On the carcinogenic effectiveness of ionizing radiation at low dose rates

The paper gives a brief account of present hypotheses of the BEIR, the UNSCEAR, the NRPB and the German Research Centre for the Environment and Health (GSF). These hypotheses are derived either from observations in radiation biological in-vitro experiments, on results of animal experiments or on analyses of epidemiological studies. The biological effectiveness of ionizing radiation can well depend on the rate with which the absorbed dose is delivered to sensitive structures. The magnitude of this influence for the endpoint 'carcinogenesis in man', however, is not well known. Tentative estimates of different risk analysis groups for the ratios of the slopes of dose-effect-relationships for radiation carcinogenesis at high doses and dose rates as compared to low doses and dose rates (DDREF) vary between 1 and 10. There is no human evidence for values less than 1 for low LET radiations, which are of highest importance in occupational exposures. (orig./HP)