Chromosome aberrations induced in human lymphocytes by an X-radiation accident: results of a 4-year postirradiation analysis.

After occupational and medical radiation exposures structural chromosome aberrations may be induced in the lymphocytes of the irradiated persons. Many authors have estimated the radiation dose from the yields of dicentric aberrations. We analysed the influence on the dicentric yield of increasing time intervals between irradiation and blood sampling from a person involved in an X-radiation accident (radiography). During a 4-year follow-up we observed an approximately 7-fold decline of the dicentric yield up to the 25th month and thereafter an almost constant value. Since the decline did not commence until around the 10th month after the exposure, an exponential decrease of dicentric yield with time should be considered with reservation in this study, although it cannot be entirely ruled out. We conclude that in 'biological dosimetry' blood should be sampled as early as possible after the exposure. Furthermore, computation of 'half-times' of lymphocytes to allow for a delay in blood sampling seems uncertain after partial body exposures to high doses. Therefore in such cases dose estimates obtained 1 or more years after irradiation should be considered as minimum values.