The induction of chromosome aberrations in human lymphocytes by exposure to tritiated water in vitro

An in vitro dose response has been obtained for chromosome aberration induction in human lymphocytes exposed for 24 hours to tritiated water in whole blood. An RBE at low doses of 1.13 ± 0.18 has been calculated by comparison with 250 kVp X-rays. The application of these results in cases of accidental exposure to tritiated water is discussed. As expected, the prediction of dicentric yield from acute exposure to HT0 does not agree with observed values indicating that the G function of Lea is not applicable in this case if an approximately two hour break repair time applies. The proposal of Edwards and Lloyd that a proportion of long lived breaks can account for this discrepancy would explain these results. Although an X-ray dose response for dicentric aberration induction in human lymphocytes can be used to provide an approximate dose in cases of exposure to tritiated water, a more accurate calibration is desirable. In this experiment the in vitro exposure of G₀ lymphocytes to HT0 over a period of 24 hours has provided this information and yielded a value for RBE at low doses of 1.13 ± 0.18 with respect to 250 kVp X rays.