if a fanma radiation monitor tm a pasture outside the Nevada Test Site shows a reading of .087 r/hr at 12 hours following the time of a nuclcur te.*, weasured at three feet above ground level, this inlicates the ajparently maxinmun safe level, since the permissitle standard for continuous exposure from a source esterna’ te tae tody ix 3.9 r/year (effective biological jose), which i5 ewivalent to a doce rate of .087 r/hr at l2 hours fcliowing a test. however, if a milk cow feeds on this pasture and its milk is freshi» tonsumed by a small child, this concausion tecomes inval.d. Under *hese circumstances it can be shown that this same gamma reading (1.e. .087 r/hr) probably reflects a concentration of iodine 131 in the grass, which after passing into the cow's milk and being consumed by the child may deliver to the child's thyroid gland a radiation dose of 175 to 1200 rads. This dosage exceeds even the safety Standards ‘or radiation vorkers (30 rads to the thyroid per year) by a fertur of 5 to 49 and is so high as to represent a csericus po'2antial cause of thyroid cancer. Thus she UU. conelusi¢cns regarding safety in the Nevada Test Site region become it.valid if it can be shown that the readings or which ti-v are based were taken in the reyions in which cilk cove graz2 cna creduce milk that is freshly consumed by cnildren localiy. Our study of a nunber of regions around the Nevada Test site shows that in many cases fallout sufficleatly intense to contair. such excessive amounts of iodine 131