Relative Biological Effectiveness of Tritium Beta-Particles and Co 60 Gamma-Rays Measured by Lethality in CF1 Mice

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Abstract
The effect on mice of a single exposure to tritium (in-jected intraperitoneally as HTO) was compared with the effect of expo-sure to Co60 gamma-radiation. The gamma-radiation was delivered at a rate comparable to the exponentially decreasing dose rate of tritium resulting from the elimination of tritium water and its intensity was attenuated by means of a moving conical lead shield. Tritium beta- particles were 1.7 times as effective as Co60 gamma-radiation in pro-ducing mortality in 30 days. Calculation of the maximum permissible body concentration for tritium in man, with 1.7 taken for the relative biological effectiveness of tritium beta-radiation, gave a value of 3.7 [mu]c and maximum permissible concentrations (for continuous exposure) of 5 x 10-6 and 0.1 [mu]c/cc for air and water, respectively.