Induction of chromosome aberrations by 90Sr beta-particles in cultured human lymphocytes

Human blood was irradiated with beta-particles from an external source of 90Sr. The source was a rolled piece of silver foil, active dimensions: 100 X 12.5 mm, incorporating 3.7 X 10(8) Bq (10 mCi) of 90Sr/90Y. After culturing for 48 h, the dicentric yield in the lymphocytes at the first metaphase was measured as a function of the dose in the blood. The aberration yield fitted the linear-quadratic function well, which is consistent with the single-track and two-track model for aberration formation at low LET radiation. The curve for 90Sr beta-rays was compared with a curve for 60Co gamma-rays. The main difference between the coefficients was in the alpha values. With respect to 60Co gamma-rays, the RBE calculated from the dose-effect relationships for dicentric production was 2.8 at the dose of 0.14 Gy; it decreased with increasing doses. The distribution of dicentrics was consistent with the Poisson distribution but showed a tendency to over-dispersion in the region of higher doses. A reason for these discrepancies is discussed.