i _ 26 "The dose to the GI tract is determined by the quantity of fission -" products entering the body by ingestion and inhalation. 7 ments of this quantity are available, however. No direct measure- Some gamma spectrometer measurements of faecal samples were carried out in the United Kingdom in _ April-May 1959, which was the period of highest fallout contamination in air in that year. The United Kingdom measurements show an average daily ' exeretion of 150 pCi/day in 214 g faeces in addition to the total natural potassium activity of 577 pCi/day. Allowing for there being some beta- active nuclides that are not gamma-emitters, the dose-rate in the faecal material would be about 10 urad/day, 3.7 mrad/year and about half this for the adjacent tissue in the lower large intestine, which is the part of the GI tract sustaining the greatest dose." "The Measurements suggest that the dose-rate to the lower large intestine was less than 2 mrem/y during this period of very high air contamination and that the average dose over the five-year period 1955-1959 was less than 1 mrem per year. These calculations suggest that the dose to the lower large intestine from this cause is negligible.” Within the United States, almost any exposure to a particular nuclide has ‘fallen within a range of a factor of 2 regardless of annual rainfall or any ‘other climatological characteristics. Thus, when an average value is used to describe the broad exposure of the people of this country it should be satisfactory for public health purposes. First the individual response to radiation or other stimuli is probably more variable than a factor of 2 and second the