Influence of γ irradiation on the development of neoplastic disease in mice. III. Dose-rate effects

The influence of dose rate on the carcinogenic effectiveness of ¹³⁷Cs γ rays at dose rates of 45 rad/min or 8.3 rad/day was investigated using RFM/Un and BALB/c/AnNBdf female mice. Data on a number of reticular tissue and solid tumors are reported. For all tumor types examined, reducing the dose rate decreased the tumorigenic effectiveness of the radiation exposure. In addition to data on the presence or absence of dose-rate effects, information is also provided on the qualitative and quantitative influences of dose rate on the form of the dose-response relationships. The results from the experimental systems examined indicate that the influence of dose rate cannot be described by a single model. The difficulties in interpretation of studies on dose rate and the need for a better understanding of the basis for dose-rate effects are discussed.