RADIATION-INDUCED CHROMOSOME ABERRATION YIELDS FOLLOWING AN ACCIDENTAL NONUNIFORM EXPOSURE

Chromosomal aberration yields were obtained from short term lymphocyte cultures made at various times after an accidental partial body expos ure to Ir-192 gamma rays. A rapid decline in the frequency of chromoso mal aberrations (CA) has been observed during the first year of follow -up. Dicentric frequencies reduced to one-half, one-third and one-four th of the original values at 160 days, 240 days and 1 year post-irradi ation respectively. The decay of dicentric frequency occurred with a h alf-life of approximately 168 +/- 32 days. A non-Poisson distribution of dicentrics and the presence of a few multi-aberrant cells were cons istent with the nonuniform localised exposure. On the basis of the non -poisson distribution of aberrations, the fraction of lymphocytes irra diated was calculated to be 18%, and the portion of the body exposed a s approximately 53%. The mean yield of dicentrics + rings during the i nitial sampling is 0.195 per cell. Based on the coefficients of aberra tion production obtained from in vitro acute gamma ray dose response c urve, the estimated dose is 1.3 +/- 0.3 Gy.