Changes in chromosome aberration frequency in Chinese hamster liver related to LET and microdose distribution

The effect of radiation quality on the frequency of chromosome aberrations in liver cells was determined by exposing animals to either 60Co gamma irradiation as a reference standard or to radionuclides that deposit in liver; 144Ce, a beta emitter, 238Pu, 239Pu and 241Am, alpha emitters, and 252Cf, an isotope which emits alpha, fission fragments, neutrons, and gamma rays. All the radionuclides were injected as the citrate which resulted in a large fraction of their total activity being deposited in the liver. With the exception of acute gamma exposure, all dose response relationships could be adequately described by a linear equation. Quality factors for the different LET exposures were derived by comparing the slopes of the dose response curves. Using protracted 60Co exposures as the reference, the quality factor for the beta emitter 144Ce-144Pr is 1. Quality factors for the alpha emitters 238Pu, 239Pu and 241Am ranged from 11 to 20 which seems to be higher than the value of 10 used in establishing radiation protection standards. The factor derived for 252Cf was 10. The lower quality factor compared to pure alpha emitters was attributed to the ineffectiveness of fission fragments in producing measurable chromosome damage