Estimation of the risks of ionising radiation

Probably more is known about the quantitative relationship between exposure and carcinogenesis for radiation than for any other carcinogenic agent. Nevertheless from the brief review given here it is obvious that even for radiation the data are meagre and often not appropriate to the problems of setting dose limits for the protection of radiation workers. ICRP derived a quantitative relationship between exposure and risk of cancer induction and used it to justify their recommended dose limits for exposure. This was done by proposing that the acceptable risk should be about 10(-4) per year. No doubt there will be many other views expressed on acceptable risk which is quite clearly a political issue. If other views prevail and an alternative value is adopted then the dose limit will have to be changed by reference to the dose-risk relationship. This new feature of radiological protection which follows automatically once a quantitative relationship between dose and risk has been recommended, does not seem to be widely recognised. The comparative method of assessing acceptability of actual radiation exposures by comparing cancer mortality data with other industries, does have the advantage that in principle the results of the comparison should be simple and understandable to workers, managers and the public. However, the one analysis of mortality data which is available for a group of radiation workers at Hanford, has lead to a considerable controversy over the method of analysis. The author thinks that the way ahead in radiological protection must lie in the study of cancer morbidity and mortality and not with the theoretical approach where predicted cancer mortality is compared with death rates from industrial accidents, which is the approach used by ICRP in Publication 26.