Abstract: | Purpose:?Quantitative analysis of cancer risk of ionising radiation as a function of dose-rate.Materials and methods:?Non-tumour dose, Dnt, defined as the highest dose of radiation at which no statistically significant tumour increase was observed above the control level, was analysed as a function of dose-rate of radiation.Results:?An inverse correlation was found between Dnt and dose-rate of the radiation. Dnt increased 20-fold with decreasing dose-rate from 1–10?8 Gy/min for whole body irradiation with low linear energy transfer (LET) radiation. Partial body radiation also showed a dose-rate dependence with a 5- to 10-fold larger Dnt as dose rate decreased. The dose-rate effect was also found for high LET radiation but at 10-fold lower Dnt levels.Conclusions:?The cancer risk of ionising radiation varies 1000-fold depending on the dose-rate of radiation and exposure conditions. This analysis explains the discrepancy of cancer risk between A-bomb survivors and radium dial painters. |