Fission-spectrum neutrons at reduced dose rates enhance neoplastic transformation

Abstract

We have studied the effect of reduced dose rates of radiation on neoplastic transformation using the C3H/1OT1/2 mouse embryo-derived cell line developed by Reznikoff et al.¹. In this cell system, transformation can be measured by scoring the foci of piled-up cells that occur after the loss of contact inhibition of growth. We report here that reduction of the dose rates of fission-spectrum neutrons (of mean energy 0.85 MeV) from 38.5 or 10.3 to 0.43 and 0.086 rad min⁻¹ has no effect on cell killing but increases transformation frequency. These data are in contrast to previously published results obtained with ⁶⁰Co γ rays where reduction of the dose rate resulted in a marked reduction in transformation frequency^2,3. Although cancer induction in man involves many factors besides those at the cellular level, the implication from our findings is that the risk of cancer induction due to work-related exposure to neutrons in the nuclear power industry may be greater than previously thought.