Do carbon ultrasoft X-rays induce exchange aberrations in cultured mammalian cells

Preliminary experiments are described on the production of chromosome exchange aberrations in cultured human diploid cells and V79 Chinese hamster cells by carbon ultrasoft (photon energy 0.278 keV) X-rays which produce electrons of track length < approximately 7 nm. The results were compared to the effects of irradiating cells with 'hard' (150 kV) X-rays under similar conditions. The results suggested that the frequencies of exchange aberrations from carbon X-rays were not dissimilar to those from 150 kV X-rays. These data are inconsistent with previously-proposed models of radiation action which predict that radiations with track lengths as short as those produced by carbon X-rays should be unable to produce exchange aberrations. (U.K.)