Dose-rate dependence of chromosome aberrations in human peripheral blood lymphocytes irradiated in vitro.

Dose response relationships were studied in dicentric chromosomes in human peripheral blood lymphocytes exposed in vitro to 60Co gamma-rays in accumulated doses from 0.10 to 4.0 Gy at dose rates 1.0, 0.1, 0.01, and 0.001 Gy/min. The coefficients for the linear, quadratic and linear-quadratic relationships were calculated by the fitting method of least squares. It was found that the linear-quadratic model y = aD + bD2 was most suitable for the dose rates used. The effect of dose rate was manifested in such a way that at accumulated dose of 2.0 Gy the frequency of dicentric chromosomes was decreased by more than 50% if the dose was applied in 33 h than when it was given in 2, 20 or 200 min.