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Radiologists and radiotherapists were one of the earliest occupational groups to be exposed to ionizing radiation. Their patterns of mortality provide information on the long-term effects of fractionated external radiation exposure. British radiologists who registered with a radiological society between 1897 and 1979 have now been followed-up until 1 January 1997, and the mortality experience examined among those who registered with a society after 1920, when the first radiological protection recommendations were published. The observed number of cancer deaths in those who registered after 1920 was similar to that expected from death rates for all medical practitioners combined (SMR=1.04; 95% CI 0.89-1.21). However, there was evidence of an increasing trend in risk of cancer mortality with time since first registration with a radiological society (p=0.002), such that in those registered for more than 40 years there was a 41% excess risk of cancer mortality (SMR=1.41; 95% CI 1.03-1.90). This is probably a long-term effect of radiation exposure in those who first registered during 1921-1935 and 1936-1954. There was no evidence of an increase in cancer mortality among radiologists who first registered after 1954, in whom radiation exposures are likely to have been lower. Non-cancer causes of death were also examined in more detail than has been reported previously. There was no evidence of an effect of radiation on diseases other than cancer even in the earliest radiologists, despite the fact that doses of the size received by them have been associated with more than a doubling in the death rate among the survivors of the Japanese atomic bombings.

The National Radiological Protection Board has recently carried out a reappraisal of the annual genetically significant dose (GSD) to the population of Great Britain arising from the practice of diagnostic radiology. The current value of 120 muGy (12 mrad) is indistinguishable from the value determined 20 years ago despite a 48% increase in the number of X-ray examinations performed per head of the population. This is mostly due to a large decrease in the contribution from obstetric radiology and to a marked reduction in the gonadal doses delivered to children for nearly all types of examination. The GSD and the frequency of X-ray examinations in Great Britain would appear to be considerably lower than those found in other industrialized countries and seem unlikely to result in more than 100 cases of serious hereditary ill-health per year at genetic equilibrium. On the other hand, diagnostic radiology is responsible for 87% of the GSD from all man-made sources of population exposure in Great Britain and there is evidence from the data collected for this reappraisal that radiological protection measures could be improved so as to reduce significantly this large contribution without detriment to patient care.

A follow-up study of over 14,000 patients treated with a single course of X rays for ankylosing spondylitis demonstrated a substantial excess risk of developing cancer. Previously the excess risk of leukaemia has been related to the estimated mean radiation dose to the active bone marrow but detailed estimates were not made of the radiation doses to other organs. In the present work, data extracted from the original treatment records of a random sample of one in 15 patients have been used to make dose estimates, using Monte Carlo methods, for 30 specific organs or regions of the body and 12 bone marrow sites. Estimates of the mean and median organ doses, standard deviations and ranges have been tabulated. Detailed distributions are presented for six organs (lung, bronchi, stomach, oesophagus, active bone marrow and total body). Comparison with the earlier bone marrow estimates and more recent theoretical estimates shows good agreement.