Effect of tritiated water on germ cells and fertility

The relative biological effectiveness (RBE) of tritiated water (HTO) was sought by comparison with the results of tritium simulation using Cs-137 and the results obtained by irradiating with Co-60 gamma rays and fission neutrons (Cf-252) for reference, using as index the lethal effect on mouse newborn oocytes. The method was to inject various doses of HTO once into the abdominal cavity of ICR mouse on the 14th day after birth and the survival rate of oocytes were calculated. As a result, the number of surviving oocytes decreased exponentially depending on the dose of HTO or Cs-137, and 1.1-3.5 was given as the RBE. Further, the resutls of the tests with Co-60 and Cf-252 that were made for reference showed the lethal effect on oocytes to be stronger in the order of Cf-252, HTO, Co-60 and Cs-137. The effects of HTO and Cs-137 on the reproductive capacity (RC) were also studied raising the female mice which were exposed to HTO or Cs-137 as same procedure. The mice were delivered of litters four times in two years. The HTO or Cs-137 induced diminution of RC may be dose dependent and seems to be non-stochastic. (author)